single stage gear reduction

[Danjr1]

Afternoon all,

Am looking to venture away from the drill motors and gearboxes and into home-made gear reductions. What i cant get my head around is the easiest way to make such a system? i understand how to mount the motor and its pinion, and how to attach the spur onto a wheel but how to mount the wheel on an axle and mount the axle. i know it will use bearings etc but i was wondering if someone knew of a quick and simple way of building such a system.

I would want to use 100mm or 125mm robochallenge wheels, mod 1 gears, replica or original speed 900s on 22.2v

cheers

dan

[maddox10]

Re: single stage gear reduction

The Hannibalito series of robots uses the MSR gearbox. Comes in 2 flavors. 4.5-1 or 6-1 gearratio.
An example with the 6-1 gearratio.

Nothing more than a lasercut steel plate, 15mm steel axle, M8 bolts and HDPE wheels. No bearings, but bronze bushings.

Further.
Biggest gearratio you can do in a single stage is 8 to 1.

Mod 1 gears. 12 teeth gear on the motor, 96 teeth gear on the wheel. (means 98mm outside diameter). That's close to the 100mm wheel . Too close, you'll be driving on the gear in no time, and ever bit of debries will be hit. Not a good idea.

So, we drop a bit. 12 to 90. = gearratio 7.5.

Speed 900 = 550rpm/V 22.2V means =12210rpm =1744 rpm on the wheel.

100mm wheel*1744rpm= 32.8km/h

Of course, with 125mm wheels the scenario changes, but still it will be bloody fast.

[Mouldy]

Re: single stage gear reduction

Further.
Biggest gearratio you can do in a single stage is 8 to 1.

Mod 1 gears. 12 teeth gear on the motor, 96 teeth gear on the wheel. (means 98mm outside diameter). That's close to the 100mm wheel . Too close, you'll be driving on the gear in no time, and ever bit of debries will be hit. Not a good idea.

So, we drop a bit. 12 to 90. = gearratio 7.5.

Speed 900 = 550rpm/V 22.2V means =12210rpm =1744 rpm on the wheel.

100mm wheel*1744rpm= 32.8km/h

Of course, with 125mm wheels the scenario changes, but still it will be bloody fast.

Not true- why put a 12T pinion on the motor when your trying for the lowest gear ratio, if you can put on a 10T?...

It would then become;

10 to 90. = gearratio 9:1

[maddox10]

Re: single stage gear reduction

Dave, you're right. You could get a bigger gearratio. Technobots has a Z10 and a Z120 mod 1 gear in store. Combine this with a 125mm wheel and you have a 12-1 gearratio, with 1.5mm groundclearance below the gear.
You also can use the trick of the first RAF machine in RW, the very flat, triangular, torpedo armed (pneumatic spike) , if I recall correctly, Typhoon. They milled the 12mm axle of the Bosch 750 so it became a Z10 gear.
Putting this in a 6mm axle, you get a Z4,

Several reasons why I give a Z12 Mod 1 gear the preference.
Speed 900 has a 6mm axle. Some Johnson variants (the Speed 900 is a Johnson motor) have a 1/4 axle.
A Z10 has a inner diameter -for the teeth of 10-2.5mm= 7.5mm, 1.25mm or 1.1mm of steel under the teeth. Do you think that is enough?

Guideline of mechanical enginering is max gearratio with normal gears or sprockets in 1 stage is 8 to 1. Everything above that is rape.
I did find some 10-1 epicyclic gearboxes from an Italian manufactorer. But those are rated very low on imput force.

Sorry to be conservative in this respect. But I dare to say that the track record of the MSR single stage drivetrains is proven.

I know of some combat failures.

1) Hannibalito I, using an MSR 12-54 @10S NiMH, at the XFM Halloween special, after a hit on the unprotected 900 by Little Hitter, what shattered 1 magnet. (this was solved by adding 5mm of HDPE armor)
2) Kashei, what used the MSR 12-54 with 6S Lifepo4 on 110mm wheels. The low grade ali gears didn't take the strain, and shredded teeth like a maine coon cat in the Sahara.(this was solved by electronic restraints put in the TX, and the new variant will use less V, 6-1 gearatio and 7075T6 ali gears.)
3) Plofbox, after a hit from Hornet straight on the gear.(unprotected wheels.... what a surprise)

4) Satanix is a strange case (that uses another MSR drive). It wasn't dependable. Untill I had the opportunity to work on it. I still don't know what the secret was. The only thing I did was giving everything just a tad more clearance.

[Danjr1]

Re: single stage gear reduction

The replicas on eBay have 5mm axles so I'd go for the smallest sized pinion. Would like to use 125mm robochallenge wheels but I think it will be easier to make my own! I'm thinking of using 6mm Ali plate instead of the steel though?

[Mouldy]

Re: single stage gear reduction

Wasn't saying your gearboxes were un reliable... Was just saying if you wanted a lower ratio in a smaller space it can be done... I'm running a 10t mod1 on my speed 900s and so far it's been fine.

[maddox10]

Re: single stage gear reduction

Dave, don't forget I talk to Inventor on an almost daily base. He's also the inventor/provider of the MSR gearbox. I just finish those to the wishes of the user.

Oh well. I leave it to you. I won't advice a Z10 for a 6mm axle. Especialy not with an overvolted Speed 900.



Danjr, the 5mm axle replica's are much higher RPM/v motors with a lot lower torque.

[Danjr1]

Re: single stage gear reduction

http://www.ebay.co.uk/itm/300511267976? ... 1126wt_689

These ones? Bit of a shame as the real ones are 4 times the price!

[maddox10]

Re: single stage gear reduction

If you buy me 8, I'll deliver 2 fully finished MSR 12-72 with 100mm wheels in exchange.

[Mouldy]

Re: single stage gear reduction

Dave, don't forget I talk to Inventor on an almost daily base. He's also the inventor/provider of the MSR gearbox. I just finish those to the wishes of the user.

Oh well. I leave it to you. I won't advice a Z10 for a 6mm axle. Especialy not with an overvolted Speed 900.

You mean Dennis? He helped design mine also.

[Danjr1]

Re: single stage gear reduction

If you buy me 8, I'll deliver 2 fully finished MSR 12-72 with 100mm wheels in exchange.

i guess thats without motors? lol

[Danjr1]

Re: single stage gear reduction

Been sketching and come up with a thwackbot running 2 eBay speed 900 motors per wheel (2wd), 125mm wheels with a ratio of 7.5 to 1 (although, according to the maths, top speed is a little low for a thwackbot at 13mph). Designed my own version of those msr gearboxes which could accommodate both motors and act as part of the chassis.

Maddox, how much do you reakon it would cost to have two 125mm diameter 25mm thick discs made? With some machining to the centre of each?

[maddox10]

Re: single stage gear reduction

Danjr.

I ment, the exchange would be 6 motors for my supply and a set of MSR 12-72 drives for you (2 motors are for you then).

If I have to buy 6 Speed 900's at the local shop, I would have to cough up ‚225.

Now, your idea of a dual motor per wheel setup, with 900's, that's a hugely powerfull drive, what will need a serious speedo. But not that difficult to build.
Speed of such a setup is depending on voltage. With 12V you get 13mph (20km/h) , @22.2V you'r thinking 23mph (37km/h)
(also, the pricetag on a Z90 mod 1 gear is £30 and weights 850 grams)
On the HDPE disks, let us discus that with PM's.

[maddox10]

Re: single stage gear reduction

Dave, don't forget I talk to Inventor on an almost daily base. He's also the inventor/provider of the MSR gearbox. I just finish those to the wishes of the user.

Oh well. I leave it to you. I won't advice a Z10 for a 6mm axle. Especialy not with an overvolted Speed 900.

You mean Dennis? He helped design mine also.

Dennis= Inventor.

[Danjr1]

Re: single stage gear reduction

when designing such gearboxes, how much overlap should you allow in the design for meshing the gears? im using MOD 1 gears which have a diameter or 14mm and 87mm (this includes the teeth)