How do you guys deal with sprokets?

Get all your technical information about electric bikes here.
Post Reply
User avatar
Beagle123
10 kW
10 kW
Posts: 627
Joined: May 02, 2007 2:35 am
Location: Los Angeles

How do you guys deal with sprokets?

Post by Beagle123 » May 04, 2007 4:24 am

I'm using this gear motor from Unite:

<a href="http://www.unitemotor.com/unite/en/Prod ... 9001904</a>

It has a "dual D Bore" that is flat on two sides and round on two sides. It looks like this:

<a href="http://www.partsforscooters.com/127-7;j ... 5">picture of sprocket</a>

But its different. Aparently it fits a 420 chain and it has 10 teeth.

My problem is that my gear hub accepts sprockets with betewwn 14 and 24 teeth. So to make this setup work, I need to get a 16 to 18 tooth sprocket to fit the motor, and it should be sized for bicycle chain.

I could weld the existing sprocket to a 18 tooth bicycle sprocket. However, if I mess it up, I won't have any sprockets (I can't even find the replacement part).

I can potentially make a sprocket from steel on my drill press, but its a lot of work.

This is perhaps the biggest issue facing us when building our bikes. It's easy to buy a motor, and controller etc. But the we aleays NEED that ssprocket!!

How do you guys do it? Where do you look to find sprockets like mine? What do you do when you can't find the damn thing?

Thanks to all of you for all the great info on this site.
Last edited by Beagle123 on May 06, 2007 2:57 am, edited 2 times in total.

User avatar
safe
100 GW
100 GW
Posts: 5701
Joined: Dec 22, 2006 12:14 pm

Post by safe » May 04, 2007 7:55 am

I'm assuming you are using this motor:

Image

I've got the same motor ready for a future project and I was planning to simply weld onto the existing gear a new sprocket. I've done this stuff a lot on my existing bike and have gotten pretty good at it. If you screw up, you simply grind off everything you've just done and do it all over again. :shock:

You do know that "420" is the same pitch as a bicycle chain, but the width is wider. This means you could either upgrade to a "420" chain or you could grind down the sprocket to make it thinner so as to fit a bicycle's 1/8" or 3/32" width. You could even use the motor to spin the sprocket while you ground it down with the (handheld) grinding tool. You would be surprised at how well this works. However, it sounds like you need 18 teeth, so you can't do this.

User avatar
fechter
100 GW
100 GW
Posts: 11992
Joined: Dec 31, 2006 3:23 pm
Location: California Bay Area, USA

Post by fechter » May 04, 2007 8:43 am

You might be able to bolt the sprocket on.

I think you'd want to make a backing plate out of a big washer and sandwich the motor sprocket between the backing plate and the new sprocket. Line up the bolt holes with the space between teeth on the motor. This way you could unbolt it later. You might need to use countersunk holes to get enough clearance.
"One test is worth a thousand opinions"

User avatar
Beagle123
10 kW
10 kW
Posts: 627
Joined: May 02, 2007 2:35 am
Location: Los Angeles

Thanks, I welded it

Post by Beagle123 » May 05, 2007 3:43 am

Hi fecher and safe:

Yes that is my motor. I was making the sprocket on my drill press, and decided to "go for it" and weld the only sprocket I have to a 18 tooth bicycle sprocket. It worked!!!

Its ALMOST perfect. Its about 1/2 mm off center, but its almost unperceptable. You really have to struggle to see it. In fact it may be perfect.

<a href="http://img24.imagevenue.com/img.php?ima ... .JPG"><img src="http://img24.imagevenue.com/loc1039/th_ ... 1039lo.JPG" border="0"></a>

<a href="http://img158.imagevenue.com/img.php?im ... .JPG"><img src="http://img158.imagevenue.com/loc1145/th ... 1145lo.JPG" border="0"></a>

I just took my bike on its maiden voyage! IT's awesome. I was amazed at the power. It plowed up a steem hill, no problem. It zipped up to 20mph in a few seconds. I have a Shimano 7 speed hub on it, but I don't have the shifter yet, so I'm stuck in one speed. I can't wait. I'm going to have an emotional breakdown if I don't get it soon.

I plan to do an extensive post in the photos and videos section when Its done.

My problem now is that the chain keeps falling off at top speed. I"m using bicycle chain, and it has to go a long span between sprockets (maybe 2 1/2 feet) How do you keep the chain on the sprockets? It's alignment is a bit off, maybe 1/8 to 1/4 inch. If the alignment is correct, could I expect bicycle chain to be able to span 2 1/2 feet without failing at 38 rpm?

I love your bike, safe. I want you to put a gear hub on it.

<a href="http://img5.imagevenue.com/img.php?imag ... .JPG"><img src="http://img5.imagevenue.com/loc581/th_54 ... _581lo.JPG" border="0"></a>

<a href="http://img143.imagevenue.com/img.php?im ... .JPG"><img src="http://img143.imagevenue.com/loc864/th_ ... _864lo.JPG" border="0"></a>

I was up until 4am reading both of your posts. Thanks.

More power to you guys.


P.S. Where's a good place to post my images? What do you guys do?

Lowell
1 MW
1 MW
Posts: 1708
Joined: Jan 12, 2007 4:33 pm
Location: Vancouver

Post by Lowell » May 05, 2007 3:53 am


User avatar
safe
100 GW
100 GW
Posts: 5701
Joined: Dec 22, 2006 12:14 pm

Post by safe » May 05, 2007 7:27 am

Looks like a good choice of components. The motor and internally geared hub will work well together. That's a good combo. Nice. 8)

As for the chain problems...

You have suspension and your pivot point is not centered at the same location as your front sprocket so when you hit a bump (or even when you simply sit on the bike) you will get "sag" in the suspension which will allow the chain to get loose. Add to all this that the swingarm probably flexes a lot and your alignment might not be perfect and you will have all kinds of problems.

I'd advise a chain tensioner. You could probably convert an old derailler arm and wheel to a tensioner. You want to have a "spring effect" to keep the chain snug and this will also solve your problems with the front sprocket being slightly off. This picture shows the right location, but it lacks a spring. You want the tensioner positioned so that it takes up the "slack side" and not the "power side" of the chain. Motorcycles have been doing this for years...


Image

User avatar
fechter
100 GW
100 GW
Posts: 11992
Joined: Dec 31, 2006 3:23 pm
Location: California Bay Area, USA

Post by fechter » May 05, 2007 9:29 am

cool looking bike :D

What was it to begin with?
"One test is worth a thousand opinions"

User avatar
Beagle123
10 kW
10 kW
Posts: 627
Joined: May 02, 2007 2:35 am
Location: Los Angeles

This image from imageshack (Thanks for the tip)

Post by Beagle123 » May 05, 2007 10:56 pm

Thanks. I think it looks cool too. It was a 1977 Batavus VA moped in its past life. It was addicted to oil. I took it in and cured it of its addiction:

<img src="http://img517.imageshack.us/img517/8010/dscn0319do0.jpg" alt="Image Hosted by ImageShack.us">

Price $85

safe, thats a great chain tensioner. I don't know how you can find a picture like that so quickly. amazing. Its a great idea. I'd like to have the chain just stay on the damn sprocket if its possible. One of the things I like about the bike is that everything fits together so nicely. My inner perfectionist wants that.

I rode this morning and the chain didn't fall off. Im going to wait and see if it heals.

<img src="http://img186.imageshack.us/img186/3053/dscn0320bf3.jpg" alt="Image Hosted by ImageShack.us">

By the way, if you look closely at the picture, you can see that the motor is attached to the same piece of thick steel that attaches to the back wheel. The body and the seat are one piece, and the back wheel and motor are another piece. IT piviots just above the motor. So theoreticly it shoudn't slack at all. I was very lucky to have that spot to mount the motor.

User avatar
Beagle123
10 kW
10 kW
Posts: 627
Joined: May 02, 2007 2:35 am
Location: Los Angeles

Post by Beagle123 » May 06, 2007 1:45 am

safe wrote:
I'd advise a chain tensioner. You could probably convert an old derailler arm and wheel to a tensioner.


Motorcycles have been doing this for years...


Image
I was under the impression that motorcycles just have a big, thick, less flexible chain goingfrom sprocket to sprocket. YOu meaan they have a hokey little device with a spring in it like on a 10-speed bike?

I didn't know that.

I'm starting to like your idea better and better. I was just thinking about why I should even risk having the chain come off when a little guide could make it work 100% reliably. It seems like a good idea.

It seems like all I really need is the guide part. I don't really need the tension part. Perhaps I could buy something that is just a channel with sides that are as wide as the chain that just keeps it from veering in any way. Do they sell that?

Who makes the device in your picture? Where can I get one?

User avatar
Miles
100 GW
100 GW
Posts: 11436
Joined: Mar 16, 2007 4:15 pm
Location: London UK

Post by Miles » May 06, 2007 3:28 am

Beagle123 wrote: Who makes the device in your picture? Where can I get one?
I believe that one is no longer made.

Here are some others:

http://www.jensonusa.com/store/product/ ... eator.aspx

http://www.rhythmcycles.com/xcart/custo ... 299&page=1

http://www.bikemannetwork.com/biking/c/SSCHTEN

User avatar
Beagle123
10 kW
10 kW
Posts: 627
Joined: May 02, 2007 2:35 am
Location: Los Angeles

Post by Beagle123 » May 06, 2007 9:38 pm

Thanks! That first one looks really good. I noticed that you can set the distance that the roller is away from the arm. That's perfect.

Post Reply