24" wheel instead of 26" for more torque?

[joecool]

Hi Everyone,

Name's John, am 42 and live in Ottawa. Couple days ago I noticed on a stretch main road littered with lights and traffic about 6 kms long, that a bicyclist was just peddling along without breaking a sweat and because of red lights, turning vehicles and minor jams that he made it to the same destination as me in the same amount of time. Difference was I was using a V6 burning gasoline that is costing me $400 a month with the insane gas prices that will probably only go higher.

So, it occurred to me that I should look into an electric conversion once and for all. I dabbled with the idea a year or two ago but nothing came of it. But in my research of kits out there I zeroed in on GM3 for my aluminum framed KHS mountain bike. I have ruined my knees over the years with motocross and pedaling isn't really something I should be doing at all.

I have never tried an e-bike before and was curious about the torque and if dropping to a 24" rim from a 26" might gain some oomph. Or does the 48v setup have plenty as it is with a 26" rim?

Also, anyone know of a bag type thing that the 48v10ah battery would fit into nicely so it just looks like storage space? I was thinking I want to have the batt pack slung under the main cross bar in some fashion.

I googled my trip and it's 14km one way to work. There is a couple of hills... well one is a lengthy incline really. I'm hoping the batt pack will be able to get me to work. I'm guessing it can. I can charge at work for the trip home.

Any other things I might need to know is welcome as well

Thanks,

John

[truly_bent]

Hi John.

Having just been through GM boot camp on the differences between the various MP motors, it's my belief that you wouldn't get any more torque with the 24". The only motor size that's configured any differently from the others is the 16" (wired Delta). All the others have their windings configured the same way (wired Wye).

As for the battery holder. Why not get one of the sealed aluminum packs like this one: http://www.goldenmotor.ca/products/48V10AH-LiFePO4-Aluminum-Cased-Battery.html. It's pretty easy easy to mount with the plate provided. Having said that, I just bought a 48V 20AH battery housed in a black hardshell case and am trying to figure out how i'm going to mount that one as well.

Gud luk wit yer projekt...

[joecool]

Thanks for the reply... that is actually the battery pack I am going to order I was just hoping to find some sort of bag like other ebikes have for their batts. It's not super important, I just like the look. I want to make this a super clean install and will try my hardest to make this look like a regular bike as possible.

About the rim size.. I was just thinking that a smaller rim would gain me more climbing power simply because there is less wheel to turn. I guess it would be compared to running it in a lower gear.  But I suspect from videos I have seen that the MP3 has enough torque as it is and I don't need to mess with smaller rims to gain torque. My bike has 26" rims and my thought was put a 24" on the back to gain a little more torque. I'll just order the 26 though.

I'd like to hear from others who have the 48v10ah pack and how far they can go on a charge.

The free wheel on my bike is a 9 gear. I have read that this might be too large and wont fit? There is a 6 gear in the website.... do I need to order that?

Thanks again,

John

[truly_bent]

I'm obviously new to this myself, but I did see a video of someone (i think it was Gary of goldenmotor.ca) fitting a 7 gear cluster - barely. I've just ordered my 26" wheel and I ordered the 6 gear cluster with it, just to be sure.

If maintaining all my gears had been a top priority, I would have gone with a mid-drive setup. I used to think that mid-drive was the only way to go, and I still concede a couple of advantages to that camp, but these new hub motors with their higher torque ratings make up a lot of ground. Plus they're quieter and I love quiet (ever actually listen to an EcoSpeed at full chat?).

I also ordered the torque arm. I figured at $28 a torque arm is pretty cheap insurance against the axle spinning and doing nasties to your wiring. I've read arguments pro and con about using a torque arm on the rear (it seems to be pretty much agreed that a torque arm on the front is a must), but i'd rather err on the side of caution here. The MP motors are rated at 1440 watts. That's damn near 2 full horsies (746 x 2 = 1492) trying to spin that axle.

I was thinking about your "improved torque on a smaller wheel" question. The smaller wheel will spin up to the max efficiency rpm quicker than a larger wheel, which might feel like it's producing more torque. I think it doesn't actually produce more torque so much as get into the "fat torque" part of the graph quicker - because it's getting up to higher rpm sooner. I could be wrong about this though (as I've been wrong on a number of issues) and it's best to ask one of the resident professori before laying down your hard earned dollari.

On the issue of battery size... rather, of battery capacity. The 10AH batteries are usually capable of 20 amps continuous discharge and the 20AH of 40 amps continuous. I figured for a motor that's rated at 48V 30A (equals that magic number of 1440 watts again), i'd better be able to feed it at least the current it wants. I guess that means a 15AH battery is best suited - for one hour flat out.

[joecool]

I have almost decided to go with a Ping 48v15ah brick. I really like the aluminum cased w/ key GM batts but for the same price I can get a 15ah pack and charger shipped. GM wants $85 for a charger. It's a better deal I feel for me because I can do all the needed wiring myself and plan to have a lunch bag carrying case setup with the charger in there as well so I can unstrap and carry into the office with me for a charge. The only thing I don't like about the MP3 is the proprietary internal controller design.

[truly_bent]

joecool;

I think moving the controller inside the hub was an intelligent move on GM's part; from a marketing point of view anyway. Electric bikes are moving "main stream" and it sure does simplify wiring considerably. GM is probably trying to target a demographic that's less "hands on". I'm a tinkerer myself and opted for a third party external controller, but I have to say, when my controller came in I momentarily wished for something simpler when I took stock of all the wires hanging off that sucker (5 heavy gauge + 33 lighter gauge wires grouped among 10 connectors - I kid you not).

I've been looking at controllers for a while, and when I happened across GM's external unit I thought they'd done it right. It handles sufficient power and has pretty much all the options you're likely to want - at a reasonable price. The reason I opted for a different controller was because I didn't know at the time what voltage I wanted to run and didn't want to be limited to 48V. If GM had a 60V or 72V max controller I likely would have stayed put.

My understanding is the internal MP III controller is virtually the same as the external version. The external version does look a bunch easier to swap for a new one, but I suspect there isn't that much of a time saving. Gary has a video floating around somewhere (http://www.youtube.com/watch?v=ofXCj_Dd10U) wherein he swaps two internal controllers between two wheels in the time it takes to... ummm, watch the video.

So... ummm, watch the video before deciding.

[joecool]

Yeah, it's not a real big deal that it's an internal controller. My thinking was if I had an external I could carry an extra. My knees are pretty bad and having a controller fail would leave me stranded. No peddling for me so having that fail safe is very easy on my mind. 

[joecool]

I was wrong when I said the GM batt packs don't come with chargers. It says right on GM's page that it comes with one. No one caught that 

So, after shipping from China and possibly getting nailed for more from customs it is not really cheaper to buy from Ping. Plus Gary's packs have the case and the key so it's probably better. I feel better ordering from Gary anyway. I decided on the 48v10ah. If, in the future, I like this bike so much and want more range for weekend jaunts I will order another 10ah and have two.

I ordered everything I will need including the Cycle Analyst for a rear wheel setup. I read on GM's site that if you don't buy the CA to control the motor with you need to order the USB cord to do it. I want to keep tabs on all the numbers anyway because I enjoy that kind of stuff so I just splurged on the CA.

I had to choose the thumb throttle because the MP III twist throttle is out of stock for a week. I think I'd prefer the twist throttle but in the end I don't think it's going to matter one way or the other. If I want a twist in the future I will just order it.

I just need to buy a battery bag for the back (I like stealthy look) that has some extra compartments for charger and other odds and ends then I am good to go. I am hoping to find one with an arm strap so I can carry it into the office and no one will know there's a battery and charger in there.

Anyone know where I can get one?

Thanks

[joecool]

Got everything in the mail. Only thing that I noticed was something rattling around inside the charger so I opened the side cover to let it drop out. It was the fan blades for the little cooling fan. It looks like it just sits on the motor and is held there magnetically so I placed it back. When it runs it makes a bad noise so I have contacted Gary about. I wouldn't be able to charge it on my office like I need to.

Also, one of the brake levers does not engage the regen. I'm wondering of this is a setting in the controller. I can't get the software to install so still working on that. They should really fix that install package.

Other than that everything looks ok. One thing that kind of irked me a little was 2 days after I purchased everything there was a special offer where you got the $150 Cycle Analyst for free.

[Bikemad]

John, the regen (and power cut-off) should work the same from either brake lever because they are both wired in parallel. Software regen settings would affect both levers, not just one.

Unplug the brake connector and make sure the two pins are both straight and correctly aligned.
If everything looks ok with the pins on the plug but it still won't work from both levers when they are fully plugged in, try swapping the brake lever plugs over to the opposite sockets (1 and 4) and see if regen still works from the same brake lever.
If it's no different, the problem will be somewhere on the switch, wiring or plug of the lever that doesn't activate the regen.
However, if regen works on the other brake lever when plugged into the opposite sockets, then the fault will be somewhere within the control harness multi connector, and as it's a sealed unit, it will probably need to be replaced.

Once you have identifed where the fault is, let Gary know which part is faulty.
If it's a brake lever problem, make sure you tell him whether it's the left or right hand lever (1 or 4).

Alan
 

[joecool]

ok, swapped them wires to the 4-connector thing and now the regen only comes on when I use the other.

So this means faulty break lever assy? I will check with my meter for continuity through the pins tonight.

Loving this thing though. 50kmh down a hill and 42 on the flats and 30 up the hills I encounter.

[Bikemad]

ok, swapped them wires to the 4-connector thing and now the regen only comes on when I use the other.

So this means faulty break lever assy?

if regen works on the other brake lever when plugged into the opposite sockets, then the fault will be somewhere within the control harness multi connector, and as it's a sealed unit, it will probably need to be replaced.

Just to clarify what I said before, you're simply swapping the brake lever plugs over (not the levers) so if one brake lever activated the regen before, but with the plugs swapped over the other brake lever now activates the regen instead, the fault is not the brake levers, their switches, wiring or plugs. It will be a poor connection somewhere inside the 4 way multi junction block on the front control harness that the four separate plugs fit into:


Alan