Open Column Launch Engine from Kit

[zeeprogrammer]

Good news. It's assembled.
Sad news. It's not a runner.

There's at least 2 problems with it...

1) I think the piston is a bit too loose and air is getting around it. I may have overdone it when trying to fit. In addition, I suspect the cylinder bore is not true and that may have fooled me a bit. Part of the problem I believe, is that when the holes were made in the ends of the cylinder, particularly for the columns, metal was pushed towards center.

2) The rotary valve has a number of issues with it. For one, it's a tad short so it moves back and forth between the pillow blocks. That makes it difficult to keep the valve grooves aligned. For another, as I mentioned earlier, I think the grooves may be a little off and don't line up with the coupling as well as they could. This is probably minor in that they were fully exposed...just not centered. Third, but I don't know if this is an issue, the ends of the grooves are not cut correctly (as I also mentioned earlier.)

At a minimum, the cylinder will have to be redone. The piston may be okay. The rotary valve? I don't know.

So...do I put this on the shelf and get started with the next engine? If it were just me, for a number of reasons, I probably would. In making it run, will I truly learn something that I otherwise wouldn't? Keep in mind this is just my initial reaction.

I think the 'offset' on the rotary valve can be fixed by slotting the two holes that hold the pillow block. Unless I'm missing something...I think the placement of the grooves is alright too (but I haven't checked all of the ports). Lastly, I doubt the ends of the grooves are critical.

The bigger issue I think, and probably the one easiest to rectify is the cylinder. But I believe I'll find that the piston has to be redone too.

The engine does turn over a few revs but at high pressure. I have a pancake compressor so most likely I lose air too quickly to keep the engine running. I wonder if I should try the air compressor I use for tires etc. It has no storage tank...it just keeps running. If you spin the flywheel by hand...it spins pretty easily. Wouldn't that be a sign of no compression and a bad piston/cylinder fit?

Not a big disappointment mind you. If I do nothing else but put it on a shelf...I'm pretty proud of what I accomplished. And if I don't make it run...there's the next one!

Well I'll sit back and see what the reaction is. :big: (There are examples of this engine around so it's not like it can be particularly interesting to see this one run.)

Robert: Just got your post. Not to worry. As for the grooves...well you can see what I said above. Thanks.

 

[vlmarshall]

Zee,
It LOOKS great, I'd get it running!
Crank the engine over with the intake and exhaust plugged, if it STILL spins freely, blame compression.
Sounds like the cylinder bore may have gotten bellmouthed a bit. Would it be easier for ya to make a new piston, and straighten/enlarge the cylinder bore to fit?

Get some brass shim stock and a punch kit, and make a few thrust shims to stop the endplay in the valve.

I don't think you're too far away from having a running engine on your hands.


Great work, bud.

-Vernon

( Here's a cheap version of that punch set that I'm going to try, I use a much more expensive-but-identical-looking set at work all the time.
http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=95547 )

 

[zeeprogrammer]

Crank the engine over with the intake and exhaust plugged, if it STILL spins freely, blame compression.
Sounds like the cylinder bore may have gotten bellmouthed a bit. Would it be easier for ya to make a new piston, and straighten/enlarge the cylinder bore to fit?
Get some brass shim stock and a punch kit, and make a few thrust shims to stop the endplay in the valve.

Thanks Vernon.

Plugged the intake and exhaust. Spins freely. One other possibility would be leakage around the rotary valve. Doesn't seem to be - but I need to do some more checking.

My largest reamer is 9/16. I'd have no problem going for another but would boring be good enough?

Shims...good idea. But you'd see it. What's wrong with slotting the holes? They're over-sized anyway.

The Punch Set...another tool! And no doubt someone's going to say I can make them.

'bud' huh? Just had to get that reminder in didn't you? :big:

 

[Foozer]

Good news. It's assembled.
Sad news. It's not a runner.

[
There's at least 2 problems with it...

1) I think the piston is a bit too loose and air is getting around it.

2) The rotary valve has a number of issues with it.
So...do I put this on the shelf and get started with the next engine? If it were just me, for a number of reasons, I probably would. In making it run, will I truly learn something that I otherwise wouldn't? Keep in mind this is just my initial reaction.

If you spin the flywheel by hand...it spins pretty easily. Wouldn't that be a sign of no compression and a bad piston/cylinder fit?

Piston would have to be really "loose" to stop a runner, with air applied rotate the flywheel and feel for the "push" the air applies upon the piston, you can get a rough idea of the engines timing.

Odds are its your valve, hard to tell from the photo how far into the stock the slot goes (looks like the ends are close to the stock C/L from the photo) or how its keyed to the crankshaft. Piston just past TDC intake valve should begin to open. Piston near BDC intake valve should be closed, exhaust valve begins to open. Piston nearing TDC exhaust valve closing and cycle repeats. If the intake is open when the piston reaches BDC on the power stroke its return trip is blocked by the air pressure.

The intake duration only needs a little squirt of air to pressurize the cylinder forcing the piston down. The exhaust should open at or before BDC to allow the piston unrestricted movement back to the top.

You'll have it running in no time, little tinkering. Stick a piece of card stock in the valve stock with an on end photo. That way a better look at the timing can be made by those here that have more experiance with this valving system.

Looks good, I see a beam engine in your future

 

[mklotz]

Don't shelve it! You *must* make it run! "Debugging" an engine is a critical skill and you need the practice. More importantly, you need the boost to your self-confidence. No matter how long it takes, you need to get it done.

Perhaps this will help - Of 33 or so engines in my collection, I've never built an engine that didn't run. OTOH, I've built only maybe four that ran the first time they were assembled. Post assembly fiddling is a fact of life.

Before you start remaking parts...

Lube everything that moves (don't forget the piston) if you haven't already. Something like turbine oil is a good choice or, lacking that, 3-in-1 or sewing machine oil will be fine. Also, bubbling oil after you supply air will indicate leaks if they exist.
(Don't go nuts if you see a few bubbles - that's expected since the engine has no real seals.)

Check that you've got airflow to the (revolving) valve. With the shaft removed, apply air and use a wet finger or whatever to ensure that air is actually getting to the valve. I offer this only for completeness. I don't really think this is your problem.

Fiddle with the valve timing. Sometimes a small change in the phasing is all that's needed. Especially so given the "ramp" caused by using the wrong cutter. Consider shimming it if it's loose between the bearing blocks. (Perhaps there's enough slop in the bearing mounting holes to loosen the screws and push them a tiny bit closer.)

Check the piston fit by pulling the plastic hose off the cylinder, cover the port with your finger, and use the flywheel to drive the piston upwards. You should feel at least some resistance from the compressed air. If the engine turns over easily by hand, you probably don't have any piston/cylinder binding. I refuse to believe that, with all the care you've shown so far, the fit is so bad that you don't have some compression there.

If you do remake parts, remake the valve first. I'm more skeptical of it than of the cylinder/piston. Even if the latter have problems, the engine should run (perhaps at higher pressure) if it's being valved correctly. I would expect an engine like this to run on 5 psi or less. If it doesn't run at, say, 20 psi I would almost certainly suspect a valve problem.

BTW, it looks great!

 

[zeeprogrammer]

Odds are its your valve, hard to tell from the photo how far into the stock the slot goes (looks like the ends are close to the stock C/L from the photo) or how its keyed to the crankshaft.

You'll have it running in no time, little tinkering. Stick a piece of card stock in the valve stock with an on end photo. That way a better look at the timing can be made by those here that have more experiance with this valving system.

Looks good, I see a beam engine in your future

I 'foresee' Marv saying the same about the valve. I'll investigate further.

Not sure I understand what you mean by an end photo? Happy to do it though.

Thanks for the support Robert. Yes...very interested in a beam engine some day.

 

[zeeprogrammer]

Don't shelve it!

Of 33 or so engines in my collection, I've never built an engine that didn't run. OTOH, I've built only maybe four that ran the first time they were assembled.

Lube everything that moves (don't forget the piston) if you haven't already.

Check that you've got airflow to the (revolving) valve.

Fiddle with the valve timing.

Check the piston fit by pulling the plastic hose off the cylinder, cover the port with your finger, and use the flywheel to drive the piston upwards.

BTW, it looks great!

I'll keep at it. Given my prior posts...you probably knew that. I need to increase the time between thought and keyboard. (Didn't I learn that lesson just a few posts back?)

Lubed everything. I even 'poured' oil into the plastic tube so that a goodly amount was trapped...then blew into it with my mouth. It was like blowing bubbles in a glass of milk with a straw. Well not that bad...but it was easy...and a lot of the oil was found around the base. It was auto oil 30W.

Yes, air gets to the valve...you can even see it pushing on the oil that was left behind in the clear tube.

Remember too, that I said at high pressure it turned a few revs. Still the valve?

How do I fiddle with the valve timing? Turn it in relationship to the crankshaft? The setscrew sits on a flat. I suppose I could have screwed up the grooves relative to the setscrew. But I was pretty happy with it.

I'll check the piston fit as you suggest. It's a good idea. And while you refuse to believe it...I was surprised how the piston just slipped through when I dropped it in. Maybe overdid trying to fit...maybe the cylinder isn't truly round. When trying to fit piston the gap due to the oval would only have gotten bigger.

Thanks Marv.

 

[Foozer]

I 'foresee' Marv saying the same about the valve. I'll investigate further.

Not sure I understand what you mean by an end photo? Happy to do it though.

Thanks for the support Robert. Yes...very interested in a beam engine some day.

From the top so can see haow far into the daimeter of the valve the slot goes.

Original plan said to use a 1/2 dia cutter? and the depth of cut is? You used a larger diameter cutter, same depth of cut? That will throw the overall timing off. Can use a larger dia cutter if the depth of cut is adjusted. Will just make a more restricted passage but probably not so much as to affect the run or not run condition.

 

[zeeprogrammer]

Some more thoughts...

What if the cylinder had a taper to it?

Also, recall that the bore was made before the cap and column holes were drilled and tapped. Remember I mentioned that I thought (tapping) the holes might have pushed metal into the cylinder? Might this be the reason the piston didn't fit anymore? Then, as I tried to fit the piston...I simply increased the gaps between the cylinder wall and the piston between each of the areas where the holes were?

Is it worth trying to measure the cylinder to see?

If I redo the valve I'll have to get the proper saw. Not a problem...just letting everyone know it'll be a little time.

Foozer: Same depth of cut... 0.031". It doesn't seem like it would be significant but I haven't done the math to see how much the grooves would have been lengthened.

Thanks.

 

[zeeprogrammer]

No photo...but here's a diagram.
Looking from the top and folding up the sides.

The rightmost groove is closest to the shoulder of the valve. It's about 0.11" away. The leftmost groove was supposed to be 0.20". It ended up a little short...0.19" or so.

That's why I drew the intake with the groove a little to the right. But it's completely clear otherwise.

The exhaust is similar but better.

The port to the cylinder shows both grooves.

I think it should be okay. But that might still leave:

1) Timing - did I cut the grooves in relation to the crankshaft correctly? I think so.
2) Timing - are the longer grooves a problem? I don't know.
3) Leakage around the valve? I don't think so.

I also did as Marv suggested and unhooked the clear tube, applied air to the intake, and turned the flywheel by hand. There's certainly air coming out that would go into the clear hose. And it stops as you turn the flywheel cutting off the intake.

Is it worthwhile to try something more viscous in the cylinder to see if it blocks more air and provides more pressure on the piston. Hmm. Wouldn't that mean more resistance for exhaust stroke?

Thanks.

 

[Foozer]

Some more thoughts...

What if the cylinder had a taper to it?


Foozer: Same depth of cut... 0.031". It doesn't seem like it would be significant but I haven't done the math to see how much the grooves would have been lengthened.

Thanks.

Taper with low air pressure could effect, but still wont stop a runner. Performance and engine efficiency degrade with loose fits but even a 49 nash with 500k miles on still is runnable. My little wobbler has so much piston clearance it hisses at ya, but it still goes 'round

0.031 thousand depth of cut? Your valve looks to be 0.500 in dia so a 0.031 depth of cut with a 0.500 cutter would look like the dwg. Nothing like your actual. Now I'm confused, easily done too.

 

[zeeprogrammer]

0.031 thousand depth of cut? Your valve looks to be 0.500 in dia so a 0.031 depth of cut with a 0.500 cutter would look like the dwg. Nothing like your actual.

It probably would have helped had I drawn end points of the grooves.

One groove begins at 34 degrees and ends at 235. The other begins at 129 and ends at 324. Looking down the bore of the valve...you would see two 'C' shaped grooves, one offset from the other.

Your picture is right as far as how it would look taking the initial plunge cut. Then rotate the part while cutting. Remember the pic of the rotary table?

Or am I not understanding?

 

[vlmarshall]

Can you connect an air source, disconnect the valve from the crankshaft, and turn the valve by hand while holding the crankshaft? I'd like to see just how much force that piston and cylinder can generate, rule out the piston fit, and work on the valve and timing.

Just a thought.

 

[Foozer]

It probably would have helped had I drawn end points of the grooves.

One groove begins at 34 degrees and ends at 235. The other begins at 129 and ends at 324. Looking down the bore of the valve...you would see two 'C' shaped grooves, one offset from the other.

Your picture is right as far as how it would look taking the initial plunge cut. Then rotate the part while cutting. Remember the pic of the rotary table?

Or am I not understanding?

It my morning over caffeinated brain that failed to get it : New info helped

Now it makes sense, the increase in dia cutter effect would be minimal,

Now the shetch looks more like your actually. Timing check

 

[zeeprogrammer]

Can you connect an air source, disconnect the valve from the crankshaft, and turn the valve by hand while holding the crankshaft? I'd like to see just how much force that piston and cylinder can generate, rule out the piston fit, and work on the valve and timing.

Not sure I follow. I would feel the force on the valve, right? If I felt anything at all...I would have no idea how much is too little, too much, or baby bear. If I felt nothing...maybe that's the clue?

Foozer: You seem to agree then that any difference due to cutter diameter would be minimal.

Timing check? I'll re-verify the part. Maybe I missed something and cut the thing wrong.

Thanks all.

 

[vlmarshall]

Not sure I follow. I would feel the force on the valve, right? If I felt anything at all...I would have no idea how much is too little, too much, or baby bear. If I felt nothing...maybe that's the clue?
Timing check? I'll re-verify the part. Maybe I missed something and cut the thing wrong.

Thanks all.

Not a force on the valve, a force on the piston. I'm just tossing out ideas.

 

[zeeprogrammer]

Gotta go to the store. I have one hand holding the hose to the engine and the other hand holding the hose onto the air gun and activating it. I don't have any clamps and I don't think a barbed connector will be strong enough. My feet are too far away and my other appendages are worthless.

 

[zeeprogrammer]

Not a force on the valve, a force on the piston. I'm just tossing out ideas.

And I'm trying to catch (please reference my last post re: appendages) ;D.

...oh...I just typed a couple of whizbang sentences that would have made you look foolish. Instead...it would have been me. So we'll just set those aside for a better day.

Good idea. I'll try it.

 

[vlmarshall]

...I just typed a couple of whizbang sentences that would have made you look foolish. ... So we'll just set those aside for a better day.

Haha, bring it. ;D Can you shoot video? I'll bet that you'll have that thing running in a short while, and I'd like to see it moving.

 

[Foozer]

Foozer: You seem to agree then that any difference due to cutter diameter would be minimal.

about a 2.8' increase 34' to 36.8' thereabouts, yup minimal. Timing should be on the conservative side keeping with the "beginners kit" theme