single stage gear reduction

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

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.
http://users.telenet.be/P3/Mario/Alex%20Finished.JPG
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.

Quote:

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Originally Posted by maddox10

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.

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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

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.

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?

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.

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.

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

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

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

Quote:

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Originally Posted by maddox10

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.

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You mean Dennis? He helped design mine also.

Quote:

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Originally Posted by maddox10

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

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i guess thats without motors? lol

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?

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.

Quote:

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Originally Posted by mr_turbulence

Quote:

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Originally Posted by maddox10

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.

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You mean Dennis? He helped design mine also.

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Dennis= Inventor.

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)

The overall diamater isnt important...the PCD and tooth count is what you need to know... half the PCD of each gear... then add them together that will give you your exact distance between centre's...if you dont have a milling machine or a precise way to drill it, you might find this difficult to make...Just add a tiny bit on top of the centre distances... its better to have them further apart then too close.

Look at this link to find out the PCD of you gears when you know the tooth count;
http://hpcgears.com/newpdf/spurgears_1.0mod.pdf

the design uses gears from technobots so getting the PCD is easy. Thanks for the help. Just trying to confirm that i can get the 6mm ali plate for the mounts, and that it will be able to bend to 90 degrees and what radius that would be.

Quote:

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Originally Posted by mr_turbulence

The overall diamater isnt important...the PCD and tooth count is what you need to know... half the PCD of each gear... then add them together that will give you your exact distance between centre's...if you dont have a milling machine or a precise way to drill it, you might find this difficult to make...Just add a tiny bit on top of the centre distances... its better to have them further apart then too close.

Look at this link to find out the PCD of you gears when you know the tooth count;
http://hpcgears.com/newpdf/spurgears_1.0mod.pdf

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Thanks for the help. The distance is 49.5mm so in the design, should i factor in 0.1mm or more do you reckon? I'm probably going to be asking Kenny to machine these parts for me as i cant trust myself with measurements this exact! i do remember from having RC cars that the gears should not be super tight together or is this factored into the design of larger gears?

Projects dead, was going to be overweight! Thanks for all the help anyway.

What would be more powerful?

Four Argos gearboxes with 18v motors, overvolted to 22.2v. Running on 75mm wheels

Or

2 speed 900 replicas, reduced down by 7.25 to 1, ran at 22.2v. Running on 130mm wheels

Both set-ups use electronize escs (if two speed 900 motors was used, could you have two speedos per motor?)

Cheers

Dan

In this way, the speedo and batteries will limit the total available power.

The Speed 900's will demand a Sidewinder or stronger to give their potential. And then the 130mm wheels will prove an advantage.

I'm using 30a electronizes so am i right in thinking if i use two per motor, ill get 60a possibly from each motor? I'm using lipo so easily can deliver that sort of power

The only result you'll have with 2 speedo's feeding 1 motor is 2 dead speedo's.

To make it simple. A speedo works because it cuts up the electricity in parts, and these parts can be shortened or lengthened.

You could sy, 1 minute is 1000 parts (the whole thing will buzz @1KHz) and each part can be run from 0 to 100%

0 is no power, 100 is full trottle. Now the cutting up is done with mosfets in most speedo's. For explanation function, these mosfets are tiny electricaly switched switches.

Now, try to switch 1 lightbulb with 2 switches. Each switch is in a different room, and you will have to switch exactly at the same time, otherwise you'll have a short.

Get it now. Thanks! The sidewinder has been discontinued now so I'll scrap the whole project for now me thinks

No need too, you can use that 130mm 7.5-1 gearratio speed 900 setup at a much lower voltage and still get respectable power.


Let us say, 10S NiMH=12V

Speed 900@12V=6600 rpm

6600/7.5=880rpm

130mm*pi*880=359216mm/min= 359216/1000000*60=21.5km/h

Even dropping back to 3S Lipo gives you 19.9km/h
Or 3S LiFePo = 17.7km/h

So what your saying is if I run a speed 900 on a 30a electronize at 22.2v, it will probably blow the esc?

The ESC will be a limiting factor.

On the other hand, if 666W per side ain't enough, you're in the wrong weightclass.

But, the Speed 900 setup as you propose runs a tad fast, doesn't it.
42km/h is a tadoverkill.

So, why the persistent use of the 22.2V? It's not if a 2450mAh 3S Lipo is that expensive.

Have a 6s lipo so makes sense to use what I've got. Thank you for your help by the way.

Strange reasoning. ‚20 to have a battery that is lighter, smaller and more useable for the idea, of trowing a complete idea in the garbage can?

Also, if you want to use the 6S to drive a spinner, even then a seperate drive-battery ain't the worst idea you can implement.

What do people think of these pinions?
http://www.fxaeromodels.com/product_inf ... ts_id=4671

From brushless rc helicopters, just a bit worried about durability

I don't like Z10 gears on a Speed 900.

The Graupner Speed 900 axle is 6mm.

Inside diameter of the teeth is Z*M-(M*2.5)

Amount of Teeth * Module -(module*2.5)

10*1-(1*2.5)=7.5mm

With the 5mm hole, the teeth have a foot of (7.5-5)/2=1.25mm
With the 6mm hole, it's even worse. (7.5-6)/2= 0.75mm

It doesn't get better if you have an original Johnson motor with the 1/4 axle. (7.5-6.35)/2=0.575mm

probably will go for the technobots z12 mod1 for the pinion. no drill motor would ever demand 30 amps or over would it? (except in exceptional circumstances)