Overclockers Dream

[derf]

I have in all laced up and connected to my ku65, 1/3rd shunt soldered. I'm pulling 17.5 amps peak, at about 40v

C'mon then, how far do you think I should push it?

what do you get in terms of speed and hill climbing? im building it into a Raleigh twenty with an 8 speed sturmey hub at the rear (if it doesn't cut it, ill fill it with oil and push up the amps)

 

[Alan Quay]

what do you get in terms of speed and hill climbing? im building it into a Raleigh twenty with an 8 speed sturmey hub at the rear (if it doesn't cut it, ill fill it with oil and push up the amps)

I haven't checked, but I'd guess around 18mph in a 26" rim. At 20" I estimate 14 mph.

It's not a very tourqey motor in 26" at 17-18 amps, but if you push it to 22A it should be plenty in a 20" wheel.

 

[derf]

I haven't checked, but I'd guess around 18mph in a 26" rim. At 20" I estimate 14 mph.

It's not a very tourqey motor in 26" at 17-18 amps, but if you push it to 22A it should be plenty in a 20" wheel.

crikey, to be honest that sounds pretty disappointing? it was originally designed for 700c at 24v as you know - which means (you're running it at 40V?) something like 28/26 times 24/40 times 18 - I'm guessing around 10 or 11 mph. that sounds really slow?

 

[twinkle]

l make that 24mph

26/28 x 40/24 x 18 = 24 mph

but l went to school before calulators were used
regards Emma

 

[Alan Quay]

crikey, to be honest that sounds pretty disappointing? it was originally designed for 700c at 24v as you know - which means (you're running it at 40V?) something like 28/26 times 24/40 times 18 - I'm guessing around 10 or 11 mph. that sounds really slow?

It's not 40v, it's 36v. (alternatively, it's not 24v, it s 27v)

If you run it in a 20" rim, you want to use 36v.

 

[derf]

l make that 24mph

26/28 x 40/24 x 18 = 24 mph

but l went to school before calulators were used
regards Emma

and I had some bad beaujolais which didn't help, but at 24V it must be slower than at 40, no? and 28 is not much bigger than 26...(I'm hoping you're right, I don't want a lemon)

 

[derf]

It's not 40v, it's 36v. (alternatively, it's not 24v, it s 27v)

If you run it in a 20" rim, you want to use 36v.

yes, I guess I might be greedy, was having visions of 20 plus mph

 

[Alan Quay]

yes, I guess I might be greedy, was having visions of 20 plus mph

With a 20" wheel you might get 18 mph if you go to 48v, but at 18 amps you are pushing the limits of what this thing can handle - it might work, it might melt.

But frankly, who wants to travel at 20mph on a Raleigh twenty?

 

[derf]

With a 20" wheel you might get 18 mph if you go to 48v, but at 18 amps you are pushing the limits of what this thing can handle - it might work, it might melt.

But frankly, who wants to travel at 20mph on a Raleigh twenty?

that is true, call me crazy, but I was trying to replicate a kalkhoff sahel compact at a fraction of the price with more retro chic (without the impulse 2 and maguras sadly), was also hoping a Raleigh twenty on fat 406 schwalbe big apples might be a little more exciting. the thing that puzzles me is that that is around 900 watt (sorry if I got it wrong again), which to me seems a whopping amount of power (I'd expect cracking speed for that)?

 

[Alan Quay]

W=V x A
Or
864 = 48 x 18

Watts is a measure of power. That power could be applied as high current, low volts (eg 36A 24v), or low current, high voltage (eg 18a, 48v).

Both examples yield the same power.

Given that your motors speed (without load) is proportional to volts, and that it's torque is proportional to current (amps), then you need to work out the correct balance of speed/torque for your application.

As Scotty would say, 'You cannie change the laws of Physics', or as Mike Higgins would say, ' You can't pi55 a pint into a half pint glass'.

 

[derf]

W=V x A
Or
864 = 48 x 18

Watts is a measure of power. That power could be applied as high current, low volts (eg 36A 24v), or low current, high voltage (eg 18a, 48v).

Both examples yield the same power.

Given that your motors speed (without load) is proportional to volts, and that it's torque is proportional to current (amps), then you need to work out the correct balance of speed/torque for your application.

As Scotty would say, 'You cannie change the laws of Physics', or as Mike Higgins would say, ' You can't pi55 a pint into a half pint glass'.

that makes much sense, to stretch a metaphor, I'm not sure whether this particular half pint glass is in fact giving the half pint of, erm, evacuation it promised..

 

[Deleted member 4366]

I think it'll be pretty good at 48v with 15A, or you can go to 12S lipos (44V) and say 17A. Has anybody established its no-load rpm yet?

 

[johneb]

Thanks d8veh & Friendly1uk for letting us know about these motors. I'm really tempted to get one but being a novice, I'm prevaricating about the bush due to being unsure whether it will meet my needs - primarily help with hill-climbing (not bothered about top speed). I'd be building it into a 26" rim and already have a 36v 17Ah Silverfish battery.

 

[Alan Quay]

I think it'll be pretty good at 48v with 15A, or you can go to 12S lipos (44V) and say 17A. Has anybody established its no-load rpm yet?

If I get a chance, I'll confirm tonight. It's quite high, possibly 260 ish.

 

[Alan Quay]

Ok, no load speed is a whopping 370 rpm (ish, no Speedo to confirm, had to count it manually with a cable tie bashing the mudguard.)

 

[twinkle]

Ok, no load speed is a whopping 370 rpm (ish, no Speedo to confirm, had to count it manually with a cable tie bashing the mudguard.)

no load on a 20" wheel l make about 22 mph assuming 80% efficiency , about 17 mph

regards Emma

 

[derf]

no load on a 20" wheel l make about 22 mph assuming 80% efficiency , about 17 mph

regards Emma

what is the efficiency of a hub motor usually? after an intoxicating ride on a kalkhoff Sahel I've decided to put this hub on ice until another idea strikes and go for a bpm2

 

[twinkle]

my e-shopper is still on the cards after l get back from holiday.
By then most of the bits will be waiting for me
regards Emma

 

[Deleted member 4366]

Ok, no load speed is a whopping 370 rpm (ish, no Speedo to confirm, had to count it manually with a cable tie bashing the mudguard.)

You must be able to count bloody fast. 370 rpm is over six times a second, I reckon 230 rpm is more like it.

 

[johneb]

Is one of these likely to be any use to me for help on hills? 13 and a half stone and legs that can only propel a bike on the flat