Yet Another Webster Begins

[coulsea]

The CM6 plug is fine for a Webster, the 1/4 32 plug is common in the model aeroplane world and is perfect for an Upshur size engine. some of the cheaper Chinese ignitions can be a problem with burning out the hall sensors but I have had no problems with a rcexl model plane ignition, I have one ignition box with a hall sensor on each engine. naturally some will say that you didn't really build all of the engine if you didn't build the ignition and spark plug yourself.

 

[stevehuckss396]

What fits that 1/4-32 thread?

Should I be looking for mechanical points or is there an electronic system that people use?

1/4-32 is the standard thread for a glow plug so model makers started making spark plugs with the same thread so a new engine could be started on glow plugs, dialed in, then switched over to spark ignition. Just one less thing to worry about when trying to get a fresh engine running. 1/4-32 spark plugs are available here. Also good quality 1/4-32 taps made in the USA.

http://www.miniaturesparkplugs.com/


Electronic ignitions can be fired using a hall sensor or points. One of my fellow MDMC members is building a Webster and is going to use the points from a 46-47 Nash or a 45-52 willy's because they are physically small. Roy sells a Barebonz CDI made specifically to be triggered by points. $45USD. That can be found here.

http://www.cncengines.com/ic.html

 

[stevehuckss396]

Electronic ignition systems are very fragile, and are not tolerant of bad grounds. If you get a bad ground it burns out the "hall effect sensor" and then you have to buy another.

You don't need to worry about that. You will be using points and they won't burn out. Also the CDI has a lot more energy than a normal 70's style system so it will net a better running engine.

A cheap coil and condenser will run 30 - 35 bucks. May as well give 10 more for a good ignition that has enough energy to jump a half inch gap.

Not telling you what to do. Just telling you what I would do.

 

[CFLBob]

Thanks everyone.

I used to do all the routine stuff on my cars when the ignitions were points, coil and capacitor, back when periodically cleaning and gapping the plugs was required. When electronic ignitions replaced that and made that maintenance less necessary, I learned a little about them but long since forgot. As an electronics guy, that's more my "home field" than mechanical and designing one would be closer to up my alley.

I think I'll get a CM-6 and a CDI.

 

[Brian Rupnow]

Actually, the coil is the expensive part. They run $50 Canadian here. The points and condenser are about $16 total. The CM6 sparkplug costs about $17 or 18 dollars.

 

[CFLBob]

The CM-6 plugs are $5.60 at the Advance Auto Parts store a couple of miles from here. I didn't think to shop for the other parts.

For the moment, I don't need the plug.

 

[CFLBob]

My first piece is complete. Well, the tap for the CM-6 plug isn't here yet, but that doesn't need the spot on the mill.

One hole broke through into the 1.000 x 0.500 bore - the bottom 4-40 hole in this view. Should I just put something like a small setscrew in there, or will the actual, designed in screw be enough to seal that? I believe this must be the combustion chamber.

 

[Brian Rupnow]

Try it with just the screws that hold the valve body on first. Dip the screw that goes into that broke thru hole into some Loctite before installing it. The trouble with putting in a set screw is that when the engine heats up and the vibration from running, that the set screw could work loose and fall into the combustion chamber, which is really bad ju-ju.

 

[CFLBob]

What do you think about a dab of Bondo, or another epoxy in the hole?

 

[Brian Rupnow]

You are getting into "Try it and see" territory. Remember--if it is in the combustion chamber it is going to see fire and pressure.

 

[Chophead69]

Please do not use bondo. If u need anything after u determined it does present a issue then use jb weld. And use a set screw if u like with it. It will not come out and it wont hurt ur project

 

[CFLBob]

Please do not use bondo. If u need anything after u determined it does present a issue then use jb weld. And use a set screw if u like with it. It will not come out and it wont hurt ur project

Thank you.

 

[CFLBob]

Broke a tap.

I was working on the base plate and broke the tap on the first 6-32 hole I was working on.

I think I'm going to get an annular cutter and then cut a plug to put into the hole. I've never bought one of these, so I don't know how to size it. If I wanted to cut out a quarter inch plug with the tap embedded, is that about 3/8 annular cutter? I think they're sized by outside diameter, not inside. The smallest I see is 7/16" anyway.

Is there a better way to cut out the tap?

 

[Brian Rupnow]

Try a 1/16" carbide end mill. That has worked for me in the past. There is a process using warm water with alum powder dissolved in it to maximum concentration. It will dissolve the tap but not bother the aluminum. You have to soak the part in a glass container of this liquid for a couple of days. I haven't used that method, and I see mixed reviews on how well it works.

 

[CFLBob]

That's the same things I've read about the alum. This piece is still full sized, so about 8x9". Not sure I have anything big enough to soak it in anyway.

The old trick of whacking it with a hardened nail punch worked. The tap is out. Before I give up on 6-32 and make those 8-32. I'll try making them 50% engagement holes, which is a .116 bit vs. the .107 for 75% that I used.

These are two different things being mounted to the base. I can't tell what they are from the plans at this point but going to 8-32 is about 1/32 diameter bigger.

 

[CFLBob]

It's a base plate.

The drill press seemed to have too much slop in it because the countersinks look and feel rough. I tried increasing the speed (cutter RPM) thinking it was chatter but that had no effect.

I have the tool paths set for the sides. This is set for a half inch EM, while I used 3/8 on the base. Other than the fact that my half inch EM might not be as sharp, I don't see where it matters. I do this kind of layout to save raw material.

I also have the CRS for the Cylinder chucked in the big lathe. Not sure which one becomes the next part.

Onward.

 

[CFLBob]

Time to update on progress. Most of the shop time in the last couple of weeks was spent in the cylinder. The prints say "12L14 Steel or Cast Iron". I ended up buying 1018 Cold Rolled Steel on my shopping session, so that's what it's made out of.

I spent some time trying to figure out how to transfer the marks for the four 4-40 screw holes, given tools I have, and eventually decided to chuck up the cylinder on my Sherline rotary table and drill the four holes as a bolt circle. I did the tapping using my drill press as a vertical guide and then spotted and drilled the other two holes on the drill press.

Overall view (on the Sherline/A2ZCNC mill)

The cylinder isn't finished; it's about .010 short of the .873 recommended in the drawings. I managed to break my telescopic gage for measuring the ID and am awaiting the replacement. I still have to make the piston and lap that to the match the cylinder.

If anyone is reading this and has experience with Viton piston rings, are those a good match to this engine? From what little I know, they should be.

I need to improve my fixturing before I cut the sides (tool path in previous post). I need to make another couple of clamping spots.

 

[Brian Rupnow]

Bob--I run Viton rings in all of my i.c. engines with great success. The only time not to use them is on a two cycle, where the piston has to pass over open ports in the cylinder wall. Use a 1/16" cross section Viton o-ring . Make the slot in the piston .094" wide x .058" deep. You only need one ring.---Brian

 

[te5745]

Bob--I run Viton rings in all of my i.c. engines with great success. The only time not to use them is on a two cycle, where the piston has to pass over open ports in the cylinder wall. Use a 1/16" cross section Viton o-ring . Make the slot in the piston .094" wide x .058" deep. You only need one ring.---Brian

How do you achieve the finish needed to not destroy the ring? Nickel plate?

 

[Brian Rupnow]

No, just bore or ream to size and hone the cylinder with a 3 stone brake cylinder hone. I also add a bit of 2 cycle oil to my naptha gas, about a 50:1 mix . I actually have worn rings out, although it is unusual. However, by the time a ring wears out the inside of that cylinder will be polished like glass.