Bob Shores Little Angel

[cncfreak]

I'm going to try any produce Bob Shores little angel. Has any one here build this unit. I'm thinking of inlarging it a little. Just looking for pointers.
Latter.

[WOODKNACK]

I has thinking about getting that last year. let me know how it looks. Im still interested in building one too!

[Spinnetti]

Hi... I'm building the 'Hercules' which is basically the same thing (also by Bob), but smaller.

So far, I'm doing it all 'by hand' (No CNC), but I am playing with the head design in INventor 8. As is my nature, I'm redesigning the whole thing as I go, so its slow going. Currently I'm taking a diversion to build a crank grinder.

The plans and castings are worth the money he asks, though the dimensions tend to be scattered and not all drawings agree with each other. I tend to redraw them in cad so I can 'test fit' the parts.

There are several good shows around the country, and some folks have made some truly amazing engines...

[NOCARRIER]

This is some pretty neat stuff !

Could you possible shed some light on your venture of bulding a crankshaft grinder.

[I.C.O.N.]

I recently bought the plans for the little angel and got the material all laid out. But these 60-70hr weeks are slowing me down. I plan to do as much as is worth while on CNC. I am going to try and transfer everything to cam and write one lathe program to pump out a bunch of different parts from 1" stock.
Bob seems like a great guy, every time I have a question on the drawings he comes back with the answere the next day.
I can't wait to reallly dig into it.
If anyone else is going to go through this on cnc's maybe we could get together on the cad drawings and programs. I power by mastercam.

[Spinnetti]

Originally posted by NOCARRIER This is some pretty neat stuff ! Could you possible shed some light on your venture of bulding a crankshaft grinder.

Most of the engines call for milling or cutting the journals on the lathe. I did that once and hated the hard interrupted cuts and chatter on my lathe. I also had a hard time getting the counterweight sides cut correctly. Most guys just cut a crank out then bolt on the counterweights, but I want my cranks and cams to be just like modern automotive stuff.

There is a newsletter now out of print called strictly IC that has various plans for making cam and crank grinders. I'm designing my own, but using ideas from some of these. If you do a web search, Bob still sells all the issues, and they are worth the money. I bought every issue ever published.

Basically the grinder is a couple shafts, with the ability to cut on a eccentric. Its really hard to describe though. Take a plate and mount a grinder on it (in my case, a belt driven shaft powered by a Porter Cable router motor). Pivot one end, and the other end is held off the horizontal plane by a micrometer screw. This sets the diameter. Another shaft holds a chuck that can be adjusted off center to get the throws. Another motor turns that shaft. I'm making mine a bit more complex with 3 shafts and the middle one can hold an eccentric pattern so I can use the same tool to cut both Crank journals and Cam lobes. I know I probably just confused you, but like I said, its hard to describe!

[NOCARRIER]

I think I have an idea of your explination of a cam grinder.

Am i correct in saying that it works somewhat similar to a key copying machine?

But instead of cutting flat keys, the stock it is rotated on one side which is directly connected to another part of the machine that, when turns causes the cam portion to rotate under the grinder.

With an eccentric to cause the grinder to "rise" and "fall" onto the stock you are grinding.

How do you design the geometry of the eccentric to cut the journal?

Super cool stuff !!!!!

I guess that after you design the eccentric all you got to do is flip 180 degrees for intake and exhaut.

[Spinnetti]

Originally posted by NOCARRIER I think I have an idea of your explination of a cam grinder. Am i correct in saying that it works somewhat similar to a key copying machine? But instead of cutting flat keys, the stock it is rotated on one side which is directly connected to another part of the machine that, when turns causes the cam portion to rotate under the grinder. With an eccentric to cause the grinder to "rise" and "fall" onto the stock you are grinding. How do you design the geometry of the eccentric to cut the journal? Super cool stuff !!!!! I guess that after you design the eccentric all you got to do is flip 180 degrees for intake and exhaut.

Oh yeah! A key cutter machine is the basic concept. I guess you figured out what I meant after all!

On the lathe, turn the basic cam and the maximum diameter of the lobes, then grind the profile.

The distance between the pivot shaft and the profile (cam) shaft sets the 'scale' of the final part. For instance, you can changed the location of the pattern shaft to get 1:1 or 1:2 or 1:4 motion.
I planned to get an old cam of something (or use one of my new race cams for my race car) to establish a profile. If you want to get really fancy, just do the profile in cad, use your CNC mill to route out the profile in some .250 or so thick stock, and mount it on the grinder shaft with a set screw. By marking it and using a dial wheel, you can simply loosen it up on the shaft and rotate it to the next spot to cut the next cam lobe.


Cheers,

Dave.