Anybody want to guess---

[mocaquita]

Hi,
Looks like you're coming along on your beautiful Webster quite nicely! I was looking at your picture of the rocker arm being machined and I think I see an endmill being used in a drill chuck. Bear in mind drill chucks are designed for movement in the Z axis only. No side movements for these. If you're side milling, the chuck can work its way off the taper and fall off. A real safety issue to be aware of, no one likes a loose spinning chuck. You'll have strength and runout issues in a drill chuck also. Not trying to be a jerk here, just wanted you to be aware.

Dave

 

[cfellows]

Looks real good, Brian. I always look forward to seeing your progress!

Chuck

 

[black85vette]

Keeping an eye on the progress. Like how you use the illustrations to show your plans.

 

[Longboy]

Looking good for Webster up in Canada there Brian. You're gonna like the Viton piston ring setup. Simply it works and wears well. Model engine carbs do the job here too. For the Webster, a .10 -.15 engine size is right. I have an OS .10 carb and I have just gotten a Traxxis .15 buggy carb I wanna try from Ebay as a vender had brand new carbs on auction I got with shipping for less than $20. Tower Hobby had new OS carbs the right size around $30 plus ship. Cruise the Ebay listings for your carb needs. On my avatar photo is my "Camel" Stirling engine. The 2.25 in. dia aluminum flywheel is spoked with #10 flat slotted brass machine screws file finished flush with the flywheel outer diameter. Different purpose than your brass slug enhanced flywheel but the same contrast in materials. 8) Dave.

 

[Brian Rupnow]

Hi,
Looks like you're coming along on your beautiful Webster quite nicely! I was looking at your picture of the rocker arm being machined and I think I see an endmill being used in a drill chuck. Bear in mind drill chucks are designed for movement in the Z axis only. No side movements for these. If you're side milling, the chuck can work its way off the taper and fall off. A real safety issue to be aware of, no one likes a loose spinning chuck. You'll have strength and runout issues in a drill chuck also. Not trying to be a jerk here, just wanted you to be aware.

Dave

Dave B---Thanks for your concern. I am aware of that safety issue, and when using a larger end mill in steel I mount the cutting tool in a proper sleeve and draw bar set-up. For light cuts in brass or aluminum with a small cutter, I generally just mount the cutter in the chuck. I wouldn't go so far as to recomend the practice to others, but it works for me.---Brian

 

[Brian Rupnow]

Longboy---Do you have the part number for the Vitin o-ring, size information, or any info about the size of groove required in the piston?

 

[Brian Rupnow]

So here we are, with all the "Large Bits" finished and trial assembled. I haven't bought a spark-plug tap yet, and there are a couple of small oil holes missing, but for all intents and purposes, the big pieces are finished. I'm just about to start on the "fIddly bits" which are the valves and valve housings.--And I'm getting close to the time when I have to order the gears and get this piston ring business sorted out.

 

[cfellows]

Ah, yes, now you're getting to the parts that always give me the most trouble... the fiddley bits! But I'm sure you'll hammer it out much quicker than I would.

Chuck

 

[bearcar1]

I've been enjoying the journey so far Brian. That flywheel will set your Webster apart from the crowd as they say. Carry on old boy!! :big:

BC1
Jim

 

[black85vette]

Nice to see the big parts all together. Starts to give a sense of progress. Anxious to see your build of the valve assembly. I have yet to do one like that. Take lots of pics. stickpoke

 

[crankshafter]

Hi
This is going to be a real runner when it's finish. Really nice work Brian.
I see you are using bronze- bearings at the main-shafts as per plans. I used roller-bearrings. Are you going to use point ignition? If you are, I suggest you to mount the points on a separate disc w/radial slots for easy adjustment of the ignition timing.
If I going to build( def. I will :big I will do it that way.
If it's not clear, I will try to make a C.O Cad.
CS

 

[Longboy]

Longboy---Do you have the part number for the Vitin o-ring, size information, or any info about the size of groove required in the piston?

........O-rings are sold by size rather than pt.# in hardware stores. This is true for metric dimensioned rings also. The cyl. bore is 7/8th (per plan) so the correct size is 7/8 outer 3/4 inner 1/16th o-ring. A P1 cutoff tool is 1/16 in width and you just need a few .000 more height. The ring has to float in the groove so the height and depth of the groove will be greater than the ring size. The test is gripping the piston and to rotate with your fingers a lubed (WD40) ring around the groove for correct groove height. For the depth cut the ring does not protrude the outer piston diameter. The test is to install the lubed ring onto the piston and insert into the bore. If it doesn't go, increase your depth cut 2-4 thousandths at a time till it moves into the cylinder . If it goes in but shudders moving piston up and down the bore your close. The ring is dragging or rolling in the bore. Another few thousandths depth cut will get you there! You may want to use a round stock slug with just a practice groove to set your dimensions with the cyl. bore then tranfer to your finished piston. Let me know how it worked out ! Dave.

 

[Brian Rupnow]

I just got the following information form Hercules o-ring. For a reciprocating seal, such as you have with a piston in a cylinder, the O-ring size is dictated by the bore of the cylinder. Thus, a 0.875" bore will take a 7/8" o-ring. O-ring sizes are "Nominal"---this means that a 1/16" o-ring is actually 0.070" in cross section. I was told to make the ring groove in the piston .055" to .057" deep---this will leave the outer diameter of the o-ring sticking out past the side of the piston by 0.013 to 0.015", radially, so the actual outer diameter of the o-ring will now be 0.901" to 0.905" diameter. I was told to make the ring groove 0.095" wide, so that means there will be 0.025" total side clearance on the o-ring. I'm not sure I trust this information, as the person I spoke to didn't seem too sure himself, and I don't want to ruin the piston by machining the wrong size groove. I think I will now talk to a different o-ring mfgr. and get their opinion.

 

[cfellows]

I just got the following information form Hercules o-ring. For a reciprocating seal, such as you have with a piston in a cylinder, the O-ring size is dictated by the bore of the cylinder. Thus, a 0.875" bore will take a 7/8" o-ring. O-ring sizes are "Nominal"---this means that a 1/16" o-ring is actually 0.070" in cross section. I was told to make the ring groove in the piston .055" to .057" deep---this will leave the outer diameter of the o-ring sticking out past the side of the piston by 0.013 to 0.015", radially, so the actual outer diameter of the o-ring will now be 0.901" to 0.905" diameter. I was told to make the ring groove 0.095" wide, so that means there will be 0.025" total side clearance on the o-ring. I'm not sure I trust this information, as the person I spoke to didn't seem too sure himself, and I don't want to ruin the piston by machining the wrong size groove. I think I will now talk to a different o-ring mfgr. and get their opinion.

Brian, this kind of agrees with what I've heard before. I believe the width of the o-ring groove should only be .006" - .010" wider than the o-ring. And, I believe the depth of the groove should be .004" - .006" shallower than the thickness of the o-ring. That's the way I've got my Plumbing Parts engine set up and works fine. You'll likely have to chamfer the bottom of your cylinder bore slightly and use oil to get the piston w/o-ring into the cylinder. Those o-rings will shear of if there are any sharp edges.

Chuck

Chuck

 

[Brian Rupnow]

Okay guys--Here is the "scoop". I went over and picked up two Viton O-rings (one for a spare), and they gave me a photocopy of the page that they based their information on. I chose a 1/16" cross section based on info posted by Longboy (Which in reality is actually 0.070"). So, based on the top line in the chart,--The groove depth should be .055" to .057" and the groove width should be 0.095". A Viton o-ring is good for temperatures up to 400 degrees F.You can see one of the o-rings I got, laying on the chart in the top right hand corner.

 

[Brian Rupnow]

I also picked up a set of points and a condenser while I was out, and ordered an M10 x1 tap and an NGK CM6 sparkplug. I ordered the gears from W.M. Berg this morning.

 

[Brian Rupnow]

The points and condenser are a perfect fit on the engine, as per plans. The only thing I noticed is that a #10 screw is a very tight fit through the hole and slot "as provided" in the points----That was quickly remedied by running a 3/16" drill though the holes in the points.

 

[Brian Rupnow]

Crankshafter---I understand your reasoning with putting the points on a seperate piece to enable "timining" the points, but first I will try it "as per plan".---I looked on the web link at all the other people around the word that have had success building and running the Webster as built "per plan" so I will try it that way first. If I find that point timing is an issue, I will add a seperate mounting disc later.

 

[Brian Rupnow]

Progress was made in leaps and bounds today----I went over to my tooling supplier and picked up an M10 x 1 tap and a 9 mm drill, then over to Partsource to pick up the smallest sparkplug I've ever seen. (As recomended by the fellow who done the Webster plans I'm working from). Then home to make the ignition cam. That was the easy one. Then the exhaust cam---And I had absolutely no idea how to machine it. So---I made it up as I went along. First I turned a .712 diameter onto a peice of 3/4" mild steel out of my "parts" pile, then reamed a 3/8" hole in it while it was still in the lathe and then parted it off to 3/16" thick. I coated it with layout die, and after establishing a centerline on the face, I scribed a 9/32 radius and layed out the two tangent lines that lead up to the "lobe", and walked it over to my vertical belt sander and put two "flats" on it---then I was stuck!!! Thought hard for a while, then went and scrounged up an old 5/8" shoulder bolt and turned it to 9/16" diameter, with a 3/8" diameter "spigot" on the end of it, then drilled and tapped a 1/4"-20 thread in the center of it. I slid the cam disc (which now had two flats on it) over the spigot and locked it in place with a 1/4" shcs. Now that I had a "handle" of the desired diameter, I took it back over to the belt sander and "hand bombed" the cam untill it matched the diameter of the "handle' everywhere except where the lobe was supposed to be. As my old electrical engineer used to say "TEFC"---Totally Effective, Fantastically Crude----but it worked like a charm. I'm sure this method would be frowned on by a machinist with more skill than myself, but Hey---it worked.

 

[Brian Rupnow]

And here's a bigger picture of my "fixture"----The easy ignition cam is on the left---The difficult exhaust cam is on the right.