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Originally posted by Knightrous:
Has anyone ever had a 100w scooter motor fail in combat?
I think Glen didn't even kill the one in Visceral with that epic 36v 1:1 drum setup.

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Yeh that was 300/500W version. Not quite as reliable.
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Steven Martin
Twisted Constructions
http://www.botbitz.com

I don't remember killing one. From memory i took the endcap off, advanced it as much as i could and ran threaded rod through it to clamp it together and used it for battleshed haha Surprisingly powerful!

They're a decent motor if underpowered. On 36v i don't think they'd be that bad at all.
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www.demon50s.com - Minimoto parts
http://www.youtube.com/user/HyzerGlen - Videoooozzz

I put the Dewalt 18V motors thru the tentacle torque calculator with various voltages and gear ratios. At 22V and a 27:1 reduction the motors will draw 26.6 amps each to spin a 4" wheel. That works out at 1170 Watts total - way more than the smaller scooter motors can provide! The 500W scooter motors are larger and probably heavier than the DeWalt motors so there isn't much advantage to them apart from the higher thermal mass. The overvolting and gear reduction give a theoretical top speed of 17.7 KPH - way faster that K2 and more in line with Touro Light. That's all theoretical - the reality could be dissapointing...

The reason for picking a 27:1 ratio is that I already have P60 and P80 gearboxes in that ratio, so construction and testing can begin immediately. Building a plywood test platform with 27Kg of concrete on top will give some answers on top speed, acceleration, heating and all the other things we need to know.

The scooter gearboxes might have to go into another project, however they could still be useful with a future brushless drive. the Ebay seller listed a 4.5:1 reduction, so a 2 stage gearbox gives 20.25, a good ratio for an outrunner. Alternatively, they could be hooked up to 500W scooter motors to make a wedge bot for practice matches.

With 4 motors, at that speed they are going to burn out i'd suspect. Dave in the uk that visits this forum occasionally has a 6wd feather with tons of magnets in it and i dont think he has made it 30 seconds into a fight without smoking a motor. Even if it did work the setup would be on the ragged edge.

The dewalts are good - but they're super inefficient and thats the downfall. If you have the parts see how you go though.
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www.demon50s.com - Minimoto parts
http://www.youtube.com/user/HyzerGlen - Videoooozzz

Its all theoretical calculated numbers - the real numbers will be less favourable, particularly the top speed. After looking at about 5 years of lightweight fight videos, two wheel drive looks OK and bots with well supported DeWalts don't seem to break them too often - still wise to test them to get the voltage, gearing and supports right. The nice thing about the DeWalts is the set-up cost; I already have 1 motor, several compatible gearboxes, Victor 885 controllers, etc. I just need 1 more motor and some adaptor plates to couple the motors and gearboxes.

I put an alert on the HK reversable ESC and the motor so I can get a set when they come back in stock - I don't want to rule out anything at this stage.

I was looking at the Oatley 300W scooter motors - slapping one of the scooter gearboxes on the front would give 667 RPM at 24V - not a bad speed with a larger wheel. It could power a cheapo wedgebot for sparing practise.

The Turnigy Trackstar motors just came into stock in the AUS warehouse - ordered a pair for testing, even if the matching ESCs are not in stock.

I've got a Turnigy TrackStar 150A 1/8th ESC on the way for testing the BotBitz brushless drives. It's got a reprogrammable reverse and there are good report of them actually working on 6S (as advertised). Will hopefully find out how good the reverse setup is soon. The bonus is, if it works out well, the Aus warehouse has plenty of stock
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https://www.halfdonethings.com/

Is that the TTS-150A? I had a look at the programming card and it had 3 reverse options, none of which looked like instant reverse - hopefully I am wrong about that as the other specs are excellent.

quote:

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Originally posted by Glen:
With 4 motors, at that speed they are going to burn out i'd suspect. Dave in the uk that visits this forum occasionally has a 6wd feather with tons of magnets in it and i dont think he has made it 30 seconds into a fight without smoking a motor. Even if it did work the setup would be on the ragged edge.

The dewalts are good - but they're super inefficient and thats the downfall. If you have the parts see how you go though.

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I just got back from holidays and the drive system is starting to turn from planning into reality. Here is a disassembled 3 stage P80 gearbox:



The gears are all 12mm wide but there is no technical reason why the 1st and 2nd stage gears can't be narrower; the torque decreases in those stages, so I plan to machine down the 2nd stage gears to 8mm and the 1st stage to just 4mm. This will fit 3 stages into a regular 2 stage gearbox like the one pictured, saving weight & space.

The 4" x 2" Colson wheel will turn down to 42mm wide, providing plenty of grip. With these parts and an 18V DeWalt motor, the total length is around 200mm

I simulated the KE of the disk weapon; with a 325 x 25 x 25mm cylinder (no teeth or spokes yet), the weight is only 4.85Kg and at 7,000 rpm it would have a very handy 30,500 Joules of KE. That's just for a disk, so there is plenty of weight to add spokes and teeth I wonder how hard it would be to make and balance a two part disk with a Bisalloy rim and titanium spokes to get more KE for the same weight?

Are you able to calculate the gyroscopic forces?
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So even the rain that falls isn't actually going to fill our dams and our river systems

There must be a way, but the only option I know of is to build a prototype.

http://www.totalinsanity.net/tut/mechanical/gyroscopiceffect.php

I spend way too much time on the internet...

be careful cutting the gears down.
*hopefully* the teeth are hardened lol
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Mechanical engineers build weapons, civil engineers build targets