Yet Another Webster Begins

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CFLBob

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I agree with you on the looks. It's pretty unsightly. I think I'll be doing your approach.

WebsterCounterWeight.jpg
 

CFLBob

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I'm roughing in the piston now, and based on what I was reading over at Brian's Vertical Hit and Miss engine,
https://www.homemodelenginemachinist.com/threads/verical-hit-and-miss-engine.31370/page-14#post-328819

I thought I'd check into cast iron rings for this. The Webster drawings says:
PISTON RINGS - 3/32" X .875"
(2) REQD.
SOURCE: OTTO GAS ENGINE WORKS
(410)-398-7340
2167 Blue Ball Rd
Elkton MD 21921-3330
http://www.dol.net/~dave.reed/otto.html

The website doesn't work so does anyone know if Otto Gas Engine Works is still around? Where can I get these?
 

werowance

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this is his email address to.
Dave Reed <otto@ringspacers.com>
 

CFLBob

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CFLBob !
What is happening with this build?
@minh-thanh - thanks for asking and bringing this back up. I got tied up working on things damaged by the lightning strike and didn't get back into the shop until last week. It has taken me a while to remember where I was. The lightning was back in August and stuff still was dying until a few weeks ago - and I hope I've replaced the last of the blown up things.

I have questions about fitting the piston that I was coming here to post about when I saw your post.

GoingAgain.jpg


I got this brake cylinder hone because I could feel little ridges on the inside of the cylinder wall with my fingertip. They're better but I can still feel them. The piston is very close to fitting but sometimes acts like it fits better when I rotate it a bit as I try to get it into the cylinder. I think I'm within the last thousandth of being the right size.

My question is that I don't really know how to fit a piston with rings. Without the rings in, how loose should it be?

All I know is that the drawing says the piston should be 0.873 while the cylinder should be 0.875 lapped. I think the cylinder is 0.876 or .877 now, with the bumpiness and not being lapped. The piston is either 0.873 or very close.

Both of them are very close and this is not the time to be rough.
 

werowance

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on mine, the rings fit just right with .876 which is where my cylinder was at after laping. I didn't use a hone on mine, just an aluminum lap with some 600 then 800 then 1000 grit laping compound I bough on ebay, came in what looks like what my wifes skin cream comes in, little white plastic jars smaller than a baby food jar. when I inserted the ring into the cylinder without the piston to see what the gap was, there was hardly any gap at all. the inside of the cylinder was smoothe and shiny unlike what a chevy 350 would look like after coming from the machine shop that was honed rather more like what a cox model aeroplane engine would look like. maybe not that smoothe but close. but the fact that at .876 I had hardly any gap on the ring I bet it would have still ran if I were at .877 or .878 even, really cant say for sure but I felt better when I saw almost no gap.
 

minh-thanh

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Hi CFLBob !
I got this brake cylinder hone because I could feel little ridges on the inside of the cylinder wall with my fingertip. They're better but I can still feel them. The piston is very close to fitting but sometimes acts like it fits better when I rotate it a bit as I try to get it into the cylinder. I think I'm within the last thousandth of being the right size.

My question is that I don't really know how to fit a piston with rings. Without the rings in, how loose should it be?

All I know is that the drawing says the piston should be 0.873 while the cylinder should be 0.875 lapped. I think the cylinder is 0.876 or .877 now, with the bumpiness and not being lapped. The piston is either 0.873 or very close.

Both of them are very close and this is not the time to be rough.

With the cylinder in all the engines I did:
I often try to make it seem "straight" and shiny - like polishing (I think I cannot afford and have the tools and machines to make it to the level of the oil's molecule :D)
I call it: seemingly straight because I know for sure the cylinders I've made, none of which are perfectly straight, A little taper at TDC no problem
With a piston without rings: it moves smoothly within the cylinder
piston with rings: I can push it in the cylinder with my fingers with a moderate amount of force
Rings and cylinders: I usually choose a clearance of 0.02 mm (cylinder and ring made of cast iron)
A little information, hopefully useful !
 
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CFLBob

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With the cylinder in all the engines I did:
I often try to make it seem "straight" and shiny - like polishing (I think I cannot afford and have the tools and machines to make it to the level of the oil's molecule :D)
I call it: seemingly straight because I know for sure the cylinders I've made, none of which are perfectly straight, there's a little bit of TDC no problem
With a piston without rings: it moves smoothly within the cylinder
piston with rings: I can push it in the cylinder with my fingers with a moderate amount of force
Rings and cylinders: I usually choose a clearance of 0.02 mm (cylinder and ring made of cast iron)
A little information, hopefully useful !
I think that's useful. When I measure with the telescoping gages and calipers, it seems like the thousandths digit varies more than I'd like in both the piston and cylinder diameters. Maybe .002 or even .003. It has made me more aware of temperature variation while working and not over or undercutting because of the size of the work changing. It makes me cautious about thinking I've got everything exact.
 

CFLBob

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I wrapped my brake cylinder hone in 150 grit sandpaper and ran the lathe for a while. I could still feel the roughness.

Then I went to 220, 320 and 400 sandpaper. I can still feel the roughness, just a lot less rough than when I started. I took this picture. I manipulated it a little to try to bring out the differences so the surface is better than this looks but it's definitely not "like glass." I guess it comes down to how fine a roughness I can feel. I've read we can feel .005", but I sure hope these ripples are smaller than that. 150 grit is .0067", so it should be smoother than that, all the way down to 400 that's .0025"

Cylinder_Smoothed.jpg


The offset circle at top is the center of my lathe chuck. Just left of bottom dead center in the cylinder, you can see what looks like a bump but is one of the chuck's jaws.
 

minh-thanh

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CFLBob !
if the graphite piston lasts long in the cylinder of the flame eater engine you have made, you can make the cylinder surface like that it will be fine.
Don't worry too much about the cylinder surface being shiny or gray, some members have advised me: "It's whatever you feel comfortable with" !!
The flame eater engine is much harder to run than 4-stroke engines, you have succeeded with it there is no reason why you are not successful with this engine .
 

CFLBob

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if the graphite piston lasts long in the cylinder of the flame eater engine you have made, you can make the cylinder surface like that it will be fine.
Don't worry too much about the cylinder surface being shiny or gray, some members have advised me: "It's whatever you feel comfortable with" !!
The flame eater engine is much harder to run than 4-stroke engines, you have succeeded with it there is no reason why you are not successful with this engine .
The flame eater still runs and that's my encouragement.

I did some measurements on the cylinder last night and I think it might be 0.878" diameter at the end that gets the spark plug. The piston is roughed out at 0.874. I haven't cut the slots for the rings, because the cylinder is on the lathe.

I think I'm going to keep going. I have enough steel to make another cylinder, but I'd rather not unless I really need to, and I'll find out once it's built.
 

minh-thanh

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The flame eater still runs and that's my encouragement.
I have enough steel to make another cylinder, but I'd rather not unless I really need to,
Do not be too important the diameter of the cylinder, if the diameter of the cylinder is larger or smaller, just make the piston according to the new size of the cylinder. It is always easier to make a new piston than to make a new cylinder.
Just making the cylinder as you were with the flame eater engine is fine .
 

CFLBob

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I spent some time figuring out what to do, since I suspect the cylinder might be too big now. I had piece of aluminum bar, just about the 0.873 final size about 2.5" long. I thought I'd turn down about half the length down to 0.5" diameter and chuck it in the lathe, then before machining the features inside the piston, I'd put the rings on it and see how the piston feels. After this machining and then running a green Scotchbrite on the cylinder to take off any burs, the piston falls in the cylinder, but it doesn't fall "fast". That seems pretty good. I think the goal is that when the rings are on, I should need to push my piston handle to get it fall, right?

PistonRingTest2.jpg


I don't know how to get the piston rings on. Those are the ones that Webster recommends in the drawing, 3/32" X .875" from Dave Reed at Otto Gas Engine Works. Since the OD of the rings is about .002 more than the OD of my piston and they fit snugly in the slots I cut, I have to "stretch" them to get them into the rings and I'm not having much luck. I'm trying to be gentle and not bend them. Or not bend them too much.

How do I get those piston rings in there?
 

Brian Rupnow

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Coat piston and rings with 30 weight oil. Set ring on top of piston and gradually work one end of ring down into top groove. Then work as much of the ring as you can (about half of it) down over the top and into the groove. Hold your breath. Push the remaining part of ring out so that it is resting on the land above the groove. Taking great care not to notch the piston with the sharp inside corner of the ring, work that part of the ring down so it snaps into the groove. I then put the second ring onto the piston from the other end. This avoids having to work second ring past first ring installed. This scares me right to death every time I do it.---Brian
 

aka9950202

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I run my engine with 1 piston ring. There are 2 slots as per the plan on the piston. My rings all snapped when trying to install the second ring. I had made 6 rings in total.

Good luck with your model i hope you have better luck than I did.

Cheers,

Andrew in Melbourne
 

CFLBob

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Well, thanks to Brian's suggestion, I got the rings in the piston but can't get the piston into the cylinder. The rings appear to stick out more in some places than others. Not loose, that I can tell. Possibly bent?

Piston_W_Rings.jpg


Considering they're standing well above the piston, it makes sense I'd have troubles getting the piston into the cylinder.
 

Brian Rupnow

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Next amazing trick--You should have put a 20 to 30 degree lead angle on the end of the cylinder opposite the head.(That is total included angle). That way with 30 weight oil, prayer, and tap-tap-tap on end of connecting rod, the lead in taper will compress the rings as the piston slides in. (piston, wrist pin and con-rod must be assembled first). If you haven't put the included angle on the cylinder, you can try using a small gear clamp as a ring compressor and put the piston in from the other end (although I haven't done that--too much chance of breaking a ring).
 
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