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Spockie-Tech
Site Admin
Joined: 31 May 2004
Posts: 3160
Location: Melbourne, Australia
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Should I tell him how much work it was to get Inspector General's drive even *semi-reliable with those large diameter white wheels on drill motors ?
Or let him learn it the hard way ?
Oh, Alright, got to help the newcomers..
It *can be done, but don't expect to just bolt them on and have it work for more than 5 minutes before smashed gears and melted motors happen.
Those big wheels have *way too much weight and rotational inertia for the umodified drill motors and gearboxes to handle.
You need beefed up gearboxes (I used AndrewMods, but I think there are newer options now.. Aaron would probably know), soft rubber bushed anti-shock motor mounts to flex a little when you go from full forward to full back (or an ESC with ramping) to avoid the reversing shock.
The stock tyres are *heavy, I drilled radial holes in mine to lighten them, for weight saving and also eases the reversing load, although it also improves the traction somewhat, which isnt always a good thing.
You cant drive them from the center plastic hub either, you'll just shred the plastic threads. You need a metal threaded insert hub with an arm from the hub to the wheels edge and a bolt to move the drive attachment point out near the edge to avoid massive torque on the hubs. (mine had a balance weight on the opposite side, since I.G. was *fast and the wheels turned quickly)
I also had an outside edge bushing, so the wheels were supported on *both sides, and so werent placing all the side load on the gearboxes. Make sure you support the gearboxes *and the motors with your mounts. Those little dinky plastite screws wont hold the motors in place under severe impacts if the mount only supports the gearbox.
The standard hooflungdung motors wont handle *any overvolting driving those size wheels.. even stock 12v is iffy. After destroying several sets, I replaced the stock lecrap motors with quality johnson branded motors with stronger brush holders, and removed the internal plastic fans (they would melt and jam the motors).
At the end of I.G's iterations, I was experimenting with a tube encasing the motors and a small 40mm fan in the middle driving air through them *all the time, since its when they are stalled and pushing on another bot that they generate the most heat, and the internal fan isnt doing anything if the motor isnt turning much.
The little Red Wheels are about as much as a stock drill setup can handle and be semi reliable. They are lightweight and limited traction, which helps save the drill motor from big loads.
Most stock drill motors are like old school rotary engines, or early turbo-4 cylinder motors. they are simple, light, cheap and powerful. The hard part is getting them to be *reliable.. Combat is really stressing them.
Usually you have to sacrifice one or more of the other 4 attributes - (making them complicated, expensive, heavy or low-powered).
If you're thinking all that sounds too complicated for a first bot, then go for the easiest - low power.... it will make life easier for your ESC and batteries too. you can turn up the volts and power later when you get some experience and feel like fixing broken stuff
drive them off low voltage to limit the power to stop them breaking, and/or limit the maximum throttle power in your radio, and put slew-rate-limiting or ramping in the radio or controller, so they reverse gently.
*edit - I just noticed Jules already reccomended that further up.. Words of Wisdom. Power is fun, but it breaks stuff. _________________ Great minds discuss ideas. Average minds discuss events. Small minds discuss people
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Sat Jun 06, 2015 7:25 pm |
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