Anybody want to guess---

[Brian Rupnow]

I then made up a couple of round plugs with stepped diameters---the smaller diameter turned to fit in the reamed hole in the end of the rod, and the larger diameter to match the large diameter at each end of the rod.--I inserted the plugs and used them to trace around with my scriber, so that I would be able to clearly see the finished sizes when the plugs were removed.

 

[Brian Rupnow]

And this is the result---Nice clear lines to see---Then I trimmed away the unwanted material with my bandsaw. I try to leave about 0.030" of metal for the final step after sawing.

 

[Brian Rupnow]

This next step, I had never done before. Everything else I have "rounded off" was done on my big stationary belt sander, "by eye". That method wouldn't work in this situation, so I did it in the mill. I made up a small fixture block which held a pin the correct size to fit the end of the con rod over. (Two different fixtures, because two different sized holes in the con rod ends.) I must say it worked well, but I didn't like getting my fingers in that close to a revolving cutter. First I tried it bare handed, but that was too scary. Then I put on a pair of leather work gloves, all the time remembering all the horror stories about gloves being sucked into revolving machinery. To say I was being very carefull would be an UNDERSTATEMENT!!!! At any rate, the process works very well, and I still have all 10 digits.

 

[Brian Rupnow]

I think the results speak for themselves. I am very happy with the way this connecting rod turned out, and I guess that my next part to build will probably be the piston and some bushings for the rod ends.

 

[Mosey]

I then made up a couple of round plugs with stepped diameters---the smaller diameter turned to fit in the reamed hole in the end of the rod, and the larger diameter to match the large diameter at each end of the rod.--I inserted the plugs and used them to trace around with my scriber, so that I would be able to clearly see the finished sizes when the plugs were removed.

You might consider buying a compass to lay out those circular lines. You can get very sweet old Starretts for cheap prices on EBay. Quicker than making plugs.
Also, I suggest using hard material for those fixture blocks and pins. Less wobble than aluminum.

 

[Brian Rupnow]

Mosey---I'm a design engineer. I've got a whole drawer full of compasses. Hard to use though, after the holes are already drilled. ;D ;D ;D I did have the lines drawn on there, just as you suggest, but the drilling and reaming raises enough swarf that it wipes them away.

 

[mklotz]

I've got a whole drawer full of compasses. Hard to use though, after the holes are already drilled.

Drill a hole in a suitably sized ball bearing and mount it to one of the compass arms.

 

[Brian Rupnow]

Marv---What a marvelous idea!!!! I could have cheated and just put a piece of appropriate sized stock back in the reamed holes and used a compass, but I already had a "plug" of brass with the two diameters I needed on it. The aluminum piece took me 5 minutes to turn. And Marv---Thanks for taking the time to have a look at the post, and for commenting.

 

[black85vette]

Sometimes I feel a bit like I'm working in a vacuum here.

Brian; I am somewhat torn when I have nothing useful to add or no questions to ask. Hate to just keep repeating "Looks great so far". But I am taking notes and plan to try a couple of new techniques I have seen in this build.

So: looks great so far. Keep up the nice work. Thm:

 

[ozzie46]

Nope! Not working in a vacuum.

We're here.

I following so many threads if I commented on them all I wouldn't get anything else done. ;D ;D ;D


Ron

 

[vlmarshall]

Looks great so far. ;D


Sorry I didn't post sooner, I was busy chasing a ball bearing around on the floor with a hand drill.




Well, I could have been. ;D

 

[Maryak]

Brian,

Following along, gotta agree with B85V.

Speaking of old tricks - A wooden plug in the hole with a piece of brass nailed to the end gives a good centre for an already drilled hole.

Just another way to skin the cat.

Best Regards
Bob

 

[Metal Butcher]

Brian your build is coming along real well, Nice work!

If you ever decide to make the ball end caliper that Marv suggested, please post the set up and machining information. I would like to have it as a back up solution to the standard lay out procedures I use. But, I can't picture the set up for drilling a hole in a ball bearing. Every time I try to handle one it runs away on me, and I imagine its like trying to grab hold of a greased pig!

Good tip Marv, thanks.

-MB

 

[zeeprogrammer]

Sometimes I feel a bit like I'm working in a vacuum here.

You're not. I always read your posts.

 

[Brian Rupnow]

Thanks for the comments guys.---Metal Butcher--You'll laugh when you read this.---I too was wondering just how on earth do you fixture and locate the center of a ball to drill it, back a couple of years ago when I was building the fly ball governor. --You put it in a 3 jaw chuck in your lathe and drill it with a drill mounted in a tailstock chuck. Works like a charm, and once somebody pointed it out to me, it was so glareingly obvious that I felt kinda foolish!!!

 

[cfellows]

Chuck--So whats the verdict on your adaptation of Jan Ridders "fume" carburetor? Are you 100% happy with it?-Would you recomend that I go that route for my first internal combustion engine. If there is something better, what do you think it is, and do you have any idea what they cost. I am an absolute "babe in the woods" when it comes to this small an induction system.---Brian

Yes and no. From a performance perspective, it's outstanding. Easy to adjust the air mixer, starts first time, every time, and never misses a lick. However... there's no throttle adjustment, so the engine takes off and runs full tilt unless you have it governed. You can adjust the speed somewhat by making the mixture run rich, but it also makes the engine run uneven. So, it needs some kind of butterfly or other adjustable restrictor between the engine and the air mixer.

Chuck

 

[Metal Butcher]

Thanks for the comments guys.---Metal Butcher--You'll laugh when you read this.---I too was wondering just how on earth do you fixture and locate the center of a ball to drill it, back a couple of years ago when I was building the fly ball governor. --You put it in a 3 jaw chuck in your lathe and drill it with a drill mounted in a tailstock chuck. Works like a charm, and once somebody pointed it out to me, it was so glareingly obvious that I felt kinda foolish!!!

Thanks Brian. I know the three jaw will center (roughly) and hold it. However, It may or may not be accurate enough for the application in this case. Holding it in the two jaws of a milling vise does not appear to be an proper set up, as it likely damage the ball bearing, and/or vise jaws.

Since a ball bearing is hardened steel vs soft brass, it makes it difficult if not impossible to drill with the HSS drills that the average hobbyist like me might have.

After putting in a little thought I came to the conclusion that holding the ball bearing in a collet, and drilling it with a carbide drill drill bit would be the only approach I would venture to try, without annealing the ball bearing first.

-MB

 

[shred]

I made a flattened ball bearing for squaring rough stock a while back: http://www.homemodelenginemachinist.com/index.php?topic=4409.0

Easy to do in a collet block-- put the bearing in a small pocket or somewhere so it doesn't roll around, and stick an appropriately sized collet on over it and tighten up.

 

[mklotz]

I've used the collet with a backstop technique for drilling balls on a lathe.

If you want a somewhat firmer grip than the collet can apply, you might consider a variant of the jig I used to drill some small brass balls for my PMR model horizontal mill...

http://www.homemodelenginemachinist.com/index.php?topic=1415.msg10262#msg10262

For drilling spheres on a mill or drill press, two flat plates with holes and some clamp bolts will work. Here's a version in wood that I used to drill some wooden spheres for a friend...

http://www.homemodelenginemachinist.com/index.php?topic=6852.msg73678#msg73678

 

[Brian Rupnow]

I started out my Sunday by taking the cylinder off the frame and honing it. I have an old brake cylinder hone that I bought about 30 years ago, and since I never ever throw tooling away, I thought it had rested in the drawer long enough. I set the cylinder up in my vice, coated everything liberally with cutting oil, chucked the hone up in my variable speed hand drill, and had at it. I maintained a "medium speed" with the drill, and kept moving the hone from one end of the cylinder to the other as it revolved. you have to be very carefull while doing this, because if you slide it too far out either end, it gets exciting real fast. (If you have ever used one of these things, you know exactly what I'm talking about!!!) I'm not sure if the results will ultimately make any difference to the way the engine runs, but I figured it wouldn't hurt anything.