Crawler Crane Undercarriage Project

How would you make these idler rollers?

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I need to make 12 of them. I am starting with 3/4" round aluminum stock. They have a taper to help clear the drive dog tabs on the pads. This is one of those things that I look at and think " that shouldn't be too hard", and then when I start making them I end up with two or three and NONE of them are the same. I had been trying to make the taper using the side angle on my right hand turning tool bit, but that is problematic when it comes to doing the second (or left hand side if the part stays chucked up for the entire process, which I think it should). So, now it finally dawned on me, use the compound to make the taper.

My problems are:
Keeping concentricity. (I think I solved this by NOT over drilling the center hole, so that when I pull the stock out, I don't start off on the next part with an off center hole.)
Getting the same length on the shoulders on each side.
Getting the center rib in the center.

I am using my dial indicator on a mag base to move the carriage in as I turn the shoulder.
Should I be doing this with the part chucked once for the entire part? If so, should I be using a left hand turning tool for the left hand shoulder and Turing away from the chuck?

I think this all comes back to one of my very first questions when I got started with the lathe, "how do you know what steps and what order and how to decide what tool or procedure"?

Thanks for any tips or suggestions.

Jim
 
Sounds like you're on the right path...drill just deep enough to clear the made part, turn the shoulders down on both sides (enough that the front shoulder on the next part is already cut), with enough extra that the material removed by your parting tool cuts the rear shoulder of the first part and front shoulder of the second part to tolerance/spec.

Chip on, Jim!
 
I got some of my Enco order today and it had some of the 2-56 screws I was waiting on. I think I can shape the ears on the pads and get smooth operation.
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Jim
 
It is ALIVE! Got some good stuff done today on the crawler project. I still don't have the upper or lower rollers on yet so alignment is still a problem and without the lower rollers the ride is a bit bumpy. ;)

Here are two videos, one showing the crane in action on my pond sea wall loading sand into a toy dump truck. The shorter video is a closeup of the crawler on the bench.



Jim
 
Sometimes I would use a little layout die on the bed where the magnetic base is mounted to see if I might have bumped it while machining. A very nice project.
 
I made pins and idler rollers for top and bottom. They really helped smooth out the pads as they transition onto the tumblers at each end of the frame. I have a diggin video uploading now but it will be a while to finish. Here is the shop test video...


Jim
 
Crawler update.

I am in the process of changing the style of the drive tumblers on my dragline crawler undercarriage. I machined a few new drive dogs for track pads and made a new main and center idler wheel. I need at least four more small idlers then I can test the new design.

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Jim
 
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