3000 Watt 72 Volt ? surley to fast at 5400rpm !

[sjpage]

Hi,
I recently built myself an electric bike with a 350w crank drive motor geared to 200rpm , it clocks 20mph in top gear with a 44 tooth front crank, this is fine for me
so I though I would build a off road bike and found this

http://www.amazon.com/Fastest-Electric-Bike-Torque-Speed/dp/B00FGCZPYI

only after asking the question it seems this motor goes at 5400rpm , surely this would be way to fast for a crank drive or any at that matter it would require a gearbox - the seller told me that it's max speed would be 40mph , somehow I get the feeling that is wrong

am I correct in thinking this would be useless and I would be better going for something like this
http://eclipsebikes.com/chainwheel-bottom-bracket-1680-watt-ebike-p-1073.html

thanks
hoping someone can help

stef

 

[DanGT86]

40 mph seems perfectly reasonable for 3000 watts. I would think there is a reduction gearbox involved although it is not obvious in the picture. Did you look at the 3rd picture with that "exten tube" on the bottom bracket? I would stay away from this kit just based on that picture. Given the choice between the two, the second kit from eclipse looks better. Most of the kits I have seen on here appear to be higher quality than the two options you posted. You have come to the right forum for doing research on mid drive kits for sure.

What did you use on your first bike that you mentioned?

Here is an interesting overview of crank drive kits.
http://www.electricbike.com/mid-drive-kits/

Good luck.

 

[sjpage]

thanks for the reply

I believe the 3000w goes at 5400rpm with no gearbox , I would have thought this would be way to high

think I may go for the 1680 Watt 48V kit , though would have really liked above 2kw, if anyone knows of any geared mid drives 2kw upwards ?

for my first project I used a 350w 24V geared motor , it pulls on the flat 22mph up hill it drops to around 15mph
however you have to be working the gears all the time for best performance - pics attached

Stef.

 

[Dauntless]

Speed: Up to 95km/h. Included Parts: . . . .Triple FreewheeI ChainwheeI 48T/48T/32T Tooth Bottom Bracket

Sometimes the accidental imagery: What's the difference between 'Surely' too fast, and "Surley" too fast? That bike wouldn't take no lip from you as it was taking off.

You have to remember that 5400rpm is probably unrestricted. It gets slower under the load. That 44 front, what's the back? To go 40mph you'll need over 500rpm for the rear wheel. If it's a full 5400rpm and the rear is 5t, yeah, you'll be at 40mph. 10t would get you to 80mph, assuming it's the full 5,400rpm. Etc. etc. Oh, and I think I count a 24t on the freewheel for the crank, while the shroud over the motor sprocket isn't as big as that 24t, there'd be something smaller under it, so there should be some reduction there.

I hate to just tell you 'Hey, don't worry about it, no way it'll do that 5400rpm. It just COULDN'T go way fast. (Could it?)' But I just seriously doubt it will. Deathbike (Now THERE is 'Surly too fast') at 30,000w, able to top 80mph. That one is so much heavier, of course. So you might even approach 50mph at 3000w, but you can restrain yourself, can't you?

If you're fairly close to content with 350w, almost 5 times that at 1650w should be enough, right? It's cheaper anyway, if you're unsure about the bigger one, it's your choice.

Oh, before you buy a whole new drivetrain, have you tried higher voltage with this one? Bigger controller?

 

[ferret]

thanks for the reply

I believe the 3000w goes at 5400rpm with no gearbox , I would have thought this would be way to high

think I may go for the 1680 Watt 48V kit , though would have really liked above 2kw, if anyone knows of any geared mid drives 2kw upwards ?

for my first project I used a 350w 24V geared motor , it pulls on the flat 22mph up hill it drops to around 15mph
however you have to be working the gears all the time for best performance - pics attached

Stef.

For a midrive kit at these power levels, look into Lighting Rod's:

http://www.lightningrodev.com/

http://www.endless-sphere.com/forums/viewtopic.php?f=28&t=57720

 

[sjpage]

Lighting Rod's look good though a little to expensive for me, (sorry should have said I can get the kit advertised on amazon for $529 from cyclone-tw.com)

I don't want to up my 24V , though it is tempting but this speed and power is fine for me on the road

what I really want is to build something like a Stealth Bomber , my idea is to butcher up a decent MBike and create a new frame
to hold the batteries and motor hidden away as the Stealth Bomber is.

My only worry is if i find 1680 Watts is not enough off road and once I've committed down that route it could be an expensive mistake .

stref

 

[steelefist]

Hi. I have this kit. I'm working on refinements now. The torque is superb and I am currently only running it at 48v/2000W

http://endless-sphere.com/forums/viewtopic.php?f=28&t=56655

 

[sjpage]

Hi steelefist

do you have any video of the bike running ?

Stef.

 

[steelefist]

Not a good one yet. I have just today ordered an sj1000 action camera from amazon to record some performance videos. I have a plan to greatly reduce the chain noise too. Should have a good video in a 4 or 5 days!!

 

[karelski]

Hi, I have this kit as well.
http://www.eclipsebikes.com/chainwheel-bottom-bracket-1680-watt-ebike-p-1073.html
Actualy with Kelly controller KBS48101L, 35A, max. 100A, 24-48V and LiPol battery 44,4V for now 12Ah. Max. current on cycle analyst more then 60A.
Not yet tested more km, but it seems to me there will be problem with motor overheating. I have motor with cooling fins, cooling fins seems to me unsufficient

I want to try Kelly controler KBS72121X,55A, max. 130A, 24-72V and 66,6V battery - I dont know if motor will survive ? :x

 

[philwangcore]

I like your DIY 350w setup. IMHO, 20mph is a great speed for an e-bike and your setup looks like it's efficiently using the motor and battery.

My ebike, 1000w motor geared to the left side of the rear hub, peak efficiency at about 36 mph, leaves something to be desired. Sure I get plenty of torque/power assist as I'm peddling up hills, but I'm lugging the motor, it's not efficient. I also get plenty of torque/power pushing me to about 40 mph, but it's hairy going that fast on a standard bike even on firm pavement. Although 1000 watts gets me to 40 mph, I avoid that because it's way too fast to even peddle, it takes a while for the rim brakes to slow me down, and if I'm going down hill, I need about 150 feed to stop plus maneuverability feels sluggish at speed. The turns are very wide. On motorcycles, small and large, 40 mph feels natural, but on a regular bike, it's jarring. I would prefer if my bike were geared for 25 mph (future project perhaps).

When I ride it off road, I'm typically going 5-15 mph. I can't imagine going 30 mph on gravel and tree roots, and large rocks. However my bike isn't geared efficiently for such a slow speed and the motor gets hot and the batteries have a short range. Still, the 1000 w motor running at est 30% efficiency still pulls me up hills pretty well so long as I'm peddling.

So anyway, my point is, from personal experience, high speed isn't all that fantastic or useful. I guess it's nice to show off once in a while but I don't typically go fast unless on a clear unobstructed strait, and then it's all motor because I cannot peddle faster than 30 mph even in high gear. You don't need a huge watt motor to get help you get to 40 mph or pull you up off road hills. What is valuable is efficient gearing which helps you get best use from the batteries you carry.