Homebuilt Newbie

[monkoffunk]

Hi all, and hello. I'm new to electric bikes, and I don't even have a bike yet. I've just received a Golden Motor Magic Pie I ordered, and I have 4 11Ah Haze Gel Cells (lead acid) on order. I'd planned to keep these in panniers maybe?

Now I have my motor, I plan to get it spoked into a wheel. Can I just go to any good bike shop with my new bike and ask them to spoke the new hub into the front wheel? Any idea of cost?

Also, I've heard that the forks might not be able to stand the stress of this quite powerful motor. So when choosing a bike, is there any advice any one can give me?

Another question: Do any of the bikers use the frame of the bike for the negative/ground connection of their electric bike, or is that a bad idea?

I planned also to to use a double-throw, double-pole switch so that I can switch the battery bank between 24V (2 parrallel banks of two 12V in series) and 48V (four 12V in series), the idea being 24V for range, and 48V for performance. I have a diagram of the setup if anyone wants to see it.

I'm aware also that this bike I'm building might not be strictly legal..

 

[NRG]

"...I'm aware also that this bike I'm building might not be strictly legal....."

What do you mean 'might be'!

Welcome to the forum! What made you choose the MagicPie out of interest?


Firstly, SLA's are cheap, plentiful but very heavy, I'd guess yours will weigh in at +16Kg, that's a lot of weight to mount on a normal bike and they can adversely affect the handling. The motor must be another 6Kg or more so you're adding 22~24Kg of extra weight along with yourself to the bike, for me that's way too much...for my first attempt at a DIY bike I used a Cohnis motor and SLA's similar in weight to yours... it was not too long before I replaced them.

However, as you have ordered them the wheel build will be important, whilst I'm sure a competent LBS could lace the motor it may be best to use somebody who has done it before, like SJS Cycles....they did my build using a small geared Bafang motor in a strong Rhyno rim , cost was around £100 inc shipping, I suggest you give them a call they are very helpful and know their stuff.

Forks will need to be strong, if you have steel then they are better than the Aluminium ones either way I would recommend some sort of torque arm to stop the motor turning in the dropouts.

I've never used the frame for earth return but I don't see why not. Your switch idea for the battery is neat and should work OK. Don't forget to post a build thread with lots of pics....we like that sort of thing! Good luck.

 

[monkoffunk]

Thanks for the warm welcome NRG!

Yep, I have worried that I have gone overboard on the batteries and weight...

I chose the Magic Pie because it just seemed a good deal for a beginner, what with the controller integrated into the hub, and a flexible voltage and power output range. It arrived very quickly from China, sadly with no manual, though I believe it can be got electronically. I'm asking GM for a copy at the moment.

Thanks for all the hints, regarding the torque arm, is that something someone can fit, or is it a DIY job? I'm not particularly mechanically minded, more electrically so...

I will post some pics as soon as things start to progress.

 

[Trevor Holloway]

Earth return

I'd be very wary of using the frame / forks as an earth return as you would be expecting the electrical power to be transferred through the steering head bearings so would not provide an ideal conductor (greased up ball bearings).
I have heard of steering head bearings fusing up when people have been using the motorcycle frame as a conductor when welding on the forks.

 

[onmebike]

I'm not familiar with the motor your planning to use but two points I've picked up on may be of concern.
Firstly, the ground/neg connection through the frame may have continuity problems with a front wheel drive because of the steering bearings not being an ideal connection between forks and frame, this may be worse with suspension forks.
Secondly, the switched voltage's. Assuming your using a controller that has a maximum voltage handling of say 48volt, will the controller allow the use of 24volt or will the low voltage cut out, kick in?

 

[NRG]

Ah, yes, good point on the forks guys. The MagicPie is multi voltage capable, the controller is built into the wheel.

There are commercial torque arms available if you hunt around, I think ebikes.ca sell them or you could simply use half a spanner and jubilee clip to stap it to the fork leg, steam punk style

If contemplating lacing the motor yourself there's very good info on Sheldon Brown's web site and here: Online Spoke Calculator for Hub Motors

Also some of the members on here have done it themselves so may be able to advise....

 

[monkoffunk]

I was more thinking of just saving a bit of wire between the front and back of the bike, but not necessarily having the ground connection at the fork, the negative wire could connect to the top of the frame. Advice taken on board though.

Regarding the voltage, my understanding of the magic pie is that it's integrated controller will handle a range of voltages from 24V to 48V, up to an absolute max of 60V, so the setup should be legitimate.

 

[monkoffunk]

There are commercial torque arms available if you hunt around, I think ebikes.ca sell them or you could simply use half a spanner and jubilee clip to stap it to the fork leg, steam punk style

If contemplating lacing the motor yourself there's very good info on Sheldon Brown's web site and here: Online Spoke Calculator for Hub Motors

Half a spanner and a jubilee clip sound quite agreeable actually. Regarding the spoking, I suspect i'm best off leaving that to the professionals Thanks for the link though.

 

[averhamdave]

Have you a link to the supplier please. Have been looking at these motors for the last couple of years. All looks good then all of a sudden they get a bad review and I'm put off! They must be fairly good now because Alien are using them.
Thanks, Dave

 

[monkoffunk]

Have you a link to the supplier please. Have been looking at these motors for the last couple of years. All looks good then all of a sudden they get a bad review and I'm put off! They must be fairly good now because Alien are using them.
Thanks, Dave

Obviously I haven't had enough experience with mine yet to know if it is any good. They are made by Golden Motor (www.goldenmotor.com). Some problems I've heard of with them are that the owner of the company is a little arrogant, which may or may not be true, I think perhaps he's just someone who gets a bit tetchy about criticism.

The second issue I heard of with the magic pie specifically I think was of overheating, though I think that may have been more the earlier ones, and also seems to be more (excuse the generalisation) Americans who think they can go up a steep hill without pedalling for miles and then wonder why the motor shuts down.

Build quality wise, it's certainly feels like a substantial bit of kit. Will be eager to get it running when the batteries arrive hopefully on Monday.

 

[drillam]

I wouldn't be too concerned about the weight. My self build has about a 14Kg Lifepo type battery and a big rear hub motor weighing about 8Kg, I weigh around 95+ Kilos and I also take a lot of shopping on the back paniers and in my backpack. All this on a cheap mopuntain bike, no problems really apart from the front end is a bit light and so I'm in the process of making a couple of battery boxes to mount to the forks to even things up a bit.
Good luck

 

[monkoffunk]

That's reassuring, I suppose it's just suck it and see. Being a front hub motor, that at least balances some weight forward. The batteries were at least cheap, less than £90 delivered (when they eventually arrive), yet seem quite high quality in terms of cycle life.

 

[Old Timer]

monko

Hiya and welcome. Now I don`t wish to sound harsh but you would be prepared to drill and fix a wire to the front end of the frame and then drill and fix a wire to the rear of the crossbar so as not to have to run a short length of decent wire around 2` ?? is that correct or am I missing something.

One of the things you`ll learn about rattling around on an E bike is that you need all electrical joints and connections 100% and preferably soldered with good quality cables. Doesn`t the new front hub come with a cable connected? (3 or 8 wires)?

 

[monkoffunk]

monko

Hiya and welcome. Now I don`t wish to sound harsh but you would be prepared to drill and fix a wire to the front end of the frame and then drill and fix a wire to the rear of the crossbar so as not to have to run a short length of decent wire around 2` ?? is that correct or am I missing something.

You're not missing anything. I guess I was just thinking aloud. Clearly it works for cars, but then they are routing a LOT more connections. If I added extra electrical items, I though it would be nice to just use the positive wire and tap the ground of the frame. But you're right, it's probably more hassle than it's worth.

One of the things you`ll learn about rattling around on an E bike is that you need all electrical joints and connections 100% and preferably soldered with good quality cables. Doesn`t the new front hub come with a cable connected? (3 or 8 wires)?[/QUOTE]

It does come with cable yes, I was probably just being silly.