Well, the dreams of a brushless Abrams made some major steps forward tonight. A long time ago I purchased the original gearboxes that DKLM was selling for the metal lower chassis designed for the HL Leos. I thought how hard can it be to adapt to an Abrams? I found out...it didn't work. That was of course after I gutted all the standoffs and supports out of the stock chassis. So I decided to redeem myself and get the combo to work. What was killing my build was the length of the brushed RS-550 motors. The were 65mm long which made them too long to fit in the Abrams chassis and maintain the correct track spacing. I saw a brushless conversion of the DKLM gearboxes online and felt like the shorter brushless motors would allow me to mount the gearboxes. I didn't want to go the same route as the other person that converted to brushless since he drilled new holes for the motor mounts. I wanted to use the stock mounting holes. After and exhaustive search and a 3 week wait from China, my 550 brushless replacement motors arrived. I ended up going with a 1650KV 3650 (36 is the diameter and 50 is the length in mm) brushless motor. The motor also has the same 3.175mm shaft so the pinions moved over to the new motors without issues.

Top view.


Front view.


Mocked up height.


Shaft support.


New motor up close.


Old Motors


Length comparison.

Love what you have done! It is going to be a super fast Abrams once everything is sorted out. I run mine with traditional 390 brushed motor at high voltage (9+) and they are fast tanks (scale 50-55mph), cannot wait to see what speed you can achieve with brushless power adapted to an HL Abrams.

It is fun to watch the modern tanks rip across terrain at high speed. Unlike a WWII tanks where it can looks odd, with modern tanks properly balanced it does not. Just a friendly word of warning the speed leads to harder driving which leads to finding things to jump LOL. Here is one of mine getting some "air" just the other day. These HL Abrams hulls and suspensions are far tougher than most would expect. Looking forward to following your progress as going brushless is something I have been looking at in the near the future.
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I don't want it too fast. The lower KV rating motors have less RPMs per volt. Being that it still has gearboxes to gear them down and increase the torque, I'm hoping the speed is within reason. It will be powered by an OpenPanzer TCB. Just can't do any testing yet since my brushless ESCs haven't arrived yet.

Being that a governed abrams can do 55mph no problem on flat terrain I was fighting to get to that speed. I upped my battery to a home made 12v 5ah Nimh. Real pain to make fit the way I did and if I had it to do over again I would remove the battery box, split the battery sections in half and put one stick down each side and the ibu in the middle.
Any way, my turret flips around fast and the tank is super fast with a dual rate switch on my transmitter I can drop down to half speed for engagement maneuvers and flip to high speed for crossing our huge field.

I have the red 390s in it. All the motors we have available are basically 12v motors. The IBU is plenty capable of driving 12 volts. Its fast.

So far I only drove the chassis and its a tad squirley to maneuver at top speed. But that is really only for crossing the field. I wanted fast turret rotation and that's what I got.
It would be easier to control if I had metal and rubber tracks.

OH MY! 12 volts!

My Abrams runs with an IBU3, now you got me thinking. Did you need to do anything besides just changing the battery?

So the OP board can run 4s lipos btw (that is 17V btw) and does it no problem when paired with the Scout or Sabertooth ESCs I ran in my drift Tiger 1. I used x2 3660/3000kv motors on 4s on the 3:1 gearboxes, it was not only fun as heck but destroyed most of my suspension each time I took it out. It was absolutely hilarious taking it on the local car track, people loved it. Due to the height I could never get the top on but man was that lower chassis fun to play with. I know I have pictures of it somewhere, I'll look when I get to my house later and see if I can find it. I think it is like 3+ years old actually....
I've always wanted to go brushless in the tanks (at scale speed of course) due to the larger availability and better specs available for the motors. We could get a much better scale speed with 540 motors and adjusting KV ratings to the tanks. Mainly getting specs for BL motors are the killer for me. I like being about to adjust final speed by the motors. With a gear ratio of 39:1 (you have to use the 3:1 type, the 4:1 type doesn't have enough room to mount on top of each other) there is plenty of torque in those motors to drive as fast as you want and still have the low speed power to creep along. It really helps if you have something like the OP though as there a ton of ways to adjust speed without using things like dual rates which effects the sounds (you don't get the max revs if you D/R the limits) however that is one of the best ways I've found to do it as well and it is super simple to do.

Yes I am using the OP board, but it will be paired with some Hobby King brushless ESCs. I really like the idea of using these gearboxes because they are enclosed. Should eliminate gear oil or grease flinging. I will be beefing up the lower hull also.

I think you will like it. OP has that speed limit by percentage that really helps with higher voltage stuff. The momentum and inertia settings are fun to play with as well, I bet with a brushless application it will be even better. I actually haven't done a BL tank on OP, I bet with a sensored BL motor it would be awesomely slow...

My brushless ESCs arrived the other day so I can start playing with them using the Open Panzer board. I might have some time in the next week or so to get a rolling chassis working for the Abrams. I've finally been able to get stuff organized enough after buying my new house and moving to do some work on my hobbies. The DKLM gearboxes have all metal gears in them with bearings so I'm not expecting the gears to fly apart... Need to actually fabricate a mounting plate for the gearboxes and finish cutting the hull reinforcements.

Finally had a chance to make some progress on the chassis improvements. I had a couple of sheets of 3/16" ABS plastic laying around so I decided to put it use on the tank. Made thin cardboard templates of all the pieces to ensure fitment before cutting them out of ABS. Right now everything is just dry fitted. I have some screws holding certain parts together. It makes the entire chassis very stiff. The center compartment will hold the batteries in the lower part and there will be another ABS sheet above the batteries where the electronics will mount. Batteries and electronics will be mounted with velcro. Of course some relief cuts will need to be made for the turret rotation and other things, but that's why the parts are just dry fitted and not permanently mounted. Being that I can take them out, I can make running changes when I find fitment issues. I'll probably be sealing up the suspension holes to keep the interior of the tank clean and dry. Anyway...at least it's progress...



Parts layout


Parts layout side shot


All parts dry fitted - front view


Dry fitted - rear view


Routed the bottom of the motor mount plate so it will sit even. Flattens the interior.


Dry fitted side view


Future home of a speaker


Speaker box open

This suddenly got a whole lot more interesting I'll be watching here!

Rich,

I've been dry fitting the top this whole time also to make sure things won't interfere. Still haven't decided what method I'm going to use to attach the top (probably magnets). What specifically gave you a problem under the turret? I know I will have to allow some room below it for the 360 degree turret slip ring. I'm planning on using the metal x2 version of the turret rotation attached to the upper hull so I will need to cut down the rear bulkhead by the front of the gearboxes. Haven't quite decided yet on what I'm going to use for the recoil and elevation. Been looking at the DKLM metal one and I'm aware there is a recoil/elevation unit specifically for the Abrams (Clark?).

Why didn't you just use a 3S LiPo?
Better current delivery about half the size and easy to use.
Scale top speed would be about 6km/h (about the speed of a fast walk).
The only advantages I can see are longer runtimes and slightly better low speed control.
But of course, as with any hobby...
Because you can !!

Do you use it to tow your trailer as well, it must have toque to burn