Request Help and Ideas for Improving my eBike

[Ryland]

If your motor is getting hot (to hot to touch) then it needs to be cooled, a muffin fan blowing air in past the brushes should do the trick, a higher air flow would be ideal if you were making long trips with it but a muffin fan isn't going to draw more then a few watts.

Tires are going to help, Schwalbe Big Apple tires are a LRR tire and are pretty light weight for their size, they also have higher load ratings then a lot of narrow racing tires.

[govman6159]

Originally Posted by Ryland

I have a rear hub motor with a 7 speed free wheel on it and I've never had an issue with shifting gears, I've also never had an issue with it cutting out going up hills, but that would be because the speed controller is undersized and has a thermal shut down that is kicking in, so a higher power speed controller might be something to think about, even if you don't upgrade the motor a higher voltage speed controller will help you cut the losses in the wires as long as you don't over speed the motor, your speed controller limits the voltage to the motor at part throttle, so you could have a 96V battery pack and speed controller and as long as you didn't give it full throttle the motor would never see that full voltage, but the number of amps in the wires between the battery pack and speed controller would be much lower and at 22mph your motor would still only be seeing 24v or whatever voltage it requires to go 22mph, of course that would be a bit of over kill, but going with a speed controller that can handle higher amps and maybe a step up in voltage could be your best investment.

So, it's my controller that's causing it to cut out? I'm using the six pin "diagnostic" throttle control. The symptoms/indications I get are:
When going up a hill, sometimes the power cuts out (usually near the top of the hill). The red and green led's on the battery level indicator flash (battery SOC is green or full). I reset them by cycling the power switch and proceed on.

If I upgrade to a more robust controller, what would you recommend? I'm thinking a 36 or 48V 1000W controller (probably 48 so I'd have the option to upgrade to a 48V motor later). Since my batt pack is 24V, the motor would never see any higher voltage but, it may allow for higher current than the motor could handle. What potential problems could this cause? Could this burn out the motor's windings? I really don't want to burn out the motor b/c they are expensive (to me anyway) but, I would like to eliminate this problem of cutting out.

Can you give me some recommendations on controller upgrades?

Also, regarding your rear hub motor, you say you can still shift gears but that doesn't affect the gearing of the hub motor to drive the bike right? What I was referencing about shifting gears is that I can vary the gearing that my motor sees by shifting to a lower or higher gear. It was my hope that I would be able to use the bikes transmission to more efficiently use the small motor (original hope was to gain top speed but this has proved more difficult than anticipated. Now I'm looking to gain more low end torque thru gearing). I know most eBikes are focused on assist but, my ideal is little or no human assistance (unless you want to) because I'm lazy (lol).

[govman6159]

Originally Posted by Patrick

1) I like the idea of the triathlon bars to get you into a tuck and reduce wind resistance. Maybe a 2nd throttle could be hooked up to allow you to use the triathlon bars?

2) Can you add a heatsink to the motor so it doesn't cut out so soon on the hills?

3) Can you increase the pressure in your tires or change to higher pressure tires to reduce rolling resistance?

4) How about moving the batteries to a flat plane inside the diamond of the frame to reduce frontal area and wind resistance? Try to make it only one battery thick so the pack is riding in the wake of the downtube. This would also lower the CG and help improve handling.

1) I'm sure a 2nd throttle is possible, just wire it in parallel.
2) The motor doesn't get too hot. I'm thinking its torque or controller related. I'm pretty sure my controller is cutting power to protect the motor from overtorque/overcurrent conditions but, I'm just guessing as my knowledge is not really up to par on this.
3) I'm running 100 psi front and rear already.
4) This is what I set out to do but there is simply not enough space for 16 cells inside the diamond. This is a small frame bike. If I upgrad to a "large" frame" (say 19 or 20), I may be able to do that.

BTW, what is CG????

[Patrick]

CG is Center of Gravity. Center of mass - Wikipedia, the free encyclopedia

[govman6159]

Well, I received and installed the 14-34t rear freewheel yesterday. I rode the bike to work today and here's my results.

Pros: When I select the 28t front sprocket and the 34t rear sprocket, I have much more low end torque. This equals getting up to speed quicker and a better ability to climb hills. I was able to keep the bike up to 13mph up a hill that normally slows me down to 7mph and... the motor/controller did not cut out when in this configuration. The pickup from 0-15 is amazing and, I'm at 19mph b4 I know it.

Cons: With 28t front/34t rear selected, 20-21 is my max speed (I believe due to rpm limitations of the motor). The next cog below 34t is 24t. This is too large of a step down for the motor and it has a hard time gaining any more speed on the flat or slight upgrade. I was only able to reach 22, or better, on a downgrade but, I was able to reach 25 on a slight downgrade (crouched position). The motor/controller did cut out twice this morning when in the 28t front/24t rear configuration.

Thoughts/Observations: I believe I need a "custom" freewheel. My thoughts are 34/30/26/22/18/14/11t. Going from 34t to 24t is just too big of a jump for the small 24V/500W motor to handle at once. If I could slowly step down the R/R, it would be more beneficial and easier for the motor to handle. It would also provide a smoother transition of motor torque to the drive sprocket.
I would also benefit from switching to a 26/36/4xt front sprocket for initial speed bursts but, I'm going to hold off on that for now. I believe that 22/32/42 would give me even more low end torque/pickup but I'm not sure how necessary that is. I know that I've never used the 48t front sprocket (ever) and I rarely use the 38t front sprocket.

Plan of action: I'm going to attempt to take the old freewheel (11-28t) and the new freewheel apart and create a custom freewheel as close to the ideal one mentioned above. It will probably be something like 34/28/24/20/16/14/11t. Is this possible to do?? The old one is a SunTour 11-28t and the new one is a Shimano 14-34t. If not, what are my other options (or do I have any)? My strategy is to make one change at a time, evaluate the results and decide whether to keep that change or where to make a new one (using the process improvement procedures proved by the Japanese automakers of the 80's and still in use today). It seems when you solve one problem, it always causes a new one.

Other news: I saw a 36v/1000W motor on Ebay (Currie motor). I am in communication w/ the seller to try to get the motor and controller. I also saw this motor and it looks pretty tempting too. Does anyone have any experience with that motor?

[Ryland]

higher end speed controllers step back the throttle as they heat up to prevent damage to the controller cheaper controllers just shut down when they reach their limit, 500 watts at 24v is only 20amps, a cheap hill climbing option would be a double pole double throw switch that would allow you to switch to bypass the speed controller all together to eliminate the controller over heating issue, the double throw switch would allow you to cut power to controller and a fraction of a second later have full power going to the motor without the speed controller being in the way, before solid state speed controllers a simple on off switch or a few switches hooked up to different strings of batteries was common, it's hard on the motor to give it full power from a dead stop but once the motor is up to full speed/power it's not going to care and going this route is going to cost you about $15 in switches and wire, I'd opt for a 30amp switch, a single pole double throw switch would work as well, switching the positive side, but switching both legs is better.
Going with a higher amp speed controller shouldn't burn out the motor.

[Ryland]

Rolling Resistance | Schwalbe North America

Some info on low rolling resistance bicycle tires.
A number of companies now offer E-bike tires that have stronger side walls, are made to handle the extra weight and speed of an E-bike while being LRR tires.

[govman6159]

Well, I've been riding the bike to work for a week now with the new gear rings and the results are really good. Motor controller cutoffs have pretty much been eliminated. The only time it has cut out is when I'm in a higher gear (trying to get more speed). When I crouch into a tuck, I can eak out about 25mph but it does take a while to get there.

No word from the guy on the 36v/1000W motor.

I purchased a new crank b/c the sprockets on the stock one are slightly bent from years of use/abuse. I'm hoping to gain a little less mechanical resistance from this. I plan to undertake the replacement tonight.

I am satisfied with the performance of my ebike but, there is always room for improvement. I am very happy w/ the performance of my battery pack. 24V/30ah is pretty robust and its what I would recommend to anyone using this setup. SLA is too heavy. I probably use about 60% of the packs capacity during my commute which should allow for years of use on these batteries.

I am contemplating purchasing a new Trek 7.3 FX and swapping everything over to it. This bike is my initial prototype but it has lots of issues not related to the ebike mods (ie: bent sprockets, derailer issues and just general mechanical inefficiencies from age). Or, I could just fix the issues on this bike. We'll see how the front sprocket replacement goes. If that works good, I might just fix this bike.

[govman6159]

Here's an issue I would like advice on:

If you look at how my front sprocket has been modded (see attachment), I have a front freewheel bearing bolted on to the currie 96 tooth #25 sprocket. I then bolted that to the OEM crank sprocket(s). The problem is that I didn't get it exactly centered and its off balance (due to the bolts I used to attach the two together). What I would like to do is get the new sprocket(s) perfectly centered and aligned with the 96 tooth currie sprocket (the currie sprocket is pretty much perfectly centered on the freewheel bearing, I was able to do this by using the threads on the currie sprocket and the threads on the freewheel crank).

How can I make sure I get the new sprockets perfectly centered on the currie sprocket and... How can I balance the whole assy?????