How to measure chain/sprocket size?

[Jay64]

I'm getting to the point where I need to buy a front sprocket to fit on the Kolls motor for my first converison build. I was kind of thinking that I would just use the stock chain and possibly the rear sprocket from the stock chassis. I wasn't sure what the chain size was, so I went down to the scooter shop where I bought the bike (without the bike) to ask them what size chain or front sprocket came on the bike they sold me. Their reply was that they had no idea. Eventhough I told them the exact model that they sold me, they said every single one comes with a different chain size, there is no standard for that bike. I asked them if they were marked at all...no. How can I measure it to find out what the size is...you have to bring it in, but we are closing now till after the new year. wtf? They can't tell me how to measure it, but they can supposedly tell me what size it is if I bring it in??? I did some searching online and found that if I measure pin to pin on the chain it will tell me what size I have, but they only listed #35-#45. And my chain is smaller then those. The guys at the scooter shop said that they were sure it wasn't a #25. The measurement I got was 0.30" or 7.7mm. Does that mean it is a #30 chain, or is there some other way of checking that? The other site I was looking at said that the #35 was 3/8" or 0.375, so it doesn't look like it is a straight conversion from decimal size, but maybe close?
On the other hand, the only D-shaped front sprockets I could find were #25. Should I just convert the whole thing to #25?

 

[Lessss]

Beats me :-( I'm bailing the same boat. see http://endless-sphere.com/forums/viewtopic.php?f=3&t=2964&p=42163#p42163

 

[safe]

The measurement I got was 0.30" or 7.7mm.

Sounds like an 8mm sprocket. Hmmmm.... If I were you I'd figure out a way to switch to the #35 chains and sprockets because the go kart people use them and there's a large selection to pick from.

Some typical scooter sprockets:

http://www.electricscooterparts.com/sprockets.html

http://www.gokartnminibikeparts.com/split_racing_sprockets.htm

Do you have your gear ratios figured out?

That can be tricky if you have overvolted your motor. The more you overvolt the higher the top speed of the motor and so in order to make that power more usable you need to gear it down more. Ideally you want (like on a motorcycle) to be able to be hitting peak power in your top gear (assuming you have gears) at just the point where wind resistance is preventing you from going any faster. My 1000 watt bike tops out at about 40 mph in sixth gear on the flat, but the no load speed (the speed at which the motor becomes a brake) is much higher, so on a downhill I can hit 50 mph.

 

[Jay64]

on that scooter website, they have listed 8mm sprocket with #25 chain, and 10mm sprocket with #25 chain. I think that is refering to the shaft size or something. No, I don't have gears on this build. I am hoping to be able to switch out rear sprockets for different conditions like I do on my race bike. I don't yet have my ratio figured out. Still trying to figure that one out. But, even after I figure out a 'recommended' ratio, I still want to try to play around with some ratios so that I can see what effects different ratios have on EV bikes. From what I have heard so far, it goes against a lot of what I know for my ICE bikes. I'm not really sure what the current ratio is, since it has a cvt trans on it. There is a hidden gear so that even if I could figure out the ratios for the pulleys, I still wouldn't know what the connecting gear is before the final gear to the chain. Also, the pulleys don't adjust to their full potential with a load on the bike.

 

[safe]

on that scooter website, they have listed 8mm sprocket with #25 chain, and 10mm sprocket with #25 chain. I think that is refering to the shaft size or something.

Look again...

They have the #25 sprockets at the top and then scroll down and you will see that there are "8mm Chain Sprockets" too. I'd suggest getting out of the 8mm tooth size and go up to the #35 because it's just a better chain. Go by your motor shaft size to figure out what you need.

As for your gearing, which CVT are you using?

Some can be really inefficient.

NuVinci is the top of the line...

http://www.atcnuvinci.com/products_bicycle.php

http://www.fallbrooktech.com/NuVinci.asp

 

[Link]

I got a chance to try out one of those NuVinci hubs at EVS-23.

While I can't justify the $400 price tag, I do think it is very well made. It's so weird to ride a bike like that. It's so smooth. And it's weird to be able to change ratios from a dead stop. If I remember correctly, though, they aren't really useful for more powerful ebikes. The can only take so much torque. A bigger motor would probably break the thing, unfortunately.

I don't think you could get one on a pocket bike without some effort, though :wink:.

As for the chain/sprocket thing: Get a new one. Nonstandard chains are a PITA, and if you want more power, a bigger chain is just a good idea in general (less stretch, more reliable, etc.).

Let me know where you end up getting the sprocket for the motor. I've got four Kollmorgens laying around. I have a sprocket that will work, but I don't like the way that it only transfers the motor's torque through the cheap pin. I'd rather have one that fit properly over the D shaft of the motor. I've seen some sprockets that will fit the output shaft, but they are meant to be bolted (nutted?) on.

 

[Jay64]

Ok, you're right, I didn't go far enough down the page. Once I hit the rear sprockets I stopped scrolling down. All the 8mm front sprockets I saw were dual d bore (man, they totally missed out being able to call those Double Ds. :lol I need a regular d bore.
I'm not using the stock transmission. I'm trying to keep this first build as simple as possible, so I would prefer to use the stock rear sprocket and stock chain. I am not going to really be volting this thing out, so I'm not worried about stretching the chain, besides if I do, it has chain adjustments. :lol: Maybe eventually I will might change over the chain/sprocket to something more substantial, but for right now I am just building a starter project. Besides, coming from motorcycle racing, I am used to using the smallest lightest chain possible and change it out.
But does anyone actually know how to determine the actual size?

 

[iberkt]

Ok, you're right, I didn't go far enough down the page. Once I hit the rear sprockets I stopped scrolling down. All the 8mm front sprockets I saw were dual d bore (man, they totally missed out being able to call those Double Ds. :lol I need a regular d bore.
I'm not using the stock transmission. I'm trying to keep this first build as simple as possible, so I would prefer to use the stock rear sprocket and stock chain. I am not going to really be volting this thing out, so I'm not worried about stretching the chain, besides if I do, it has chain adjustments. :lol: Maybe eventually I will might change over the chain/sprocket to something more substantial, but for right now I am just building a starter project. Besides, coming from motorcycle racing, I am used to using the smallest lightest chain possible and change it out.
But does anyone actually know how to determine the actual size?

I am not sure if this is what you wanted but, here are some standard chain widths.

#25 is 1/4" pitch, 1/8" roller width
#35 is 3/8" pitch, 3/16" roller width
#40 is 1/2" pitch, 5/16" roller width
#50 is 5/8" pitch, 3/8" roller width

 

[Jay64]

Ok, according to the shop where I bought it from, he 'thinks' it is an 8mm sprocket. But after going through possible front sprockets that will work on the shaft of that motor, it looks like I am going to just do a #25 conversion for now. Is there any way to calculate what sprocket sizes to use? I have heard talk of this before, but I wasn't in the position to buy sprockets at the time. I thought everyone was saying to use the Ebikes.ca simulator, but when I went there, that just seemed to similate different power ratings for the motors that they sell. I don't expect to get the perfect combination right away, but I would like to be in the ball park. It looks like my choices for the front sprocket will be 11-14 tooth. I was looking at an 11 tooth sprocket at the shop today and damn, that thing is tiny.

 

[Jay64]

8mm chain has an 8mm spacing between each chain link and is approximately 10mm wide.

It is 8mm between links and 10mm wide. So, safe hit it on the head, it's an 8mm chain.

 

[Drunkskunk]

Ok, according to the shop where I bought it from, he 'thinks' it is an 8mm sprocket. But after going through possible front sprockets that will work on the shaft of that motor, it looks like I am going to just do a #25 conversion for now. Is there any way to calculate what sprocket sizes to use? I have heard talk of this before, but I wasn't in the position to buy sprockets at the time. I thought everyone was saying to use the Ebikes.ca simulator, but when I went there, that just seemed to similate different power ratings for the motors that they sell. I don't expect to get the perfect combination right away, but I would like to be in the ball park. It looks like my choices for the front sprocket will be 11-14 tooth. I was looking at an 11 tooth sprocket at the shop today and damn, that thing is tiny.

Ebikes.ca's calc won't do gearing calculations. but the formula is easy enough.
Rear sprocket's teeth number devided by the front teeth's number gives you the ratio.
Devide the motor's RPM by the gear ratio gives you the wheel RPM.

Then wheel circumfrence times the wheel RPM gives you the unloaded speed.
unloaded speed multiplied by the motor's efficancy gives you roughly the top speed. Thats an inaccurate way getting an estimated top speedd, but its easy and comes fairly close.

 

[Jay64]

Motor rpm: 2916 rpm @ 28v (not 100% sure on that, got that info from another post.)

Rear sprocket 60t / front sprocket 11t gives ratio: 5.45
Motor rpm(2916)/ratio(5.45)=wheel rpm: 535wrpm
Wheel circumference (45.5”) x wrpm (535)=unloaded speed: 24342.5 inches per minute 24342.5 x 60=1460550iph/63360=23mph

Is my math right here? I may have confused myself with trying to conver it to mph from inches and minutes. I also worked it out with a 44t rear sprocket, since that is what is on the bike now, and that came out to about 31mph, but I really think that sprocket will be too small to produce and decent torque. My goal is about 20-25mph. I have no idea what my motor's efficiency is, so I don't know what the actual top speed is. But I guess if I can get within about 23mph unloaded, that would be a good start for my first build. Maybe I'll try and put an 80t sprocket on there and do some wheelies.

 

[TylerDurden]

Math looks ok. Theoretical 23mph unloaded might net you 15-18mph if you assume 75% efficiency end-to-end (batt>ctrl>mot>gear>tire>airdrag).

 

[Jay64]

Cool. That will work for my first build. I just want to get the thing rolling at this point. I guess if that gets too boring, then I can do another generation version using the 36v packs instead of the 28v packs. So I guess I will go with the 11/60 gearing.

 

[safe]

After gathering some info on the 24 volt Kollmorgen with a 400 watt rated load:

No Load Speed - 3500 rpm

...and simply "guessing" that the motor resistance is similiar to other small motors of it's size and weight and design:

Resistance - 0.23 Ohms

...which places the Peak Power at about:

Peak Power Rpm - 2835 rpm

Then pluggin the data into one of my "infamous" spreadsheets and adapting for the small tires I get:

Peak Power Rpm - 22.4 mph
Actual Top Speed - 25.2 mph
Peak Efficiency Speed - 25.2 mph
No Load Speed - 27.7 mph

...which means that my existing bike already blows this away.

So where's the competitive spirit in that?

The only guys out there that I can really race with are the 5304 hub motors... otherwise I'm pretty much on my own. I was hoping you would shoot higher than this...

Future upgrades will help...

 

[safe]

If you go up to a 14 tooth front sprocket then you will be maxed out:

Peak Power Rpm - 31.0 mph
Actual Top Speed - 31.4 mph
Peak Efficiency Speed - 32.1 mph
No Load Speed - 35.3 mph

...which at least makes it more interesting.

This is assuming a 20 amp controller.

I'm not sure how many amps you plan to run on this bike, but it looks like you want to get 11, 12, 13, 14 tooth sprockets and test them all to see what "works" best.

 

[iberkt]

I was hoping you would shoot higher than this...

Oh come on safe give the guy a break
Didn't He say that this was his first build
Let the man walk before asking him to fly :wink:

 

[vanilla ice]

WTF mate. He's using this project to learn before he goes on to faster things. He's said it plenty of times.

 

[safe]

I know...

It's just that Jay will likely jump right past us and head straight towards the Electric Motorcycle Road Racing crowd since that's where he's coming from as a professional road racer. By not really trying to set too high of a mark for the "Electric Bicycle" class he's not getting too hooked on it. The choice of modifying a pocket bike over modifying a bicycle says that he's not that committed to the bicycle category. (at this point)

My worry is that he WON'T stick around after he gets this test bike completed.

For me personally I can't think of a more desireable person to have around to represent the "Electric Bicycle Road Racing" class than a professional motorcycle road racer. I'd hope he was equipped with all the best stuff and would blow everyone away. (including me)

Maybe one day I'll sponsor him on one of my bikes?

Hmmmmm.... I could bring a spare....

(maybe he could buy one of mine?)

The biggest problem we have right now is a lack of qualified racers/builders/tracks and just about everything else so every time we have someone get close to our sport we need to try to get them to stay around and add to it. There just aren't that many people who have the "skill set" as a pro level racer who are accessible to be riders in electric BICYCLE road racing. Our little sport needs more committed members.

So Jay... stick around for a while... become the first ever electric bicycle road racing champion or something...

 

[Jay64]

Um, hello Mr. Safe....I'm using 28 volts, not 24. :lol: No, unfortunately my first build won't blow away all you seasoned vets.

It's ok guys, I'm used to having a target on my back. :lol:

Actually, I never was interested in building an EV bicycle. My intention from the very start was to build an EV high performance race bike. I do have a couple of bicycles that I probably could have used for my first build, but I use them to build up my endurance for racing, so putting a motor on them would kinda kill all that. But I am game for any kind of racing...that has a motor in it. I would be willing to race an electric bike, but I have a focus on building my dream EV motorcycle, so that is the direction that I will be spending my money. If someone wants to 'sponsor' me a EV bicycle for me to ride on race day, I'll be happy to ride the wheels off that thing. 8) I realize that most people on this site are geared towards the EV bicycle scene, but I see it as one family regardless of specialty. The reason that I posted this in the bicycle tech section is because someone yells at us whenever we post a tech question in another forum. :lol:

 

[Jay64]

If you go up to a 14 tooth front sprocket then you will be maxed out:

Peak Power Rpm - 31.0 mph
Actual Top Speed - 31.4 mph
Peak Efficiency Speed - 32.1 mph
No Load Speed - 35.3 mph

...which at least makes it more interesting.

This is assuming a 20 amp controller.

I'm not sure how many amps you plan to run on this bike, but it looks like you want to get 11, 12, 13, 14 tooth sprockets and test them all to see what "works" best.

I missed this post. I think as of right now, I have an 11t front on order. I went with the #25 because that is the size of the front sprocket that fit on this motor that I could find. But now I just realized that I might not be able to find a #25 rear that will fit this particular wheel.

I was told that the motor has an internal 24v 35A controller, but can handle 30v. I will be using this stock controller for right now with my 28v packs. I have that 48v 28a controller that I will probably use later on in my upgrade. I was hoping to use the DeWalt 36v packs in the stock trim, but I just noticed that the under voltage protection is 42v. So it looks like I will have to break down the packs and build my own to use this controller.

 

[safe]

I have that 48v 28a controller that I will probably use later on in my upgrade.

Okay that's more like it...

Peak Power Rpm - 48.2 mph
Actual Top Speed - 46.5 mph
Peak Efficiency Speed - 50.4 mph
No Load Speed - 55.4 mph

...using the 11 tooth sprocket.

Now that's enough to make a race of it.

 

[Jay64]

So that's with an 11t front, is that also with a 60t rear?

 

[safe]

So that's with an 11t front, is that also with a 60t rear?

That's what I'm figuring... 11/60... but keep in mind that I don't have an accurate knowledge of things like the resistance of the motor or the peak power. There's a lack of data points for me to be 100% certain about the prediction, but if some guesswork using some pretty typical values are "good enough" then the prediction might be in the ballpark.

If you double the voltage while keeping the current limit about the same you can expect about double the power. So if you start out at 24V and go to 48V you will go from about 400W (rated) and a 500W (peak) to a 800W (rating equivalent rpm) and a 1000W (peak). And you also will be reving the motor to 7000 rpm!

My "guess" is that the powerband will look like the power/heat chart. (chart below) Notice that your heat levels will be getting a little high. So you will be dealing with heating problems when you use the machine at full throttle and low rpms. At high rpms you are okay. Basically you need to learn about the heat/power relationship (which is kind of obvious) and "deal with it" as you ride. (you can overheat your motor in one or two hard accelerations based on what the chart says) You are more likely to overheat your motor from 0-10 mph than anything you might do in the 35-40 mph range. (study the bright red curve carefully verses the black power curve)

I'm simply "guessing" about the amount of heat that the motor can handle at it's rated speed based on what an equivalent motor can handle. It's possible that the Kollmorgen can handle a lot more. So you will only know by testing it out.

Just imagine taking your race bike and sticking it into sixth gear and thinking about what the motor needs to do to pull the bike off the starting line. (and also imagine that there is no clutch slipping!)

If I were to suggest anything I might say you could go 11-65 or equivalent so as to get a little better low end. But keep in mind that it depends on your voltage. When you are running the lower voltage you need to gear it up a little more because a lower rpm range can pull more speed. (less wind resistance) But as you go up in the voltage the extra rpm pushes you up to speeds that the wind resistance won't allow you to reach so you are better off gearing a shade lower.

Maybe go:

11-70
12-70
13-70

...then you cover all your options?

(changing the small sprocket means you could likely keep the same chain length)

You are only going to know by testing it.

One last thing...

If you look at the Slope verses Top Speed chart you will see that your maximum slope to climb is realistically about 5%. Now in Florida you will never need to worry about that sort of thing, but here in Missouri I have hills that get up to about 8% so with such a gearing you would quickly burn up on any moderately steep hill. Florida flatlands don't stress a fixed gear setup, but imagine trying to take the bike up the steep hill at Sears Point. This is where not having gears will really hurt your bike's performance. (and the new turn setup makes it even worse for fixed geared bikes)

 

[Jay64]

Yeah, I have been told that I can't take these motors above 48v because it will spin the motor so fast that it will come apart. So I need to keep that in mind when I get to the stage of modifications. I am thinking about getting a few rear sprockets for testing. I think I will go with big jumps in the gearing. It's looking like I will be getting something in the range of about 60 as my target sprocket, but I think I will also try a 78 (largest I could find for this size) and a 44 (stock size). This large jump in gearing will allow me to test some major differences and actually see/feel what it relates to in real world settings. And no, I definately don't need to worry about any hills. :lol: On my race bike I have 4 different front sprocket sizes and 8 different rear sprocket sizes to be able to get the exact gearing that I need for different tracks. However, I think for this project, I won't really need that. Eventually I might try to put some type of transmission or something on it, but for now this is just a test bed to get me started on the larger project bikes.