Author Topic: Woody - but not quite a Forest  (Read 1374 times)

Offline Jasonb

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Woody - but not quite a Forest
« on: June 09, 2019, 02:23:39 PM »
I have always liked the look of the Forest engine reproductions that Wayne Grennings produced and thought that I might have a go at a smaller one myself. Chances of getting the non compression carrier flame ignition to work at the smaller sizes even if I could make up a suitable cocktail of gasses was slim but I thought it may work as a flame licker using the proven mechanicals of my Chuky and Alyn Foundries Chuk as a basis.



Graham from Alyn had said that it would not be easy and he was right, I could not get it to run due to a few factors. Firstly the Evan's beam linkage of the crankshaft adds more drag, you can't easily get a clean flame with the shutter rods etc directly above and the biggest problem was with the can being so close to the shutter it tended to push it off the port face.

I had always had it in the back of my mind that if I could not get it to run as a flame licker it may be possible to convert to an air/steam engine with poppet valves much like the Jowitt engine I made a while ago. Even this was going to be difficult due to the lack of room so a couple of weeks ago I decided that a spool valve may work and made up the various part which resulted in a running engine.













It will run even slower than this but starts to get a bit jerkey as it is only single acting, at this speed it will run for at least 20mins on my small compressor without the tank needing to refill so not too noisy to run. It was an interesting project with a few more first crossed off the list such as first spool vale, first Evans bean and first spiral cooling fins.


Another successful project for the Red Devil and Green Dragon combination

J
I won't do a full build thread but will in coming posts describe the major bits
« Last Edit: June 09, 2019, 02:27:13 PM by Jasonb »

Offline b.lindsey

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Re: Woody - but not quite a Forest
« Reply #1 on: June 09, 2019, 02:40:53 PM »
Fine looking engine Jason with some unique characteristics as well like the spiral fins!!  Well done.

Bill

Offline Brian Rupnow

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Re: Woody - but not quite a Forest
« Reply #2 on: June 09, 2019, 03:22:51 PM »
Jason--That is just beautiful. Amazing machining and paint job. You are a credit to all model engine machinists.---Brian

Offline Dave Otto

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Re: Woody - but not quite a Forest
« Reply #3 on: June 09, 2019, 03:59:44 PM »
What a cutie!
Beautiful work Jason.

Dave

Online Twizseven

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Re: Woody - but not quite a Forest
« Reply #4 on: June 10, 2019, 12:53:42 PM »
Jason,

Lovely work as usual.  What I want to know is how do you find time to go to work, let alone do any family/home related stuff.  Do you work 24hrs a day?

Colin

Offline Chipmaster

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Re: Woody - but not quite a Forest
« Reply #5 on: June 10, 2019, 07:12:37 PM »
Very nice complete with a superb finish.

Andy

Offline Jasonb

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Re: Woody - but not quite a Forest
« Reply #6 on: June 10, 2019, 07:51:46 PM »
Thanks for all the comments, on with the build.

The base plate was bandsawn from some 16mm 6082 plate and the two long edges flycut to size. Then with the plate held horizontally in the vice the two ends were squared up.



Then a full 12mm height x 1mm deep pass all around formed the rebate, I used a 2-flute aluminium specific cutter which gave a nice finish.



Then using a set of co-ordinates taken from my Alibre drawing the convex part of the ogee moulding was cut in 0.5mm vertical increments around the four straight edges





Luckily I had a ball nose cutter which meant that the concave part of the moulding was a lot quicker to cut.



While still in the vice the various holes were drilled and tapped, the smaller blind holes with a spiral flute tap and the M8x1 through hole with a spiral flute which just pushed the long spirals of swarf out the bottom of the hole and no need to keep backing off the tap to break the chips.



The base was then transferred to the rotary table to round and mould the corners, I decided to do every other cut on these.



It was then just a case of blending the stepped cuts into a nice flowing shape with files followed by some Emery cloth.



The two lugs for the Evans beam to pivot on were worked onto either end of a small length of brass.



Then sawn off and rounded over, again on the rotary table.


Offline Zephyrin

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Re: Woody - but not quite a Forest
« Reply #7 on: June 11, 2019, 08:25:19 PM »
Wow, beautiful model !
The original gas engine had a rotary valve in the cylinder head, as your engine uses air, such valve could be used.
I'm anxiously waiting for the spiral fins machining...

Offline Jasonb

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Re: Woody - but not quite a Forest
« Reply #8 on: June 11, 2019, 08:41:51 PM »
Thanks for that do you know what date it is from?

The one I based my model on was the 1883 slide valve 1/15HP engine, if I were making it again from scratch the exhaust would come out of the valve block rather than the one I made to suit the flame licker engine. The air does come out of a hole in the top of the valve block so most of the way there.

Details of the one I based it on here https://sites.google.com/site/grenningmodelscom/1883-forest-slide-valve-engine-reproduction

Offline 10KPete

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Re: Woody - but not quite a Forest
« Reply #9 on: June 11, 2019, 11:04:11 PM »
Jason,
Your pics have not been showing up lately. All I see is a box from PhotoBucket saying "Oops, your image was linked incorrectly. Please visit your account for the correct link".
Pete
Craftsman, Tinkerer, Curious Person.
Retired, finally!
SB 10K lathe, Benchmaster mill. And stuff.

Offline crueby

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Re: Woody - but not quite a Forest
« Reply #10 on: June 11, 2019, 11:26:52 PM »
All pics have been showing fine for me...  :shrug:

Offline b.lindsey

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Re: Woody - but not quite a Forest
« Reply #11 on: June 12, 2019, 01:01:20 AM »
Working for me too.

Bill

Offline Jasonb

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Re: Woody - but not quite a Forest
« Reply #12 on: June 12, 2019, 07:16:02 AM »
All look OK for me too both here and on another forum where I posted the same. PB was a bit slow the other day so maybe not showing if you only looked then.

Offline Zephyrin

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Re: Woody - but not quite a Forest
« Reply #13 on: June 12, 2019, 02:17:31 PM »
I took these pictures in an expo on Fernand Forest a few years ago near Paris, in Suresnes, where Forest was born.  it was figures of a patent of 1882 for a gas engine.
I have not yet succeed to obtain a copy of the patent.
Note that the cylinder head also has spiral fins !
I have some more details :

Offline Jasonb

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Re: Woody - but not quite a Forest
« Reply #14 on: June 12, 2019, 03:36:49 PM »

Note that the cylinder head also has spiral fins !

And tapered ones at that :o, looks like the whole head is tapered to match the internal taper which is what gives the "fit" or the rotating valve in the head much like you find on drain cocks.

Offline Jasonb

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Re: Woody - but not quite a Forest
« Reply #15 on: June 12, 2019, 07:11:52 PM »
The cylinder started out in much the same way as the Chuky with the ctr mark of the bore in the 50mm cast iron bar set to run true.



It was then faced, bored and a small spigot added to locate the cylinder head.



Reversed in the chuck the OD of the finned area was turned round and the end gently faced once the tailstock support had been removed.



Over to the mill and the port face was machined flat



Then to width



Followed by milling the port, this was sized for the flame licker version but could have been a lot smaller for the air/steam engine. I also had to subsequently drill and tap two M2.5 hols for the new valve block.



With a change to the horizontally mounted rotary table the rest of the lower part of the cylinder was milled round.



Now for the fun part of machining the spiral cooling fins. The rotary table from ARC has a 72:1 reduction so for ease of machining I opted for a 7.2mm pitch spiral which meant that for every turn of the hand wheel the milll table would need to move 0.1mm, as this was a bit coarse I opted for half a turn of the handle and 0.05mm x-axis feed per plunge cut of a 5.5mm 3-flute cutter. The two ends of the spiral were feathered out further with a 3.0mm cutter.

Just over 1000 plus plunge cuts later this is what I ended up with.





This picture shows the machining marks left by the plunge cuts which were cleaned up with a file and the whole "casting" given a once over with the Dremel to give it that cast look.



I think it could do with some legs next








Offline Dave Otto

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Re: Woody - but not quite a Forest
« Reply #16 on: June 13, 2019, 12:49:43 AM »
Nice bit of carving there Jason  :ThumbsUp:
I have been wondering how you made the cylinder.

Dave

Offline crueby

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Re: Woody - but not quite a Forest
« Reply #17 on: June 13, 2019, 12:57:46 AM »
The spiral fins are spectacular, very well done!

Offline Jasonb

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Re: Woody - but not quite a Forest
« Reply #18 on: June 13, 2019, 07:25:41 AM »
Thanks again for the comments.

I had finished this engine as a flame licker just before I got the CNC so if doing it again would certainly have used that to do the moulded profile around the base and the possible addition of a 4th axis would have made the spiral a simpler job.

Bit more about CNC when we come to the legs.

At least I only had to make one rather than a batch like Wayne did though in this case castings were probably the best option as he would have had to farm out the CNC work.


Offline Zephyrin

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Re: Woody - but not quite a Forest
« Reply #19 on: June 13, 2019, 07:47:22 AM »
that's machining Jason, congratulations !  thanks to share these pictures.

Online Alyn Foundry

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Re: Woody - but not quite a Forest
« Reply #20 on: June 13, 2019, 02:47:43 PM »
It's a beautiful model engine Jason, well done!

As you have found, a horizontal format Flame licker/gulper is quite difficult to get running. And with the port so close to the flywheel the flame tends to get " wafted " everywhere so that cooler air enters and less of a vacuum is formed.

I was particularly pleased to see the pictures posted by Zephyrin showing Monsieur Forest's alternative
" rotary " ported ignition and exhaust system too.

A few will know that " carrier flame ignition " only works well with Hydrogen rich gases due to the rapid burn aspect. This system lasted a couple of decades before more effective means of ignition were used like hot tube and both low and high tension electric methods.

Non the less, it's a credit to you and you may be interested to know that when I first acquired my Leek number 3 atmospheric engine that had also been converted to run on compressed air!

Cheers Graham.

Offline Johnmcc69

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Re: Woody - but not quite a Forest
« Reply #21 on: June 13, 2019, 03:14:51 PM »
Beautiful work Jason!

 How long did it take to cut the spiral on your mill? Is the flywheel a casting or a fabrication?

 John

Offline Jasonb

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Re: Woody - but not quite a Forest
« Reply #22 on: June 13, 2019, 05:09:07 PM »
Thanks for the interest Graham, it certainly was a job to get a decent flame in the space available. Just about to post some photos in your Allman thread.

Probably took a couple of hours to do the main spiral then I needed a break. Came back and did the ends with the smaller cutter which were helical on one size and straight on the other so probably 3 hrs total machining.

I did rig up a simple depth stop on the quill so it was just a case of 1/2 turn of the rotary table, 0.05 on the DRO x axis then pull the lever and so on.
« Last Edit: June 13, 2019, 05:28:28 PM by Jasonb »

Offline Jasonb

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Re: Woody - but not quite a Forest
« Reply #23 on: June 13, 2019, 08:14:30 PM »
Sorry, forgot to say the flywheel is the only casting used.

The "cylinder head" which incorporates the bearing supports started life as a piece of 5mm plate which was marked out and the bigger bits of waste material roughly sawn off. This was then clamped to a scrap of aluminium on the rotary table for drilling the various small holes and some to define the internal corners. Three of the holes were carried on at tapping size into the ali plate and then tapped so some additional screws could be used to hold the part while the main hole was bored.



The two clamps were then removed and the outside milled to shape.



The flame licker design needed a chamber for the spring and valve, this was bored out on the lathe and then transferred to the mill to shape the outside leaving  a flat area into which the exhaust stack would screw.



Jumping forwards a bit the parts including two bearing supports have been silver soldered together, bearing caps screwed on and the assembly mounted back onto the ali plate to bore first the top bearing hole.



And then the other, in both cases the bearing was used to gauge the size of the hole



Hard to resist a quick trial fit



A bit of milling and the bearing caps start to take shape



Then roughing out the curved top which was finished off with a file



Final bit of machining was to drill and tap two radial holes for the legs to fix to.



A quick talking to with a grinding point in the Dremel knocked off all the hard corners and added a bit of texture to get the cast look.


Offline Jasonb

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Re: Woody - but not quite a Forest
« Reply #24 on: June 23, 2019, 08:05:40 PM »
The crank web was first turned from some 40mm bar.



before transferring to the mill to drill an dtap a hole for the crank pin, after which it was parted off a little over thickness and then milled to the counterbalanced shape.



After Loctiting to the 6mm shaft the assembly was put back in a collet to machine the web to thickness, I like to do it that way so that the face the pin will tighten up to is at perfect right angles to the shaft axis even if the loctite joint had of been a bit off. The two other fittings were not needed for the air/steam version.



Another curved spoke flywheel casting the same as I used on the Muncaster Entablature engine was soon machined up to a firm push fit on the crankshaft.



Time for a quick play to see how my suppliers bearings run, i can't really complain about this.

t=3s
« Last Edit: June 23, 2019, 08:16:26 PM by Jasonb »