My outback mountain board

[patrickza]

Ok so time for my second build, something completely different, an outback mountain board.

This is my latest toy:

It has space between the board and frame for some batteries and electronics, as long as I can keep them low enough not to interfere with the turning:

Ok so that's all I have for now, but this is what's on the shopping list unless you guys can convince me otherwise:
1) 12s of the Headway 31120S cells - Yes I know I should be going lipo, but I already have 6 of these left over from my bike build, and another 6 will be a cheap add-on and give me a 38.4v10AH pack.
2) Turnigy 80-100-B 130Kv Brushless Outrunner - nothing like a little overkill to get that ev grin nice and wide.
3) Turnigy Monster-2000 200A 4-12S Brushless ESC - I'm also considering a caste creations unit, but the price is much higher. Thoughts?
4) TURNIGY 5-7.5A (8~42v) HV UBEC for Lipoly - Will this handle the headways at 44v fresh off the charger or should I get something else?
5) 14 tooth 1/2" sprocket for #25 chain.
6) 90 tooth sprocket for #25 chain.
7) Hobby King GT-2 2.4Ghz 2Ch Tx & Rx - In case of emergency jump off the board, this should make that easier, and maybe one day I'll add a steering servo and make the board come pick me up James Bond style
8 ) Turnigy Watt Meter and power Analyzer - Cheaper than a cycle analyst.

So am I on the right track at least? One of the big issues I have so far was trying to get a decent gear ratio going. With a 14:90 my top speed would be about 25mph, too fast for a board like this. I doubt I'd ever want to go over 20. A 1:10 ratio would give me a top speed of 17.5mph which is what I'd consider about right for this build. Anyone know where I can get either a smaller front or larger rear sprocket?

Then some advice on the ESC. I need to have e-braking (with the friction brake as my emergency anchors). The ESC above and the castle creations both have soft/hard/none options, but the castle creations is more expensive, though I've heard it's the best around and has the smoothest start up so I might not get thrown off the back of the board as often. Opinions please.

Anything else I might have missed?

 

[EV4LIFE]

Hi there,
I'll pass on whatever knowledge I have, with the turnigy 200A monster, I believe your going to have syncing issues, if you dont push first or something, there are a couple of threads with attempts of this esc, but it is not the best, and many have gone poof(Burtie's findings=>http://www.endless-sphere.com/forums/viewtopic.php?f=28&t=12768&start=45), definitely go with a castle creations, recumpence have been using them almost flawlessly, just add caps, and still sorta roll from the start.
With CC you can also buy the castle link I believe, and pretty much program anything you want, including throttle curves.
If your elec. savvy enough add hall sensors and a bl sensored controller, instant acceleration.

And you WILL NEED some sort of working mech. brakes, do not rely on the e-brakes of your esc, especially considering that these are plane esc's which don't even use breaks, well they do, but it won't stop a moving board with human on it, maybe ghetto mod some disk brakes on or something, I don't trust the flappy friction break for the speeds your going to be using it at.

In regards to sprockets, the HXT your using has a 12mm dia. shaft but your posted 14tooth sprocket has 1/2 dia. bore which is just a bit over 12mm it would be better to get a 3/8 I.D. sprocket and redrill.
To get a suitable gear ratio, I think you would have to either do a two stage (complicated and less efficient), get an even smaller sprocket (getting hard to find), lower voltage (less efficient, sucks more amps) or or rewire from delta to wye (star) which drops the motor rpm by about 0.57 of original and increase torque by theoretically 1.73, which means you can use some more suitable sprockets (this requires opening up the motor).

Regards,
Martin

 

[patrickza]

definitely go with a castle creations

In regards to sprockets, the HXT your using has a 12mm dia. shaft but your posted 14tooth sprocket has 1/2 dia. bore which is just a bit over 12mm it would be better to get a 3/8 I.D. sprocket and redrill.

Thanks for the info, I had a feeling I was going to have to go for the castle creations ESC. I'll look around and see if I can find one at a decent price. I've been looking for a 12mm sprocket but the metric sizes seem hard to find. A couple of websites interchange the 12mm and 1/2" sizes, but 1/2" inches = 12.7mm. Is the .7mm too much of a gap?

Maybe I should start looking at UK sites for metric sprockets. I'll also check some local sprocket places and see if they dont have something in 12mm.

Edit: Just did a quick search and might have struck gold. Here is a 9 tooth 12mm bore sprocket, does that look like it'll do the job: http://www.bearingstation.co.uk/products/Sprockets/Sprocket_-_Pilot_Bore/Pitch_0.75_Inch/6SR9

ReEdit, maybe not, a 90 tooth sprocket with this bore seems to be 55cm across

 

[dontsendbubbamail]

Another way to do the sprocket is to get one with a 1/4" hole and drill it to 12 mm. McMaster-Carr has a wide selection of #25 sprockets.

http://www.mcmaster.com/#roller-chain-sprockets/=5xhcsf

Bubba

 

[torker]

I was wondering how you are going to run a 90t sprocket with that little back wheel. Running it wye sounds good. If you can run half the rpm. it would make things a lot easier. I'm sure you could have it shipped to someone on here that could mod it for you.

 

[patrickza]

I was wondering how you are going to run a 90t sprocket with that little back wheel. Running it wye sounds good. If you can run half the rpm. it would make things a lot easier. I'm sure you could have it shipped to someone on here that could mod it for you.

Here is an electric scooter wheel of the same size running the 90 tooth sprocket.

Fits fine, but you're absolutely right, the wye setup would be perfect. I'm not well enough versed on motor internals to do the change myself, otherwise it would definitely be the way I'd go, along with fitting some hall sensors so I can use a sensored controller. If someone volunteers I'd be very grateful, but I'll keep looking for sprockets in the meantime...