Dual Motor off-road bike conversion

[Rudy Pekau]

Converted my older bike into a dual motor version for off-road riding, 2 motors 500W each, peak power 1400 W, max torque 160 Nm,
top speed 45 Km/h, one rear rack battery 36 V with 16 Ah , a second battery 36 V with 15 Ah in the triangular middle section of the bike which contains
also two controllers, pedal assist for each wheel individually, also two throttles which can be operated independently or together.
Suspension would be good for both wheels which would make the ride a bit softer.

 

[TomD]

Off road? Hope the spokes are good quality, but could be a death wish regardless with rim brakes to slow down all that weight, not to mention relatively high center of gravity in the rear.

 

[Rudy Pekau]

Off road? Hope the spokes are good quality, but could be a death wish regardless with rim brakes to slow down all that weight, not to mention relatively high center of gravity in the rear.

Spokes are 12wg, I do not go down very steep hills, I am an active senior , well adjusted V-brakes with good brake pads are just fine for gravel roads, works great on moderate terrain,
the battery weight in the rear does not make a big difference in the center of gravity location.

 

[tomjasz]

the battery weight in the rear does not make a big difference in the center of gravity location.

I read this warning often and agree with you. I think in many cases it’s someone repeating what they’ve read not experienced. TomD is pretty astute so he may have some experience. I find that flat foot frames with longer wheelbases like the Electra Townie completely mitigate any tippy feeling with a rack mount. As always someone’s experience may be different.

 

[tomjasz]

well adjusted V-brakes with good brake pads are just fine for gravel roads, works great on moderate terrain,

After all aren’t they 26” discs?

 

[harryS]

Nice. Got torque arms on the front motor?
.
I guess the true off-roaders that get both wheels off the ground can feel the weight of a high mounted battery. For me, a rear rack pack makes no difference when cornering on pavement, and you won't find me leaning on gravel.
.
Have two mountain bikes to convert for relatives when it gets warmer. Putting disks on both, just for looks. Gets expensive if you don't have the wheels already or frame mounts, but the disk hardware is cheap, Mechanical disks aren't much better than good v-brakes. You want to go full hydraulic. That is not much more expensive than mechanical.

 

[Rudy Pekau]

Nice. Got torque arms on the front motor?
.
I guess the true off-roaders that get both wheels off the ground can feel the weight of a high mounted battery. For me, a rear rack pack makes no difference when cornering on pavement, and you won't find me leaning on gravel.
.
Have two mountain bikes to convert for relatives when it gets warmer. Putting disks on both, just for looks. Gets expensive if you don't have the wheels already or frame mounts, but the disk hardware is cheap, Mechanical disks aren't much better than good v-brakes. You want to go full hydraulic. That is not much more expensive than mechanical.

Front and rear wheels have torque arms of course, I would not ride without them.Yes, going on gravel or soil requires caution, especially
when it is not packed, I am only an occasional off-rider.

 

[TomD]

I read this warning often and agree with you. I think in many cases it’s someone repeating what they’ve read not experienced. TomD is pretty astute so he may have some experience. I find that flat foot frames with longer wheelbases like the Electra Townie completely mitigate any tippy feeling with a rack mount. As always someone’s experience may be different.

I started with a build years ago (before the evolution of ebike batteries) where the only options were to put a series of drill batteries in rear or find creative ways to insert them in frame. Granted it was rear hub, not a dual hub setup, but I gave up on it as it was so tippy. Maybe this isn't so bad with front hub and batteries in frame and rear. I stand by my assertion though that all the weight and rim brakes is a recipe for disaster. There is no substitute for being able to stop on a dime when it comes to life vs. e-wheelchair or death.

 

[gromike]

I agree that good brakes are a must but trying to stop on a dime might leave you flying. There is a bit of art to stopping a two-wheeled bike from a fast speed, and a panic stop can cause a self wreck. It is always better to brake before one needs to clamp the binders.

 

[TomD]

True, I witnessed a rider in front of me come to an abrupt stop to avoid a car not paying attention pulling out in front of him off. It wasn't pretty but he stopped just short and lived another day.

 

[tomjasz]

I started with a build years ago (before the evolution of ebike batteries) where the only options were to put a series of drill batteries in rear or find creative ways to insert them in frame. Granted it was rear hub, not a dual hub setup, but I gave up on it as it was so tippy. Maybe this isn't so bad with front hub and batteries in frame and rear. I stand by my assertion though that all the weight and rim brakes is a recipe for disaster. There is no substitute for being able to stop on a dime when it comes to life vs. e-wheelchair or death.

I’ve run every one of my bikes on an MSF course testing braking distance and avoidance drills. That convinced me to sell me 3 BBSHD builds on mid level bikes with best quality rim brakes. KoolStop eBike pads made a difference but not enough at 30+MPH to make me feel secure. My 36V dual MAC build was a climbing monster and limited to 20Mph or less had excellent brake response. All 4 builds had rear mounted batteries and/or rack and down tube Dolphin cases. All were on longer wheelbase base frames and none ever felt out of balance with added rear weight. I also noted that even with healivy loaded rear rack grocery runs on mid drive builds with DT batteries I never felt tippy. IME speed is more of a factor than weight. At least on my builds with top shelf Tektro rim brakes and KoolStop pads. At <20MPH my 26” discs are as powerful as any commonly used hydraulic. Add Magura 4 piston and there’s no match, but how many eBikes have top notch 4 piston hydraulic brakes?

To summarize, for me and in my limited experience, speed and frame geometry dictate balance and braking efficiency.