Engine Valves

[davidyat]

Ved,
OOHHH, I like it! Looks like you are experimenting with using what we learned from the Sun-Planet Engine? For now, until you perfect the design for this one, I think I'll tackle Brian Rupnow's simplified beam engine. I've thought about an IC engine, but the ones out there look like more than I'd like to chew on. Keep me posted on your progress.
Grasshopper

 

[vederstein]

OOHHH, I like it! Looks like you are experimenting with using what we learned from the Sun-Planet Engine?

Yup. My experience with poppet valves is not good. As I've written before, when I tried to make a Webster I had a hell of a time getting the valves to seal even after several attempts. Eventually it went onto the shelf of shame then to an old gear-head co-worker to whom I gifted.

I know it's a crappy combustion chamber design. Generally you'd want a hemispherical chamber or one that causes a "squish". But I'm going for simple here. I don't see why a piece of roundstock shuttling in a reamed hole wouldn't have sufficient sealing. The method works for stirling engines and they have near to no power density. I guess I'll find out.

But if the idea doesn't work, making a new head and incorporating poppet valves shouldn't be too much of an issue.

I have the ignition on order. When I receive it I'll measure it up and figure out how to incorporate it into the design.

...Ved

 

[vederstein]

I've been quiet on this for some time, but I have been working on the engine:

The machined components are from the past few weeks and the castings I poured today. (I'm quite happy with how the gears and the cams turned out.)

...Ved.

 

[vederstein]

I machined the base casting and assembled the bottom end (minus the piston).

Overall, not bad, but I will need to rethink the connecting rod. My earlier connecting rod design from my Sun-Planet engine (Contessa) worked quite well. I may have to do something similar here.

 

[vederstein]

Well, now I know spool valves don't work for an IC engine. I got no compression.

I guess I need to redesign the head and try conventional poppet valves.

...Ved.

 

[teeleevs]

Conventional valves are the way to go but you have to bore the valve guide and seat at the one setting. Picture 1 is of a Hit n Miss engine I built about 10 years ago but I could never get it to run, even the miniature igniter worked, 2 the valves were made in two pieces, head was 10mm about 3/8" And stem 35mm long about 1.350" x 2mm dia 0.078" . Pic 3 a test setup I suspected valve leaks so my friend Gil made up this plate and put the valves under 20 psi pressure and no leaks detected. We will have to re-bore the cylinder and remake piston and rings. 4 I had several attempts to make the rings, they were made from a MAN valve guide. 5 this Galloway was the closest I could find on the internet to an engine my father and I used on the Central Queensland Gem Fields in the 1960s it had no manufacturers markings on it whatever, I did find out that Galloways were made in Queensland under license, 6 the miniature made entirely from memory, no photos or drawings were available.
Ted from down under

 

[vederstein]

Thanks Teeleeves.

As I've written before, I had such a bad experience with my failed Webster that I went with this spool valve concept. I tried several times to make the Webster valves with no luck sealing. I knew the route I took on this design was risky, but it's more within my skill set. I also designed the engine to redesign the head if my spool valves failed.

On contemplation, I have one possible way to recover. I don't know if the leak is from the valve spool or the spool guide. I'll disassemble and put some form-a-gasket to ensure a seal between the head and the valve guide.

I'm not expecting this to work, but it's worth a shot.

...Ved.

 

[vederstein]

Thus far all my attempts have failed.

I've redesigned the engine for poppets and made the valves and vale guides twice. My second try I get a bit less valve leakage, but no engine run. Not even a single fire with ether as a fuel. (Yes I have spark). I have no compression.

I can turn the engine with a drill, put my finger over the inlet or exhaust port and hear air getting sucked in from the other port. I disassembled the bottom end and manually ran the piston up into the cylinder. I can hear the air leak out of the valves.

I've tried valves from 303 stainless and 12L14 leaded steel. My valve seats are 360 brass. Should I be using some other materials? Is there a way to "coin" the valve seat to exactly match the valve? At this point I don't care if the engine wears out after running for five minutes, I just want a running engine. I've lapped the valves with a very fine grip lapping compound and can see a very good finish on the not-so-sealing surface.

I'm about to give up. This project has lasted far longer than I expected. It's cost far more than I expected. I'm about just say screw it, redesign the cams, and turn this thing into a steam engine. But I'll wait if anyone has any insights.

...Ved.

 

[danallen]

I had a terrible time getting the valves to seal on my first internal combustion engine - a Farm Boy. What ended up working was mounting the valve guide in the lathe in a 4 jaw chuck. Put in a perfectly straight rod that just fits where the stem goes. Indicate it until it runs true in two places as far apart as possible and then cut the valve seat.

 

[minh-thanh]

vederstein !
Maybe i'm wrong, but when i see your plan picture, it seems the valve and valve guide are wrong.

 

[Richard Hed]

Thus far all my attempts have failed.

I've redesigned the engine for poppets and made the valves and vale guides twice. My second try I get a bit less valve leakage, but no engine run. Not even a single fire with ether as a fuel. (Yes I have spark). I have no compression.

I can turn the engine with a drill, put my finger over the inlet or exhaust port and hear air getting sucked in from the other port. I disassembled the bottom end and manually ran the piston up into the cylinder. I can hear the air leak out of the valves.

I've tried valves from 303 stainless and 12L14 leaded steel. My valve seats are 360 brass. Should I be using some other materials? Is there a way to "coin" the valve seat to exactly match the valve? At this point I don't care if the engine wears out after running for five minutes, I just want a running engine. I've lapped the valves with a very fine grip lapping compound and can see a very good finish on the not-so-sealing surface.

I'm about to give up. This project has lasted far longer than I expected. It's cost far more than I expected. I'm about just say screw it, redesign the cams, and turn this thing into a steam engine. But I'll wait if anyone has any insights.

...Ved.

I have to admit, I know nothing about this, but is it possible to putt some fine lapping material on the valve seat and put the valve in and grind with that? It might work.

 

[vederstein]

is it possible to putt some fine lapping material on the valve seat and put the valve in and grind with that?

Yeah, I did that. I also took the head and with the valve(s) and valve guide(s). Spring loaded them from the rear and turned them in the lathe to lap the valves. That's how I got the very smooth finish on the actual mating surfaces.

(I think I just suck.)

 

[ranger]

Thus far all my attempts have failed.

I've redesigned the engine for poppets and made the valves and vale guides twice. My second try I get a bit less valve leakage, but no engine run. Not even a single fire with ether as a fuel. (Yes I have spark). I have no compression.

I can turn the engine with a drill, put my finger over the inlet or exhaust port and hear air getting sucked in from the other port. I disassembled the bottom end and manually ran the piston up into the cylinder. I can hear the air leak out of the valves.

I've tried valves from 303 stainless and 12L14 leaded steel. My valve seats are 360 brass. Should I be using some other materials? Is there a way to "coin" the valve seat to exactly match the valve? At this point I don't care if the engine wears out after running for five minutes, I just want a running engine. I've lapped the valves with a very fine grip lapping compound and can see a very good finish on the not-so-sealing surface.

I'm about to give up. This project has lasted far longer than I expected. It's cost far more than I expected. I'm about just say screw it, redesign the cams, and turn this thing into a steam engine. But I'll wait if anyone has any insights.

...Ved.

Hi,
A couple of things, how wide are the seats in the head? If they are quite wide,do you think they may seal better if they were narrower? ( less surface area means spring strength gives more contact pressure). Do the valves have enough clearance in the guides? To allow them to float and seat fully without binding. Another thing to try is to machine the seat angle of the valve to a more acute angle (1/2 - 1 degree) than the seat in the head, then give the head of the valve a sharp “ tap “ to help seat it. When or if it starts and runs, the slight difference in angles should cause the valve to continue to “seat” itself into the head until the angles equal, by which time the seal would be as good as you could hope for.
One more thing to consider is the coarseness of the lapping compound. In these small sizes, unless you are using “ultra fine” compound, the usual “fine” grade is maybe too coarse and probably leaves tiny “tracks” for the limited amount of compression to escape!
You could try “Brasso”, or “Solvol Autosol” instead?
Doug.

 

[Richard Hed]

Hi,
A couple of things, how wide are the seats in the head? If they are quite wide,do you think they may seal better if they were narrower? ( less surface area means spring strength gives more contact pressure). Do the valves have enough clearance in the guides? To allow them to float and seat fully without binding. Another thing to try is to machine the seat angle of the valve to a more acute angle (1/2 - 1 degree) than the seat in the head, then give the head of the valve a sharp “ tap “ to help seat it. When or if it starts and runs, the slight difference in angles should cause the valve to continue to “seat” itself into the head until the angles equal, by which time the seal would be as good as you could hope for.
One more thing to consider is the coarseness of the lapping compound. In these small sizes, unless you are using “ultra fine” compound, the usual “fine” grade is maybe too coarse and probably leaves tiny “tracks” for the limited amount of compression to escape!
You could try “Brasso”, or “Solvo Autosol instead?
Doug.

Very clever!

 

[rutzen]

I had no compression on my Rumely engine I am making so I made a collet to fit the 3 jaw chuck. Just a brass bush with a slit in it. Mark the number 1 jaw position. I took a very fine cut off the valve and used Solvol autosol to lap them in. I now have compression! Having said this I haven't got it running yet - still got the ignition system to make and some other jobs.

 

[propclock]

3 very important steps to small engine poppet valves /seat. Unless you have a perfectly!
true collet or chuck the valve is best machined in one chucking.
The valve seat must be true to the valve stem.
Sounds obvious , but not trivial in practice.
Finally the valve seat width must be very narrow .
At times you are forced to make 2 or 3 valve seat cutters .
1 for the 45 degree 1 at say 30 degree ? and one at 85 degrees
to get the seat width narrow. Just like your car. But very narrow ~ .010"
If you are lucky and your valve stem bore is perfect to your seat/cage bore
leave it sharp and all is well, otherwise , seat cutters are needed.
This was a very difficult lesson for me to learn.
I am sure it has been covered extensively elsewhere in the HMEM forum
but poppet valves work extremely well in small engines , but are difficult to make .
Just my 1.414 cents worth.

 

[ninefinger]

Have you taken into consideration the volume that the intake and exhaust passages have before the spool valves? With your design you have a lot more volume in your combustion chamber/valve passages so you are going to have a relatively low compression ratio.
Not sure if you can accommodate and increase the compression (taller piston?)

 

[vederstein]

I give in. This engine has defeated me.

I started with spool valves.
I redesigned to poppet valves.
I made the poppet valves and cages again.

Hell, I trying to get a single fire and I'm using ether (starting fluid) as a fuel.

No luck.

The plans for the engine (with 3D solid models) are here:

https://www.homemodelenginemachinist.com/threads/t-head-engine-plans.32917/#post-354673
It's unfortunate, but sometimes one just needs to admit defeat.

Score Card:
IC Engine: 2
Hobbiest: 0

...Ved.

 

[ranger]

Before giving up completely, how about another head, maybe from brass, so no separate valve guides/ seats etc. OHV layout with a more conventional combustion chamber. Use the existing valve operating gear, longer pushrods with a rocker from each side to reach the valves? This should reduce the combustion chamber volume and increase compression. Or perhaps an engine like the old Land Rover, with one side valve and one overhead valve per cylinder, or less parts, and use an automatic inlet valve?

 

[vederstein]

Being that four stroke engines still seem to elude me, I made some new cams, replaced the poppet valves back to the original spool valves, and turned the machine into an air motor.

It'll get painted eventually, but I just couldn't put this on the Shelf of Shame. I just have too much money invested in it.

Here's the video of it running on compressed air...