Yet Another Webster Begins

[CFLBob]

A very Merry Christmas to all reading this on the holiday.

I would like to test the valve with a vacuum. After the change to the taper, if I put the valve in the guide as it was supposed to work, but without the pin to keep it from falling out - it falls straight through. Nothing's holding it in the valve guide. When I try the test by sucking on it with my mouth, it doesn't open. I don't know if I'm blocking it, though.

Something like this Horrible Freight tester:
https://www.harborfreight.com/mityvac-vacuum-pump-39522.html
The big problem is I have no idea what's good enough. Just a number PFA (Pulled From Air) example, if I measure that 7 PSI opens it, is that good?

 

[minh-thanh]

The big problem is I have no idea what's good enough. Just a number PFA (Pulled From Air) example, if I measure that 7 PSI opens it, is that good?

Are you asking about the pressure required to open the intake valve ?

 

[CFLBob]

Yes, I was. I'm trying to find out why it isn't working.

 

[minh-thanh]

but without the pin to keep it from falling out - it falls straight through. Nothing's holding it in the valve guide.

It seems good enough for me, if it were me I would check the springs - if the exhaust valve is airtight
I don't test the vacuum so I don't know how much pressure is enough
And :
Check the valve block and connections: make sure all are airtight

 

[CFLBob]

Thanks for your input. When I try the test of putting my mouth over the intake block, the exhaust valve isn't there. I just have the top slice of aluminum with the valve cage in it. I don't get the sensation of air coming through, like I do if I push on the valve.

What would happen if the intake valve wasn't sealed well? It seems like it would open during my test anyway, and sealing well would keep it closed during the exhaust stroke.

 

[minh-thanh]

Hi !
when I check the valve with the valve seat,
If it's airtight, I would turn the valve 45 and 90 degrees from the first position and check again. if all positions are airtight I'm sure the valve and the valve seat are airtight.
The truth is I haven't done the Webster engine yet
And I don't know what the valve block looks like
I'm just speaking the way I know it on my engine

 

[CFLBob]

In the last week, the parts for the fuel tank got in and I rebuilt it with the gasoline resistant cap and fuel line.

I tapered the valve guides on both the intake and exhaust sides. While everything was apart, I lapped the valves against the valve guides with 320 and then 500 grit optical grade abrasives mixed in some grease. The area that had been ground was visibly changed.

The exhaust valve was a little sticky in the valve guide so I built a little valve holding fixture to fine polish the shaft. I ran the valve in the lathe, held 240 grit sandpaper on the stem for a while, then switched to 500 grit sandpaper. If I hold the slice of valve block horizontally in the position where the valve should drop out, both valves drop freely. The springs work well, everything seems like it should be working.

When I crank the flywheel, I get no motion of the intake valve. I tried adding another gasket, between the valve block and the cylinder head. No difference. I haven't tried fuel, yet, I'm just pessimistic about it working.

As I've said a bunch of times, the only clues to compression I have are that if I take off the valve block and put my finger over the hole into the chamber, as the piston compresses the pressure will push my finger out of the way and make snorting sounds. With the valve block and carb in place, Webster says that as you turn the flywheel it will make that sort of sound. It does.

I was thinking of just replacing the valve assembly with a little piece of sheet metal screwed into the holes that the valve block uses. That should give me the feel test of the piston bouncing against the compressed air or resisting being pulled back.

Before running in the engine powered by my drill, I found it really difficult to get the piston into the cylinder. It would strange if it was too loose after running.

 

[minh-thanh]

"When I crank the flywheel, I get no motion of the intake valve. I tried adding another gasket, between the valve block and the cylinder head. No difference. I haven't tried fuel, yet, I'm just pessimistic about it working. "

Put some oil w20 or w40 in the valve and the valve seat:
If you get some compression with it, your valve and valve seat aren't really airtight

Make sure: Cylinder and piston - rings are airtight !!
Because if they are not airtight then you cannot get the effects you say

CFLBob
I usually test compression like this: when I pull the piston back to the BDC , when I release the flywheel ( without cylinder head , I sealed the cylinder by hand )
1 / With piston and clean cylinder: piston will go up TDC about 1/2.
2 / piston and cylinder with a little oil w40: piston will go to TDC, or at least near TDC
That compression is good enough with me.

 

[wburnett2922]

simple test but a bit messy remove spark plug fill cly about have full oil put plug back hand push piston against oil if any leaks you will see them bill

 

[werowance]

hi Bob, on my webster, turning it over by hand i cant see my intake move either. and with a video of it running i only see it move just a hair. it doesnt open as much as th exhaust valve which is mechanicaly opened.
the spring on mine is very soft. you can jus lay a finger on it with very little push and it will open.

do you have any old broken drills or grinders laying around? i ended up getting the intake spring off the brushes of i cant remember if it was the drill or grinder - i had both laying in the corner broken. they were very soft. the exhust i just used a spring out of the kit.

another thing i notice helps on mine. squirt a good squirt of 5w30 (just what i had on the shelf for wifes Yukon) on the valves so it runs down the shaft and into the ports around the shafts. i was just doing that to make sure they were lubed but then noticed it was easier to start when it was new. once it broke in it became easier and easier to start.

good luck and dont let it get you frustrated.

 

[CFLBob]

hi Bob, on my webster, turning it over by hand i cant see my intake move either. and with a video of it running i only see it move just a hair. it doesnt open as much as th exhaust valve which is mechanicaly opened.
the spring on mine is very soft. you can jus lay a finger on it with very little push and it will open.

do you have any old broken drills or grinders laying around? i ended up getting the intake spring off the brushes of i cant remember if it was the drill or grinder - i had both laying in the corner broken. they were very soft. the exhust i just used a spring out of the kit.

another thing i notice helps on mine. squirt a good squirt of 5w30 (just what i had on the shelf for wifes Yukon) on the valves so it runs down the shaft and into the ports around the shafts. i was just doing that to make sure they were lubed but then noticed it was easier to start when it was new. once it broke in it became easier and easier to start.

good luck and dont let it get you frustrated.

No broken old drills or grinders, but I have something that I should have thought of before. Guitar strings. The ones that are plain wire (not wire wound on wire) are music wire, and in particular, in one set of these I have a .013 and .010 diameter music wire about 3 feet long. If I need another diameter, there are other versions of string sets with different diameters.

I wound the intake spring with .015 music wire instead of the .013 that Webster calls for - because I have a lifetime supply of .015 from making the flame eater. Sacrificing a set of guitar strings to take one to wind into a spring isn't as expensive isn't as buying the usual amount of music wire when you include shipping and all. I may not even have to sacrifice a set. I can replace the strings on one of the guitars and take the extra few inches I cut off to make the spring.

As for the last line - too late! A friend suggested I take time off and just let it stew in the back of my head. I have some important "honey do" and "better do" jobs that can be full time for a week or so, including rearranging the shop. Maybe I'll hook up the fuel and try it. If it doesn't work, I'll stew on it for a week or whatever.

 

[Steamchick]

FYI: Stiffness is related to the cube of the radius - so for your wire: 0.015" diameter is 34% stiffer than the 0.013" wire - assuming the coils, wire material and temper, etc. are the same. A third more stiffness means the pressure to lift the valve on suction needs to be 3/4 of the pressure that opens the planned spring - so it probably makes a BIG difference to your engine. I had the same with an auto-valve on my flame eater...
K2

 

[werowance]

Bob,i encourage you to make some springs as a learning process so that i can learn from you. but in the mean time meaning tomorrow ill look and see if i still have the other grinder brush or not. if i do its yours, just a postage stamp which ill pay for from VA to FL

but if you wind the spring please share as much info as you can. yeah im asking for my benefit but i should say for eveyones.

 

[CFLBob]

Look around post 286 on page 15 - from September. I made the springs then and there was a lot of back and forth about it, along with the web page I've used as reference.

http://www.deansphotographica.com/machining/projects/springs/springs.html

 

[stevehuckss396]

If you made the spring with larger wire, you will have a stiffer spring. Wind the spring with more turns per inch (finer pitch) than the plans call for and that should lessen the stiffness. Maybe Steamchick can do some more of those fancy mathimaticals and figure out how much of a change you would need to do to get you back to where the .013 wire would have been. Or if it's even possible to get there given the fixed length you have to work with.

 

[werowance]

Thanks Bob, actually i did already read those posts and understood that you had already wound some springs. thing is - i have never done it and wanted to learn as much as i could from you on it. that said, ill digress untill i get a chance to find the brush spring. but you have a good one and good luck in the mean time. watching and hoping for you.

 

[Steamchick]

If you made the spring with larger wire, you will have a stiffer spring. Wind the spring with more turns per inch (finer pitch) than the plans call for and that should lessen the stiffness. Maybe Steamchick can do some more of those fancy mathimaticals and figure out how much of a change you would need to do to get you back to where the .013 wire would have been. Or if it's even possible to get there given the fixed length you have to work with.

Pretty simple mathemateecals...: the 0.015" wire needs 30% more turns than the 0.13" wire to soften it. - Maybe a 30% longer valve stem needed? - Or reduce the pre-compression by 30% and you will have the same opening pressure, but only 2/3rds of the full open valve stroke... The engine should start, but be limited in performance compared to the correct spring.
But there are other ways to "kill the pig" when you only have the "wrong" size of wire: Sometimes spring makers design springs to be barrel shaped... the required width at the ends, but tapering to up to twice the diameter in the middle, so to get the length of wire in fewer turns (due to the larger diameter). It's the length of wire that counts. e.g. A spring at 30% bigger diameter would only need the same number of turns as the design to compensate for the 30% stiffer wire....
Does that help?
K2

 

[CFLBob]

Pretty simple mathemateecals...: the 0.015" wire needs 30% more turns than the 0.13" wire to soften it. - Maybe a 30% longer valve stem needed? - Or reduce the pre-compression by 30% and you will have the same opening pressure, but only 2/3rds of the full open valve stroke... The engine should start, but be limited in performance compared to the correct spring.
But there are other ways to "kill the pig" when you only have the "wrong" size of wire: Sometimes spring makers design springs to be barrel shaped... the required width at the ends, but tapering to up to twice the diameter in the middle, so to get the length of wire in fewer turns (due to the larger diameter). It's the length of wire that counts. e.g. A spring at 30% bigger diameter would only need the same number of turns as the design to compensate for the 30% stiffer wire....
Does that help?
K2

Steamchick your mention of wire diameter made sense when you posted it - not the cubic relationship specifically, just that thicker wire would take more force to move. Steve's mention of more turns reducing the force to move the spring was not intuitive. Since you're commenting on it, is that because with more turns, every little piece of wire moves less? I can't see how more turns can affect the spring constant but maybe less length change as in Hooke's law?

 

[Steamchick]

Dead right Bob! I thought to mention Hooke's Law, then didn't want to blind everyone with science. Spring constant goes down proportional with length of rod in torsion. A coil spring is just a straight torsion bar coiled for convenience... The stiffness of a beam goes up as the cube of the radius of gyration. (I think... Unless you can teach me otherwise?). But if you can teach me better, then great! I've never studied spring design, or read the books (I have some... maybe I should read them?). A man with a little knowledge (or the internet?) can be dangerous!
K2

 

[CFLBob]

Dead right Bob! I thought to mention Hooke's Law, then didn't want to blind everyone with science. Spring constant goes down proportional with length of rod in torsion. A coil spring is just a straight torsion bar coiled for convenience... The stiffness of a beam goes up as the cube of the radius of gyration. (I think... Unless you can teach me otherwise?). But if you can teach me better, then great! I've never studied spring design, or read the books (I have some... maybe I should read them?). A man with a little knowledge (or the internet?) can be dangerous!
K2

Thanks for clarifying that.

Likewise, I've never studied spring design, but unlike most electrical engineers, I took the class commonly called "Deformable Bodies" where everything bends, sags, expands and all those real world things. I just don't recall anything that would help here. But it has been many, many years since I cracked that book