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Message started by Kris01 on 04/17/15 at 20:47:21

Title: Here's an odd one - transmission gears
Post by Kris01 on 04/17/15 at 20:47:21

Here's a strange idea I had.

4th gear is geared 22:23 or 0.9565. 5th gear is geared 23:26 or 0.8846.

Would it be possible to take the 22 tooth gear from 4th gear and combine it with the 26 tooth gear from 5th gear to make a ratio of 22:26 or 0.8462? Are all the gears the same with the exception of the tooth count?

I know a chain conversion or Kawi pulley swap would be easier but if this might be another option.....

Anyone out there torn down their transmission enough to figure this one out?

Title: Re: Here's an odd one - transmission gears
Post by Kris01 on 04/17/15 at 20:59:26

Here's some transmission pictures:

https://freetireair.wordpress.com/category/motorcycle-2/suzuki-savage-ls650/

http://www.bikebandit.com/oem-parts/2014-suzuki-boulevard-s40-ls650-transmission/o/m156497sch869704

Title: Re: Here's an odd one - transmission gears
Post by justin_o_guy2 on 04/17/15 at 23:19:00

I've not been inside the transmission but I would be forced to ask myself how gears with different numbers of teeth mesh unless the centers are adjusted to make room. The more teeth, the greater the circumference.
Yeah, math is involved.

Title: Re: Here's an odd one - transmission gears
Post by Dave on 04/18/15 at 03:36:36

A few of us did some looking.....and even searched other Suzuki models for a 5th gear that could be exchanged. We didn't find one that would work.

You just can't take one gear from a set...you need both as the distance between the shafts is set. The two gears have to be made to mesh properly at the proper spacing to fit the shafts.

Title: Re: Here's an odd one - transmission gears
Post by Kris01 on 04/18/15 at 07:27:19

Don't the drive gears ride on one shaft and the driven gears on another? Wouldn't the spacing already be set?

Without actually measuring, I'm assuming that a gear with twice as many teeth is twice as big in diameter. Probably not though. That would be too easy!

ASSUMING that a 5" diameter gear with 10 teeth is half the size of a 20 tooth gear that measures 10" in diameter, the idea could work, right?

Is there any resource that anyone has found that might show the dimensions of the gears that we would need? Is the shop manual helpful in this regard?

Title: Re: Here's an odd one - transmission gears
Post by Steve H on 04/18/15 at 08:42:16

It is set. That's what Dave is saying. there is x.xx" between centers. The gears have to be machined to matched pairs so that the different numbers of teeth offset each other and keep the same distance center to center.

If you move a 26 tooth in place of a 22 tooth, the 28 will be bigger around and won't fit properly with the intended mating gear.

You might also run into a problem with the number of engagement dogs on the gears being different.

If Dave says they looked and couldn't find anything, I believe there is nothing short of custom cut out there.

Mine's a 4 speed so I don't worry about the fifth that really isn't there. I just change the 4 then phantom change to other 2 about half the time. About half the time I'm changing like it's the 6 speed on the Ninja...only disappointed to find that it won't change any more past 4.

Title: Re: Here's an odd one - transmission gears
Post by Kris01 on 04/18/15 at 08:46:43

Oh well...just looking for another option. Thinking outside the box is called progress in some circles...except when you're dealing with a bike that's not compatible with any other product out there. Does that make us special? :D

Title: Re: Here's an odd one - transmission gears
Post by Serowbot on 04/18/15 at 09:44:05

I'd love a taller 5th gear... but,...
I ain't tearin' into the tranny fer' nuttin"... :-?...

Title: Re: Here's an odd one - transmission gears
Post by Kris01 on 04/18/15 at 13:56:58

I agree. I'm too chicken just to make some measurements. ;)

Title: Re: Here's an odd one - transmission gears
Post by justin_o_guy2 on 04/18/15 at 15:21:52

Here's a strange idea I had.

Don't worry,,,, All creative types have an idea in an area where they simply lack sufficient experience to really be able to know if it's possible or not.
You aren't the first..

Title: Re: Here's an odd one - transmission gears
Post by Steve H on 04/18/15 at 21:51:29

Hi Kris,

In reply #4, you were saying about a 5" 10 tooth should be half as big as a 10" 20 tooth.

In your example, the spacing between the teeth on the bigger gear will be much larger. You're dealing with the distance around the outer edge of the gear which is diameter difference*pi. 5*3.1415279=~15.7" difference in distance around.

You have to calculate the diameters of the mating gears such that the tooth spacing matches for the distance around and gives you the correct distance between centers. New gears could be made by someone with the knowledge and equipment to cut and harden them if you sent them the drawings of what you wanted. It would cost you at least a few hundred bucks. But, you could conceivably change the ratios.

There are also other problems dealing with the amount of torque put on the gears changing as their size changes. The gear engagement tries to force the gears apart when power is applied. Shafts and bearings have to be able to handle the load. The teeth have to be small enough to mesh well at the desired ratio. Too small and they can't take the load and strip off. Too big and very noisy and lots of vibration causing excessive wear.

My hat's off to the designers of transmissions. There's so much to thnk about and work with to just come up with a plausible design that will have to be refined from R&D making prototypes and trying things.

I hope something I've said makes sense. I bet Dave can explain it much better than I.

Title: Re: Here's an odd one - transmission gears
Post by WD on 04/18/15 at 23:28:18

Kris, I have a "spare" (that means junk) engine and know a shop that makes gears in the Memphis area... when shall I expect you?

Title: Re: Here's an odd one - transmission gears
Post by Kris01 on 04/19/15 at 06:43:00

Steve H:
My example was just a simple one (concerning the math). I didn't want to get too detailed with the circumference example. It would have been too confusing.

WD:
A local shop that makes gears from scratch? Is this fairly common?

I was kind of hoping some brave person would tear their transmission apart and try this so I could copy them! :D I'm a smart guy (aren't we all? ;D) but I'm not the type of person to try this on my own.

Title: Re: Here's an odd one - transmission gears
Post by Serowbot on 04/19/15 at 08:16:50

I'm smart enough not to try...

Title: Re: Here's an odd one - transmission gears
Post by Kris01 on 04/19/15 at 09:09:52

That's my excuse too!

Title: Re: Here's an odd one - transmission gears
Post by justin_o_guy2 on 04/19/15 at 09:21:44

If you have place and time, get a motor that needs top end work, split the cases, be prepared to sell parts or scrap it. But, you MIGHT just be able to put a taller 5th in...

Title: Re: Here's an odd one - transmission gears
Post by Kris01 on 04/19/15 at 11:40:50

Ok, having distances remain the same and everything has got me thinking... Use the stock pieces as they were intended, sort of.

Since 2nd gear is geared 30:19 (or 1.5789:1), what if we added a second 2nd gear in the 5th gear position but flipped it to a 19:30 (or 0.6333:1)? That would be a worthwhile swap AND we could keep the 100,000 mile belt.

Thoughts?

Title: Re: Here's an odd one - transmission gears
Post by Dave on 04/19/15 at 14:48:42

013823397A7B4A0 wrote:

Look at the part diagram again....see how the gears have bumps, machined oval holes and grooves in them? Some gears sit on a shaft and never move, some gears slide left and right and engage other gears......you just can't toss them into any position in the gearbox.

Title: Re: Here's an odd one - transmission gears
Post by Kris01 on 04/19/15 at 15:04:27

Buzzkill! :D

I'll give up now. I was just thinking out loud. I might just convert to chain.

Title: Re: Here's an odd one - transmission gears
Post by Dave on 04/19/15 at 16:29:03

The front Kawasaki pulley conversion is much nicer than a chain swap. It is neat and tidy as the original belt. The only hard part is finding someone who can machine it a bit narrower at the hub.

Title: Re: Here's an odd one - transmission gears
Post by Kris01 on 04/19/15 at 19:09:55

The only drawback I see with the Kawi pulley is you're stuck with 1 ratio. Other than that, I agree with you Dave.

Title: Re: Here's an odd one - transmission gears
Post by Dave on 04/20/15 at 07:52:07

4B7269733031000 wrote:

The only drawback I see with the Kawi pulley is you're stuck with 1 ratio. Other than that, I agree with you Dave.

Well the front pulley conversion raises the ratio by 8.7 %...which is a definite step in the right direction. With a stock engine and bike this is about as far as you might want to go.

The combined change by doing front and rear pulleys is 18%....and needs a bump in the stock HP to work well.

My bike has the double pulley conversion and an 18" rear wheel which bumps the gearing up even more.....5th gear now is only for use above 60 mph.