Author Topic: Compressed Air V8 Engine  (Read 54533 times)

chuck foster

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Re: Compressed Air V8 Engine
« Reply #105 on: August 18, 2012, 01:03:32 PM »
holy smokes, take a few days off and chucks got a v8 engine almost ready to run  :whoohoo:

as usual this engine is looking first class  :ThumbsUp:

chuck

Offline ironman123

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Re: Compressed Air V8 Engine
« Reply #106 on: August 18, 2012, 02:21:12 PM »
Mean looking engine Chuck.  Look good in a R/C boat.  Your workmanship is superior.  :ThumbsUp: :ThumbsUp:

Ray
Ray
Central Texas

Offline cfellows

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Re: Compressed Air V8 Engine
« Reply #107 on: August 18, 2012, 07:00:06 PM »
Thanks, guys.  I appreciate the support.

I need 8 springs for the slave exhaust valve assemblies, well maybe 10 if you count the 1 or 2 that will almost certainly get dropped and disappear into another dimension or at least into the neighbors yard which at it's closest point is at least 50 feet from my workbench (they are springs, after all!).

So I found a smokin' deal on ebay for exactly the right sized springs...



I didn't count, but there are supposed to be 250 springs there.  Guess I'll be building a few more engines...

Chuck
« Last Edit: August 23, 2013, 09:56:07 AM by arnoldb »
So many projects, so little time...

Offline Dean W

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Re: Compressed Air V8 Engine
« Reply #108 on: August 18, 2012, 09:12:10 PM »
Wow, it sure looks good, Chuck.  I'll bet you're even more excited to crank her up than I am to hear it!
Just good luck to find all those springs the right size, I guess.  Making them is easy enough, but like
tapping a lot of holes, it can become a chore.
Dean
In beautiful N. Idaho, U.S.A.

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Offline zeeprogrammer

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Re: Compressed Air V8 Engine
« Reply #109 on: August 18, 2012, 11:46:34 PM »
Remember that everyone. If you need a spring...you know where to go.
Although I won't be surprised he uses them up with all the great projects he no doubt has planned.
Carl (aka Zee) Will sometimes respond to 'hey' but never 'hey you'.
"To work. To work."
Zee-Another Thread Trasher.

Offline swilliams

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Re: Compressed Air V8 Engine
« Reply #110 on: August 19, 2012, 02:34:27 AM »
Looking great Chuck

Steve

Offline cfellows

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Re: Compressed Air V8 Engine
« Reply #111 on: August 19, 2012, 05:03:10 AM »
Wow, it sure looks good, Chuck.  I'll bet you're even more excited to crank her up than I am to hear it!
Just good luck to find all those springs the right size, I guess.  Making them is easy enough, but like
tapping a lot of holes, it can become a chore.

Thanks, Dean.  Yeah, I feel like I'm getting close.

Remember that everyone. If you need a spring...you know where to go.
Although I won't be surprised he uses them up with all the great projects he no doubt has planned.

Yep, I got springs.  And so far, I haven't dropped a single one.  However, within a few days I'll put them away, forget where I put them, and, eventually, begin to wonder if I really ever had them...

Looking great Chuck

Steve

Thanks, Steve,

Probably seems kind of insignificant, but today I got the holes drilled in the pistons, made the wrist pins, and attached the pistons to the rods.  I also epoxied the brass valve tube liner into the crankcase and drilled radial holes that will admit compressed air to the tubes leading to each cylinder. 



The next hurdle is assembling the rods, pistons, and crankshaft and installing them in the crankcase along with all the cylinders.  I'm guessing it will be a struggle to get everything turning over smoothly.  May have to run it in a bit using my lathe to spin it.  The only other task left is making the rotary valve tube which will be made from steel drill rod and have the large cam gear attached.  It turn inside the brass tube liner.  I'll then have to time the engine by rotating each piston to it's "firing" position then drilling a radial hole through it's respective air tube fitting into the rotary valve tube.  I know all this probably sounds complicated so I'll take as many pictures during this process as I can.

Chuck
« Last Edit: August 23, 2013, 09:56:44 AM by arnoldb »
So many projects, so little time...

Offline RMO

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Re: Compressed Air V8 Engine
« Reply #112 on: August 19, 2012, 06:40:14 AM »
I was wondering how you were going to time the engine.  I will be keeping a close eye on the process.  Looks great so far.

Mike O

Offline cfellows

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Re: Compressed Air V8 Engine
« Reply #113 on: August 20, 2012, 01:49:47 AM »
Actually beginning to feel like an engine now.  I installed the crankshaft, rods and pistons.  I had to turn it over a few times with the drill, but that was probably just to remove bits of metal and dust.  Turns over with my fingers now with little very little detectable slop anywhere.  I'm sure there is slop, but I guess the misfits are in random and opposing directions making the overall assembly feel pretty snug.



Next I guess I'll decide on a flywheel.  I could make another steel propeller, but that is a fair amount of work and I managed to get smacked by them quite a bit on the other two engines I build with propellers.  Maybe a small, thick sectioned steel or brass flywheel, like those found on older marine engines?  I'd gladly entertain any ideas...

Chuck
« Last Edit: August 23, 2013, 09:57:03 AM by arnoldb »
So many projects, so little time...

Offline rleete

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Re: Compressed Air V8 Engine
« Reply #114 on: August 20, 2012, 01:55:59 AM »
I'd suggest small (size of the large gear or so) but not too thick.  It's not gonna need a lot of flywheel to keep it going, so the less the better.  Make it steel to have some usable mass.

Offline zeeprogrammer

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Re: Compressed Air V8 Engine
« Reply #115 on: August 20, 2012, 02:04:14 AM »
Looking really cool Chuck.
Getting very exciting.
Carl (aka Zee) Will sometimes respond to 'hey' but never 'hey you'.
"To work. To work."
Zee-Another Thread Trasher.

Offline Don1966

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Re: Compressed Air V8 Engine
« Reply #116 on: August 20, 2012, 02:16:10 AM »
Chuck are you going to show us the process of making the rotary valve? I am curious to see how you do it.

Don

Offline cfellows

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Re: Compressed Air V8 Engine
« Reply #117 on: August 20, 2012, 08:38:19 PM »
Chuck are you going to show us the process of making the rotary valve? I am curious to see how you do it.

Don

Hope I can do this justice, Don.  By the way, this is the second time I'm typing this in.  I was just about finished and accidently closed the window before I posted it!   :wallbang:

The rotary valve tube actually starts out as a 3/16" length of drill rod.  The first step is to press a small flange onto the back end. 



I made the flange from 5/16" drill rod and drilled the center hole with a #2 drill bit which is about .002" smaller than the 3/16" diameter of the valve tube.  I deliberately made the flange over-sized on both the diameter and length so I could turn it to finish dimensions after it was fixed on the valve tube (which is still a solid rod at this point).  Here's how the valve tube will fit in the engine once finished.



Next I had to drill a 3.5" deep center hole in the rod.  The only bit I had which was long enough was 1/8" so that's what I used.  I had to back out of the hole, clear the chips, and add oil about every 1/8" to keep the drill on center and to keep the chips from piling up and seizing the bit.



Once the center hole was drilled, I inserted the valve tube into the crankcase from the back.  Here's a picture of the valve tube fully inserted after I had drilled the center hole.



I then attached the larger timing gear to the front part of the valve tube where it extended out of the crankcase.  Notice that the center hole does not go all the way through the valve tube.  Here's what it looks like with the valve tube installed and the two timing gears attached to the valve tube and crankshaft, respectively.  The crankshaft and the valve tube are now geared together and the valve tube will rotate at 1/2 the rate of the crankshaft giving the engine 4 stroke operation.



Here I've turned the crankshaft so that the first cylinder in the firing sequence is at top dead center (far right cylinder).



Next I attached a disk which has 4 lines scribed 90 degrees apart to the crankshaft.  These lines are used to measure exactly 1/4 turn of the crankshaft.



Here I'm ready to start drilling the holes in the valve tube.  I've already center drilled the holes in the flare fittings so it's just a matter of running the drill bit down until it hits the valve tube and drilling through to the center hole.



After drilling the first hole, I rotate the crankshaft 1/4 turn and proceed to the next cylinder in the firing sequence where I again drill a 1/16" hole through the side of the valve tube into the center hole using the cylinders flare fitting as a guide.  This operation is repeated until holes have been drilled for all 8 cylinders.  This results in 8 individual holes in the correct position for each cylinder.  Note, however, that after I finish drilling all the holes, I have to retard the valve tube timing.  As drilled, the holes are fully open when the piston would be at top dead center and in fact you want the piston to be half way through it's stroke before it's valve hole is fully open.

I hope this is a little clearer than mud.  Let me know if you have any questions.  I expect to have this engine running by the end of the day.  Or perhaps I should, ready to run by the end of the day.  Whether it actually runs remains to be seen!

Chuck

« Last Edit: August 23, 2013, 09:58:04 AM by arnoldb »
So many projects, so little time...

Offline cfellows

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Re: Compressed Air V8 Engine
« Reply #118 on: August 20, 2012, 10:16:15 PM »
It Runs!!!! And does it sound sweet.  I'll get a video up pretty soon...

Chuck
So many projects, so little time...

Offline Don1966

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Re: Compressed Air V8 Engine
« Reply #119 on: August 20, 2012, 11:03:51 PM »
Awesome Chuck, thanks for the detail step by step. I really appreicate that. The one question I have is when the drill bit goes through the rotary tube, does't not leave a  upwards bur on the tube, and will the tube come out after drilling? Do you drill slowly to keep this from happen and does this work for removeable of the tube with out problems.
Can not wait to see the video. Please gives plans for the built so some of us can build it too?

Don