Best reduction I would achieve

**mattsdragons** · 3rd December 2012, 17:18

Whats the best reduction I could achieve With the motors below on 50mm wheels on a single stage reduction?

http://www.ebay.co.uk/itm/300511267976

Had a look on technobots but ive never used gears before so am a little unsure

**PJ-27** · 3rd December 2012, 17:31

http://www.technobotsonline.com/robot-s ... lator.html

Put in figures, get answers.

I've considered this to quite some length and with MOD1 gears you start to run out of weight and space around the 6:1 mark, 4:1 is more possible. Similar story with chains and sprockets.

50mm wheels are tiny though and means you need less reduction, but most gears will be bigger than that!

**grant_ploughbot** · 3rd December 2012, 17:35

What you'll find is that with a single stage ratio you don't have alot of choice. You just need the biggest gear that can fit on your wheel and the smallest that can fit on your motor shaft. Normally that's around 5:1

If you go with bigger wheels and bigger gears on the wheel you will still get the same speed.

**Danjr1** · 3rd December 2012, 21:28

I ran those motors with a 7.5 to 1 ratio (12t pinion and a 90t Spur, mod 1). The bot ran on 120mm diameter wheels. I believe Will from team shock ran them in one of his featherweights on a smaller gear ratio so might be best to check the build diaries.

**mattsdragons** · 3rd December 2012, 21:44

Those motors at 18v with about the biggest reduction I could got on 50mm wheels 40:12 (3.3333:1) would get a theoretical 18mph out of it.... bit slow

Though slight problem, 50mm wheels and invertable with motors 52mm diameter, not going to happen

**maddox10** · 4th December 2012, 03:59

52mm diameter. Sounds like Speed 900 or clone.

Means also 3 diameters of axle. 5, 6 or 6.35mm.

With the 6.35mm you could use , in theory a gear with a root circleof 8.5mm. With mod 1 that is Z10 (Mod*Z-(2M*1.25)). A rare and expensive size.
Also, it means a gear with undercut. Meaning the teeth are weaker than what the norm allows.

If we drop to a Technobots available size in steel, mod 0.7 Z12, root circle 8.4mm, that could be survivable. On a 60mm wheel, you could add a mod 0.7 Z80 gear(outer diameter 57.4mm). Giving you a gearratio of 6.667/1

But technobots goes only to Z72. And that's 6/1

So, if I use the data from my measurments, a 6.35mm axled Speed 900 clone runs 12Krpm@12V
6-1 gearratio to a 60mm wheel = 22km/h

I must admit. I don't know how mod 0.7 stands up in the Featherweight class. Never used anything else than mod 1.

**PJ-27** · 4th December 2012, 08:22

I hope Will doesn't mind me saying this but he made up his own drive units for his latest robot with those 900Clones and given the Voltage, Motor RPM, Reduction and Wheel size that robot has a top speed of around 30mph, but in the drive test video moves around nicely!

Most people would consider 10mph a good/high top speed to aim for. Food for thought.

**Ellis** · 4th December 2012, 09:38

Getting there and maintaining is what matters. Tormenta 2 does just 10mph, but it reaches it in about 3 feet of floor space, and it has the torque to maintain it once it has hit another machine. That's why it appears quite fast. In a straight line it is easily outclassed by robots like Satanix, though.

I'd suggest aiming for a 2 stage gear reduction. It's harder but also easier, in a way. Bit heavier but allows for a stronger setup. With it you could gear those motors to say 12mph, a good deal faster than 90% of your opponents, and if others have geared to 30mph and the machine moves around well, imagine what it would be like with the freedom of torque and acceleration at 12mph.