You definitely want the bearings to be a good fit on the axle or they could wear out fast.
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Australian 2015 Featherweight champion
UK 2016 Gladiator champion

Thought the friction drive looked familiar.

I have been thinking of sportsman designs lately and Minimowers wide slow drum but without the rear wedge was one of them.

Couple of thoughts; I hinged from the top down and spring loaded the drum drive so it was self adjusting worked well, simple and reliable.
Down side of this is only works in one direction.
If you won’t to reverse drum rotation when inverted the friction wheel will tend to lift of and slip.
Minimower 2 is hinged horizontally works ok in both directions but requires more spring tension as its not self energizing.
Also I recommend using a colson wheel for friction wheel, especially if using more revs than a drill, our other drum bot Reboot ran its drum faster and with those white wheels we were gluing the tread on and still having them fly to pieces.

The original Minimower drum is exhaust tube with plastic bag trolley wheels.
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Satisfaction is proportional to effort and results.

Thanks for the feedback Rotwang!

My design currently is a horizontal spring loaded drum drive, however my robot is not invertible really, as the height of the drum/friction drive is quite a bit higher than the wheels. So I may as well go for a top-down system for reliability, thanks for the suggestion.

My initial plan was to get a tyre around the can of the outrunner motor itself and use that as the friction drive, however I will order some Colsons to be safe. Anything is better than snapping belts in competition!

The problem with outrunners is that they all have quite small bearings and don't like taking large side loads or shocks. Having a wheel or a pulley around the motor may separate it from the endbell - its usually only held on by glue & friction on a narrow flange. The weapon drive will be much more reliable If you mount the drive wheel on the motor shaft and add a bearing block on the end of the motor.
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Australian 2015 Featherweight champion
UK 2016 Gladiator champion

And hope, don't forget hope. Its usually the only thing holding my bots together let alone the motor.

So have you decided if your going to make nationals?

Steve
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Steven Martin
Twisted Constructions
http://www.botbitz.com

I should make Nationals, maybe not with the finessed bot taking into account all the factors we discuss, but with something that has two spinning wheels and a spinning thing on the front.

I didn't want to take the last spot in the 16 but I see that's changed now so I will register for nationals tonight

Awesome
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Miles Blow - Julie Pitts
www.mulesfilm.com.au
www.wombokforest.com.au

-Pickasso- Vivid Sportsman champion 2015

Haven't had access to the workshop for a while. Not sure when it'll next be open. Ah well, still plenty of time.

In other news, are car fan motors still a worthwhile choice for anything? probably a bit weak as far as weapon drives go these days right? I've got a few new 12v Toyota 2-wire ones that I'm wondering what to do with.

They use to be popular but a brushless will most likely be lighter and pack more punch…. keep em though.
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Miles Blow - Julie Pitts
www.mulesfilm.com.au
www.wombokforest.com.au

-Pickasso- Vivid Sportsman champion 2015

I'm using those exact drill motors, just checked the size and they're the same as yours. Any chance I could get a copy of the STL files you used? I don't have my own printer but I know a few people who do, planning on being nice to at least one of them I'll PM you my email.

Sure thing.
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Miles Blow - Julie Pitts
www.mulesfilm.com.au
www.wombokforest.com.au

-Pickasso- Vivid Sportsman champion 2015