Model Engine Maker

Engines => Your Own Design => Topic started by: Brian Rupnow on April 01, 2018, 03:26:27 PM

Title: Inspiration for new air motor
Post by: Brian Rupnow on April 01, 2018, 03:26:27 PM
I really, really, don't want to start another build right now. However--I have been researching all of the many different flamelicker engines, and ran across the Bengs unit. My God--It's awesome!! I wouldn't want to build a flamelicker engine, as I now have finished the Poppin by Dr. Senft, and a Stirling engine which was 75%Moriya fan and 25% me. I have I.C. engines out the ying yang. and a goodly number of air/steam engines. I really like the style of this engine, and may design a single acting air motor based on this.
(https://imageshack.com/a/img924/1640/TcX3fj.jpg)
https://www.youtube.com/watch?v=0G4OuBVb7NY
Title: Re: Inspiration for new air motor
Post by: Jasonb on April 01, 2018, 04:19:34 PM
Another similar one here you may be able to take some details from

http://www.dampfundmehr.de/bilder/hugo/hugo-1.htm

http://www.dampfundmehr.de/bilder/hugo/hugo.htm
Title: Re: Inspiration for new air motor
Post by: Brian Rupnow on April 01, 2018, 04:44:43 PM
I find it strange that the rocker arm isn't set at a 1:1 ratio. It looks like the distance from the piston rod to the pivot is twice as long as the distance from the pivot to the connecting rod. I'm trying to wrap my head around that. I don't think it changes the number of flywheel revolutions to cylinder strokes. I think it just means that you can get away with a shorter throw on the crankshaft.
Title: Re: Inspiration for new air motor
Post by: stevehuckss396 on April 01, 2018, 06:40:08 PM
I find it strange that the rocker arm isn't set at a 1:1 ratio.  I think it just means that you can get away with a shorter throw on the crankshaft.

Most if not all full size engines I have worked on have a rocker ratio greater than 1:1. I think small Chevy is 1.5:1 and big Chevy is 1.7:1 ratios.

You suspect correctly. You can get greater valve lift with a smaller cam lobe.
Title: Re: Inspiration for new air motor
Post by: crueby on April 01, 2018, 07:25:44 PM
That sure is a pretty engine. How can you not build one! 
Title: Re: Inspiration for new air motor
Post by: b.lindsey on April 01, 2018, 09:05:32 PM
I love that one Brian. That little ball valve on the top of the cylinder is rather interesting too.

Bill
Title: Re: Inspiration for new air motor
Post by: Brian Rupnow on April 01, 2018, 09:11:42 PM
Bill--that little ball valve is the exhaust valve for a flamelicker. Theory is that a Poppin doesn't need one, because pressure in the cylinder will just lift the .002" valve off the cylinder head and let pressure escape. On the flameaters with a rigid guillotine type valve, you need that exhaust valve.
Title: Re: Inspiration for new air motor
Post by: b.lindsey on April 01, 2018, 09:21:04 PM
Yes I figured as much, but I also like the more rigid look of the guillotine valve as compared to the Poppin. Just gives the engine a more solid look overall.

Bill
Title: Re: Inspiration for new air motor
Post by: yogi on April 01, 2018, 10:58:01 PM
Brian, flamelicker engines like long strokes. A 1:2 bore/stroke ratio is not uncommon. I would say the ratio on the rocker is to keep the crank more reasonable.

Yogi
Title: Re: Inspiration for new air motor
Post by: Brian Rupnow on April 01, 2018, 11:37:01 PM
My Poppin runs-- Ahhh---good. It is very delicate, and very fussy about just where the flame is positioned, but it runs. The larger more complex flame-lickers I have seen with a rigid sliding gate valve, mechanically operated, seem to be a lot more forgiving of flame position and run a lot stronger.
Title: Re: Inspiration for new air motor
Post by: Brian Rupnow on April 01, 2018, 11:50:03 PM
I have the engine all designed---in my head. The only thing I'm not sure of is the valve mechanism. Since it will only be a single acting engine, it doesn't really require a sliding admission valve like you would find on a double acting cylinder. Probably a simpler valve driven by an elliptical cam through a couple of bell crank mechanisms would work. I have an old Chuck Fellows single acting engine that I converted from it's original design to operate with a valve like this. I'll have to see if I still have the drawings of my design changes to Chucks original valve mechanism. Other than the double acting twin Stewart engine I built this winter, it's been a long time since I messed around with air/steam engines.
Title: Re: Inspiration for new air motor
Post by: Brian Rupnow on April 02, 2018, 01:55:07 AM
Ah Rats!!! I can't find the files I need. I thought I had them on a disc, but after a massive disc hunt I can't find them. I do have the original files of Chucks hit and miss engine, but not the changes I made to the valve system.--However, it's not a major issue. I have the engine here on my shelf and I can pull it apart and reverse engineer it.
Title: Re: Inspiration for new air motor
Post by: Brian Rupnow on April 02, 2018, 03:26:30 PM
Okay---We're good!! I took the old single acting engine down of the shelf and did a little reverse engineering. Now I know exactly how the valve for a single acting engine works. (I had forgotten). This is the valve my new creation is going to use. It is a very versatile valve that can be mounted any number of different ways.
(https://imageshack.com/a/img924/1441/DiPHCf.jpg)
Title: Re: Inspiration for new air motor
Post by: Brian Rupnow on April 02, 2018, 04:50:26 PM
Where do you start with something like this? Well in my case, I happen to have a pair of 4" flywheel rings that at one time were mounted on my Kerzel engine. They didn't improve the hit and miss action of the Kerzel, so they were saved for a future project. This may be it. Second consideration is ratio and proportion. If you look at a side view of the flame-eater engine I am copying the style of, you will see that there is a ratio between the outer diameter of the flywheels, the outer diameter of the cylinder, and the length of the cylinder. There is also a relationship between the center of the flywheels and the centerline of the cylinder, both vertically and horizontally. This is somewhat subjective. And of course we know that the flywheels have to be placed far enough from the center of the cylinder that they won't rub on it.--So, for now we place them where they won't hit the cylinder as they revolve. That's what is involved in the "starting point" of a layout .
(https://imageshack.com/a/img922/1078/kjn1I1.jpg)
Title: Re: Inspiration for new air motor
Post by: Brian Rupnow on April 02, 2018, 05:13:56 PM
Of course we are going to have to have a couple of supports to hold this engine up off the tabletop. This calls for milling a couple of 1/2" wide slots in the bottom of the cylinder and making up a pair of stands that will bolt to the cylinder. Right now the supports look kind of long and skinny, but the reason for that is to let the ends of the mount stick out far enough past the outside of the flywheel that I can reach down beside the flywheel with my screwdriver and put a #8 woodscrew through each of the four holes to mount this puppy to my workbench.--Don't want it to walk away on me when it's running.
(https://imageshack.com/a/img922/3492/Dvhptz.jpg)
Title: Re: Inspiration for new air motor
Post by: Brian Rupnow on April 02, 2018, 05:42:09 PM
We need a piston. There's a lot going on with a piston. The cylinder bore is .875", so we want our piston to be a "precision sliding fit" into the bore. A good enough fit that it won't fall through under gravity, but will go through with a gentle push with your finger. We don't want our piston to "cock sideways" in the cylinder, so we make it  "a bit" longer than the diameter. There isn't going to be any rings on this piston, but we need two shallow grooves around it for oil retention to help prevent air from passing around it. We want the hole for the wrist pin to be less than halfway from the closed end of the piston. This again is a measure to prevent "cocking sideways" in the cylinder. we need a slot wide enough for the connecting rod to fit into, and we want to releave a lot of material from the open end of the cylinder to prevent the con-rod hitting the inside of the skirt when it is at it's most extreme angle.
(https://imageshack.com/a/img922/2758/hf5ezr.jpg)
Title: Re: Inspiration for new air motor
Post by: crueby on April 02, 2018, 06:18:25 PM
Great to hear your comments on your design process as you go, great stuff!

 :popcorn: :popcorn: :popcorn:
Title: Re: Inspiration for new air motor
Post by: Brian Rupnow on April 02, 2018, 06:45:02 PM
What can I say about flywheels? The easiest flywheels to make are from aluminum. But--aluminum just isn't heavy enough to make a good flywheel. However, a two piece flywheel with an aluminum center and a steel outer rim work really, really well. For the artistic among us the holes in the center can be just about any shape, even the creation of curved or straight spokes is possible. Just a note here in an area I've been burned on before. Make the hub diameter large enough that you have at least 3/16" of material between the centerhole and the outside of the hub, or your set screws are going to strip out. If you have a keyway, then make your hubs large enough in diameter to allow at least 3/16" between the outer limit of the keyway and the outside of the hub, or again, your set screws are going to strip out. I like to put two set-screws in each flywheel, 90 degrees apart. If I have a keyway, then one set-screw sets over the keyway and the second at 90 degrees from it. And finally--although it isn't really critical, flywheels look a lot better with the "spoke area" relieved about 1/3 of the flywheels thickness on each side as I have shown.
(https://imageshack.com/a/img922/4742/bQ3ohK.jpg)
Title: Re: Inspiration for new air motor
Post by: Brian Rupnow on April 02, 2018, 09:45:42 PM
Well sir!!! I'm surprised right outa my pants. I have input the geometry based on a 2:1 ratio in the pivot lever, and it works. The crank "throw" is 1/2", but because of the 2:1 ratio in the pivot lever, the piston actually travels 2". one flywheel is currently hidden. Now I have to make this. I will try and put up an animation.
(https://imageshack.com/a/img924/2871/Uy7tYJ.jpg)
Title: Re: Inspiration for new air motor
Post by: Brian Rupnow on April 02, 2018, 11:26:01 PM
This is going to be amazing.
https://www.youtube.com/watch?v=SgS8hpX75B4&feature=youtu.be (https://www.youtube.com/watch?v=SgS8hpX75B4&feature=youtu.be)
(https://imageshack.com/a/img924/5346/TaykTe.jpg)
Title: Re: Inspiration for new air motor
Post by: b.lindsey on April 03, 2018, 12:31:58 AM
To be " really,really not wanting to start another build," you are sure diving into this one Brian. I agree though it is a very compelling design.

Bill
Title: Re: Inspiration for new air motor
Post by: crueby on April 03, 2018, 01:02:07 AM
Has anyone made a twin cylinder version of one of these kinds of engines? A twin of this style would be fascinating to watch. Though probably a bear to get to run right.

Anyway:
Got my popcorn ready to go!   :popcorn:
Title: Re: Inspiration for new air motor
Post by: Jasonb on April 03, 2018, 08:03:48 AM
The monitor engine is not unlike a twin cylinder version. Just the rocker arm is not straight but two arms on teh same pivot and crankshaft sits lower. Still the same principal just a lot more detailed than this simplified one.
Title: Re: Inspiration for new air motor
Post by: Alyn Foundry on April 03, 2018, 11:21:17 AM
Has anyone made a twin cylinder version of one of these kinds of engines? A twin of this style would be fascinating to watch. Though probably a bear to get to run right.

Anyway:
Got my popcorn ready to go!   :popcorn:

Yes....

A twin cylinder CHUK inverted vertical was tried but the " Bear " still rules!!

I also sketched a design for an inline " four " with manifolded intake, a pipe dream perhaps?

Cheers Graham.

As a " post script " Brian's creation would lend itself nicely to a twin piston with common bore.... ;)
Title: Re: Inspiration for new air motor
Post by: Ian S C on April 03, 2018, 01:00:20 PM
You could make the motor with two pistons in the one cylinder, with a rocker at each end, the two con rods would operate on the one crank pin.
Ian S C
Title: Re: Inspiration for new air motor
Post by: Alyn Foundry on April 03, 2018, 02:04:44 PM
You could make the motor with two pistons in the one cylinder, with a rocker at each end, the two con rods would operate on the one crank pin.
Ian S C

Forgive me Ian.

But wouldn't that be counterproductive? You'd have one piston going in and the other going out. As I see it you want both pistons working in unison, we made a single IC engine called the Moffat that used dogleged rockers off a 180 degree double throw crank.

Cheers Graham.
Title: Re: Inspiration for new air motor
Post by: Brian Rupnow on April 03, 2018, 02:30:06 PM
I'm all ready to go on this thing, except for the valve which operates off a cam on the crankshaft. I have a terrible time with the valving on these things because I don't do many of them. I have the valving on normal double acting cylinders sussed out pretty good, but these single acting ones make me a bit crazy.
(https://imageshack.com/a/img924/209/UYNVsT.jpg)
Title: Re: Inspiration for new air motor
Post by: Brian Rupnow on April 03, 2018, 02:38:20 PM
To be " really,really not wanting to start another build," you are sure diving into this one Brian. I agree though it is a very compelling design.

Bill
Bill--Thats my life. If I don't have engineering work to do for a customer, then I have nothing to do at all except design or build something. I don't watch much TV at all, and I read but right now I'm waiting for all my favourite authors to publish. I just love designing, and somehow I don't feel commited with designing like I do when I actually start to cut metal. Once I start cutting metal then it picks me up and won't let me go until I have an engine.
Title: Re: Inspiration for new air motor
Post by: b.lindsey on April 03, 2018, 02:42:49 PM
I totally understand Brian, and my comment was not a complaint at all  ;)  It's amazing how the gears start turning once a new idea gets into our brains  :noidea:

Bill
Title: Re: Inspiration for new air motor
Post by: Brian Rupnow on April 03, 2018, 03:45:33 PM
Bill--Once I get a new idea like this my head catches fire!!!
Title: Re: Inspiration for new air motor
Post by: Brian Rupnow on April 03, 2018, 06:01:30 PM
This animation shows the valve and valve mechanism in place and operating. I believe I have found good mechanical solutions to everything. Nothing "crashes" during a 360 degree rotation. The nearside flywheel is "hidden" in order to clearly see all of the parts moving. The only part I am unsure of is the valve. I re-used the eccentric cam and the valve body and valve slider from a running engine that I have, but due to the strangeness of this engine, valve events are not occurring when they should, and I don't have enough experience with valving to correct it.  If anyone with experience wishes to step up and help me with the valving, the engine will be built. In return for that help I will give them a complete set of plans for this engine. If not, it will just remain an interesting design exercise.---Brian
https://www.youtube.com/watch?v=FhpR4OAYmnQ
Title: Re: Inspiration for new air motor
Post by: Jasonb on April 03, 2018, 06:32:03 PM
It's really just a case of timing the valve to the piston, forget the crank and its linkages as it just complicates things.

You want the air to start filling the cylinder just after TDC and to have closed Just before BDC. Exhaust to open just before BDC and close on TDC. This makes sure the engine can push out all the spent air before the next lot if let into the cylinder.

I don't know if that valve allows for zero overlap but the above is how I have the single acting Jowitt Poppet valve engines set and they run well. If you can't get zero overlap then have less intake but keep the exhaust open so it does not slow the engine.
Title: Re: Inspiration for new air motor
Post by: Alyn Foundry on April 03, 2018, 06:51:05 PM
I agree.

We had a few " Desmodronic " style cams made from an exact copy of the Ernst Plank engine that I have.

Using this method means you don't have any unnecessary springs to " sap " energy.

Cheers Graham.
Title: Re: Inspiration for new air motor
Post by: Brian Rupnow on April 03, 2018, 08:27:25 PM
I feel a bit foolish even having to ask. I am supposed to be "SuperDesigner" and know all this stuff. I know what I want to happen, and I know when I want it to happen. I'm just not sure how to get there. Really, about the only variable is the offset of the eccentric and the length of the link directly above the valve itself. The rocker is equal length from the pivot shaft to the center of the crankshaft and to the center of the valve when taken in a horizontal plane. That exact same eccentric, valve, and valve body works fine on the Chuck Fellows engine that I built about 10 years ago, then modified it from Chucks valve design to mine. I am moving all of the inter-related parts with my Solidworks, but I'm not getting the same positional results with this engine.
Title: Re: Inspiration for new air motor
Post by: Brian Rupnow on April 03, 2018, 08:46:05 PM
I've just realized that my valve sequence may seem a bit funky because with the pivot in between the crankshaft and the actual valve, the valve action is reversed from what the original motor was.  Now I have to try and decide what that information actually means to me. Last night I printed out five pages of valve positions from the original motor, to determine where the valve was when the piston was at top dead center, bottom dead center, halfway thru its stroke going up and coming down, and what things looks like at 45 degrees past dead center travelling counter clockwise. I'm 99% certain that if the cam, valve, and valve body worked on one single acting engine, it should work on another single acting engine, even though the piston stroke may change from on e engine to the next.
Title: Re: Inspiration for new air motor
Post by: Jasonb on April 03, 2018, 08:50:04 PM
Yes should still work. You probably want the eccentric about 270 different to whats on the small engine. 90 degrees due to the valve being vertical and not horizontal and 180deg due to the rocker reversing the direction.
Title: Re: Inspiration for new air motor
Post by: Brian Rupnow on April 03, 2018, 10:02:56 PM
I'm pretty sure I have the valve sorted out, thanks to some help from Jason. Now if I get really, really, really bored this summer, I have something to work on.
(https://imageshack.com/a/img923/9764/S5uAAu.jpg)
Title: Re: Inspiration for new air motor
Post by: crueby on April 03, 2018, 10:36:14 PM
This summer? I am betting on this next week...!   :Lol:
Title: Re: Inspiration for new air motor
Post by: dpaulson on April 03, 2018, 11:37:00 PM
Brian 
Looks like something I would like to build
Will follow along
Title: Re: Inspiration for new air motor
Post by: Brian Rupnow on April 04, 2018, 03:12:43 PM
Sometimes it is a bad idea to make too much of a change from whatever engine inspired you in the first place. I didn't like the look of the feet that I had on the model, so I changed them to be more or less the same as the flame-eater engine in the first post of this thread.
(https://imageshack.com/a/img922/4791/DqEklb.jpg)
Title: Re: Inspiration for new air motor
Post by: crueby on April 04, 2018, 04:34:22 PM
Neat looking. You could call it the Elephant engine, four big feet, flywheels look like ears, rocker is trunk, though the flame up the butt is an issue...
Title: Re: Inspiration for new air motor
Post by: Brian Rupnow on April 04, 2018, 04:54:31 PM
Call it the elephant that's been eating Jalapeno peppers!!!  :Lol: :Lol: :Lol:
Title: Re: Inspiration for new air motor
Post by: Brian Rupnow on April 04, 2018, 08:32:44 PM
I have a theory on engine building that goes like this. Take the awfullest, most miserable part on the whole job and do it first. If you can do it successfully, then anything that comes after will be easy. The block that holds the crankshaft bearings and the pivot shaft is the hardest part on this engine. I rooted around in my box of aluminum and found a piece big enough to do what I wanted. This is kind of a trick, because you need a considerably larger piece to start with than what you finish with---especially if there are radii near the perimeter of the piece. You can't drill half a hole, so the stock needs to be large enough to leave about .100" beyond any holes that are drilled to give these radii. there are four holes to be drilled here. A 1" dia. hole on the right to give the radius I want. A reamed 3/16" hole in the upper left corner for the pivot shaft, a 3/8" hole below that to give another radius, and the center hole, bored to 0.906" for a bearing fit. You can actually see the bearing setting in there in the shot on the mill. I drilled that hole to 27/32" and bored it the rest of the way.
(https://imageshack.com/a/img922/3705/6O0rfG.jpg)
(https://imageshack.com/a/img922/3545/jkUlVa.jpg)
Title: Re: Inspiration for new air motor
Post by: Admiral_dk on April 04, 2018, 09:12:48 PM
OK Chris officially won the competition about how long it lasted before you couldn't stay of the chips Brian  ;)   :cheers:
Title: Re: Inspiration for new air motor
Post by: Brian Rupnow on April 04, 2018, 09:19:11 PM
Some quality time with my friend the bandsaw yields a part that is starting to look like the drawing.
(https://imageshack.com/a/img924/9035/Vmc3fl.jpg)
Title: Re: Inspiration for new air motor
Post by: NickG on April 04, 2018, 09:29:54 PM
Nice start Brian, no stopping you! I was going to say (but seems you have already sorted it) you could have had another port at the bottom of the bore which became uncovered when the valve was at the top of its stroke and vent to exhaust. It didn’t look like there was much movement on the valve.


Sent from my iPhone using Tapatalk
Title: Re: Inspiration for new air motor
Post by: Art K on April 05, 2018, 03:28:57 AM
Brian,
Now that you've got a start on this what are you going to work on the rest of the summer? :lolb:
Art
Title: Re: Inspiration for new air motor
Post by: crueby on April 05, 2018, 03:33:10 AM
OK Chris officially won the competition about how long it lasted before you couldn't stay of the chips Brian  ;)   :cheers:


 :whoohoo:


 :popcorn: :popcorn: :popcorn:
Title: Re: Inspiration for new air motor
Post by: Brian Rupnow on April 05, 2018, 02:01:32 PM
This morning I cut the center out of the bearing support I made yesterday, and  to finish it up nice I've made up a pair of filing buttons.  These are made from 01 steel rod, cut to the finished diameter you want on the part you are going to file ,and have a hole in the center same size as the shaft you will be using. Then they are heated to red/orange and dropped into a can of oil. They are now harder than the devils horn, so a file won't cut them. You mount them as I have shown, and then use a file to cut the aluminum part, and the filing buttons keep your file from going where it shouldn't.
(https://imageshack.com/a/img923/8954/na0eVb.jpg)
Title: Re: Inspiration for new air motor
Post by: Craig DeShong on April 05, 2018, 02:33:39 PM
Now if I get really, really, really bored this summer, I have something to work on.
(https://imageshack.com/a/img923/9764/S5uAAu.jpg)

Wow!  Summer sure comes fast in Canada  :ROFL:

With all the interest in hot air engines, I might have to consider building one.  They DO look interesting.  I'll be following Brian.
Title: Re: Inspiration for new air motor
Post by: Brian Rupnow on April 05, 2018, 02:45:25 PM
Hi Craig---Glad you stopped by and said Hi. No, not summer yet. It snowed 2 1/2" yesterday with high winds all day. I don't have any design work right now, so I'm going ahead with this engine to have something to do.---Brian
Title: Re: Inspiration for new air motor
Post by: Brian Rupnow on April 05, 2018, 04:35:40 PM
Now is that a beautiful thing, or is that a beautiful thing!! Using the filing buttons sure makes for a nice round pivot shaft boss. I keep making and saving filing buttons for applications like this. Much of the time if the radius is large I just use my stationary belt sander and "eyeball" it. I have a 3 jaw chuck permanently attached to my rotary table, so it's rather difficult to do radii on the rotary table.
(https://imageshack.com/a/img922/6020/0W9aCD.jpg)
(https://imageshack.com/a/img923/772/iShqjO.jpg)
Title: Re: Inspiration for new air motor
Post by: Brian Rupnow on April 05, 2018, 08:41:42 PM
I turned two pieces of aluminum to the correct width, i.d. and o.d. to become bearing caps. This used up two "short ends" out of my stock bin. If I do this right, when the caps are holding the ball bearings correctly, there won't be a visible gap between the caps and the main part they bolt to.
(https://imageshack.com/a/img922/2000/nRacuZ.jpg)
Title: Re: Inspiration for new air motor
Post by: Brian Rupnow on April 05, 2018, 10:37:49 PM
And now you know how I spent my day. Dang!! There's a lot of work in them bearing caps.
(https://imageshack.com/a/img922/9590/PYzfER.jpg)
Title: Re: Inspiration for new air motor
Post by: zeeprogrammer on April 05, 2018, 10:49:32 PM
I have a theory on engine building that goes like this. Take the awfullest, most miserable part on the whole job and do it first. If you can do it successfully, then anything that comes after will be easy.

I agree. But what do I do if ALL the parts look like that to me?  :Lol:
Title: Re: Inspiration for new air motor
Post by: Ian S C on April 06, 2018, 03:58:18 AM
Zee if it all looks too awfull, grab the first bit of metal and start there, flywheel or cylinder, just don't start with the piston or rings.
Ian S C
Title: Re: Inspiration for new air motor
Post by: Brian Rupnow on April 06, 2018, 01:42:57 PM
Zee--Like Ian says--"Faint heart never won fair lady". If you haven't machined enough to sort out your own strengths and weaknesses as applied to machining, then just dig in and start anywhere. After about 5 engines you'll know.---Brian
Title: Re: Inspiration for new air motor
Post by: Brian Rupnow on April 06, 2018, 06:41:12 PM
Today's work was this rather elegant little piece that looks a bit like a wishbone out of a metal chicken. Form follows function--the gap between the two arms is to allow room for the connecting rod big end to pass clearly when it rotates. There will be a second part to this linkage which runs in the opposite direction from the 3/16" steel shaft and picks up the eccentric cam movement.
(https://imageshack.com/a/img922/4138/7Wjlsx.jpg)
Title: Re: Inspiration for new air motor
Post by: Brian Rupnow on April 07, 2018, 01:11:02 AM
I had high hopes of getting the first assembly of my crankshaft completed today, but I just plain "ran out of gas". I bought the material, cut it to length drilled 3 of the four holes in the crankshaft webs--and that was all I had energy for. I like to do the initial assembly and Loctite it, then let it set for 24 hours before cutting the center out and adding the dowel pins. Ah well--tomorrow--tomorrow--
(https://imageshack.com/a/img924/5244/se5epU.jpg)
Title: Re: Inspiration for new air motor
Post by: Brian Rupnow on April 07, 2018, 04:15:51 PM
We have a crankshaft---at least a darn good start on one. I just got it assembled with Loctite. After it sets up for 24 hours I will dowel all the joints and then cut the center out.
(https://imageshack.com/a/img924/4667/hlglN5.jpg)
(https://imageshack.com/i/poGye7Klj)
Title: Re: Inspiration for new air motor
Post by: crueby on April 07, 2018, 04:44:47 PM
Nice! Looks like its going to be quite a compact unit.

 :popcorn:
Title: Re: Inspiration for new air motor
Post by: 10KPete on April 07, 2018, 04:59:44 PM
The tiny size of this engine just sunk in! It's a wee bitty thingie, sure.

Sure looks great, Brian!

Pete
Title: Re: Inspiration for new air motor
Post by: Brian Rupnow on April 07, 2018, 06:35:36 PM
Nothing says class like brass!! Con rod is finished other than a visit from the bling fairy.
(https://imageshack.com/a/img924/6235/43nS0Q.jpg)
Title: Re: Inspiration for new air motor
Post by: Brian Rupnow on April 07, 2018, 10:25:26 PM
The tiny size of this engine just sunk in! It's a wee bitty thingie, sure.

Sure looks great, Brian!

Pete

Pete--The Senft Poppin engine is just about the smallest engine I have built. I like it, and it works great, but these eyes are just too old to be screwing around with 0-80 (1/16") threads and #2-56 threads. Unless there is a really good reason, the smallest fastener I ever use is #4-40.  I enjoy making model engines but when they get so miniature I can hardly see the parts its not really fun.
Title: Re: Inspiration for new air motor
Post by: Craig DeShong on April 07, 2018, 10:55:03 PM
Look'in good Brian.  :ThumbsUp:

I hear you about the weather.  It's going to snow tonight. Well, back to wearing sweaters and  :stir:
Title: Re: Inspiration for new air motor
Post by: Brian Rupnow on April 08, 2018, 05:39:38 PM
Well, that takes care of most of the major linkages. Crankshaft has been drilled and dowelled. The link that goes over to the elliptical cam is a bit odd, so I may do it next.
(https://imageshack.com/i/poRKucwAj)
Title: Re: Inspiration for new air motor
Post by: Brian Rupnow on April 08, 2018, 11:24:11 PM
This afternoon I made a start on the cylinder. A great big scaly old piece of cast iron, with a finish on it like a ponderosa pine. It was about 2 3/8" diameter and had came right from the foundry that cast it that size. I used a brazed carbide tool to bring it down to within about 0.010" of finished size, then changed to a HSS tool for the final cut to bring it down to 2", running about 400 rpm.  I don't want to take it out of the chuck, so I will move my tailstock back out of the way and rig my steady rest to support the end opposite the chuck while I drill/bore/ream the 7/8" hole in the center.
(https://imageshack.com/a/img924/2841/kNX7n9.jpg)
Title: Re: Inspiration for new air motor
Post by: b.lindsey on April 09, 2018, 01:07:15 AM
Looks like you got a nice finish on it Brian regardless of its heritage :)

Bill
Title: Re: Inspiration for new air motor
Post by: zeeprogrammer on April 09, 2018, 01:42:20 AM
Form follows function--

Oh how I wish.

Yes...I've been looking in. Very interested in seeing this.  :popcorn:
Title: Re: Inspiration for new air motor
Post by: Brian Rupnow on April 10, 2018, 12:16:21 AM
HoooYahhh--it goes round and round and nothing crashes. There isn't a lot of clearance anywhere, but a miss is as good as a mile!!
(https://imageshack.com/a/img924/6605/DI7ikQ.jpg)
Title: Re: Inspiration for new air motor
Post by: Brian Rupnow on April 10, 2018, 01:45:06 AM
I'm getting to the point where I have to be careful of what gets done next. The cylinder is still up in the lathe, and before I tear down the set-up I will put my steadyrest on the end opposite the chuck and drill/ream it to 7/8" diameter. Since this engine will have a ringless piston but still require a "very good" sliding fit, I will lap the piston into the cylinder. This requires that I hold the piston in the chuck, and with the lathe turning slowly I use either diamond paste or aluminum oxide 600 grit, and hold the cylinder by hand, slowly sliding it onto the piston in a back and forth movement. This is a "by feel" fit, and it's not uncommon for it to "grab". When it does, you want to be able to let go of the cylinder very quickly. I used this method on the two cycle engine I built, and it worked perfectly, but is more than a little scary. As you can see in the attached picture, there are three flats to be machined into the cylinder, but I won't put them on it until after the piston fitting is over with. I want to do that while the cylinder is a simple cylindrical shape, so nothing on it can grab my hands and wind me up in the lathe.
(https://imageshack.com/a/img924/2029/oaR6t1.jpg)
Title: Re: Inspiration for new air motor
Post by: Brian Rupnow on April 10, 2018, 04:45:45 PM
The cylinder has the steady rest on it to keep it from flopping around with so much "stick-out". The hole is being drilled in stages, first a 5/8" drill, then a 3/4" then a 27/32" drill, and after that I will bore it to 0.875".
(https://imageshack.com/a/img924/5125/ZtsEHt.jpg)
Title: Re: Inspiration for new air motor
Post by: cfellows on April 10, 2018, 06:13:50 PM
Hey Brian, I'm following along quietly.  Nice build, I've always like air engines and I have seen and liked this style before.  I also always figured this style would make for a great solenoid engine since stroke could be shortened and the bottom end travel could be fairly linear.

Chuck
Title: Re: Inspiration for new air motor
Post by: Brian Rupnow on April 10, 2018, 06:44:18 PM
Hi Chuck--I'm so glad that you joined in and had a look. So---We have a cylinder and a cylinder head. I didn't use the reamer at all. I drilled it out to 27/32" and finished up with a hefty brazed carbide boring tool. The finished bore as of now is 0.873". The best thing about this cylinder is that it was free. Nah, I actually paid for it on some other job and the 7" long piece of cast iron was a left over . Next up will be to machine a piston.
(https://imageshack.com/a/img922/7873/40EiP6.jpg)
Title: Re: Inspiration for new air motor
Post by: Brian Rupnow on April 10, 2018, 10:06:16 PM
After honing the cylinder with my variable speed drill and a 3 stone brake hone, then lapping it with 600 grit aluminum oxide paste and one of my new laps, the bore is setting right on 0.874" (near as I am able to measure it with a telescoping bore gauge and a micrometer). I think that rather than lapping the piston into the cylinder, I will make an external lap and bring the piston down until it matches the cylinder bore.
Title: Re: Inspiration for new air motor
Post by: zeeprogrammer on April 10, 2018, 11:38:08 PM
I think that rather than lapping the piston into the cylinder, I will make an external lap and bring the piston down until it matches the cylinder bore.

An 'external lap'? I've never seen that (newbie alert!). I'll be interested in seeing that.
Title: Re: Inspiration for new air motor
Post by: Brian Rupnow on April 10, 2018, 11:55:40 PM
Carl--See post #131 in this link. The external lap is setting on the ways of the lathe.---Brian
http://www.modelenginemaker.com/index.php/topic,5852.120.html
Title: Re: Inspiration for new air motor
Post by: zeeprogrammer on April 11, 2018, 12:43:51 AM
Ah. Thanks.
Title: Re: Inspiration for new air motor
Post by: Brian Rupnow on April 11, 2018, 11:37:25 PM
This afternoon I made the piston. It's so new in this picture that it hasn't even had the tit machined off the end yet. Tomorrow I will decide exactly how I'm going to fit it to the cylinder, and will face it to the correct length, getting rid of the tit in the process.
(https://imageshack.com/a/img923/5274/SdX6Oi.jpg)
Title: Re: Inspiration for new air motor
Post by: Brian Rupnow on April 12, 2018, 01:35:46 AM
I think I may have to go to larger flywheels. The flywheel input to the sliding piston is at a 1:2 mechanical disadvantage. That means that the flywheels need to be considerably larger than on a "normal" engine where the flywheel ratio to piston travel is a 1:1 ratio. I have looked at a number of videos of this engine as a flame-eater, and they all have larger flywheels. My original thoughts were to have a 4" o.d. flywheel. Now I'm thinking of larger diameters. A 4" nominal diameter pipe has an actual o.d. of 4.5" (dotted outline on drawing). I have to think on this for a bit, and as I have other parts of the build to complete, I have time to roll this idea around in my head a bit.
(https://imageshack.com/a/img923/458/alfWXY.jpg)
Title: Re: Inspiration for new air motor
Post by: Jasonb on April 12, 2018, 07:12:50 AM
Brian, most of your other engines with similar size bores only have ONE flywheel, as this engine has two you may well have already doubled up the momentum required.

Also as quite a few are 4-strokes you are only firing on alternate revolutions, your air motor will "fire" once per rev so that is also double the force going into the crankshaft.
Title: Re: Inspiration for new air motor
Post by: Brian Rupnow on April 12, 2018, 03:40:05 PM
I had the four jaw chuck up on the lathe, and decided to see if there was anything on this engine which would require the four jaw. Sure enough, the elliptical can still had to be machined, so that's what I did this morning. You can see it setting in place on the crankshaft. Now I change back to the 3 jaw and fit the piston to the cylinder.
(https://imageshack.com/a/img922/685/t8VyVi.jpg)
Title: Re: Inspiration for new air motor
Post by: Brian Rupnow on April 12, 2018, 06:19:44 PM
I have achieved an almost perfect fit between the piston and the cylinder. It doesn't show in the picture but the entire piston has taken on that uniform dull finish that comes from lapping. The piston will slowly fall thru the cylinder under the force of gravity, but if I put a hand over the bottom of the cylinder the piston stops. I have to go and keep an appointment now, but when I get back I will explain a bit more about how this was done.
(https://imageshack.com/a/img923/5769/S1Q7Qm.jpg)
Title: Re: Inspiration for new air motor
Post by: Brian Rupnow on April 12, 2018, 08:56:27 PM
Here's a little story on how I sized the piston to the cylinder. In shot one, you see the piston, a short piece of threaded rod with one end turned to fit into the piston where the con rod goes, and a hole in it for the wrist pin. The shaft laying in line has the end turned to fit inside the piston, with a shoulder on which the piston can set, and a 5/16-18 tapped hole in the end. The turn down at the other end of that piece of shaft is not needed.--it just happened to be there. In shot #2 the threaded rod is mounted in the piston. You can't see the wrist pin, but trust me--it's there. The retaining set-screws that hold the wrist pin in place are tightened down--I don't want the wrist pin to drift to one side and score the cylinder wall. Shot #3 shows the piston tightened onto the piece of shaft, with the piston skirt setting on the register. Shot #4 shows the shaft with piston mounted in the lathe chuck, and picture #5 shows the cylinder started on over the piston. The piston is coated with #600 aluminum oxide paste. The piston diameter has been turned to a diameter that just starts to fit into the cylinder, but not quite. (About .001" interference). It is important that the shaft have an outside diameter about 0.050" less than the outside diameter of the piston. we only want to lap the piston---not the shaft supporting it. The lathe is ran at about 60 rpm, and the cylinder is held by hand and slid back and forth over the piston. making sure that the piston extends out of the cylinder about 1/2" at both ends of the stroke. At first this requires a strong grip, but the aluminum oxide paste works very quickly and it loosens up quickly. This is where you want the cylinder to be simply round with no features, so that if it "grabs" you can quickly let it go.
(https://imageshack.com/a/img924/4226/VUQ5Wa.jpg)
(https://imageshack.com/a/img922/7026/QfSNza.jpg)
(https://imageshack.com/a/img924/7576/yipkVf.jpg)
(https://imageshack.com/a/img923/5443/lg4tLk.jpg)
(https://imageshack.com/a/img923/6811/xrWFB7.jpg)
Title: Re: Inspiration for new air motor
Post by: Brian Rupnow on April 13, 2018, 01:30:30 AM
Dug deep into the Rupnow fortune today and ordered a set of 5" cast iron flywheels from Martin Model and Pattern for this new engine. I have a ridiculous number of home built engines with every conceivable type and style of flywheels on them, all made by myself except for the ones on my Rockerblock engine, which I had water-jet cut. Figured it was time to spend a bit of money on something "store-bought".
Title: Re: Inspiration for new air motor
Post by: bent on April 13, 2018, 10:45:30 PM
Wow, you are chugging right along, Brian!  :popcorn:
Title: Re: Inspiration for new air motor
Post by: Brian Rupnow on April 13, 2018, 11:31:33 PM
This is something you may find interesting. Due to the way this engine is laid out, I can't have a normal tappet riding on the cam. Instead, the bronze shaped cam follower fits around the cam and is pinned to the 3/16" rocker shaft, as is the yoke which will operate the air valve. As the crankshaft rotates, it will move the cam follower in a rocking motion, that will in turn cause the end of the Y shaped piece to move up and down, to operate the air valve.
(https://imageshack.com/a/img923/5311/t0Ly0h.jpg)
Title: Re: Inspiration for new air motor
Post by: Brian Rupnow on April 13, 2018, 11:41:37 PM
The solid model has been updated to show it with the new 5" diameter flywheels I have ordered, (I think they are much better in proportion than the previous 4" diameter ones.) In one of the models the near side flywheel is hidden so you can see the cam follower and the Y shaped lever that controls the air valve.
(https://imageshack.com/a/img922/4646/imMPTE.jpg)
(https://imageshack.com/a/img922/6840/LHmBqP.jpg)
Title: Re: Inspiration for new air motor
Post by: crueby on April 14, 2018, 12:54:37 AM
Ah, clever. Took me a bit of staring at the drawing and parts to realize why the cam follower has an oblong opening, my brain was assuming the normal back/forth type eccentric, neat how you have it rocking the arm.

 :popcorn:
Title: Re: Inspiration for new air motor
Post by: Brian Rupnow on April 14, 2018, 01:07:09 AM
I can't remember where I've seen that before, but it is neat. I have so many pieces of so many machines in my head that I don't know what I don't know, ya know!!! :pinkelephant: :pinkelephant:
Title: Re: Inspiration for new air motor
Post by: Jasonb on April 14, 2018, 07:12:25 AM
Graham had the slot on his Nattie engine. so the shutter is not constantly moving like it would on the usual eccentric with no play.

https://www.youtube.com/watch?v=2eorVwM7n64
Title: Re: Inspiration for new air motor
Post by: Brian Rupnow on April 14, 2018, 06:56:47 PM
I was flying right along, beginning initial assembly. Then I opened the box with my #6-32 taps in it. The bottoming tap was broken off (I remember doing that and had meant to replace it). The blind holes for the taper tap are only 0.470" deep, and the taper tap bottoms out before it starts to cut a full size thread. (these are the bolts which hold the support feet to the cylinder.)  There is nowhere in town to buy a replacement tap.---Ahh bugger!!! Oh well, I've done enough for today anyways.
(https://imageshack.com/a/img924/373/5YNUDQ.jpg)
Title: Re: Inspiration for new air motor
Post by: Brian Rupnow on April 15, 2018, 02:42:54 PM
The ball nosed endmill does add a very nice feature when it is used. What doesn't add a nice feature is when you misread your own drawing and put two counterbored holes in the wrong place. Damn, I hate it when I do that!!! Fortunately, the tops of these counterbored holes will be hidden under the air manifold. So--clean it up, set it on a piece of cardboard, and fill the two offending holes with J.B. weld. When the J.B.Weld sets up, I will rebore the holes 0.100" inboard of where they currently are.
(https://imageshack.com/a/img922/2186/5YsbZ1.jpg)
Title: Re: Inspiration for new air motor
Post by: Brian Rupnow on April 15, 2018, 10:48:24 PM
Totally bummed out here. Two solid days of ice storm. I'm even tired of machining things. However, I did accomplish one thing today. The pivot bracket that fits onto the open end of the cylinder has to be silver soldered together in a jig. The bracket is brown in color, made from 3 separate parts. the jig (green) was made from two pieces of scrap out of my bin. The three shcs in the jig are an exact copy of the bolt pattern in the open end of the cylinder.
(https://imageshack.com/a/img923/8855/EqX92Y.jpg)
(https://imageshack.com/a/img922/1965/7YzQ54.jpg)
Title: Re: Inspiration for new air motor
Post by: Brian Rupnow on April 17, 2018, 02:36:59 PM
I think I seen reference made to the steps involved in machining a cast flywheel somewhere on this forum. Could someone please direct me to that link?---Brian
Title: Re: Inspiration for new air motor
Post by: cwelkie on April 17, 2018, 02:51:23 PM
It's short on detail but the beginning of this thread shows how I approached the cast flywheel on a Stuart No.8.  I was happy with the result. Kudos to the original Model Engine Builder article.
http://www.modelenginemaker.com/index.php/topic,4790.0.html
Title: Re: Inspiration for new air motor
Post by: Brian Rupnow on April 17, 2018, 05:27:47 PM
Thank you C Welkie. I haven't received my flywheels yet, but I'm trying to sort out the logical steps involved in machining them.--Brian
Title: Re: Inspiration for new air motor
Post by: Brian Rupnow on April 17, 2018, 07:56:48 PM
The parts to make up my pivot bracket have been machined and set up in my jig to be soldered. I don't have a real warm fuzzy feeling about this, because I just know that the solder is going to run onto my socket head capscrews and make them part of the assembly as well. Not a total loss, because if that happens I will just machine the capscrews out afterwards. Wish me luck.
(https://imageshack.com/a/img922/4451/xwpuiR.jpg)
Title: Re: Inspiration for new air motor
Post by: Jasonb on April 17, 2018, 08:16:50 PM
Coat them with typewriter correction fluid "Tipex" and the solder won't stick to them.
Title: Re: Inspiration for new air motor
Post by: Brian Rupnow on April 17, 2018, 11:38:53 PM
So, there we have it. The jig worked just as intended. As I had feared, I managed to solder all three socket head capscrews  into the assembly. I have used White-out and other agents to stop the flow of silver solder in the past with so-so results, but this time I didn't have room to use it. Not a huge problem--I flipped the part over and milled the screws out from the back side of the jig with a 1/8" carbide endmill. After a period of sanding, filing, and "fettling" I have a respectable soldered assembly.
(https://imageshack.com/a/img924/7853/ueAkjO.jpg)
Title: Re: Inspiration for new air motor
Post by: crueby on April 18, 2018, 12:04:26 AM
Great looking part!


 :popcorn: :popcorn: :popcorn:
Title: Re: Inspiration for new air motor
Post by: Brian Rupnow on April 18, 2018, 04:33:26 PM
I was able to save the cylinder head. Moving a hole and a counterbore by about   3/4 the diameter of the original hole is always a tricky proposition. I filled the "bad" holes with J.B. Weld about two days ago. Set things up this morning in the mill vice and very cautiously put the new holes in with a 1/8" milling cutter (plunge-cut). Once the new holes were in, I used the correct drill (which was 0.130" diameter) and drilled thru the two holes. Once the correct holes were in, I used the correct counterbore. All went well, and the counterbores in question will be covered by the valve block.
(https://imageshack.com/a/img923/368/TpbdN3.jpg)
Title: Re: Inspiration for new air motor
Post by: Brian Rupnow on April 19, 2018, 12:04:39 AM
Today marks the first full assembly of all the parts so far (except the piston). I'm fairly pleased. Things will start to look a lot better when my flywheels arrive. I still have to make an oil cup and drill/tap the cylinder for the cylinder head. The cylinder head is finished, but I still have to make the valve body that sets on the cylinder head as well as the valve rod itself and the link that ties things together.
(https://imageshack.com/a/img924/6277/qIFJni.jpg)
Title: Re: Inspiration for new air motor
Post by: crueby on April 19, 2018, 12:09:55 AM
As it sits, looks like a mechanical puppy.


 :popcorn:
Title: Re: Inspiration for new air motor
Post by: zeeprogrammer on April 19, 2018, 12:55:28 AM
Today marks the first full assembly of all the parts so far

Yay!

(except the piston).

Boo!

It's coming together. I know you were somewhat bummed a few days ago. Going better now though! Right?
Title: Re: Inspiration for new air motor
Post by: Brian Rupnow on April 19, 2018, 01:51:02 AM
Yah, I never stay bummed for long. Weatherman is calling for mid sixties temperatures by Tuesday. I'm just tired of endless winter.
Title: Re: Inspiration for new air motor
Post by: NickG on April 19, 2018, 08:40:00 PM
As it sits, looks like a mechanical puppy.


 :popcorn:

Wow, the resemblance is uncanny but sure it won’t look like one with the flywheels on!


Sent from my iPhone using Tapatalk
Title: Re: Inspiration for new air motor
Post by: Craig DeShong on April 20, 2018, 01:12:28 AM
Brian
I’ve machined buckets of railroad wheels and a few flywheels so I have a bit of expertise.  The best advice I can give you is when you center the flywheel on the lathe do not focus on the center hub but rather on the inside of the outer rim (see (photo).  You will be machining the outside of the flywheel “true”, so if it is out of round, your machining will fix that.  If the hub is a little off center, no one will notice’ but if the inside of the rim doesn’t run “true” it’s very noticeable. Does this make sense?
Title: Re: Inspiration for new air motor
Post by: Brian Rupnow on April 20, 2018, 01:18:11 AM
I have to make a new angle for my dangle!! The straight pivot bar that rocks back and forth as the engine runs is just too close to the cast cylinder when the piston is at top dead center. It won't let the crankshaft make a full revolution. I have milled, filed, and sanded away the end of it until I finally decided "This ain't going to fly". I have a new one designed that still keeps all of the important pivot points in the same plane, but the bar has a curve added to the bottom so it will clear the pivot bracket and the end of the cylinder.
(https://imageshack.com/a/img922/1807/o9LG2B.jpg)
(https://imageshack.com/a/img924/417/evmbEK.jpg)
Title: Re: Inspiration for new air motor
Post by: Brian Rupnow on April 20, 2018, 01:25:48 AM
Yes Craig, it does make a lot of sense. CWelkie has posted the method he used in post #95 of this thread., where he make a "fixture" from wood that was a "precision fit" into the inside of the outer rim and about 2 or 3" thick. The fixture was mounted in a large chuck and the cast flywheel was held in place by "capture plates" across the spokes. This allowed them to machine the outer diameter of the flywheel to be concentric with the inner diameter, face both sides of the rim, and machine the centerhole and one side of the hub all in one set-up.---Brian
Title: Re: Inspiration for new air motor
Post by: NickG on April 20, 2018, 04:13:26 PM
Couldn’t you just put it in the 4jaw and clock that rim turn the bits you need to then put on an arbor and turn the rest?


Sent from my iPhone using Tapatalk
Title: Re: Inspiration for new air motor
Post by: Brian Rupnow on April 20, 2018, 06:29:11 PM
Couldn’t you just put it in the 4jaw and clock that rim turn the bits you need to then put on an arbor and turn the rest?


Sent from my iPhone using Tapatalk
Probably--i haven't got the parts yet, so I will have a clearer idea of how to go about it when I have the parts in my hand.---Brian
Title: Re: Inspiration for new air motor
Post by: Brian Rupnow on April 20, 2018, 09:30:37 PM
I got off early this afternoon from my "real" job, so I came right home and built a new pivot bar for the engine I am working on. Now, although everything is very "stiff" I do have it so that the crankshaft can rotate thru a full 360 degrees. There is still a fair bit to be done on this engine, but I always think it's a milestone when I get all the big pieces together and can go thru a full rotation of the crankshaft without something going "clunk".-----And I have no idea why Mr. Hand is in the preview!!!
https://www.youtube.com/watch?v=q0mZefCfBoE
Title: Re: Inspiration for new air motor
Post by: Brian Rupnow on April 20, 2018, 10:35:03 PM
These guys just showed up in the mail. They measure about 5.1" o.d. with a 0.520" wide face. I was expecting them to be a little heavier, but since I never bought flywheels before, I wasn't sure what to expect. Hopefully, they will serve the purpose. I guess I'll find out as I go along. I have paid over $100 Canadian funds for these, including the shipping by mail. I have to wait and see my bank statement before I'll know how much more than $100 they cost.
(https://imageshack.com/a/img923/5866/YkB5wM.jpg)
Title: Re: Inspiration for new air motor
Post by: NickG on April 21, 2018, 07:52:35 AM
Were you expecting aluminium castings Brian? I thought they would be iron, I see why you are using two now.


Sent from my iPhone using Tapatalk
Title: Re: Inspiration for new air motor
Post by: MJM460 on April 21, 2018, 10:52:56 AM
Hi Brian,

In a flywheel, you are not looking for mass, but moment of inertia.  Mass is only a small part of the equation for moment of inertia. 

Each little bit of mass has to be multiplied by its distance from the axis of rotation squared.  So if you place the rim twice as far from the axis, it contributes four times as much to the moment of inertia, even when you thin down the dimensions so the larger diameter rim is the same mass.  The units of moment of inertia are kg.m2.

It is quite possible to make a larger diameter flywheel from aluminium with less mass than a smaller steel one, but similar or larger moment of inertia, so just as effective for your engine flywheel.

I don't want to hijack your thread, which I never miss reading, so I will add a little on how to do the calculations in my thermodynamics thread.  I often stray into other theoretical areas on that one.  Please let me know if you would rather I took an alternative approach.

MJM460
Title: Re: Inspiration for new air motor
Post by: Brian Rupnow on April 21, 2018, 02:17:13 PM
Those flywheels are cast iron. Brand new cast iron with no rust. They pass the magnet test. I never thought about aluminum flywheels.
Title: Re: Inspiration for new air motor
Post by: NickG on April 21, 2018, 06:53:52 PM
Brian that’s good, they look like alu on the pic! Surely mass is the biggest pay of the equation as that’s is the multiplier I.e a lead flywheel of the same proportions will have a greater moment of inertia than an aluminium flywheel due to the mass x


Sent from my iPhone using Tapatalk
Title: Re: Inspiration for new air motor
Post by: Brian Rupnow on April 21, 2018, 07:37:39 PM
The cylinder head and the valve body are finished and assembled. I spent a couple of hours chasing down "tight spots" in the assembly, and now I have it so it will turn over very easily. I'm going to take the rest of today off and read a book!!
(https://imageshack.com/a/img922/8579/0z04WV.jpg)
Title: Re: Inspiration for new air motor
Post by: Brian Rupnow on April 22, 2018, 02:49:28 PM
Who can tell me where I can get outside circlips  that fit into a groove cut into a 1/8", 3/16" or 1/4" shaft, and the tool that you use to insert them? I always have a bunch of 1/8" pivot pins on the stuff I build, and never have a good way to keep them in place. I know there is an insertion tool for metric circlips, but I have never seen one for inch size circlips. Circlips are also known as external snap rings. I have a terrible time trying to put them on with pliers. Before I can get one in place, I have lost five others zooming across my room and disappearing forever.--Whoops---I may have answered my own question.--I checked out the Spae Naur catalogue looking for alternative names for these things, and I see that they sell the tool.-Brian
Title: Re: Inspiration for new air motor
Post by: b.lindsey on April 22, 2018, 03:48:09 PM
Wow, that is quite a nice resource Brian...the catalogue is 2000+ pages  :o

Bill
Title: Re: Inspiration for new air motor
Post by: Brian Rupnow on April 22, 2018, 07:35:02 PM
No real work going on today. I'm just dicking around to see how I'll hold these flywheels to turn them. I think that I can assume that the spokes are all in one plane. If I cut a piece of 4.1" dia. wood x 1 1/2" thick and turn it round, with a centerhole large enough to clear the hub and hub radius, then make up five metal brackets, I can make the brackets to a thickness that when screwed down tight will firmly grip the 5 spokes. Then I can hold the round wooden part in my lathes four jaw chuck. I don't want the wood to register on the inner diameter of the outer rim, nor on the hub area. I want it to have a bit of "float" so that when the yellow screws are tightened down the wood is not being positioned by the rim nor the hub. Then I will dial in the four jaw so that the inner side of the outer rim is  concentric to the spindle. This will let me machine the outer diameter and the bore and possibly the two sides (not sure about that yet), so everything should be concentric and in plane with the spokes.
(https://imageshack.com/a/img923/8382/QAEESt.jpg)
Title: Re: Inspiration for new air motor
Post by: crueby on April 22, 2018, 11:00:25 PM
That holder should work well. One thought about using wood for the plate is that it will crush a bit in the jaws, and screws can work during interrupted cuts. I've done similar holders, had those issues. You may want to consider layering in a aluminum plate to hold the screws and to grip in the chuck.
Title: Re: Inspiration for new air motor
Post by: Brian Rupnow on April 23, 2018, 05:15:48 PM
Just finished machining flywheel #1.-A totally different experience!!! I have never machined a casting before. My lathe and I are both dirtier than a pig from iron dust. The picture I posted earlier of my proposed set-up seemed to work very well. I can't get over how far out many parts of the casting were from the finished ideal, although I understand that is typical with sand cast parts. In this one set-up I was able to machine the outer face of the flywheel, both sides of the rim, cut off and true up the outer diameter of the hub, and finish the bore. All that remains is to flip the flywheel around and hold it by the outer rim in the chuck to face the far side hub.
(https://imageshack.com/a/img923/7904/vsb7fh.jpg)
Title: Re: Inspiration for new air motor
Post by: bent on April 23, 2018, 05:38:13 PM
Reading along with interest, Brian.  I recently picked up a cast iron flywheel from Martin's, and have similar issues to yours, I like the plug/jig approach. 
Title: Re: Inspiration for new air motor
Post by: Brian Rupnow on April 23, 2018, 05:42:22 PM
I love the proportions. I think the 5" diameter is perfect.
(https://imageshack.com/a/img924/2861/OASzEC.jpg)
Title: Re: Inspiration for new air motor
Post by: zeeprogrammer on April 23, 2018, 06:17:03 PM
Yeah...that's looking good, Brian.
Title: Re: Inspiration for new air motor
Post by: Brian Rupnow on April 23, 2018, 11:39:21 PM
Not hard work, just a lot of work. and it's something new that I haven't done before. Both flywheels are fully machined except for the set screws. I am going to have to spend some quality time with my Dremel tool to clean up flash lines between the spokes, but overall I'm happy with my results. I also have to figure out how the guy who's flame-eater inspired this build got the machined areas of his flywheels so shiny.
(https://imageshack.com/a/img924/6485/j16pa5.jpg)
Title: Re: Inspiration for new air motor
Post by: crueby on April 23, 2018, 11:46:03 PM
Looks terrific, great style for that engine.


 :popcorn:
Title: Re: Inspiration for new air motor
Post by: b.lindsey on April 24, 2018, 12:51:35 AM
The flywheels fit the scale of the engine very nicely Brian. At this rate it will be running soon.

Bill
Title: Re: Inspiration for new air motor
Post by: Craig DeShong on April 24, 2018, 12:55:06 AM
Look'in good Brian.  Cash iron will polish up like a mirror.  Chuck the flywheel in your lathe and go down through the sand papers.  When you get to 2000 grit you will have a mirror finish.
Title: Re: Inspiration for new air motor
Post by: Brian Rupnow on April 24, 2018, 01:21:32 AM
And now---Here's the rest of the story. I machined everything with  an HSS tool, with the lathe running at 200 rpm. Most of the time my depth of cut was 0.010". The flywheels cleaned up at 4.950" outer diameter, 0.472" wide, with 0.70" diameter hubs, and of course I drilled and reamed 0.375" center-holes to match the crankshaft. The original castings were 5.1" diameter x 0.520" wide. I only machined enough away from each surface to get past the casting finish.---Brian
Title: Re: Inspiration for new air motor
Post by: NickG on April 24, 2018, 06:01:55 PM
They look good Brian, decent castings will the cast surfaces be getting any paint?


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Title: Re: Inspiration for new air motor
Post by: Brian Rupnow on April 24, 2018, 09:43:42 PM
Yes Nick, I think I will paint all of the cast iron pieces. I haven't painted any of my engines, but this time I believe I will.
Title: Re: Inspiration for new air motor
Post by: Brian Rupnow on April 25, 2018, 01:14:02 AM
I've whittled this thing down to the point where there are only two pieces left to make before I can try to run it. I need the 1/4" diameter valve and the link that attaches to it, but I'm too tired tonight to make anything. I started the valve this morning before I had to go across town on one of my "real" design jobs, then promptly screwed it up when I returned home this evening. But--Tomorrow is either going to be really exciting or else very disappointing. I'm still not 100% certain that I have the valve designed properly, but it's basically a "cut and paste" of the valve I built a few years ago when I redone the Chuck Fellows engine. I can paint and polish things after I know the engine is going to run.
Title: Re: Inspiration for new air motor
Post by: Brian Rupnow on April 25, 2018, 09:06:35 PM
Well, we didn't quite get there today, but we got awfully close. I have two gaskets to make and I have to set the valve timing, but other than that I think I'm ready for a trial run.----Tomorrow
https://www.youtube.com/watch?v=58RaNBUE09I
Title: Re: Inspiration for new air motor
Post by: Craig DeShong on April 25, 2018, 09:35:22 PM
Lots going on there Brian.  It's going to be an intresting engine to see run.  It looks,GREAT  :Love:

Good luck tomorrow, i'm pull'in for ya!  :-*

Title: Re: Inspiration for new air motor
Post by: NickG on April 26, 2018, 12:35:28 PM
Yep, looks great Brian.


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Title: Re: Inspiration for new air motor
Post by: Brian Rupnow on April 26, 2018, 01:51:56 PM
Morning has come, my gaskets are made, my engine is timed, but it won't run. OH POOP!!! Howevah--if I disconnect the link which runs from the Y shaped yoke and lift/lower the actual valve "by hand" I can find one position where
 air is being passed to the cylinder (and this thing is strong considering the 7/8" bore), and one position where no air is being passed to the cylinder. This may simply be a matter of tailoring the length of the link so the two  positions I found "by hand "correspond with the max/min positions of the yoke. Maybe an adjustable length link until I find the "sweet spot".
Title: Re: Inspiration for new air motor
Post by: Craig DeShong on April 26, 2018, 01:59:34 PM
 :facepalm:   :noidea:   :stickpoke:   :ThumbsUp:
Title: Re: Inspiration for new air motor
Post by: Brian Rupnow on April 26, 2018, 02:57:40 PM
So--Here we go with the old adjustable link trick!!
(https://imageshack.com/a/img923/8387/OyKT2p.jpg)
Title: Re: Inspiration for new air motor
Post by: Brian Rupnow on April 26, 2018, 04:59:41 PM
So--all it took was a little bit of patience and a bit of luck, and Hey Presto--We have a running engine. It's beautiful!!! I have painting and polishing yet to do, but the design is proven. I will be selling the plans to this engine for $25 Canadian funds. Thank you for all sticking with me through the build.---Brian
https://www.youtube.com/watch?v=zDU2BIC701c
Title: Re: Inspiration for new air motor
Post by: crueby on April 26, 2018, 05:25:59 PM
Very nice runner, great sound to it too!    :whoohoo:
Title: Re: Inspiration for new air motor
Post by: zeeprogrammer on April 26, 2018, 05:30:56 PM
Congrats Brian!
Looks and sounds great.
You do sound like a happy man in the video.  :ThumbsUp:
Title: Re: Inspiration for new air motor
Post by: Brian Rupnow on April 26, 2018, 05:53:22 PM
Zee--I'm always glad when an engine I designed runs. On some engines I didn't get happy right away, but eventually they all ran.
Title: Re: Inspiration for new air motor
Post by: Craig DeShong on April 27, 2018, 02:13:33 AM
 :whoohoo:  looks and sounds great !  We all had no doubt that it would run.  Congratulations.  Let's drink to your success  :cheers:
Title: Re: Inspiration for new air motor
Post by: Larry on April 27, 2018, 03:26:22 AM
Congratulations on another great design !
Title: Re: Inspiration for new air motor
Post by: b.lindsey on April 27, 2018, 12:07:10 PM
Another nice one Brian. Congrats on a very interesting design.


Bill
Title: Re: Inspiration for new air motor
Post by: ShopShoe on April 27, 2018, 12:45:16 PM
Congratulations Brian,

That's an interesting design and looks and sounds great running.

I'm looking forward to the paint.

ShopShoe
Title: Re: Inspiration for new air motor
Post by: Brian Rupnow on April 27, 2018, 04:23:15 PM
Now here is a very interesting shot. I gathered up all the random pieces of sandpaper I could find, and mounted the flywheel on a 3/8" arbor and put the arbor in my lathe. With the lathe rotating at 250 rpm. and working on the face only, I first wrapped #180 grit paper around a flat stick and held it against the rotating face. I kept the stick and sandpaper moving a bit, for a slow count of 50. Then I repeated with 220 grit, always keeping the stick and sandpaper moving just a bit for another count of 50. Then I repeated with 400 grit, then with 1500 grit, then with a pad of "ultra-fine" Scotchbrite held in my hand--no stick. The face had by that time taken on a mirror like finish. I was so pleased with this that I then done exactly the same thing to both sides. At this stage I have not used any buffing wheels nor compound.
(https://imageshack.com/a/img924/1607/sxtnon.jpg)
Title: Re: Inspiration for new air motor
Post by: Brian Rupnow on April 27, 2018, 05:31:00 PM
Both flywheels were given the same sandpaper treatment, then polished with an old Eastwood polishing kit left over from my hot-rodding days. all buffs were ran at 450 rpm. First a sisal buff with emery compound, then a spiral buff with stainless compound, then a loose cotton buff with white rouge. It certainly makes a big change from the machined cast iron finish.
(https://imageshack.com/a/img923/5215/LCbYG0.jpg)
Title: Re: Inspiration for new air motor
Post by: Brian Rupnow on April 27, 2018, 05:50:52 PM
A few pages back in this thread I was asking about e-clip insertion tools. I found out that Spae-Naur in Kitchener Ontario has external retaining rings (which are less fat than an e-clip but do the same thing) and also sell the installation tools. The tools aren't cheap---about $40 each, but I figured that after 27 engines I deserved them. So--I got 100 of 1/8" shaft external retaining rings, and 100 of the 3/16" shaft external rings, and the tools to insert both sizes.
(https://imageshack.com/a/img924/2982/Gu3pni.jpg)
Title: Re: Inspiration for new air motor
Post by: gbritnell on April 27, 2018, 09:26:54 PM
Another unique engine for your fine collection Brian. Cast iron can be made to look like chrome if one wants to spend the time finessing it.
Congratulations,
gbritnell
Title: Re: Inspiration for new air motor
Post by: Brian Rupnow on April 27, 2018, 09:38:18 PM
Thank you George. I'm glad you stopped by and had a look.---Brian
Title: Re: Inspiration for new air motor
Post by: Sleddog on April 27, 2018, 10:54:21 PM
Very nice Brian. Quite unique. Congratulations

Jack
Title: Re: Inspiration for new air motor
Post by: Brian Rupnow on April 28, 2018, 12:04:29 AM
A question now, related to the finishing/painting of the flywheels. The flywheels are made from a split pattern, and the split is exactly on the center of the spokes. There isn't a lot of flash, but there is a definite ridge on each side of the spokes and the inside center of the outer rim. Now, I have the option of sanding that ridge away with my Dremel tool, but in so doing it will leave a smooth surface which does not match the general "as cast" surface of the rest of the flywheel where I haven't polished it. I definitely don't want to sand away the "as cast" surface on all the flywheel. Maybe I should just leave the ridge alone and paint everything that I didn't polish today. Opinions please, and pointers from those who have painted flywheels themselves.---Brian
Title: Re: Inspiration for new air motor
Post by: Craig DeShong on April 28, 2018, 01:53:52 AM
Looks,great Brian, and the flywheel polished up nicely.  I leave my flywheels alone, filing down any ridges, then paint.
Title: Re: Inspiration for new air motor
Post by: Brian Rupnow on April 28, 2018, 08:04:55 PM
I can't even begin to tell you how well these retaining ring inserters work. After years and years of having small retaining rings fly across the room and disappear forever into swarf and cobwebs, this is just like magic. It still takes a certain finesse to load them into the spring loaded jaw of the insertion tool but nothing compared to the old needle nosed pliers trick.
(https://imageshack.com/a/img923/7239/OLkKFN.jpg)
Title: Re: Inspiration for new air motor
Post by: crueby on April 28, 2018, 08:24:02 PM
Will those tools remove the rings as well?
Title: Re: Inspiration for new air motor
Post by: Brian Rupnow on April 28, 2018, 08:37:28 PM
I don't think these tools will remove the clips. I have a scribing tool with a sharp end that will pop them off.
Title: Re: Inspiration for new air motor
Post by: Brian Rupnow on April 28, 2018, 08:50:30 PM
It's time to start blowing this thing apart for painting and polishing. Fortunately this is an extremely easy engine to dismantle. I have to buy a new 8" spiral buffing wheel, as my old one is clogged up and difficult to use. I will polish all the brass bits and paint the cast iron cylinder and cylinder head and the aluminum feet. I like the colour of the original flame-eater that inspired this build, so will probably go for the same blue. I'm not going to spend a lot of time prepping for paint. Probably just wipe everything down with laquer thinners to get rid of any grease or oil, then buy a can of Tremclad rattle-can paint to paint it with.
Title: Re: Inspiration for new air motor
Post by: Art K on April 29, 2018, 04:31:24 AM
Brian,
The new engine looks and runs great! Nuthin like bright shiny flywheel.
Art
Title: Re: Inspiration for new air motor
Post by: Brian Rupnow on April 29, 2018, 01:18:46 PM
A note to those who are building this engine from my plans--
(https://imageshack.com/a/img922/6741/uYY90T.jpg)
Title: Re: Inspiration for new air motor
Post by: Brian Rupnow on April 30, 2018, 10:13:24 PM
I got notification by email that my 8" spiral buff and buff rake were shipped out today from Pennsylvania. I'm so sick of making little engines that I could run in circles and bite myself. Our snow is finally gone here, and I took the day to drive up to Bancroft and visit my ancient mother who will be 98 years old in August. Nice day, good visit, nice trip. Once I get this engine painted and polished, I sincerely hope that nothing else catches my fancy until next fall.---Brian
Title: Re: Inspiration for new air motor
Post by: Brian Rupnow on May 01, 2018, 07:34:23 PM
Temperature went nuts today, up to almost 80F. (Wonderful) I hustled my butt down to Canadian Tire and bought a rattle-can of dark blue Tremclad paint, masked off the shiny parts on my flywheels, then set everything up in my main garage and painted it. All of the cast iron is painted now (except the piston which won't see any paint). I've never been a fan of rattle can paintjobs, but for something this size it isn't worth buying separate paint and reducer. I'm quite happy with the colour.---Brian
(https://imageshack.com/a/img922/9267/nbHa6C.jpg)
(https://imageshack.com/a/img924/9241/GVFaqZ.jpg)
(https://imageshack.com/a/img923/766/UVuUHE.jpg)
(https://imageshack.com/a/img922/2531/hLsFIO.jpg)
Title: Re: Inspiration for new air motor
Post by: Brian Rupnow on May 02, 2018, 12:05:35 AM
I just spent 20 minutes in the garage, untaping the flywheels and washing any blue paint off the sides of the flywheels. The paint always "migrates" under the tape edges when you are masking off steel, and if you don't catch it just at the right time it is very difficult to clean off-----leaves a ragged looking edge. You want the parts dry enough that the paint won't stick to your fingers, but still not absolutely dry. A rag wrapped over the end of your finger and wetted with paint thinners works excellent for this, but it's a rather delicate process. Someone asked if I was going to clearcoat the polished face and edges of the flywheels, and I said no, because all of the polishing compounds you use are wax based and will protect it from rusting.--That is still correct---But--if you are going to paint the flywheels you have to be sure and remove all of the wax first with strong laquer thinners. So--consequently, when my paint is fully cured I will apply a bit more "final polish" compound to the unpainted surfaces.
Title: Re: Inspiration for new air motor
Post by: Brian Rupnow on May 02, 2018, 04:27:40 PM
I'm down to the point where everything is painted and polished. I had hoped to capture some of the brilliant shine on the brass, but it doesn't show up very well in this picture.---And---when I went to take another shot I got the "Charge Battery" message on my digital camera. Reassembly should be a fairly simple exercise, but I just got a call from one of my customers and that will eat up my afternoon. Tomorrow I will put it all back together. When it's all blown apart like this, there aren't very many pieces, are there.
(https://imageshack.com/a/img922/6880/Vu8UQD.jpg)
Title: Re: Inspiration for new air motor
Post by: Brian Rupnow on May 03, 2018, 07:52:16 PM
The painting and polishing is finished, and the engine is reassembled. I'm very happy with the way this engine turned out. I've built so many engines over this past winter that I hope not to start anything else between now and fall. Thank you to the people who have followed this build on the forum.---Brian
https://www.youtube.com/watch?v=8Mjw4YLCt9E
Title: Re: Inspiration for new air motor
Post by: crueby on May 03, 2018, 07:55:28 PM
Excellent engine Brian, thanks for having us along for the ride!

 :cheers:
Title: Re: Inspiration for new air motor
Post by: NickG on May 03, 2018, 07:58:26 PM
Looks great in its paint Brian, another interesting engine.


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Title: Re: Inspiration for new air motor
Post by: Kim on May 03, 2018, 09:47:21 PM
I'll say!  This one is fascinating, as are all of your engines. They always have a hook to them.
Nice video too.
Kim 
Title: Re: Inspiration for new air motor
Post by: Tennessee Whiskey on May 03, 2018, 11:27:52 PM
Engine looks and runs great Brian. Be sure and keep us up to date on your gardening projects on the “gardening thread” since you aren’t going to be doing anymore engines till the fall  :stir: :stickpoke:

Cletus
Title: Re: Inspiration for new air motor
Post by: Craig DeShong on May 03, 2018, 11:43:36 PM
Nice  looking model Brian, and it runs good to  :cheers:
Title: Re: Inspiration for new air motor
Post by: Dave Otto on May 03, 2018, 11:49:27 PM
Nice job Brian, she looks and runs great!


Dave
Title: Re: Inspiration for new air motor
Post by: bent on May 04, 2018, 10:30:32 PM
Interesting the way it turned out.
Title: Re: Inspiration for new air motor
Post by: b.lindsey on May 05, 2018, 01:12:09 AM
Great runner and very nicely finished too Brian. Well done!!

Bill
Title: Re: Inspiration for new air motor
Post by: Brian Rupnow on May 07, 2018, 04:32:53 PM
About a week ago I ordered an 8" buffing wheel and a buff rake from Eastwood. Of course I was too impatient to wait another week to finish polishing the engine parts, so I bought a 6" buffing wheel locally to get the job done. Today, my order showed up. My God--What a ferocious looking beast that buff rake is!! I've never had one before now, so wasn't sure exactly what to expect. This thing looks like it would scrape the barnacles off the Titanic.
(https://imageshack.com/a/img924/5929/Y0OqFr.jpg)
Title: Re: Inspiration for new air motor
Post by: b.lindsey on May 07, 2018, 08:21:03 PM
Brian, it that beast supposed to just fluff up the buff and remove excess rouge etc. or what? Have never tried one. Would be curious as to before and after pics.

Bill
Title: Re: Inspiration for new air motor
Post by: crueby on May 07, 2018, 08:49:46 PM
Over time, the buff gets clogged up and hard with rouge and metal, the rake cleans it out and refluffs the wheel, just like a diamond dresser does on a grinding wheel. Mine looks a lot like that one. Don't need to use it very often, but it gets the wheel back to useful again. It does remove some of the outer layer of cloth. I use it on a cloth layer wheel, not sure about on a hard felt wheel. Careful of the angle you use it at, so it doesnt dig in and get grapped.
Title: Re: Inspiration for new air motor
Post by: Brian Rupnow on May 07, 2018, 10:25:33 PM
I will start a new thread with before and after pictures. Some of my buffs are just terrible right now. Really matted, full of brass and aluminum particles, just awful. I have been thinking about buying a buff-rake for about 25 years but have never actually had one. I don't want to try it right now, because my lathe and machine shop are clean as a whistle, and I just know this is going to be a filthy job.
Title: Re: Inspiration for new air motor
Post by: crueby on May 07, 2018, 10:48:21 PM
I will start a new thread with before and after pictures. Some of my buffs are just terrible right now. Really matted, full of brass and aluminum particles, just awful. I have been thinking about buying a buff-rake for about 25 years but have never actually had one. I don't want to try it right now, because my lathe and machine shop are clean as a whistle, and I just know this is going to be a filthy job.
Definitely, the rake throws up a bit of a particle cloud, good time for dust mask and vacuum.
Title: Re: Inspiration for new air motor
Post by: b.lindsey on May 07, 2018, 11:01:53 PM
Guess I don't need to rush right out and buy one then  :lolb:

Bill
Title: Re: Inspiration for new air motor
Post by: Ian S C on May 08, 2018, 03:37:15 AM
From what I'v seen of polishing shops at foundries, you really need another workshop in an other building, they are usually a right old mess, with fluff hanging from the rafters,and all up the walls.   Ian S C
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