I took the advice of Richard L. in the FAQ thread and broke in my metal gearboxes. I was very surprised on how poorly the gears meshed in advance, and was very disappointed to see that the tophat bushings were loose in the chassis in several instances. I JB Welded the bushings in place in advance, then got to work.

Once the bushings were not spinning instead of the shaft, I found the gears had several binds and tight spots when turning them by hand. I degreased, starting with foaming engine degreaser, finishing with Simple Green and hot water. As I did not have any valve lapping compound (ok, I could not find my lapping compound- we moved from a house with a big two car garage to a house without any garage), so I used paint buffing compound. My advise is to use something that is easily removed with the cleaning system you have. My rubbing compound was water soluble and was still a royal pain to get off. I started with 15 minutes each way at low speed with a hand drill (I felt my press was running too fast even at the slowest speed). I cleaned the compound out and reoiled the bushings and tested. They were better, but not yet where they could spin freely. So, back on with the rubbing compound and another 15 minutes each way on each gearbox. This time after cleaning them and reoiling the bushings, they actually spun free after giving the output shaft a spin. I am so impressed! I greased them up wit ha very light grease and away they go.

While I had the drive disassembled, I broke in the motors as well as Richard L. also recommended. I did not want to desolder the motors and break in on the bench though. I just ran them sitting in the tank base free at the lowest speed I could with the trim tab. I ran them an hour, half one way and half the other. I don't know if they will run any better but I feel confident that I did what I could.

As I used a light grease, I know there will be a mess. So, I used some light gauge lexan I had kicking around to build wrap-around splash guards. I'll add a pic or two at the end so you all can see. I held them in place by putting the front and rear screw in thru them underneath. It was a real pain to work around them to screw the drives down but I believe it is worth the extra aggrivation. Oh, and you can see that I have trimmed the smoke tubes as suggested- they stuck out and looked butt-ugly!

Last thing to do for now is to install a tiny laptop fan I have. I'll need to drop the voltage- it runs on 5 volts, so I'll need to dig up a 50 ohm resistor to knock off 2.5 volts. BTW I have a TK-RX 13 receiver board- anything I need to watch out for, or should I just order a RX14 board right away? It should last a while with the fan cooling the heatsink, but is there any significant difference between the two?

I love my Pershing!


Dmon1996

Good job on the gearboxes. I wouldn't get all worried about which board to use. Running the white capped Suntechs is very safe, they are low speed, high torque and do not draw a lot of amps. You really don't even need the fan with those motors but it's nice to have as insurance in case the tank encounters heavy resistance someday or extreme temperatures.

Well, I have ordered a pair of Graupner SPEED 400 7.2V Electric Motors from Hobby Lobby on the advice of this forum. So I did not want to take the chance of overheating with the more aggressive motors and frying something. I honestly do not know what motors are in my tank- I bought it with the metal gear set already in place. Or sort of in place- I had to disassemble and fit them properly to be satisfied. On both sides I had shafts jammed against the plastic body.... and all it took was 15 seconds with my Dremel tool to make a proper fit.

I've tried my tank and am really happy with the increase in power and the smooth action now. And it has power now- I tried to hold the output shaft while it was turning- no way I could stop it!


Dmon1996

Sounds nice Dmon! I am currently preparing to break my gearbox and motors in, just missing some grinding compound. I hope my box will turn out as good as yours did

Btw, I want to add a cooling fan to my board aswell. Could you please tell me were to solder the fan and maybe what fan you recomend?

Thank's for sharing!

The fan connects where the main board gets its power: negative from the battery and positive from the middle of the switch - you can put another switch in-line to independantly turn the fan on/off (cold days, short runs etc)

I was also going to connect the fan to the power switch and battery ground. I salvaged the fan from an old Dell laptop I had kicking around (I'm a computer tech). But a good place to find computer fans is Princess Auto if you are in Canada- they have all kinds of that stuff in their salvage section. Barring that, I'd look at a CPU cooling fan from a computer shop. Be carful on voltage- you want a 5 volt fan, not a 12 volt. And you'll need a resistor in series with the fan to drop voltage.

The way to figure out the needed resistance is figure out the voltage drop you want (2.5 volts or so as as full battery shows at about 7.6 volts fully charged), the current draw of the fan (on mine it's 0.05 amps), then divide the voltage by the current- 2.5v/0.05 amps. This gives me 50 which is ohms. A great resistor color code calculator is at http://www.dannyg.com/examples/res2/resistor.htm.

Man, it's almost as much fun customizing your tank as it is to run it!


Dmon1996

nice work DMON

don't worry mate the modding bug won't let you stop there[][][][][X(][X(][X(][X(]

Speed400s are sweet! Have you installed them yet? You'll definitely need a fan for those motors! I ran my Pershing with them one day without the fan and blew 1 of 4 transistors trying to pivot deep in sugar sand. The motors now reside in the BullDog and the results are well documented on it's build page.

See my builds for a variety of wiring diagrams.

The motors are on order, but the fan is already in. See pic. Do you think this is enough, or should I add a larger heatsink as well? I have lots of heatsinks from old CPU's, and I have thermal compound.... all I'd need to do is cut a heatsink to fit and screw it onto the existing one.... [8D]


Dmon1996

Nah, I left the original heatsink alone. My Pershing's fan is located a little down lower on the side of the battery box and facing the heatsink. This Pershing is running the hotter black capped Suntech 385s which are slightly less powerful then the Speed400s.