Close Encounter with the (new model) GnG 36v. 250w mid-drive kit

jackhandy

Esteemed Pedelecer
May 20, 2012
1,820
323
the Cornish Alps
Last Wednesday I received a missal from Parcel Force, kindly letting me know that my eagerly-awaited ebike kit was in their Plymouth depot and, if I wanted it delivered, I'd better cough-up £12 vat & £8 handling charge:

Bummer!.... But they had me by the much-quoted, so pay-up I duly did; to have the (rather small) package delivered on Friday afternoon.

No instructions whatsoever: Not even a wiring diagram, but the controller leads each had a little paper label, so that's all-right then.

As expected, the motor sits below the bottom bracket, reducing ground clearance, with no option to mount it ahead of the down-tube. As I'm fitting it to a full-susser with good clearance & don't intend stump-jumping or other knutt-cracking acrobatics, this shouldn't be a deal-breaker.

However, the fact that it's only anti-rotation fixing bolts to the horizontal chain-stay most certainly could be, because the bike don't got one! (or 2, as do most hard-tails).

But, I'm getting ahead of myself - Never a great idea when dealing with ebikes :p
So, having previously wipped-off the pedals, cranks & bottom bracket (odd name for a threaded hole), offered-up the motor unit.... and it wouldn't fit! The down-tube on the saracen is oversize & oval, terminating in a fairly large flat bottom, which the motor mounting-plate was fouling.

Out with the small angle-grinder with a thin cutting disc & chopped-out about 10mm of the pretty substantial steel mounting plate. I cut this a bit deeper than strictly necessary, but didn't want to have to haul it all off again if something else should cause it to foul if I needed to change the angle-of-dangle of the motor.

D8veh gave a lovely write-up on removing & replacing the bottom bracket & this kit follows the same procedures - Thanks d8veh.

Where it now digresses is that there is only one chainring with this kit & the bike's chain goes 'round the new chainring, OVER the motor sprocket & under the idler; so you will need to split the bike's chain & add a few links, so get a couple of joiners now: I added 7 links, but I think that was probably a couple too many - Time will tell.
I threaded the chain wrong side of the motor sprocket first off & didn't realise I'd cocked-up until I tried turning the pedals, so had to split the chain again & do it proper.

Now for the seriously non-standard bit - How to stop the whole shebang rotating about the bottom bracket & very probably diving into the back tyre, with predictable results. I hope I've solved the problem with about 200mm of 25mm stainless angle, welded into an L and bolted from 2 of the motor mounting plate, to a short vertical tube on the main part of the frame. The alternative would be to fabricate a stay from the front of the motor mounting plate to the down-tube & U-bolts, I guess.

The full-grip throttle supplied is mounted on the left handlebar, as I quite like the twistgrip gearshift on the right: This means it's working fore-side-back, but should be rectified when I get a thumb throttle.

The controller fits quite nicely under the rear damper & the cabling will be tidiedup once the speedict arrives from China. The battery will probably have to go on a seat-post rack, unless anyone can suggest a better mounting point that I've missed.

The controller is marked 36v: 250w: 31.5v(presume LVcutoff): I think it's 16a by the type no.
Does anyone know the dimensions of the 350w brushless motor? This one's body (without endcaps) measures 102.5mm dia. x 450mm: Just pondering whether the 2 might be the same internally :rolleyes:

Haven't had chance to get it on the road yet, but will report on performance, noise etc. as soon as I can.

rps20121202_motor right[1].jpgrps20121202_bracket[1].jpgrps20121202_controller[1].jpgrps20121202_saracen right[1].jpg
 

Old_Dave

Esteemed Pedelecer
Sep 15, 2012
1,211
2
Dumfries & Galloway
You can alter the throttle, turn the magnets over and mod the spring, I did my GNG kit one following the instructions over on the endless forum.


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Old_Dave

Esteemed Pedelecer
Sep 15, 2012
1,211
2
Dumfries & Galloway
O'h forgot to say that with the single chain 350w brushed kit I added 4 links to the chain


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Old_Dave

Esteemed Pedelecer
Sep 15, 2012
1,211
2
Dumfries & Galloway
In case you can't find it, this is the one I went by...
Endless-sphere.com • View topic - Left Hand Throttle ?

Taking it apart and the spring adjustment is close enough to the one I got from GNG to be able to get the idea, the magnets different (from memory its a one piece) but just turn it arround

Put a dab of tipex or felt tip on it before removing so you know which end is which :D
 
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morphix

Esteemed Pedelecer
Oct 24, 2010
2,163
119
Worcestershire
www.cyclecharge.org.uk
I had a mishap y'day with testing my motor and didn't wire the motor fully to the controller, but old Dave helped me out.. I think finding your way, improvising and learning stuff even if you stumble a bit is part of the fun of self-building! This could get seriously addictive, I'm already thinking about my next build and haven't even finished this one! A crank drive motor or mid drive is intriguing, I did consider that on Mezzo which would have left the beautiful 11T-26T gears intact..but I opted for the cheaper and easier option this time round..(saying that, it's not me who has to build the rear wheel!).

It's good when several members are doing builds at same time and you can follow the progress of the builds.. I enjoyed the write up Peter and the pics :)
 
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alfie

Pedelecer
Jul 20, 2011
43
0
The Ebay guy sent me this information for wiring the 250w 36v (original) controller:

1. The thick Black and Red wires from the controller are positive(red) and negative( black) wires for the battery
2. The thick blue and White wires are positive and negative wires for the motor
3. The three thin wires in a connector are for the throttle
4. The thin black and yellow wire in a connector are optional for break puller( break pullers not included in the kit)
 

jackhandy

Esteemed Pedelecer
May 20, 2012
1,820
323
the Cornish Alps
Just out of interest, alfie; if you lift the back wheel what no-load speed do you get in 1st. & top gear?

I didn't specify wheel size when I ordered & I'm pretty sure I have a motor wound for a 12" wheel :confused:

I get 14mph in 1st. & 28mph in 7th. (28 & 14 t. respectively) & it doesn't climb at all well...
 

Old_Dave

Esteemed Pedelecer
Sep 15, 2012
1,211
2
Dumfries & Galloway
Increasing the available watts by either modding the existing controller or replacing it with a 350w version will help with the climbing (check that motor temp doesn't get to warm / hot)


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alfie

Pedelecer
Jul 20, 2011
43
0
Just out of interest, alfie; if you lift the back wheel what no-load speed do you get in 1st. & top gear?

I didn't specify wheel size when I ordered & I'm pretty sure I have a motor wound for a 12" wheel :confused:

I get 14mph in 1st. & 28mph in 7th. (28 & 14 t. respectively) & it doesn't climb at all well...
I am waiting for tomorrow night to try and complete my build. There is no reason to suppose that mine is going to be any different from yours. I discovered with 700c wheels the fixing points are blocked by the wheel and the sidestand housing. I have managed to lash something together with zip ties and hot glue but I fear that I should have used steel cable ties and not the pound shop ones for the bracket to have any realistic chance of resisting the torque ....

Actually from what your saying I might be all right!
:D
 
D

Deleted member 4366

Guest
Just out of interest, alfie; if you lift the back wheel what no-load speed do you get in 1st. & top gear?

I didn't specify wheel size when I ordered & I'm pretty sure I have a motor wound for a 12" wheel :confused:

I get 14mph in 1st. & 28mph in 7th. (28 & 14 t. respectively) & it doesn't climb at all well...
The crank-drive motors are wound to give the best power at the best cadence. The speed comes from only your gearing. You can get a new free-wheel with a bigger first gear - say 34T, which will help, or you need to graft a smaller chainwheel onto the existing one.

Other options for climbing better would be a 36v battery, which will increase torque and speed of the motor and bike, a 350w controller, which will increase the torque of the motor and speed of the bike, or open up the controller and see if there's a shunt to solder to increase the current from the controller, which can probably get it up to 350w for no cost.
 

jackhandy

Esteemed Pedelecer
May 20, 2012
1,820
323
the Cornish Alps
D8veh, are you saying there is no specific motor for a 26" wheel? or suggesting ways I can compensate for my cock-up with what I have?

The motor is 36v. 250w. and I think the controller is 16a. which means the motor currently (pun) has access to 550/650w.(is that right?). So shunt soldering is a cautious possibily, particularly as I have a Speedict on order.

I ran the bike up my test climb today, with the watt meter and camera running, but had too much sky in the frame and couldn't read the damn meter. But... it used 3.8 ah in 4 miles and the battery was down to 32 volts, so I reckon it's pulling serious current as it is.

a megarange freewheel is going to be essential, as the new-type chainwheel is 44t.
 
D

Deleted member 4366

Guest
It sounds like you might be changing gear to soon. Let the motor spin a bit to get into its more efficient zone. 3.8aH in 4 miles sounds a bit high. If you had the bike in a gear, which kept the motor speed too low, and then held full throttle, it could cause a lot of wasted battery energy. I must admit that I'm not too sure about the efficiency curve for a brushed motor, but I'm guessing that it would be similar to a brushless one. It will produce more torque at low speed, which makes it feel more powerful, but you'll get more power and speed if you let it spin up a bit. A lower first gear will allow it to spin more when climbing steep hills.

The motor in a ceank-drive should be wound to turn the crank a bit faster than your comfortable speed. What speed the bike goes depends on your gearing. A hub motor turns the wheel directly, so the winding has a direct affect on speed.