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GRINDER GEARBOXES


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timmeh
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Joined: 20 Jul 2004
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Location: Victoria


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GRINDER GEARBOXES

Bunnings is selling 500watt angle grinders for $18 if anyone is thinking of buying them for the gearboxes
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Post Sat Sep 04, 2004 8:56 pm 
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timmeh
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Location: Victoria


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How strong are the grinder gearboxes?

And what gear ratio are they?
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Post Sat Sep 11, 2004 4:33 pm 
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Glen
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not very strong IIRC, george had a few broken ones at the annihilator. i think inspector general broke one at robowars too.

i think they are 2.75:1 ratio.
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Post Sat Sep 11, 2004 7:10 pm 
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Spockie-Tech
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Joined: 31 May 2004
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Location: Melbourne, Australia


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I.G's gearbox just had the pinion gear securing nut come undone at Robowars, which allowed the pinion to spin on the shaft without transmitting any power.

we tried to weld it back on, but clagged up the gear in doing so.. I think George's gearbox broke from a side-load whack against his wheels, but I'm not sure, so I'll let him confirm or deny that.
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Post Sat Sep 11, 2004 8:54 pm 
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Nexus
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Joined: 17 Jun 2004
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Well I have only ever broken one actually and that was just in the flimsy way I mounted it. The drive train was still working but because the mounts broke the wheel fell a bit thus bottoming out the robot.

Another thing to keep in mind with the damage on mine was that it took a lot of hits when the wheels where off the ground which is really bad, better to have your wheels on the ground if they are to be hit.

Never got round to using the large holes in the grinder and reduced the surface area of the mount as well so it was only a matter of time before that broke.
Even other robots that have had problems its always the same issue and thats how its mounted. I think IG just broke a rivet which secured the grinder to the extended motor shaft.

I dont blame the grinders but, if you have problems with them its basically beacause you havent mounted them properly.

I still think they have a lot of potential and am redoing the mounts as we speak.

The thing to keep in mind is they are moulded to fit on a plastic circular ring shape and this gives it a broad surface area to distribute impact forces.

The grinders that I have seen that have broken are because the knocks have been from a certain angle that force the grinder to want to pivot on one side thus putting a lot of pressure on a small area.

Trick is to mount it so it is in contact with as big a surface area as possible as well as well as using multiple dregrees of mounting. ie Pinscher only used the 4 holes on the bottom used to hold the original plastic case on, these arent really made for this sort of stress. (was slack and didnt bother using all the holes even though I thought I should)

The ones I am replacing the XU1 with will be using the same 4 holes as well as the very large threded holes top and bottom and also 3 threaded holes on the face of this particular unit so that means it is mounted on three different sides not one as before.

Team Hellbent asked a similar question about some stell pressed bearing housings and would they work in a spinner.
The answer to both those questions is the same.

Bearing housings for spinners and angle grinders for drive share the same considerations. The individual parts themselves will do the job but its how good you implement it into a sytem to absorb shock impacts. Your robot is only as strong as your weakest link and that generally is something a builder hasent done or considered.

Consider good mounting and when designing visual the robot being twisted and get an idea of how much movement there is and have you allowed play in necessary components.

I have only come across ratios of 2,7:1 could have been 2.75:1 but wasnt counting beesdicks at the time just by eye.
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Post Sat Sep 11, 2004 9:18 pm 
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