View Full Version : Daymak Drive electric conversion for bicycles

27 September 2014, 1529
This seems like a really neat idea, especially if they can actually manufacture and sell it for the proposed price of $700. Marketing it through big box stores seems like a great idea to get the public exposed to e-bike riding. http://cleanrider.com/daymak-drive-system-magic-wheel/

28 September 2014, 0628

In the hope of avoiding coming across as an insufferable ass, I will wait several hours to talk about this thing.

28 September 2014, 0636

Here is what my son-in-law, who owns an e-bike conversion that he built from a commercial kit, had to say about the Daymak Drive device:

Wow, I'm surprised someone actually built that. It reminds me of the solar powered car that some guy built in China.

Ok let's run the numbers...

250W motor and a 12Ah * 36V battery.

The battery can power the motor for 12 * 36 / 250 = 1.728 hours.

Assuming a speed of 20mph then that's a 34.56 mile range (or 55.62 kilometers).

If the battery charges at 1km of range per 1 hour of sunlight then a full recharge takes almost 56 hours.

For someone who lives in Arizona and recieves 12 hours of bright sunlight a day that's only 5.5 days for a full recharge.

Its a good thing it can also be plugged in.

28 September 2014, 1324

Your son-in-law gets it. This thing is wrong in so many ways. It is kind of like a cellphone built into a toilet paper roll. You can do it, but is it a good idea?

Solar panels are great. You can even buy lightweight, flexible ones that are 20+ % efficient if oriented correctly to the sun. On a solar car, where you can cover the whole top surface, you can actually trickle charge pretty well. Tiny panels stuck on the side of a wheel is a cynical joke.

Putting your battery where you will maximize heat and impact is a very bad idea as well.

And this is all before we talk about weight distribution , and unsprung weight. I realize that most bicycles don't have mechanical suspension, but the tire provides about 1/2" of pneumatic suspension. There is still a huge advantage to putting the mass in the center of the wheelbase, as opposed to all at one end. For changing direction quickly you want the mass in the center. Not just for zigzagging through S curves, but also for going over bumps. In the case of my e-assist bicycle, the motor, battery, and mounts come to 40 pounds. The wheelbase is 62 inches. The 200 pounds of me and drive components is located a third of the way from the back axle (50/50 would be ideal for this situation). When the bike goes over a bump, that 200 pounds only needs to rise 1/3 as far, as it would if over the front axle, and 2/3 as far when going past the rear wheel. That is a huge reduction of impact on tire, rim, and spokes, and also greatly improves the likelihood of the tire staying in contact with the road.

I know that many e-assist bicycles have hub motors, and even a few motorscooters. But have you ever seen a commercially available car with wheel motors? Millions have been spent by Michelin, and Japanese and Chinese companies trying to bring one to market. Somewhere there is a video of the latest version of the Japanese SimDrive car driving through a parking lot at walking speeds. The sound of the wheels chirping, as they bounce over the speed bumps, is very instructive.

28 September 2014, 1418
As someone who also has built up an e-bike (http://www.evalbum.com/676), I totally agree on the gimmicky nature of having solar cells on this thing. As they say in Texas, useless as teats on a boar.

I found that for hill use (San Francisco) hub motors have limited utility, and decided to go the route of running a hub motor driving a tandem-style chainwheel so I could take advantage of the gears, in my case a 14-speed Rohloff. This pupply will haul 400 lbs up a 30 degree incline, very slowly, but it will make it. And it will do 20 mph on the flat.

29 September 2014, 0727

Sweet ride! The StokeMonkey has always been my favorite e-assist kit. You may want to update the link. Since they switched production to GrinTech, in Canada, they have a new link.

30 September 2014, 1119
Thanks, Warren. I'll correct that old page.

I am glad to see Todd finally found a home for StokeMonkey that was kind of an albatross around the neck of his new successful bike business in Portland. I helped him develop the prototype of the motor mount and enjoyed working with him.