HELP WITH MY BIKE

[danmansuttmeier]

I've bought a Currie motor 1000w for $72 on Ebay, the controller for $46 on Ebay, two 35Ah SLA batteries for $120 on batterymart, and the throttle for $10 on Ebay as well. I am using an old mountain bike with three front sprockets that could be shifted during riding. I will remove this front sprocket shifting feature and Im going to have the motor with its 15 tooth sprocket chained to the mountain bikes biggest front sprocket. Then I will have the mountain bike's chain on the smallest sprocket which then goes to the rear sprockets which i will leave alone so I can shift while riding. I am arranging it this way because I am worried about the bike not having the power to move my 160lb self. I want this bike as fast as possible. I am hoping the arrangement of gears i just described give the motor the greatest mechanical advantage possible. Yes I will lose my pedals in doing this and I will weld pegs so it is no longer a bicycle but a electric bike i guess. I do not want to spend money on e-brakes so i will be using the stock bicycle brakes which will put me over the handlebars if i stop as quickly as possible. Do you see any problems with what i just described for my bike? Any suggestions for the gearing, maybe a different arrangement of the chains and sprockets? Do you believe with this setup of parts and gearing the bike will be able to pull me along?

 

[danmansuttmeier]

As soon as i start this build i will post pics and performance data if requested

 

[dumbass]

Because you didn't mention it I am going to assume that you ar not planning on using a frewwheel between the motor drive and the peddle drive. If this is the case this setup will at the very least get you hurt. First off I am guessing the top speed you can peddle using the smallest front sprocket is maybe 12mph if your lucky. That motor even on the large sprocket is going to eat you alive. Again I am guessing it will be running at least 3000rpm. Do the math.....3000rpm*15t = 45000 / 48t big sprocket = 937rpm....Did I make a mistake or are you saying you can crank those peddles at the speed?

Bottom line you need a freewheel between you and the motor. Even if and when you get your gearing right if you slip off a peddle the peddle will come around and take out your ankle several times until you stop the motor.

 

[danmansuttmeier]

Well the freewheel idea is too complicated for my simple mind. But even though i sorta mentioned it i plan on cutting the pedals off and putting pegs on the sides. What i did like was that math you were doing. With the motor on the biggest sprocket and bike chain on the smallest I think this is possible. I just wish i knew the speed it would be. Do you think with my batteries and motor that this bike will have some pep?

 

[REdiculous]

If I'm understanding correctly, then that 937rpm would be at the crank right?...so you'd probably want another 2:1 reduction so the wheel only spins up to 468rpm. That'd give you 27.8mph w/ a 20in. diameter wheel/tire.

What's the smallest sprocket on the crank and what've you got on the wheel?

 

[danmansuttmeier]

Hey thanks for the help. On the motor is a 15tooth sprocket. On the crank of the bike is 3 sprockets which i had said before. I wanted to hook the motor to the biggest front sprocket on the bike which is 48 tooth. Then the bike chain would be on the smallest front sprocket which is a 28tooth. Then the rear of the bike has the normal 7 sprockets. The smallest rear sprocket is a 12 tooth sprocket. The rear tire is also 23inches in diameter. What do you think the top speed would be and will this bike even move with this gearing?

 

[Sturdly]

Better check the chain size of the sprocket on the motor. Typically those motors have a #25 chain size sprocket, not compatible with a MTB chainwheel or sprockets at all.

 

[dumbass]

Assuming all your chains are the correct size here'as how to calculate your "NO LOAD WHEEL SPEED". It's all about the number of teeh you are moving per minute. Then calculate in the wheel size and finally the the MPH. IF you have Excell I maybe able to find a simple program I wrote to calculate the final wheel speed. All you need is to plug in the numbers and it spits out the answer.

 

[dumbass]

OK, I did some quick calculating for you and I have bad news for ya. Yuo need to add a gearbox or atthe very least a secondary sprocket setup. Making the following assumptions;

15t motor sprocket
3000 RPM motor
48t large crank sprocket
36t small sprocket
32t large rear sprocket
13t small crank sprocket
26" average wheel

When running the motor at full power with no load teh wheel will be turning at 80.77 MPH in the lowest gear and 119.3 in the higest gear. Your peddle speed at a 75 cadance per minute will be 6.46 MPH in low and 21.21 MPH in high. As I said this is with a no load but even at 50% you would be flying. Beside the motor will never pull at these ratios. That's why you need to use another (seconday gearing setup or a gearbox. By teh way I still think your making a big hurt mistake on not using a freewheel. I know you want something cheap but how much do you think if will cost to set a broken foot?

I think all my calculations are correct but anyone that find an error please feel free to correct.

Bob

 

[jdcburg]

Hi Bob - I believe he plans to cut off the pedals and cranks and replace them with pegs, so he won't have to worry about the cranks turning.

Hi Danman - welcome. If you want to pedal along, you can get everything you need for a freewheel from SickBikeParts.com. They’re really pretty easy to put together and if you pedal a little it takes a lot of the strain off the motor, especially at startup. Just contact jim@sickbikeparts.com if you have any questions. He's very good. Also from them you could get a smaller sprocket (as low as 24T) and a 48T large one, plus a kit to hook them together. There is a calculator you can use to figure out bike speed based on the rpms, tire size and the sprocket sizes, front and rear. It is at http://www.arachnoid.com/bike/. You have to figure the rpms of the front sprockets as Bob described: Find the motor rpms. I believe it is 2600 for that motor. Then count the number of teeth on the motor sprocket (15) and divide it by the number of teeth on the driven sprocket (where the pedals used to be). The sprockets have to be for the same size chain - typically Currie motors come with a #25 chain sprocket and #25 isn't bicycle chain, as Sturdly wrote. You might be able to find a 9 to 11 tooth bicycle chain sprocket for the motor. If you have a 10 tooth driving a 48 tooth, you just divide 10 by 48 to get 0.21. Multiply your motor rpms (2600) by 0.21 and you get 546. That’s the rpms at the pedal crank. Using the Bicycle Analyzer, set the tire size at 23 in., pedal cadence at 546, front gear at 24 and rears at 32 (lowest gear) and 12 (highest gear). Press “analyze my bike” and you’ll find the speeds are 28 mph and 74.7. You could put the numbers in for the gears in between if you want but that motor would be overloaded in anything but 1st and maybe 2nd. Without pedals, it would probably fry trying to start you off even in 1st. If you put some sort of reduction on it, maybe 2 or 2.5 to 1, it would probably work. You could leave the 15T #25 sprocket on the motor and put a bearing-supported shaft someplace between the motor and the bottom bracket (where the original pedal sprockets are). Then you could put a 30 tooth #25 sprocket on that shaft and on the same shaft put a 10 tooth bike sprocket. Run a #25 chain from the 15T to the 30T and a bike chain from the 10T to the 48T on the bottom bracket spindle. The 15 to 30 reduction is 2:1 so it will reduce your final rpms at the cranks by half to 273. So then the top speed would be 37.4 mph. That should give you enough low end power to use that Currie with you and 30+ pounds of battery. Just remember that's a lot of weight. At those speeds, that can really stress the frame. It's also a lot of weight to stop in a hurry. Speed can be dangerous. Keep us posted - jd

 

[danmansuttmeier]

Hi JDCburg that post was the most helpful thing I have probably ever read ever lol. Budget is a big issue and those freewheel setups cost a good amount. I think i will add a jackshaft like u suggested somehow inbetween the motor and big sprocket somehow since i need to change chains anyway. Another question i have is about my controller. It just came in today with no wiring diagram. It's a Yiyun YK43. The throttle and controller have the same connector except they r both male. The throttle has blue, red, and black wires. I'm guessing it goes to the three wire cable coming from the controller. I would do red to red, black to black, and I THINK white from the throttle to the blue of the controller (please confirm this). Then the large red and black wires on the controller go to the battery. BUT what does the large blue wire go to? Also what does the yellow and black wires in the 2 wire connector go to a on/off switch? Here are pics i took of everything

 

[jdcburg]

Hi Danman - That looks like a good bike to convert. Lots of space between your legs for batts, etc. You can find a wiring diagram for the controller at TNC Scooters. Try this page http://www.tncscooters.com/YK43B.php. If that's not it, go to the main electric parts page http://tncscooters.com/partsdb.php?type=ES and try to pick out the right one, then go to the specs page for it. They have quite a few to pick from. Prices are pretty good so if necessary you could buy a new one from them.

You should be able to put together the freewheel cranks for $71 + s&h if you don't need a new cartridge, $87 if you do. I think it's money well spent. Worst case, you can convert back and you've got a bike you can sell.

You have lots of options on the reduction stuff. Currie makes a planetary reduction unit available at http://www.allelectronics.com/make-a-store/category/540/Rotating-Parts/1.html for $9.50. There are other ways to go. Half the fun is designing it when you should be doing something else that "needs" to be done - jd

 

[dumbass]

Hi Bob - I believe he plans to cut off the pedals and cranks and replace them with pegs, so he won't have to worry about the cranks turning.

- jd

Hi JD, yeah, your right. To be honest I remembered that as soon as I read your posting. I sometimes allow myself to be overly concerned when someones bigest worry is the budget. We should all have a budget but not at the price of our own safety. I agree with the jack shaft. that's what I installed on my bike and motors it already had gearboxs. But I wanted a better way to be able to mount freewheels on both of them. Thanks for the correction. Bob

 

[danmansuttmeier]

ok guys new plan with the gearing. The motor does have a 15 tooth #25 sprocket. What if I put a 65 tooth #25 sprocket in place of the large front sprocket on the bike. Then I replace the small front sprocket with a 13 tooth sprocket. This would make the bike itself a jackshaft instead of adding one which complicates everything. I plan on cutting the pedals off anyway why not just make it the one jackshaft am i right? And thanks for the post about motor controller I could not find my exact one but I found one close and I am hoping its the same wiring.

 

[deardancer3]

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PLease someone double check me, my eyes are not what they used to be, but,

that looks like a rear triangle with stays that are crimped and not brazed.

If so, you should get those brazed. Crimped rear stays are not good for ebike weight, power and speed.

d

 

[jdcburg]

That gives you 15.7 to 44.5 if in fact your outside tire diameter is 23 inches. It's probably borderline whether 24V SLAs will have enough guts to handle the load without sagging too low and causing the controller to cut out. Also there are the recurrent safety concerns - too much speed and/or weight on a bicycle frame can lead to disaster, and you may be pushing it on both. Think about having EVERYTHING on the bike checked by a pro. That was a good catch, deardancer - jd

 

[dumbass]

Just an FYI if your interested.......you do know the bike your talking about building is not legal to be ridden in the USA on the streets or bike trails. Right? I know this may not be your concern but I thought I would throw it out there for you so when you see a cop car you at least play it cool.

One of the problems with all our calculations is we don't know the speed of the motor or the true size of the tires. So can you provide this info.? We also are not taking into acount for load loses which will be significant especially hauling around all that lead.

Bob

 

[deardancer3]

ya gotta have pedals that work.

Yeah 20mph max under e-power, 1hp max, (legal items for legal low power ebike being equal to a bicycle) those are items that are not conspicious while riding.

But having pedals and having your feet rotating while you are moving, gives observers the impression of a "Bicycle" and that you are pedalling while moving.

REmove the pedals, have your feet always stationary, you loose that impression and attract attention of the law; that will cost you a lot.

Not only are you not legal, you are conspicoulsly not legal-- much worse. unless you are planning on a moped, which in some states is ok, but a big deal in others.

d

 

[danmansuttmeier]

hey guys i have my battery rack almost finished. The batteries are HEAVY they weigh 40lbs together. The true tire diameter is 23inches. The motor is a 1000w Currie motor and at 24v is 2200rpms. With my calculations if i remember right i was going to be 14.5mph to 34.7mph. I've seen videos of bikes with half the amperage and half the motor do 30mph so I also dont understand why mine wont do 30mph as well. I also dont understand the comment about the rear sprockets on the bike not being brazed. Can you go into more detail?

Also about the whole legal thing and pedals everyone keeps warning me about. I in no way care about the law with this bike or pedaling it. I will not use this as transportation as I live in a very rural area where an e-bike would never last all the way to work. I also have very minimal cop worrys around here because even if a cop did stop me they would worst case tell me don't do this again. This bike will be a fun cruise ride bike for down the road. Thats why all i care about is this bike hitting 30mph which is why i went with the biggest motor and batteries i could find. I am an electrical engineering student and an avid speed demon which is why I have always wanted to build one of these. I would have gone with a gas engine but that is boring.

 

[dumbass]

OK, based on my calculation your speed range is 15.8 - 38.88 mph with no load. You should expect maybe a 25% or more lose factor for your load making your range about 11.85 - 29.16. As for the gearing and motor the bike should do 30 mph with little or no problem. The problem is going to be your battery pack is going to have a high degree of sag. I have 4 ebikes the smallest motor being a 360w 24v motor and with peddle assist I get about 29 mph. So like I said you should have no problem getting 30 mph with a good pack. Time will tell how well the lead hold up. The high discharge is going to be very damaging to them though even if they do perform for you. So don't expect them to hold up very long.

Bob

 

[danmansuttmeier]

If i charge them after every ride what is your estimate on how long they will last?

 

[mwkeefer]

Dan,

Be sure when you are just done the ride (as soon as your done) you plug in those SLAs for charging, if you let them sit a while between discharge and charge (more than a minute or two is my rule) they will sulphate and that will cause them to die faster (less cycles).

On my first SLA experienc with my GoPed (a while ago but relevant due to similar loads) - I managed to kill the brand new batteries (I had ordered them when I bought my GoPed used) in < 40 cycles. When I ordered the new set, someone asked me how I charge... I was only charging as needed, not every time I was done a ride. SLA likes to be stored / kept at float (max) voltage and letting a discharged SLA sit (or partially discharged) will cause the battery to sulfate.

Other than the weight, relative short life cycle and lower power density... the SLAs should do fine (for now).

-Mike

 

[danmansuttmeier]

Thanks for the heads up Mike. I have my sprockets on the way and the battery rack welded and made. Once the sprockets come in and i have them on the bike I will post more pics. Mounting the motor seems like the biggest challenge for this project. Any1 have any tips on mounting this thing?

 

[dumbass]

If i charge them after every ride what is your estimate on how long they will last?

I honestly can't answer your question. With my SLA packs the motor to AH ratio was within a normal range (360w with 18ah packs). I no longer use these packs very often but I'm sure they must have 100 cycles on each pack and could go another 100 cycles and maybe several hundread more cycles. The point is I was very good to my packs. I rarely used more then 50% to 60% capasity and always charged then as soon as I returned home even on a short ride. I always maintained them at full charge. If you do the same you will maximize your packs. But no matter what you do you are running a large motor on small packs so you are discharging them at a very high rate. Remember the AH rating is determined based on a 20 hour discharge. You will be sucking them down in less then 30 minutes. This is a killer of any batteries especially lead batteries.

 

[danmansuttmeier]

wait dumbass why would i be sucking them down in 30min. The batteries are rated at 35aH and the motor max current is 34 amps. Wouldn't these batteries last a much longer time than 30min?