Werowance builds a webster

[bill70j]

When in doubt--use a little #638 Loctite on the thread. I guarantee that it will not unthread, but if you want to disassemble it after the fact, a wrench will break the Loctite bond quite easily. I never used any left hand threads when I built my engine. If you guys are going to mess around with these little engines, then you damn near have t have a bottle of green Loctite.

Thanks, Brian.

Appreciate the years of knowledge you bring to us neophytes. Especially in this case as regards your Webster crank design, valve lapping knowledge, offset cam machining info, and Viton ring specification.

I have incorporated your Webster mods, along with those of many others who post here, and am near first "pull."

Bill

 

[werowance]

need a little help, looks like the best approach to doing the head is using a boring head on the mill. but since its a blind hole (refering to the combustion chamber) how does one not end up will several grooves on the inside bottom of the head? on the lathe I can flatten than back out with a skim cut from center to edge and it will be flat (learned that on this site a few years ago). with a boring head I don't have that ability, I would have to stop and turn the screw and start again. only direction I can go is up/down when the mill is running to bore a hole. so whats the technique here? I looked and several builds and they all used the boring head. I was about to just drill for the spark plug hole then transfer to the lathe and 4 jaw. but it does seem easier to keep it in the vice so after that's done the other holes could be drilled and tapped without having to edge find all over again.

 

[bill70j]

I used the lathe method you describe. I find it much easier to bore to dimension on the lathe rather than on the mill.

I first drilled the M-10 hole and the screw holes on the mill, then tapped the screw holes while still in the mill vise.

After that, I transferred the piece to the lathe and chucked it up in the 4-jaw to bore the hole. I later tapped M-10 hole.

 

[Brian Rupnow]

It wouldn't matter if there were annular grooves on the inside bottom of the head. Nobody will see them, nobody will know about them except you.--Kinda like wearing dirty underwear!!! It won't have any effect on how the mixture burns. it was 10 years ago that I built my Webster, and I don't remember what method I used.---I just checked post #29 in my Webster build, and it seems that I did my cylinder head on the milling machine with a boring tool.
https://www.homemodelenginemachinist.com/threads/anybody-want-to-guess.7687/page-2

 

[werowance]

i really didn't make much progress this long weekend.... found I don't own a m10x1.0 tap or a 9mm drill so I ordered that. then i just started looking for and squaring up material. i have the head squared up and marked out, the valve blocks rough cut and the crank shaft to outside diameter and 1/2 extra long. found some 1/4 drill rod for the cam shaft but didn't cut it yet and called it a day. the head came from a huge plate of 3/4 inch aluminum that was nasty dirty and greasy but it was a free piece given to me so i cant complain...

 

[werowance]

on the points, the screw that goes through the pivot hole, should that be a shoulder bolt so that it doesn't tighten up to much on that area? saw somewhere on an engine build that the points were eratic because the screw was to tight.

then next question, on the rocker arm spring, i had an old Honda starter recoil spring and rope and thought i was going to use that. well the spring ( i left my notes at home so these are guesses from memory) is about .218 wide and plans call for .281 and then thickness is about .022 thick and plans call for .010. do you think this will still work out? i also have an metal bandsaw blade that i broke the other day, its pretty springy, i could grind it to size and thickness maybe? defanetly not going to be able to cut it though.

 

[Brian Rupnow]

Just use a standard #10 socket head capscrew, but before you do, run a 3/16" drill down thru the pivot hole on the points. That will take out very little material, but will let the points pivot freely. Put a dab of Loctite on the portion of bolt threads that screw into the sideplate.--Only a dab, and don't get it on the points. Your spring will work fine. For the other bolt which locks the points at some specific setting, I find that a #6 button head capscrew works really well.

 

[werowance]

looking around to see if I can find some ball bearings to substitute for the brass rod bush on the crank side and it seems I can get .250 id ball bearings with the correct .375 od that the plans call for. on the .250 the plans say that should be .281. do you think .250 on the crankshaft would be strong enough for this engine? would be nice to use ball bearings instead of brass bushing bearing on it.

also picked up a 9mm drill for the spark plug hole on lunch today. hope to get some shop time tonight and get back to work on the head.

 

[bill70j]

would be nice to use ball bearings instead of brass bushing bearing on it

932 bearing bronze would work, but agree brass would not be as effective. Same with the wrist pin bushing. Not sure about using ball bearings in a conrod application.

 

[Brian Rupnow]

1/4" rod will work for the crankshaft.--then again, you shouldn't have trouble getting 9/32" i.d. bearings.

 

[werowance]

well we now have a head. it didn't give it up easily though... broke a drill in it but fortunately it had gone far enough to just make a dimple on the other side, I used a spring loaded center punch to get it started then ground the tip of a sheetrock screw to a very small tip and managed to drive it out without damaging anything. got it all bored and bolted up.

 

[werowance]

 

[werowance]

now onto the cylinder. looking at the plans I see no indication of what the outside diameter should be. maybe I'm overlooking it I'm not sure. I'm thinking since the head is 1.5 then maybe the outside of the cylinder should be to? I happen to have a piece of 12l14 in 1.5 dia but ill have to take a light skim cut on it so that will probably make it 1.45 or so. you all think this will be good enough or do I need to source some larger material?

 

[Brian Rupnow]

Yes, you can make the outside dia. of the cylinder a bit smaller without any trouble.--Brian

 

[werowance]

so you think 1.45 is good?

 

[Brian Rupnow]

Yes, 1.450 is good.

 

[werowance]

still tossing around the bearing idea on the rod. now I m considering needle bearings like you would find on the rod of a chain saw. for the crank shaft where the bearings would run on, I'm thinking drill rod hardened and then polished? or am I just looking for trouble there and just stick with doubled up ball bearings? just thinking about things since I cant do any machining right now.

 

[Brian Rupnow]

Don't use needle bearings. Use 0.281" diameter ball bearings. Okay--I just did a web search and I couldn't find 9/32" ball bearings. Your other options are to use 3/8" diameter ball bearings and put a sleeve in them to bring them down to 9/32" or else to use oilite bronze bushings.

 

[Cogsy]

I agree with Brian that you don't need needle rollers. Needle rollers will generate more friction than balls and your shaft needs to be appropriately hard (not just 'any old hard') and tremendously smooth as well or you will get failure quite quickly. The only reliable way to use them would be to install an inner race for the needles to run on and then you have about the same weight and size as balls. The needle rollers will have a higher load rating than the balls but you don't need a high load rating in this application.

 

[werowance]

about to get the bore done on the cylinder. now I know why its called "boreing" becaue its a real bore going that slow and so many passes. I have to stop and find something else to do to wake me up.... started out with a sharp "V" shaped grind on the cutting tip till about .840 for fast cutting and then reground it to more of a "U" shaped tip for better finish. I'm at about .860 as of last night and called it quits, its like watching paint dry in and out slowly 3 full sets before advancing to a deeper cut so I don't end up with a taper hopefully. picture below is with the "V" grind on the tip. its a homemade boring bar with a broken drill bit ground as the cutting tool and a set screw in the tip. works pretty good. its what I used on the flame eater engine build on 303 stainless - this is 12L14 I'm cutting for this engine.