Traction problem with Big Bear

[Deleted member 4366]

The weight will stop me pulling wheelies [emoji468][emoji41][emoji106]


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I was thinking the same thing. I had a 500w BPM running at 30 amps from a rack-mounted 6kg 20Ah battery. It would nearly always wheelie when I did a quick start. One time I did a real Hi Ho Silver coming out of Tescos. I think yours would probably be OK though, as you only have 2/3 the torque and a lighter battery.

 

[Woosh]

I think yours would probably be OK though, as you only have 2/3 the torque and a lighter battery.

MH runs the SWX02 from the same 20A controller, I expect he gets the same torque at over 8mph, below that, he may lose 10%-15% but gains in better traction.

 

[Marwood Hill]

I was thinking the same thing. I had a 500w BPM running at 30 amps from a rack-mounted 6kg 20Ah battery. It would nearly always wheelie when I did a quick start. One time I did a real Hi Ho Silver coming out of Tescos.

Ha ha i can imagine that [emoji15][emoji468]. 500W eh!!![emoji15]



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[Marwood Hill]

I’ve been out testing again. Acceleration is so much better with the RWD. Not a hint of wheel-spin whatever the gradient and surface. I have tried our killer hill. The BPM FWD on a dry surface is more powerful. I would have liked to have brought it into use with a second throttle on that particular hill. But no, i cannot do that, it wouldn’t be that silly road legal thing!


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[anotherkiwi]

I’ve been out testing again. Acceleration is so much better with the RWD. Not a hint of wheel-spin whatever the gradient and surface. I have tried our killer hill. The BPM FWD on a dry surface is more powerful. I would have liked to have brought it into use with a second throttle on that particular hill. But no, i cannot do that, it wouldn’t be that silly road legal thing!

We'll hide our eyes and look the other way... About the fifth time I was passed (in a car) by a moped with no muffler doing 70 km/h (legal limit 45 km/h) I stopped worrying about "road legal".

 

[Marwood Hill]

Will the rear wheel with freewheel and brake rotor that i’ve taken off the Big Bear fit a normal bike? I’m thinking of putting it on our local sales page. How much is it worth?


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[Woosh]

I’m thinking of putting it on our local sales page. How much is it worth?

A new BPM motor costs £175, second hand may be £75-£100.
it's difficult to find a buyer for just the wheel. If you have a donnor bike, it may be worth converting it using the BPM motor wheel and buy a kit like you were planning to do.

 

[Marwood Hill]

A new BPM motor costs £175, second hand may be £75-£100.
it's difficult to find a buyer for just the wheel. If you have a donnor bike, it may be worth converting it using the BPM motor wheel and buy a kit like you were planning to do.

I mean just the back wheel as it is. Will it fit a non electric bike?

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[Woosh]

sorry! yes, it will, it's a standard part.
26" rim.

 

[Marwood Hill]

sorry! yes, it will, it's a standard part.
26" rim.

Thanks. Is £20 a fair price to put it at or less?


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[Woosh]

Thanks. Is £20 a fair price to put it at or less?


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it's fair.

 

[Marwood Hill]

it's fair.

Thanks, i will try.


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[Deleted member 4366]

The problem is the postage. It's quite tricky to find a box the right size, and if you do, it will be above the minimum size for Collect plus and My Hermes, so you have to get a special quote from Parcel Monkey or similar.

 

[Marwood Hill]

The problem is the postage. It's quite tricky to find a box the right size, and if you do, it will be above the minimum size for Collect plus and My Hermes, so you have to get a special quote from Parcel Monkey or similar.

Yes, the postage is more than the wheel is worth. I’ve put it on my local Facebook Marketplace for £10. Collection only
P.S There was a newish Big Bear on there a few days ago for £700. Looks like it’s sold now.


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[Marwood Hill]

How effective should a rear disc brake be? This new disc gives the same result as the original. It doesn’t give much stopping power like a rim brake does. It certainly wouldn’t stop me in an emergency. For example, if the front cable broke. Would hydraulic give better braking?

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[Woosh]

yes, it would - approximately about twice the braking power because the pads are larger and the effort is far less.

 

[Deleted member 4366]

A hydraulic one would me loads better. Your present one can be improved by adjustment. The fixed pad has an adjuster screw on the back. You adjust it until it's just clear of the pad, then you adjust the front (moving) pad with the cable to position it just clear of the disc.

You can sometimes do a quick adjustment by loosening the two screws that hold the caliper to the adaptor, hold the brake on and re-tighten the screws whilst holding the brake on. That's how to set your hydraulic brake if you install one. It works on cable brakes as long as there's enough movement allowed in the slot.

When you fit a hub-motor to the back, you normally need an additional 12mm washer on the axle to bring the disc in the right position to line up with the caliper.

 

[Marwood Hill]

Thanks all. That’s my next job sorted then. To fit hydraulic brakes asap.


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[Marwood Hill]

Progress so far with dual switching. Does anyone see a problem with running a cable from the battery / controller to the handbars and then back to the motors?

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[Deleted member 4366]

Whatever you do, make sure that your connections are 100% reliable. If only one goes open circuit, you'll blow mosfets in the controller. If I turn that around the other way, do not operate the throttle or PAS if a motor stops working properly.