Magic Pie 3 questions

Positive discussion on ebikes and pedal assist bicycles

Magic Pie 3 questions

Postby OldNick » Tue Oct 30, 2012 12:54 pm

I have just had delivered two new MP3 rear wheels. They are the 1000W version, which I intend to run on 24V to drop the watts down to (pretty much) legal level. I ordered all the fruit: cruise control, pedal assist, regen braking.

SO. First question. Does anyone know where I can dl an install manual? I tried the Golden Wheel site, but the pdf download just keep dying on me after a couple of minutes. IT does not look like rocket science to get together, but I would hate to make some silly mistake.

Next. I was reading a review of this getup and the guy commented that there is considerable drag from the motor when not powered. I thought I posted here about it, but I can't find the post. Having tried to turn the axle on the wheel, I can see that there is indeed quite a bit of drag. Are the lower- wattage versions better, and is there a way around that drag, should I get caught somewhere with a flat battery...I mean short of carrying my old back wheel. :)

EDIT: And another. I have ordered some units that watch each battery cell on the LiPos. But I was wondering if anyone has experience with how well the regen braking handles monitoring the charge level, especially as I will be using only 24V 6S batteries.

Any other hints welcome as well. Thanks in advance.

BTW, regarding Golden Wheel. I actually ended up emailing to a sales rep. He was about as helpful a guy as I have dealt with, ever, on the Net. I kept on thinking of new bits I wanted as I learned of them and I just kept getting a new quote. By going through him I saved $70 on freight over just ordering off the site, and AFAICS the gear prices were better as well.

The only thing was, I was expecting just the hubs and spoke to build my own wheel and in popped two whole wheels, built for me. I decided I could work with that. 8)

The wheels were delivered from China to Perth, Western Australia on the 6th day after I made payment. These guys are smooth.

Nick
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by BNA » Tue Oct 30, 2012 4:14 pm

BNA
 

Re: Magic Pie 3 questions

Postby s3312345 » Tue Oct 30, 2012 4:14 pm

The MP is a direct drive (as opposed to internal hub geared) hence there's no way to avoid the magnetic drag. I have the MP1 and yes when the battery is dead it is quite difficult to pedal, not impossible so it still possible to limp home at about 10-15km/hr in low gear, you'll get a good work out for sure on those occasions :)

You shouldn't need an installation manual every plug is fairly well labeled and can only be connected one way.

I'm running mine with a Ping LifePo4 and the battery monitor LEDs on the throttle are pretty useless, it will go from green to dead within a km or 2. With a speedo after a few rides you get to know what your range is anyway.

Here's a tip that works for me, on the odd occasion that I have run the battery flat I can usually squeeze a few more joules out of the battery by disconnecting and reconnecting the battery plug, and once it's going I pedal as much as possible, feather the throttle and at a much lower speed so as to reduce the current draw and hence the voltage drop which will trigger the BMS cut out. This is a much easier way to limp home than to be on a completely dead motor.

Mine is almost 3yrs and 7000km old and still going, I'm actually quite impressed with it's longevity.

Good luck with yours.
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Re: Magic Pie 3 questions

Postby OldNick » Tue Oct 30, 2012 5:02 pm

Thanks for the reply.

hmmm..OK. Maybe they need to have a simple clutch mechanism to disengage the motor in soe way. However, your hints for battery saving are sound. I am hoping to get good range by seriously using this to assist in pedalling and not just let it take me. I tow 40-45Kg of trailer/dog/gear around d behind me and my old bod feels it sometimes.

It wasn't just the wiring. I now have a jpg of how that goes and anyway as you say it's pretty simple. But I have the sensor for the pedal assist and I am not sure how to mount that or what exactly it's sensing (I received no magnet etc that I can see)

I hope they are building as well they used to. :)

Nick
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Re: Magic Pie 3 questions

Postby s3312345 » Wed Oct 31, 2012 11:24 am

Well it's simple in concept I guess but in practice it's another matter. To get it to free wheel without the magnetic drag you either have to let the ring of magnets attached to the shell of the hub rotating free of the hub or alternatively have the inside armature rotating with the entire wheel, both of which isn't easy to achieve.

The if you want lower drag when free wheeling the only option is to get a geared hub but then you lose regen braking.
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Re: Magic Pie 3 questions

Postby OldNick » Wed Oct 31, 2012 12:07 pm

Yeah that's pretty much what I figured. I am sure that getting the armature to follow the magnets, or the other way, freeing the magnets, should not be _that_ hard to do. I mean look what this hub motor does already! :)

No seriously it seems to me that if the rider simply lined up two marks, then "pulled the pin" (or inserted a pin to lock the armature), or whatever, this could be doable. It's not something that needs to be automated, just strong.

Nick
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Re: Magic Pie 3 questions

Postby s3312345 » Wed Oct 31, 2012 12:21 pm

Interesting idea with the locking pins. Do post about it if you go with such a mod.
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Re: Magic Pie 3 questions

Postby OldNick » Wed Oct 31, 2012 12:26 pm

HAH! The novelty will have to wear off before I start tearing into the guts! If I ruin a wheel I will be minus parts of my anatomy I reckon! I _was_ rather more thinking that the GW people could look at it.

However it had crossed my mind....

Nick
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Re: Magic Pie 3 questions

Postby Joeblake » Wed Oct 31, 2012 1:18 pm

The beauty of the Heinzmann system is that with its gearing there's little or no magnetic drag. My smaller trike has a maximum electric-only speed of about 17 km/h, yet when I got for a lengthy ride (80+ km) my average speed comes in at about 19 km/h when in fact I'm doing most of the work myself. It only starts to drop down when I'm going up Welshpool Road. But that's when the motor really comes into its own.

I was offered the option of regenerative braking when I bought the Heinzmann, but declined given that really the only effective way of using regenerative braking is going down a long hill, and when I take off from home (Lesmurdie) I've already got a full charge on the batteries and I'm using no power descending Welshpool Road, so there's no benefit. The only other way to use regen is braking to a stop, and that's something which I find really slows me down. :lol: The amount of power generated that way I thought would be fairly miniscule.

Whilst I've got about 20 watts of photovoltaic panel on the back of my trike(s) which is sufficient to keep the battery fully charged until I start ascending Welshpool Road, have you considered fitting a set of small 24 volt panels for emergency use to just keep a small amount of power going into the battery, which MAY be sufficient to just cause the motor to overcome the magnetic drag, if as suggested you feather the throttle?

Joe
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Re: Magic Pie 3 questions

Postby OldNick » Wed Oct 31, 2012 1:54 pm

Solar is certainly worth thinking about and I can see why you would benefit, if you are riding up WPool Rd the Lesmurdie! but it' would be something I would think about very carefully. Unlike your constant use of them, if used only in an emergency I reckon the panels would not justify their own carriage in energy input. At 20W even, they would make little significant contribution to the total plan, but yeah they _might_ just overcome the drag: it's pretty strong though and I have probably made it worse by going for the more powerful motor, which I did just for redundancy of strength. Need to see how much power just stops the drag at various speeds.

HAH! And here I am dragging around a trailer full of dog and gear! :roll:

With a trike you have a much better platform for carrying the panels and using them as a constant top-up.

sigh...this was supposed to just be nice and simple...silly me done it again.

Nick
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Re: Magic Pie 3 questions

Postby Joeblake » Wed Oct 31, 2012 2:08 pm

OldNick wrote:sigh...this was supposed to just be nice and simple...silly me done it again.

Nick



Back to the drawing board, eh? :roll:

I think your idea of measuring how much power it would take to overcome the magnetic drag would be extremely useful info to have (for everybody). I've got an ammeter (which peaks out at 1 amp) which measures the current coming from my PV panels to my battery. With 20 watts of panel the BIGGEST draw I've ever seen has been .55 amp at 24 volts. So you wouldn't need a heavy duty meter for your purposes. But you'd have to work it so that you could switch it out of circuit before you really hit the throttle, otherwise you'd burn your meter out. (I've done it :oops: )


Joe
To acquire immunity to eloquence is of the utmost importance to the citizens of a democracy
Bertrand Russell
Many people feel their lifestyle has a high price, but they're quite cool with that .. as long as somebody ELSE pays the price.
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Re: Magic Pie 3 questions

Postby OldNick » Wed Oct 31, 2012 3:21 pm

AHAHHHH! NOBODY has blown an ammeter/multimeter like I did. I put it in circuit in a car, straight on the battery line, then got somebody to start the car....we live and learn

I will put the bike on a stand and rotate the pedals with no load, by hand, just waiting for it to freewheel. So it will be a pretty subjective test. I figure if I am careful and take a few readings I will get a reasonable idea.

Nick
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