Dual Hub Motor Brompton Conversion - So many questions

[iareintelligent]

So, what I'd like to do is put matching front/rear 250w hub motors both run off the same pedelec torque sensor which splits its signal to both controllers. I have a number of questions that endless forum hunting and googling just can't seem to answer.

First, would I really need more than 2 gears w/ this system? I've got a 6-spd brompton, and I was just going to remove the sturmey hub, but keep the high/low gears. Second, I've seen 120mm rear hubs, and I've seen 75mm front hubs, but I can't find a hub that is made for both front/rear that fits both. How important is is that I use the same brand/motor? What are the most reliable brands these days, or are they all kinda good? How on earth would something like this be wired? Can I run separate battery packs (locate one over the front and one near the back)? Could I mix and match? Since I plan on going pedelec, do most brushless motors resist freewheeling? Would I need to go w/ geared motors instead? The more I research, the more questions I'm coming up with than answers.

Thanks for y'alls help in advance!

 

[motomech]

Before we get into details, you need to do 2 things;
1)Fill out your profile.
2)Ask yourself what you are trying to accomplish. What are goals. Is the added complexity of 2WD worth it?
Do you want to be able to go crazy fast on a tiny bike? Do you want to be able to climb telephone poles?

I have been doing low-tech 2WD for years, but I know nothing about sm. folders, so I can't really comment on what will fit.

For street use, my main reasons for using 2WD is different than what most think are it's advantages. It's being able to have a low-powered system, which makes having a smooth, natural assist, even w/ a simple controller. Then, when power to mix it up with traffic is desired, I can use both drive systems.

Before you get too far into this, I suggest you read this and reconsider. The funds that you woiuld put into 2WD might be better spent going w/ a conversion kit where the problems if fitting it to a sm. folder have already been thought out.

http://www.ebikes.ca/product-info/brompton-kit.html

 

[dogman dan]

One 500w motor. get the skinny motor from Grin Technology.

One small gear in back is all you will need.

 

[iareintelligent]

Before we get into details, you need to do 2 things;
1)Fill out your profile.

I'll take care of that asap, thanks for the heads up!

2)Ask yourself what you are trying to accomplish. What are goals. Is the added complexity of 2WD worth it?
Do you want to be able to go crazy fast on a tiny bike? Do you want to be able to climb telephone poles?

I have been doing low-tech 2WD for years, but I know nothing about sm. folders, so I can't really comment on what will fit.

For street use, my main reasons for using 2WD is different than what most think are it's advantages. It's being able to have a low-powered system, which makes having a smooth, natural assist, even w/ a simple controller. Then, when power to mix it up with traffic is desired, I can use both drive systems.

Before you get too far into this, I suggest you read this and reconsider. The funds that you woiuld put into 2WD might be better spent going w/ a conversion kit where the problems if fitting it to a sm. folder have already been thought out.

http://www.ebikes.ca/product-info/brompton-kit.html

I want to build this for EXACTLY the reason you described. I want something w/ enough power to push 250lbs of bike, rider, and gear up a hill and the ability to mix it up with DC traffic occasionally w/ pedal assist up to 25mph, which is about as fast as I'm comfortable pushing something w/ no shocks and 16" tires w/ a basket full of belongings. As far as what will fit, I'm limited to 75mm up front and 120mm on the rear.

 

[slacker]

having owned 2 bromptons you do not want to go 25 mph, its a fine bike but it was meant for human power. small wheels accelerate very fast and can become quite unstable. Brompton is coming out with a electric assist bike soon. good luck in your endevours.

 

[amberwolf]

You might also want to look thru cwah's posts for info on what he's done with his brompton.

dunno if he's done 2wd but he likes high speeds and is on rough roads, so it might give you an idea what he's had to deal with that you might plan on as well.

As for matched motors; if you need to use them both at the same time it helps if they are both the same, but neither of my 2wd builds, listed in my signature, are matched motors; they aren't really even close to each other; one is front-rear and the other is 2x rear. I generally only use them at the same time during startup from a stop, but sometimes when pulling heavy loads (hundreds of pounds) I use both when cruising to prevent overheating of just one.

 

[dogman dan]

250 pounds including the bike is not that much weight. Any single motor paired with a 1000w controller can handle that.