Battle Harden


	Battle Hardening for Banebots 24mm gearboxes

Banebots provide a wide range of gearmotors that are easy to mount and relatively cheap to buy.

The low price is however often reflected in the low quality of the assembly. Our PDB2 kit uses two of the 20:1 24mm gearmotors and whilst they provide plenty of power and speed they quickly showed thier weaknesses.

At the first competition the gearboxes quickly began to fall apart and jam up and we only managed to keep going through to the end by borrowing motors from another competitor.

Examination after the event revealed that most of the problems derived from the fact that all the screws used to hold the gearbox together were vibrating loose. Another problem found was that the brushes on the motors were unreliable and that by moving the leads about the motors would start and stop.


	The small M2 x 4mm screws used to hold the gearmotor together have poor quality heads. These make tightening and removing them difficult. I obtained replacements from Mcmaster-Carr (Part number 92010A001)

First task is to remove and discard the banebots label (they fall off anyway!) and clean any grease of the exterior of the assembly.

Then remove each of the screws that secure the front part of the gearbox (Above, outlined in red), clean the recess of any oil with a paper towel and add a drop of Green loctite 294 (as below) and fit one of the new screws from mcmaster. Ensure screw is well tightened using hand driver. There is no need to overtighten the screw. If any of the original screws will not come out I have found that partially drilling out the head will loosen them. Heat may also work if you have a heat gun but don't overdo it!. Wipe off any excess Loctite.


	Repeat for the other two screws that secure the front part of the gearbox.

Next remove and discard the three rear screws. This allows the motor and rear section of the gearbox to be removed together. Slacken off the two screws (circled in red in the picture on left), add a drop of Loctite to each and retighten.

Carefully remove the gears and carriers from the gearbox (noting carefully where and how they go together) and then reassemble after adding some extra lubricant. I use Vaseline and this has worked for me but it is possible that a light lithium grease may be better. Then reassemble the motor to the gearbox using new screws and Loctite as before.

	Cut a 1 3/8" long piece of 1" heatshrink (I use mcmaster 7132K785) and slide over the gearbox and shrink into place as below. The heatshrink performs two functions. It prevents any of 6 small M2 screws from backing out if the Loctite should loosen and it also retains the motor to the gearbox if those screws loosen.

	Next step is to add wires, I use 20 gauge silicon wires, I used 16 gauge in the past but the excess heat to solder them and the added strain they apply to the solder tabs (and hence to the the brushes) can damage the brushes and cause intermittant contact. 20GA is quite large enough for the small currents involved in Beetles.

		Final step is to add some "shoegoo" around where the wires are soldered to the tabs. This further stabilizes the wires and brushes.


	Whilst this article specifically refers to the 24mm gearboxes the same principles can be applied to any of their other gearboxes or indeed those of other vendors .