Thorp #27 arm - what to put it in?
Posted 19 December 2016 - 10:21 AM
It says for CM150, would that be the blind bearing 16D can?
Posted 19 December 2016 - 11:07 AM
The CM150 would be the Classic 16D with a floating bearing... Thought they only made the CM160, which was a can drive, but maybe there was this endbell-drive variant.
In any case, a 16D with floating bearing.
Posted 19 December 2016 - 11:38 AM
I put a 28 Thorp in this motor for Howie. He wanted to go with something else but the Thorp is a sweet motor waiting to be put into a new build:
The new Thorp arm arrived and she's in really great shape. Almost no corrosion which is great:
I didn't even diamond turn the comm. Just polished it with some 8000 grit cloth. I'm guessing this is a Mabuchi blank judging from the scoring on the shaft to hold pinion gears in place:
Thorp instructions on the back of the package are interesting. Don't use stock magnets but do use stock brush springs. I'm going to take their advice:
Here's the gauss reading of a good stock Mabuchi magnet:
Here's the gauss reading of an Arco magnet going in this motor:
The endbell hardware gets soldered up, attached with a stainless steel machine screw and the bearing epoxied in place:
The floating gimbal bearing is also epoxied in place with Devcon Two-Ton epoxy:
I love my "Toys for Retirement". I used to drill and tap the endbell mounting screw holes by hand with a pistol drill and a hand tap.
Not any more...
My results doing this by hand and eyeball were not so good. Now they are nice square screw installations done quickly and easily:
The finished motor "in the white". It will be painted after the bare can and endbell have done their duty as a "jig motor" to build the chassis with:
I used the brass spring posts because they slip on and off. The Champion pieces are a press fit. Howie can still choose which he'd prefer:
I followed Thorp's advice and used light brush springs. The motor buzzes up nicely and draws less than 1 amp. I can always change to heavier springs if testing dictates:
I love the big honk'n magnet clip Champion used. I added .004" shim stock behind the Champion shim per Bryan Warmack's motor build article posted above. The air gap is now just over .530" and the arm is about .510".
- C. J. Bupgoo likes this
Check out Steve Okeefe's great web site at its new home here at Slotblog:
The Independent Scratchbuilder
There's much more to come...
Posted 19 December 2016 - 11:47 AM
Now to go select some parts from the vault.
Out of curiosity, would a set of Hemi magnets be a high enough level beyond the "don't use stock Mabuchi mags" warning? Haven't got a spare Arco mag and shim set and the Hemi ones feel pretty strong.
Posted 19 December 2016 - 08:37 PM
Out of curiosity, would a set of Hemi magnets be a high enough level beyond the "don't use stock Mabuchi mags" warning?
From what I remember Paul, the magnets in the Hemis aren't "all that". Better than the Mabuchi magnets, but that's setting the bar pretty low. Rick's Arcos are a full 50% stronger than the Mabuchis, and your arm is a #27. The Arcos are really tough to come by, but if you look around online and find the "Mura can-in-a-can" split shim and the matching magnets, those would be a full 50% stronger yet...somewhere close to 1000 on my meter. ***The only issue with them is that they can yield a small-ish hole, so even if your arm is .510", things can get tight. If that's the case, then you can just ditch the Mura shim and epoxy the magnets in "naked". The Thorp arms were/are really nice and the balancing in particular is spot on, it would pay to do the right thing for such an arm!
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Posted 19 December 2016 - 09:33 PM
Found the Arco shim & magnets, they're just in a 507R champion 16D rewind that I was gonna rebuild
But, do have the Mura can in can shim and mags So either to heck with the 507 for its mags & shim or the Mura ones. Will investigate both .