Boring Brick

[mrsam]

Cheers John, it certainly won't be the most impressive spinner ever built as it's being done in a very basic and low cost way. It won't cause huge damage but the idea is to have a really thick (25mm) single stainless steel tooth which will be counterbalanced, my hope is that with the rpm at between 3000-4000 it should get consistently good engagement. So really it's more a kinetic flipper than damaging spinner.

[overkill]

I think you'd be fine with a relay tbh. If you're running a lower voltage, say 6s max. Relays handle other brushed spinners like old Inertia XL's and Scissorhands (although that has now gone over to a couple of botbitz I think)

Actually, Scissorhands never used normal relays, it used a pair of 100A solid state relays. They were never terribly reliable and had to be heavily modified to resist shock damage. Scissorhands is currently using a TZ85a with custom code; its still having problems but they are likely to be my fault.

If you already have the relay and Turnigy r/c switch, use them and leave space for something bigger if the relay causes problems.

[mrsam]

I'll use them for now but take your advice and save room for something else. TBH this is only the first incarnation anyway, it will get upgraded over time but the main idea was to keep the first build as simple and cheap as possible.

[mrsam]

After looking around for a while and not having much luck in finding suitable replacements/spares for the 900 drive system i'll be putting into Hatchet 2 i have found a couple that look promising. I'll be ordering one of each of these motors and putting them through their paces, if i find that one or both work then i have a cheap source of spares, if they don't work it's not a huge loss at £16 for the two with postage and i'm sure i could find a use for them. These are the motors in question http://www.pollin.de/shop/dt/OTg0OTg...C987LG_BF.html http://www.pollin.de/shop/dt/MDc0OTg...ON_QC987G.html Both say they are rated for 12v but i'm sure i could overvolt them, i don't believe for a second that the first motor only puts out 56w though.

[adz600]

rpm is well to high

[adz600]

look for caldercraft on ebay I have two I was going to use on the axe but were not powerful enough but will proably make a great drive system

[mrsam]

I did see the Caldercraft ones but i hadn't heard great things and at £60 a pair i didn't want to spend that and have them be rubbish, maybe i'll buy one and see how it goes though.

[mrsam]

I actually had a second look, the first motor i put up is rated for 2060rpm at 12v, might still be worth trying one of those out?

[Ellis]

I'm not sure you can trust that to be accurate. It was the info on the selling page on pollin being misleading (they called the RPM at maximum power the no-load speed, which was actually 100% higher) that screwed me up with the motors for Rango. The datasheets on the selling pages often show the true figures direct from Johnson, but in the case of the lower revving motor, there is no datasheet available. No useful google results either. It might well be very low power; low RPM brushed motors are often mild, the popular s900 model was an exception.

That said, regardless of power output, that output shaft is weird as hell. I don't know if it can be removed/cut down, but even if it can be the shaft beneath is probably awkward.

The other model, at 17k no load, will need two stages of reduction. And having "racing" in the name suggests it's timed to be more powerful in one direction which would be a pain.

Sadly very little comes close to the s900.

[Eventorizon]

I know its not what you will want to hear but building a machine around a part that is no longer in production is a bad idea. Spares will be impossible eventually and it will put the whole machine out of action. Look at brushless drive motors that have the same mounts or go for something totally different, Speed 900's are gone.

[maddox10]

I do have lasercut adaptorplates that should make it possible to mount 42 or 50mm NTM outrunners were a speed 900 fitted.

[mrsam]

That sounds great mario I'll pm you

[Eventorizon]

You could go mad and go for 2 RS775 motors per side. Provided they are set up right, that would be a very punchy set up!

You can get them from Banebots, Robot Marketplace and ebay:

http://banebots.com/pc/MOTOR-BRUSH/M7-RS775-18

http://www.robotmarketplace.com/products/0-TRA5675.html

http://www.ebay.co.uk/itm/Traxxas-Ti...0-TRA5675.html

[Ellis]

You wouldn't need two. 18v 775s have superior power and torque figures than speed 900s at 12v. Once you've put a 775 through double the reduction, on paper, they outperform an overvolted speed 900.

[Eventorizon]

Well, one 775 then, but you would need another stage it seems to make the drive match or exceed the Speed 900's.