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Sep 27, 2016, 12:33 PM
Kamikaze Ace
Glacier Girl's Avatar
If it's any help, on a couple of them, instead of the stub axles, which put a load on the sides of the tubs where they mount, I took 1/8" steel brake line, and ran it from side to side for a one piece axle per pair of wheels. Used small wheel collars that slipped inside the hubs of the wheels to retain the wheels.

Also added plastic bushings behind each wheel hub for additional strength.
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Sep 28, 2016, 01:39 PM
Registered User
Rebel 1's Avatar
Hi Pat,
I see you're going to do quite a bit to fix up this tank. If you decide to do a bit less, there's a guy on Ebay that mainly sells Stuart parts but he has a few Abrams parts as well. If you need something he doesn't have listed send him a message and he might be able to find what you need.

Here's just one of his Abrams items he has listed now on Ebay: http://www.ebay.com/itm/21st-Century...AAAOxyThVTYptO
Sep 28, 2016, 01:45 PM
Registered User
Rebel 1's Avatar
The 1/9 scale 21st Abrams don't often show up on Ebay, but I just spotted one in Van Nys California for about 80 dollars but its listed as pick up only.
Nov 14, 2017, 11:14 PM
Registered User
Have one and it's in great condition almost perfect not even broken trim items . Everything works except track won't engage. Heard this is probably just a speed control issue ( corrosion etc ) Haven't opened the housing yet but your photos are perfect. Any advise on mine? No grinding or gear noise Turret turns and makes all the sounds. Also was told could just be an under-charged battery. Thanks in adavance
Nov 28, 2017, 12:32 PM
Registered User
I have one also.
got all the electronics in a bucket

put them in and powered up once and now I can not get it to do it again.

looks like 2 wire power plug connector is broke inside.

stripped wires and touched to prongs and still nothing

barrel is cracked and one small wheel is broken off.
have to figure out how to fix

kinda like your pic but mine is broke off all the way
Dec 19, 2017, 06:47 PM
Registered User
Hello, everyone. I am drawing up plans for an M1 to cut on my CNC machine. I plan on using my 3D printer for the finer details. I found a set of drawings on a Yahoo M1 group and used them as my basis. They are labeled as PATMAT Designs. I was wondering if these are your drawings, patmat2350. My attached pics show where I am at the moment. I don't have drawings for the rear of the engine area and the top deck and panels associated with that area. Do any of you gentlemen have a good scale resource you don't mind sharing?

Will
Mar 01, 2021, 12:44 AM
Where's Pamela?
patmat2350's Avatar
Thread OP
It's back!

My 21C Abrams was purchased with lots of broken parts... I think the tank got dumped on the ground or something, the way the wheels and bogies are smashed. My plan was to 3D print new better parts at Shapeways, but oh boy the cost. Project went into a box. A big box. I finally got around to getting my own resin printer, so this show may get back on the road!

Still pondering the best way to fix and/or upgrade the road wheels and bogies. But decided to look into the motors today. These are much better than the Stuart gearboxes (not saying much). The Stu has a built-in misalignment that causes gears to strip. This one has a more precise plastic cover that has molded pilot holes for the axles, so alignment should be good. But I looked inside one box and saw a mid-train gear hopping around like it was unconstrained. Hmmm.

Take it apart, and found a bent shaft. How the heck?

Still not sure if I want to use these noisy sloppy things... maybe I need to engineer an all new drivetrain.

BTW, total reduction on this box is 119:1.
From the motor pinion, gears are: (8/22) x (14/32) x (12/32) x (12/32) x (12/32) = 0.008 = 1/119
Last edited by patmat2350; Mar 01, 2021 at 01:10 AM.
Mar 03, 2021, 05:45 PM
Where's Pamela?
patmat2350's Avatar
Thread OP
So I was thinking that with some mods, these stock gearboxes could be suitable runners. Upon a little more disassembly, I see how BAD they are. Anything can be fixed... but am I better off just finding some quality gearmotors?

I found a guy who did that a few years ago, but it seems the drives were too wimpy... need something like that but bigger.

If my calcs are right, we need something on the order of 350rpm output to make a scale 30-35mph... the 21C set up only does 126rpm, no load.

.
Mar 12, 2021, 02:47 PM
Registered User

response to 21C post


ok just ran across this old post any updates?
Mar 16, 2021, 11:20 AM
Where's Pamela?
patmat2350's Avatar
Thread OP
Um, see the previous post.

But- I do have a couple new drives on the way (below).

And, I'm torn between up-fixin' the bogeys, or building a simulated torsion arm suspension (with coil springs instead of rods). A new hull is even a possibility. We'll see...
Mar 16, 2021, 11:31 AM
Where's Pamela?
patmat2350's Avatar
Thread OP
BTW, there are several Youtubes on this model. One fellow points out that the road wheels come in two flavors- black or white plastic. The black is brittle, and all my broken wheels are black. The white ones seem to be a better plastic. I scored a bunch of spares on ebay, all white, none broken... but I still don't trust them.
One possible fix- pour casting resin into the hollow space just inside the wheel OD (tire). Or fit a bunch of webs cut from plastic. The OD just isn't well enough supported to avoid flexing under load.

Another possible bogey upgrade: Fit softer springs to the bogeys. I have a bunch from McMaster, I'll try them if I keep the bogeys.


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