Motor speed control

[allotmenteer]

No, the planetary wheels are irrelevant to the measurement Paul, treat them as idlers which they are. Its just the first and last that count, 22 to 93 which is 4.227 to 1.

That's high, no wonder it's fast!
.

Ah thanks flecc, yes thinking about it they would make no difference as their teeth interlock with both the motor shaft gear teeth and the outer hub teeth, thus one tooth movement of the motor shaft equals one tooth movement of the hub casing gear. I think I counted 22 teeth but I could be (probably am?) wrong. I turned the motor by hand while watching the gear and counting how many teeth for one complete revolution of the motor. I might have a look again tomorrow.

As you say it does seem to be a fast motor flecc. I think it has got quite good torque too, at 36V. Running at 24V it couldn't accelerate up anything that looked like a hill without a lot of assistance. Now at 36V I honestly don't have to pedal unless the hill is pretty steep.

The controller in the open air is doing the trick too. 2.1 miles back from the allotment at full throttle and mostly uphill and the case wasn't perceptibly warm at all!

Oh - the motor really does look like your one flecc, even the orangey colour too. Could they be the same?

 

[coops]

Flecc beat me to it Paul, was going to say the same re: geared reduction ratio: thanks for the figures and pics, very interesting, similar design, but as flecc says thats not so surprising, and look like nylon cogs too? Does it run fairly quiet? Those teeth counts possibly not far off, it may be a slightly higher ratio than that, but if it is around 4-5:1 at the speeds you get that suggests to me it may have a high torque capacity, the amount you get depending on the controller's current limit? Knoxie got high torque with the Puma even at 37V, but at 35A current limit!! Your motor was sold as 350W rated, wasn't it? I'd have thought it should be pushing 2-3 times that at peak power/torque, so 700W+ peak output may be easily possible? From what you say, not huge torque at 24V & better at 36V, the controller currrent limit may be lower than the motor's capacity e.g. set to ~15A when it may be ok at 20A or more?

Its just a thought, though I don't see why the kit should be sold with parts which limit performance, except to make it road-legal - after all its a 36V system it seems, which was sold as 24V, so what else may be different?! Maybe current limit was built in lowered to reduce peak power such that the kit could be safely judged as legal from an "average power" <200/250W point of view I don't know if your kit could take a much higher current, and that may reduce your range significantly, but I should think it has torque potential not much less than the puma, and maybe more?!

Stuart.

 

[flecc]

the motor really does look like your one flecc, even the orangey colour too. Could they be the same?

As I remarked to Stuart recently, electric motor design for each type tends to be very similar for all makes since all use every small advance, and design is very constrained by the physics of electricity anyway. It's possible it's the same motor, though the gearing seems high, but most likely it's made by the same manufacturer. As with so many things these days, there are many products and many firms selling them, but very few actually make things, simply because of the economies of large production units. The orangey colour could result from their being one manufacturer of that material in China supplying the motor companies for example.

The motor Stuart thought was like my Quando one is quite a lot heavier as another example, and there's probably a few more motors out there very similar. As each designer makes a small advance in power or torque gain, the others will follow to get the same benefit and sameness will always result.

Look how interesting cars were in the 1920s, you couldn't even know in advance how many wheels one would have, where they'd be placed, whether it would be powered by petrol, steam or electricity, or have the vaguest idea of what the body shape and style would be. Compare that with the carbon copies on the road today, and you see the effects of "follow my leader" design.
.

 

[allotmenteer]

Yes Stuart the motor was sold as a 350W. I imagine this is the continuous rating. As for more current, the controller is meant to be 15Amp which seems low but as I've only got 8Ah batteries I wouldn't want to drain them at too high a rate. Anyway, at the moment the bike performs great so I'm not going to try to get more out of it yet.

There is a potentiometer on the controller which I have turned to the max setting. This could be controlling the amps the controller can draw, either that or it sets the max wheel rotation speed for fitting in different bikes. I know when I turn it the bike goes faster

The gears are nylon and the motor is fairly quiet. When I took the photos yesterday I regreased the cogs and bearings so hopefully that'll help a bit more.

 

[coops]

As for more current, the controller is meant to be 15Amp which seems low but as I've only got 8Ah batteries I wouldn't want to drain them at too high a rate. Anyway, at the moment the bike performs great so I'm not going to try to get more out of it yet.

Yes, if it ain't broke... don't fix it (plus think of your family, & brakes ) I was just thinking out loud really. 15A 36V is the same as the ezee Torq; quando so looks like you have the same sort of power/economy balance setup giving around 540W+ (more like 570W-600W on a full charge) peak power. The 15A current limit is probably well matched for your 8Ah batteries as you say .

Getting back to the thread topic now, finally... it never was concluded what your pot varies, was it? From what you say, it definitely varies the spin speed, so some voltage control seems likely, but you also say that at low setting you have more torque & less "spin", so perhaps it controls both speed & torque by varying the proportion of each in the total power output which may be constant? i.e. low setting = high torque, low speed; high setting = low torque, high speed; same maximum total power output for all settings?

That would be a handy adjuster, but probably should not be readjusted often: maybe adjusted once then left for reasons mentioned previously. Still, it would mean that you could adjust the torque vs speed level for your local terrain/usage - high torque for hills/pulling power or high speed for flats - may help to optimise your power consumption and maximise range too .

Now you're running at 36V, your top speed should be about 1.5 times the 24V top speed for the same original 1/2 pot setting, so maybe around 22mph: if your pot is on max then your top speed should increase over that, but torque may be lost at lower speed. I think you may get more torque for hills if you want, for a small top speed reduction, by turning the pot back down towards the original 1/2 setting .

Stuart.

 

[allotmenteer]

I'll have a play around with various settings of the pot. I think it is most likely controlling motor speed though I'm not sure how exactly. I think when it is at max setting it feels less torquey because the motor is running at a high speed which is way past the max torque point. When it's on a mid setting it feels more torquey because max motor speed is around the max torque point. The throttle sensitivity / power range would, I imagine, be different for different settings of the pot and thus this may affect the how powerful the kit seems at different pot settings.

I'll have to experiment a bit to find out. Previously I only spend 1/2 an hour or so riding and tweaking the pot so I haven't fully explored things.

Paul

 

[coops]

I'll have a play around with various settings of the pot. I think it is most likely controlling motor speed though I'm not sure how exactly.

Nor me! I think (could be a huge over-simplification) voltage mostly determines the motor speed, & current limit sets the torque level, so perhaps the pot simply changes voltage up or down, so..

I think when it is at max setting it feels less torquey because the motor is running at a high speed which is way past the max torque point.

Sounds about right .

I wouldn't adjust it too much, because of what flecc said: maybe best to just find the best balance of speed & torque for the voltage you end up using & then leave it set there . Useful to have some means of adjustment though .

Stuart.

 

[allotmenteer]

I've got a list of things to do to the bike to get it working to my satisfaction. Briefly they are:

1) Put a CPU heatsink on the controller case to further aid cooling.
2) Replace the front large chainring with a 48 tooth one.
3) Weld / braze a bracket on the downtube for the battery.
4) Weld a mounting plate on just behind the seat tube for the controller.
5) Shorten all the cables as much as possible and tidy them up / hide them.
6) Get a 3mm spacer to replace the 10mm one on the non-drive side of the hub to shift the hub over and improve chainline.
7) Get the wheel rebuilt and dished properly.
8) Put a better rear sprocket on - with a 12 tooth smallest cog.
9) Fit some decent v-brakes to it.

Paul

I've added some shimano deore v-brakes now (£20 from Europes largest Online Bike store - Buy Online.) and they make a huge difference. I now feel confident of stopping quickly from the 24-25mph speeds I'm getting from my kit. Did a 5.5 mile run to my parent's this afternoon - 16 minutes 45 seconds, 19.7 mph average! Would have been a bit quicker but for the cycle hazards / gates on the last mile or so + the booster SLA dying 2/3 mile short of destination.

I was a bit worried about over-draining the Nimh while using the booster pack but since the SLA gives up well before the Nimh I think the damage will probably occur to the SLA. I usually disconnect the SLA when the power drops off and then just ride with the Nimh.

 

[coops]

I like your balanced approach: increase the speed then make sure you can stop!

Stuart.