Tank Speed????

[DanL]

I have a Tamiya King Tiger. It has a 3:1 ratio reducer added to the gearbox. When first built, I timed and calculated the scale speed at 27mph.

I just noticed after a few weeks that the top speed is a lot slower. Timed it again and it tops out at scale 12-13mph. Checked all the Spektrum settings, battery, etc - all OK. The big change though was going from plastic to metal tracks. Could that be causing so much speed reduction???

What's a typical top speed for an RC tank?

[[ICE]monkey]

hi it could be the metal tracks , but i would leave it as it is becouse its closer to scale speed now , were the 3.1 ratio boxs added when you built it ?

[Woz]

Metal tracks add a lot of weight to the tank which'll slow it down. The tank will speed up a bit as the tracks get broken in, though it'll still be slower then when it had plastic tracks.

12-13mph is about right for the KT's top cross country speed.

[DanL]

Thanks guys.

The speed is OK with me. Just wondered if ever I did the tank war thing thhe KT would have circles run around it.

Gearbox and biggr motors were added-on after initial build.

[Saxondog]

Dan, Some members have had positive results from running new gearboxes without the tracks installed coated in cam grinding compound. This smooths any imperfections on the gears and seems to allow for less friction and better performance. This method has shown positive results on all of my Tanks,and especially my Tiger which is the most powerful of my 4 tanks.

[twelvebears]

The speed is OK with me. Just wondered if ever I did the tank war thing thhe KT would have circles run around it.

Which would be true of real life but that was because they were trying to avoid getting obliterated by that massive gun!

I'd always go for power and torque over speed anyway. It makes driving cross country and climbing more controlled and also gives better run times because the motors are under much less load.

If you're running metal tracks, the original Tamiya boxes WILL die at some point, especially if you've not added a support bearing something like this to the outer hull:

http://www.rctank.de/product_info.php?products_id=1138" onclick="window.open(this.href);return false;

If and when they do go, I'd do what I'm doing and fit a pair of these:

http://www.rctank.de/popup_image.php?pID=793" onclick="window.open(this.href);return false;

If you have a quick look at the size of the final drive gear compared with tiny one on the stock Tamiya boxes, you'll soon see why these will be far better suited. That said of course, Tamiya designed their boxes for their stock model with plastic tracks, so you can't blame them entirely....

[DanL]

Sax,
The gearboxes were smooth as silk when new. I put on the new motors and the new reduction gear set and they spun smooth and easy, so I skipped a run-in with any abrasives. The Tamiya gearboxes are surprisingly nice - ball bearings, etc.

Twelvebears,
I made a set of delrin front axle supports. The Tamiya kit gearboxes look exactly like the picture you posted. Cut brass gears, ball bearings, thick aluminum sideplates etc. The wheel bushings also fit perfectly (vs. comments that the fit was sloppy). So I think I must have a very recent kit where Tamiya upgraded some problem items.
I wont be running it much til spring (it would sink in he snow here) and I'll be seeing how it holds up outside.

Thanks for the responses guys.

[twelvebears]

That sounds hopeful. I've not seen the latest boxes so they may have made some improvements, most specifically the size if the final gear on the output shaft. This was always really small, only slightly bigger than the diameter of the shaft itself, whereas the Asiatam boxes have a significantly chunkier final gear which handles the torque better.

Time will tell of course and the boxes came with the kit, so you've not lost anything.

[DanL]

Hmmm,
The Tamiya final gear is 10mm OD. Looks smaller than the one in the pic you posted. What is the diamter of that final gear?

Anybody ever look at a rearrangement of the Tamiya gearset?