change ratio to avoid overheating?

[NeilP]

here is another set of calcs, at 60 rpm, pedal speed (cadence) that would show the speeds you would get if you changed the rear sprocket, and also included is the speeds you would get if you put a 39 tooth ring in in place of the 32.

The calculator does not work the other way so you an put in speeds and see what pedal RPM you get, so you will have to do a load of calcs yourself to get pedal rpms you feel comfortable with.

Screen shot 2012-06-05 at 14.07.08.png (143.08 KiB) Viewed 222 times

[Tench]

I built one of these Cyclone kits using the 900w motor onto a 26" mountain bike, there are pics of the build in the project one link in my sig. It has had the gearing changed slightly since we first built it, it now runs a 14t on the motor driving a 48t on the crank with a 44t driving the rear wheel through a 7 speed cassette. This bike runs a 36v 20ah ping, 0ver 40v off the charger with a 35a limit set in the CA and will quite happily pull w.o.t for 15 miles in top gear (11t at the rear) at 30+ mph with no pedaling without any heat issues.
Looking at your pics you do apear to be using the motor with built in reduction gearbox like ours, i believe the planetary gearbox built onto the cyclone motor has a 5:1 reduction so you should be looking at a maximum motor drive sprocket rpm's of 900.
Sorry i dont have any solution to your over heating issues but i would suggest it is not related to the gearing?
It may be worth stripping the gearbox off it to make sure it is not tight inside, this would create heat and the additional friction loads may heat the controller up? Take the chain off and measure the no load current draw at full throttle.

[NeilP]

Ah, more info, I had seen that there was a gearbox on these motors but had forgotten about that

[darkangel]

it is not your gearing man, it is your controller and motor

ride it till you kill it and then buy the same thing again, if you have money

[NeilP]

Yes, of course, could be something up with motor or gearbox being a bit tight that is causing the overheat issues too, but
Until the OP gets back to us, and while I have some time to kill, I will waste a bit more of yours with some more ramblings and ideas I have going round in my head about this, related to the OP's original question about changing the ratio to get the motor speed up a bit.


Edit....bugger, I worked these figures thinking you had a 14 rear, not an 18, and did not notice that the 7 tooth motor sprocket was only for the bigger motors...... Shit ....so i deleted most of this post as I made lots of mistakes..

If Guido come back with the speed and gears he is using on his up hill sections, when he feels the motor is overheating, we can work out the actual speed that the motor is running at, and see if it is really way too low and a gearing change is in order

[Tench]

Neil your getting a bit confused mate, the 7 tooth sprocket available from Cyclone is for the 1500w motor that does not use a reduction gearbox, they only supply this type of adaptor for the upto 1200w motors;

http://eclipsebikes.com/tooth-cyclone-d ... -1001.html

[NeilP]

Ah well that fucks that theory up eh:

I went back up and deleted the crap in the above post to take in to account `the info Tench just supplied

the 7 tooth I saw was here:
http://www.cyclone-tw.com/order-parts.htm

[Chalo]

If there is room for it, use a larger driven sprocket on the crank. Up to 56t should be relatively easy to find. That alone would increase your motor speed by the ratio of 56:48 for any given pedal speed, or about 17% more motor rpm than you have now, without affecting the bike's speed relative to the pedals.

If you can pedal a bit faster, then you could also use a smaller drive sprocket on the crank, like 44t or 42t. (With a 56t driven sprocket, those would be respectively 27% and 33% increases in motor speed for the same pedal speed.) Or you can use a rear hub with a wider gearing range like the Alfine 11 speed, and the wider gears can offset your need to pedal faster.

Also, if the freewheel at the motor's gearbox shaft is not already the minimum size for that freewheel thread, you should change it to the minimum. M30x1 metric freewheels are usually 14t or 15t, but you can get 13t versions. 1.37"x24 freewheels usually bottom out at 16t, but there are a few 15t units out there.

The moral of the story is that if you need to run the motor at higher rpm without pedaling at higher rpm, then the ratio at the motor input stage must increase.

Chalo

[NeilP]

do you know if the motor to crank chain, is the same pitch as the standard bicycle chain ? or is it a different type?

[Tench]

Yes the motor to crank chain is the std bicycle pitch chain, not sure which thread is used, i suspect without going to measure it that it is the m30x1mm which would allow the fitment of a 13t sprocket but what i find hard to understand is how ours happily pulls an 11t rear once upto speed without complaining which would lead me to believe it is not the gearing that is causing the heating of the motor and controller as our motor never gets above mildly warm and the controller stays at ambient temp. We have relubed the gears a couple of times during its life though, it runs very quiet now compared to when it was new.

[guido]

wow lots of feedback
cruising at 40 kph on the flat, uphill I choose the lowest gear and manage 20 kph
the axle is 20 mm and the 7 teeth sprockets are for 12 mm axles so I dont think I can manage that but yes a reduction before the crank would be optimal. I am thinking on scrapping an old 2500 Watt angle grinder for a reduction
tomorrow is a second real test day and I will also get me a second chain to try the smaller chainwheel

yes I see the added downside of heatproduction, this is just energy I should be using to get from a2b, and heatproduction can be an excessive drain on the battery, all the more reason for me to build me an extra reduction

[guido]

I will be getting myself that 56 teeth sprocket, thats an instant improvement, and maybe with the smaller sprocket on the crank for the secondary drivetrain, I might be fine

[NeilP]

wow lots of feedback

Yes, sorry about that, a lot of that is me waffling and trying calculations out....Edit..now deleted as it was all just SOOO wrong

Tench did mention that maybe a 13 was available for the motor in 20 mm

But I would take the advice also given to strip and check the gearbox
While you were at it, it may be an option to machine it to make it fit the 12 mm 7 tooth sprocket, or see if you can slide the motor to the left slightly, and get a 7 tooth welded to a 14 tooth, or make up a carrier to fit the 7 on the 20mm shaft

Near the top of this page, Tench posted his speed figures
Working that back,
30 mph = 48kph
48kph=800 meter /minute
26 inch wheel rolling radius = 2.075m
Rear wheel RPM = 385 with 11 tooth sprocket driven from 44 t crank
gives crank cadence of 96
crank turned by 48 tooth with 14 on mootor...

So motor sprocket is turning at 330
therefroe with 5:1 g/box ratio
motor turns at 1650 RPM

EDIT figures in RED are corrected RPM figures changed due to info later in the thread, it appears the ratio is in fact 9.33:1 not 5:1

So his smaller motor is running at WOT for 15 minutes at 1660 rpm (3079) taking the bike to 48 kph and not overheating

Your figures give motor speeds of 1492rpm (2784)in Nexus low gear at 20 kph and 1252 rpm (2336)in Nexus high gear at 40 kph

So your motor is running at slower speeds for sure, but is it that much slower to make that amount of heat difference?

As others ( that have experience with these units) have said, the heating may well have other causes.

Going to a 14 motor , 56 crank setup would give motor rpm of 1740 (3247)in low at 20 kph and 1415 rpm (2640)in high at 40 kph

[guido]

ok a test further and this is the outcome
I left and started climbing at once in the standard setup, 14 motorsprocket 48/48 cranck with nexus in first, climbing speed reached 32 kph without paddeling for lack of superhuman paddeling capabilities ,then on the flat max speed with paddeling in 7 gear 60 kph this was fun, until the chain broke. I was 10 km from home luckily 4 km of which downhill.
Fixed the chain and did a second run and yes I managed to overheat the motor in about 3 km, the first 2 steadily uphill. waited 5 minutes and went back.

I ordered a 56 teeth sprocket and wil get this end of the week, further more i`ll try to get a 13 teeth sprocket, all in all that wil help me get the ratios down

I was a bit unwilling to open the gearbox but I will do so tomorrow, I`ve been reading up and the internal resistance can be significant I am always avoiding this in case I wreck something

just as extra info: bike weight with rider is about 130 kg that is 286 pounds

well a few things to change and check but I`ll keep posting new results

ps something else, I was told to disconnect the processor from the battery before charging, Im not real happy with the spark when reconnecting, is that really a must? what can go wrong if I dont, reason: I want to incorporate the charger in the frame, its easier if disconnecting the processor is unnessecary

[boostjuice]

The cyclone/headline planetary gearboxes feature 9.33:1 reduction, not 5:1

The motor has a Kv of ~150

[NeilP]

The cyclone/headline planetary gearboxes feature 9.33:1 reduction, not 5:1

The motor has a Kv of ~150

Ahhh bollocks...you could have said that earlier

[NeilP]

ps something else, I was told to disconnect the processor from the battery before charging, Im not real happy with the spark when reconnecting, is that really a must? what can go wrong if I dont, reason: I want to incorporate the charger in the frame, its easier if disconnecting the processor is unnessecary

By processor, i am assuming you mean the controller. The processor or MCU is an integral part of the Controller..it is the brain inside

Spark caused by the capacitors in the controller re charging when pluggin battery back in. cAN BE ok, BUT IT DOES CHARGE THE CONNECTORS AND CAN cause damage to components inside

Look up pre charge resistor ont eh forum here... use Google Advace earch and searcht eh ES site.

basically you connect the battery first via a resistor, to allow a slow tricklle of current to charge t he controller capacitors then after they charge you quickly remove resistor and plug iin direct...rushing now as shoule be at work

Good lucvk

[guido]

here some figures of my own

Rolling radius 228 cm
14t motor sprocket/18 t rear wheel sprocket = 0,77 (cranck sprockets 48t/48t does not come in equation)
Gearbox on motor 1/9,33

Speed 38 kph uphill in first gear
first gear hubratio: 0,63
0,63x0,77/9,33 = 0,0525 = downratio from motorsprocket to the wheel in low gear
38 kph/60=633 mtr/min
633/2,28=278rpm/min rear wheel
278/0,0525=5295 motor rpm ? seems fast enough when max rpms for the motor are 4500
Now at another speed in high gear slightly downhill …………………………..
Speed 70 kph
Seventh gear hubratio: 1,55
1,55x0,77/9,33 = 0,1279= downratio from motorsprocket to the wheel in high gear
70 kph/60 = 1167 mtr/min
1167/2,28 = 512 rpm/min rear wheel
512/0,1279 = 4003 motor rpm; seems fast enough as well
Done the calcs and now I also don’t see why I need to downgear between motor and crank other than to provide a better peddalingspeed for myself, I now also think that there is another reason for the heating problem that keeps occurring. The gearbox has been checked and is not too tight, I took out a bit of grease that seemed overdone but not so much as to make a real difference.
I will put in a 56 teeth gear for my own pedaling, should arrive end of next week. I do run a 48V 32 Ah battery, I am now thinking that I am just pushing to many amps…………… Will be trying not to run full throttle all the time, see how that goes, it’s the engine running hot not the controller as much.

[NeilP]

Yes, those rpm figures, that you calculated, at these speeds, scale up from the rpm figures I worked a few posts back with the speeds yo gave earlier, so it does look the the RPM for the motor is OK.

Do you have a CA or a Watt meter you can put in line with the battery to the controller and measure the load and wattage the motor is pulling...under load and no load.

That will be a way at least to see if you are getting excessive no load currents, and therefore a problem, or if it is just that you are working the motor hard and it is just getting hot because of hard work

[guido]

placed a 56 teeth sprocket on the cranck, et voila, instant improvement. Just not as much as i hoped for, I still overheated, but its hopefull cause I could get a lot further and pedalling is way more comfortable and effective especially in the higher gears. Now a 12 teeth freewheel sprocket on the motor and its fine by me, this in combination with cooling fins should solve the entire problem.

does anyone know of a 12 teeth freewheel sprocket for a 1200 W cyclone?

ps now I have an other way of keeping the optimal rpms
using the same way of calculations as in the previous post I have calculated the speed for every hub position corresponding with 4500 rpm for the motor, this way I have to keep in mind that for a certain speed I should be in a specific gear, but its worth it, its only 7 gears anyway. the note with the speeds is stuck on the bike but I believe its something like 27 kph in first and 68 in seventh.