Throttle question

[allotmenteer]

Hello all

I've a question regarding how the throttle works / point of it / best use of it.
I have found that I am almost always using the throttle at either full power (up hills and against headwinds) or not at all (downhill, on flats and very gentle hills where I can do 15 mph + anyway). Am I right to be using full throttle all the time. Is this wastefull? Would I get better range by using less throttle? Or is the throttle clever and when I pedal as well it reduces the power the motor is using?

Now, suppose the motor can do 15 mph at full throttle. This would be 194 rpm on a 26" wheel (I think -> 26" * 3.14 * 194 * 60 / 12 = 79490.8 feet per hour = 15 miles per hour). What is the effect then of using half throttle? Would the motor only try to spin at 194/2 rpm? (7.5 mph). Or would it want to spin at 194 rpm but would need more rider effort to attain it.

Basically could I get much more range out of the bike by using the throttle carefully or should I just let rip and use full throttle whenever I want the motor to assist and pedal harder to reduce the load on the motor? Since I seem to be using full throttle most of the time wouldn't it be better to replace the throttle with a on/off switch or button?

I hope this makes sense.

Paul

 

[flecc]

Hi Paul

Bike motors are so low powered that throttles don't make much difference in high performance terms. It's in the nature of most electric motors that they tend to try to run to their optimum revs regardless of the power fed. When running on a minutely downhill stretch in still air, the motor will probably still run up to full speed at very small throttle openings.

Many pedelec bikes operate just as you suggest, with power effectively by on/off switch, and that's ok with the lowered powered ones. With those that "stretch" the legal power limits, a torque sensor helps to smooth things out, acting a bit like a throttle in some ways.

If you ride in heavy traffic with very slow movement forward at times, as at lights, a throttle can be very helpful then to avoid progressing in a series of jerks.

 

[allotmenteer]

Thanks flecc. I think the throttle seems to work pretty much like an on/off switch then.

Just to clarify, is there is any difference in:

1) throttle 1/2 open and pedalling at a certain level of effort
2) throttle fully open and pedalling at that same level of effort.

All other things remaining equal of course - slope, wind etc.

Now say that option 1 gets me 15mph. Also say the motor can only do 15mph unloaded. What happens with option 2? Does the motor only draw the same power as option 1 and I still do 15mph. If so an on/off switch would save my wrist getting sore.

Or is it a bit more complex and I would find it hard to give the same level of human assistance because the motor would be spinning with much more power and thus what would be happening in reality is that I would effectively be spinning my legs freely while the motor takes all the strain?

I don't want to fit an on/off switch if it would be wasteful of my batteries. If however, the operation of the throttle is clever (and the motor draws the same power in option 1 and 2) then an on/off switch would seem to be the way to go.

Paul

 

[flecc]

It is a bit more complicated as you've said. It very much depends which motor and it's power, whether it's operating up to a limiter to fit legal requirements, and the throttle type.

On Hall efffect throttles the action is very fierce so a true intermediate "opening" is difficult to find and hold, especially on a bumpy road. Half throttle will normally save "fuel" and if it's a motor operating well within it's power capability, or one operating against a limiter, you won't necessarily lose speed either.

Which bike is it Paul?

On the eZee models, they're powerful, so definitely keep the throttle despite the fierceness of operation since smaller openings can save "fuel". See my Throttle mod for those.

A bike with a very much weaker motor will mostly be at full throttle anyway, so there'll be little consumption cost through having a switch, and motor power "snatch" wouldn't be a problem.

 

[flecc]

OK, got the answer by looking on the "Introduce yourself" thread Paul, I take it you still have that rear hub motor.

Reading the performance details you've given, I'd definitely keep that as a throttle bike as it's clearly quite powerful but doesn't have a very long range.

A switch would lose you some range in most circumstances though it's impossible to predict an exact amount, while making low speed control more tricky.

If it's a Hall effect motor and throttle which it probably is, it's difficult to make very much difference to the range by turning it down where possible. With a lot of effort on the throttle control of my Hall effect Torq, I gain at most around 2 miles on top of the usual 15, and have concluded it's not worth trying too hard. I just ease off a bit where convenient and accept the result.

Thinking of your throttle problem with two twistgrips, would it help to swap the twistgrips over? Since you're not gear changing all the time, putting that on the left and operating it in reverse could do the trick. It's a solution often adopted, and some recumbent trike riders do that.

An alternative might be a reverse action Hall effect throttle if yours is one of those. The eZee throttle on the Torq is a left hand one.

 

[allotmenteer]

Hello Flecc

Thanks for the reply, very informative.

Yes it is the 350W rear motor from electricbikesales.co.uk. It is quite powerful I think and can do about 16.5mph on the flat with a 26" wheel (it's quite hard to get an exactly flat bit of road so it may be a little faster or slower). I find that it really helps on the hills. I have ridden a 2.7 mile test route with one long steep, one long medium and one very long more gentle slope. This route takes me 15 minutes (10.8 mph average) exactly on my speedy marin mtb with slick tyres. With the motor the time is slashed to 11 minutes (14.7 mph average) which is quite an improvement.

The throttle is Hall Effect as you thought. Switching the throttle to the left hand is a good idea, I didn't think of that. Mind you the bike is confusing enough with the brakes the wrong way round (it's a French bike!).

I think for now I'll keep the throttle and let it rip, not worrying about eeking every last drop of juice out of the batteries. Like you said, it's not really worth the effort. Better to get bigger batteries I reckon.

Thanks again for your help.

Paul

 

[tallbloke]

I find it more efficient to throttle up to full speed on the flat, then close the throttle and pedal until I'm back down to about 13mph, then throttle up to cruising speed again. This 'cadence' method seems to give the best range for me rather than pedalling along at half throttle constantly.

I have a very good quality hall effect throttle with the currie kit, which gives super low speed controllability for easing along in traffic or pedestrian shared areas.

 

[UrbanPuma]

range query

Hi,

I have recently purchased a powacycle puma electric folding bike and would like some advice on preserving the battery range.

In pedelec mode, is there a difference in the amount of work the motor is doing depending on the gear i am riding in? For example, is there more power drawn from the motor in 2nd gear and less power drawn in 5th gear?

In throttle only mode, does using full throttle drain the battery more than at half throttle?

All advice would be much appreciated as i love my bike and want to enjoy it for many years to come.

Thanks

UrbanPuma

 

[flecc]

The rule on these hub motors is that efficiency rises with revs and on hub motors is independent of whatever gear you are using.

Basically that means you should try to use the upper range of cruising speeds as the motor is most economical then. It's most wasteful at up to 8 mph when hill climbing for example, the wastage then falling as the speed increases.

Therefore the part your gears play in this is that you should use the gear that gives you the best advantage for helping the motor and bike up to speed. Generally speaking, higher cadences, that's the rotation speed of your pedalling, are best for rider efficiency, but use what you feel comfortable with to give the best contribution.

Full throttle drains more, so once up to speed, back it off enough to maintain the speed but give a saving.
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