CBR600F4/F4i 11 tooth front sprocket

[Daves]

What are the advantages and disadvantages of an 11 tooth front sprocket on the Honda F4i engine? We have used 11 tooth front sprockets for 2 years and have had no problems, but what potential problems exist?

The smallest sprocket Sprocket Specialists stock is a 14 tooth, and I know Charlie recently purchased (8) custom 12 tooth sprockets from them. Are there any other sprocket manufacturers who make 11 tooth f4i sprockets?

http://www.letu.edu/formula

Formula Photos & Links (http://what3542.5u.com/dave/fsae/formula_photos.html)

[Daves]

What are the advantages and disadvantages of an 11 tooth front sprocket on the Honda F4i engine? We have used 11 tooth front sprockets for 2 years and have had no problems, but what potential problems exist?

The smallest sprocket Sprocket Specialists stock is a 14 tooth, and I know Charlie recently purchased (8) custom 12 tooth sprockets from them. Are there any other sprocket manufacturers who make 11 tooth f4i sprockets?

http://www.letu.edu/formula

Formula Photos & Links (http://what3542.5u.com/dave/fsae/formula_photos.html)

[Charlie]

So I assume you made your own 11 tooth? How? From looking at the 12T sprockets I figured an 11 would be impossible.

-Charlie Ping

I just need enough to tide me over until I need more.

[Denny Trimble]

I believe the problems include:
-higher chain tension for a given output torque, which may require a heavier chain (530 vs. 520) and slightly heavier diff mounts
-increased vibration due to Chordal Action (http://www.ustsubaki.com/section2.html)

But to be honest, we haven't run the numbers. We usually run 13/44 to 13/47 with an F4i.

University of Washington Formula SAE ('98, '99, '03, '04)

[Daves]

I will post some photos soon of our 11-tooth sprockets installed on our past F4i engines. Maybe then you could tell me how they were made because I have no idea.

Did Sprocket Specialists used to do single-sprocket custom orders? When did they start this bulk ordering system? Would it be worth it to order 6 or 8?

http://www.letu.edu/formula

Formula Photos & Links (http://what3542.5u.com/dave/fsae/formula_photos.html)

[Daves]

Here are the photos:

2002: http://what3542.5u.com/dave/fsae/112-1232_IMG_small.JPG



2003: http://what3542.5u.com/dave/fsae/112-1223_IMG_small.JPG



This Year (to be replaced with an 11 tooth): http://what3542.5u.com/dave/fsae/112-1226_IMG_small.JPG

[This message was edited by dave_s on January 23, 2004 at 01:07 AM.]

[Charlie]

Well, that's pretty cool, I figured the diameter would be too small with 11 teeth.

-Charlie Ping

I just need enough to tide me over until I need more.

[-]

How did you guys cut your 11 tooth sprokets?

[All Wheeler]

I've done a bit of work at a gear manufacturers, and in my experience most of these type of products are cut on a hob cutter. The machining for the blanks is pretty straight forward, and you could probably do that yourself. The hob cutting of the teeth would be the cheapest part, however the splining would be a bit pricey. We worked around that problem by machining the teeth off an old sprocket, press fitting the spline into the piece that we wanted and welding around the end faces. I would think that most gear manufacturers would have the appropriate hobs for the job

[All Wheeler]

I've done a bit of work at a gear manufacturers, and I would say most products like that are hob cut. I think most gear manufacturers would have the appropriate hobs to do the job. The machining of the blank is pretty straight forward, and the cutting of the teeth wouldn't be too expensive, however the splining could be costly. We worked around that by machining the teeth off a spare sprocket and pressing the spline into the piece that we wanted, then welding each end face.

[All Wheeler]

Damn, my browser closed when I hit 'post now', so I wrote it again, but the first message worked. Dumb ass!

[-]

As far as machining a new sprocket, we were thinking of taking a larger sproket doing one or two things. The way would be to put it on a rotary vice on a mill and machine the new teeth by hand. The other way was to sweet talk the head machinest at our school and try to get him to edm cut some teeth into an old sproket. If we actually get a chance to doing this i'll try to post some pictures.

[B Lewis @ PE Engine Management]

Hi Guys,

You may want to look into having them laser cut. I have had materials as hard as 4140 cut up to 3/8" thick pretty easily. Maybe not the best solution from a production standpoint, but if you can swing it the minimum order (usually around $250)would probably get you 20 sprockets. We use this process for our trigger wheels.

Brian Lewis
Performance Electronics, Ltd.
www.pe-ltd.com (http://www.pe-ltd.com)
"Complete Engine Management Systems for $798"

[Dominic Venieri]

we had our 12 tooth sprocket made for us last year by one of our sponsors, who did it on an EDM.

www.formularpi.com (http://www.formularpi.com)
2003 Formula Student Runner-Up

[Daves]

The 11-tooth front sprockets that we used were for 525-series chains, but the pitch of a 520 and a 525 sprocket are the same. Only the widths are different. Therefore, since 11-tooth 525 sprockets are possible, 11-tooth 520 sprockets should also be possible.

We will probably purchase (1) 14-tooth 520 front sprocket since we are not actually competing this year. Then when anyone orders 11T or 12T sprockets, we will jump on the chance.

[This message was edited by dave_s on January 26, 2004 at 02:24 AM.]

[Charlie]

Ask Sprocket Specialists about the 12T. They talked about making extras when I placed my order.

-Charlie Ping

I just need enough to tide me over until I need more.

[Daves]

Charlie, who is your contact at Sprocket Specialists?

http://www.letu.edu/formula

Formula Photos & Links (http://what3542.5u.com/dave/fsae/formula_photos.html)

[Daves]

If you thought 11 was small, I just found a 10-tooth in our shop that fits the CBR600F4i! It is a black, steel one.

http://www.letu.edu/formula

Formula Photos & Links (http://what3542.5u.com/dave/fsae/formula_photos.html)

[PatClarke]

Please, before you use a 10 tooth (or even an 11 tooth) sprocket, please take a look at the chain geometry.
You might not like what you see.
PDR

I'd give my right arm to be ambidextrous!

[MattG]

Wouldn't the acceleration of the chain be fairly high as it comes around the radius of a 10T sprocket vs that of a 12T?

Although it means more weight, inertia and size wouldn't it be kinder on the chain to scale up the sprockets?

[drivetrainUW-Platt]

would like to get more ppls opinions on this gear size debate, how small can we safely go, I'm designing a diff mount smiliar to WWU's swingarm mount and would like to move the diff as close to the engine as possible by running small gears....

[Denny Trimble]

If you want to go really tiny, use a 428 chain instead of a 520 (1/2" pitch instead of 5/8"). A 13T sprocket is close to as small as you want to go, and with a 428 chain the pitch diameter is 20% smaller than a 13T 520.

[Matt W]

My team is interested in buying a 12 tooth 520 sprocket for an F4I, I have been in contact with Sprocket Specialist and we would like to not have to buy 6 right now. If any team has an extra they would like to sell please get in contact with me.