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The Triple Double Sprocket Thread, Too Much?

17K views 38 replies 19 participants last post by  Fred 
#1 ·
A few weeks ago, my friend Gerry (aka Mr. Gizmow) sent me this little jewel of a dual front sprocket assembly (13/15) with all the fixings.

Bicycle part Gear Auto part Tool accessory Hub gear




Auto part Tool accessory Bicycle part Automotive engine part Gear



I have been running a dual rear sprocket setup for about the last 3,000 miles with various size combinations including 47/50, 47/55 and most recently 55/65. A dual rear sprocket setup just barely fits between the sprocket mounting flange and the swingarm. Gerry's bombproof sprocket assembly has the sister sprocket (13 teeth) mounted inboard from the stock mounting position. Here it is mounted with the chain on the inner sprocket.

Auto part Bicycle part Gear Crankset Engine


This got me wondering if a third rear sprocket could be mounted on the inboard side of the sprocket mounting flange. In order to do this, a split sprocket would be required. I remembered that one of Gerry's project had involved a sprocket that he had split in half and I believe he bolted back together. A call to Sprocket Specialists determined that they would be happy to split a 66 tooth rear sprocket for me and they asked me if I wanted a link lock. They explained that with a link lock, they drill holes on either side of the kerf and use a couple of master links to help keep the sprocket halves from flexing. So I said sure, give me the link locks.

Here are the rear 47/55/66 sprockets mounted .

Tire Automotive tire Wheel Auto part Alloy wheel


It is tight, but there is clearance, even with my ATV rear tire. And the alignment is actually pretty good except for that rubber chain guard thingy that goes around the front of the swingarm. If this proves to be a problem, I may try to mount this guard further inboard, or possibly add a second one inboard of the stock one.

Tire Automotive tire Auto part Wheel Automotive wheel system


Do I really need a TW with 30 different speeds (or 36 if I used this setup on my TW226 6-speed)?

Of course not, but I just wanted to see if it was possible to do :cool:.

(Gerry, thanks again for giving me the opportunity to test out this prototype - it looks like a winner to me!)
 
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5
#6 ·
This:


that's a wild looking setup. We need youtube videos the those sprokets in action. I would love to see your lowest gear setup climbing a hill in first gear.
 
#5 ·
"A call to Sprocket Specialists determined that they would be happy to split a 66 tooth rear sprocket for me and they asked me if I wanted a link lock"

I was reading all the thread I could find on multi sprocket jobs just the other night and caught the "hint".. (Just one pic). Anyway I was going to get a sprocket water jetted and was trying to come up with a good idea for locking them together at the outer edge.. I like the link idea.

Thanks guys great work.
 
#27 ·
What about drilling a couple bolt holes in each half of the sprocket and then bolting together a plate on each side of the sprocket that crosses between the two halves (like the link but with beefy side plates and four "pins" (the bolts) instead of just the two? The link does look pretty decent, but just a thought... I don't pretend to fully comprehend any of this.
 
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#7 ·
I always like Mr.Gizmow's idea of a double front sprocket but to fabricate one is over my head and available tools. Yes, a hammer can't create on this one. I knew he was working on an new front dual setup since the problems of his first one had risen. All is looking good so far.

TW-Brian, why did you have to make a split rear sprocket? Was it to mount is without removing the others or something like that?
 
#9 ·
TW-Brian, why did you have to make a split rear sprocket? Was it to mount is without removing the others or something like that?
To get it behind the rear mounting flange... inboard of the rear flange.
 
#8 ·
On that "top secret" collar sitting behind the inside front sprocket, it looks like I've seen that design before, is that a stock part from McMaster Car, or another vendor?

They should put you two guys on the next TW goes to the north pole team.. :)

Land vehicle Vehicle Motorcycle Motocross Car


Its nice to see people with great ingenuity sharing ideas. Not sure if you want to take it one step further as you could, and should make this available for sale. (Once it has several thousand test miles), the countershaft clip concerns me, but not much. The sprocket links been done before, works good.

I hesitate to ask because it seems like theft of intellectual property not developing the measurements myself (maybe LT's gasket trick will fail and I'll have to pull the cover and take some measurements)

Can you disclose:
The thickness / Width of the spacer between the front sprockets.
The thickness / Width of the countershaft collar.
The size of the C-Clip, If that C-Clip groove needed machining? Or if the stock groove was ok, if so what is the washer and clip thickness in total?

You can save all the typing and just start selling kits :) lol... NO really.. I can keep asking questions until you brake down and are forced to supply them ready made. ;)

I have a CNC in the shop and a lathe but the CNC has a bad board that costs more than the TW, what a dilemma...

Ill say say it again, this board is awesome!
 
#10 ·
It looks to me on the front sprocket setup the only fabrication is the manufacturing of the spacer and the drilling of the holes for the pins. It doesn't look like the groove for the clip was machined in the pic. If so this is even a better job. "More thought, less work".. Somebody here is not a government contractor.
 
#11 ·
All the inspiration, perspiration, and credit for this dual front sprocket assembly belongs to Gerry (aka Mr. Gizmow).

Auto part Tool accessory Gear Hardware accessory


But I will do my best to answer what I can:

The thickness / Width of the spacer between the front sprockets. Gerry made this spacer at 0.303".
The thickness / Width of the countershaft collar. The collar is McMaster-Carr PN 6435K17 - One-Piece Clamp-on Shaft Collar, for 7/8" Diameter
The size of the C-Clip, If that C-Clip groove needed machining? Or if the stock groove was ok, if so what is the washer and clip thickness in total? The C-Clip is the standard clip that comes with the smaller than stock front sprockets that do not use the bolt-on retaining ring. This C-Clip utilizes the existing groove in the output shaft. The washers are McMaster-Carr PN 3088A471 - Steel Shim, Round, 0.062" Thick, 7/8" ID, 1-3/8" OD.

Auto part Gear Transmission part Hardware accessory


The above pic shows the parts that were used (the output shaft is just for illustration purposes only and does not need to be removed for this mod). The 0.004" brass shim was used to compensate for the extra clearance between the 7/8" collar and the output shaft. The splines on the inboard sprocket were removed and the sprockets were drilled for the six dowel pins that were pressed in and Loctited. The washers on either side of the sprocket assembly serve primarily to retain the dowel pins from coming out if they were to loosen.
 
#12 ·
Brian, thanks very much. I appreciate you offering that info up. Our members and their projects are what keep this great forum alive, not to mention how much everyone helps each other. You two are without a doubt top notch members!
 
#18 · (Edited)
Credit goes to our inventive Mr.Gizmo who periodically emerges from his laboratory with the most innovative creations. Machine
I am not at all surprised that the latest iteration of his dual front sprocket is so well conceived and rendered. I would vote to award him a doctorate in sprocketology if only he can explain how to readily lift chain from one sprocket to the next. Perhaps there is a solution in the works
 
#19 ·
Credit goes to our inventive Mr.Gizmo who periodically emerges from his laboratory with the most innovative creations. View attachment 30097 I am not at all surprised that the latest iteration of his dual front sprocket is so well conceived and rendered. I would vote to award him a doctorate in srocktology if only he can explain how to readily lift chain from one sprocket to the next. Perhaps there is a solution in the works

Mr. Gizmo is indeed quite slick and well named by himself too. He certainly does deserve a lot of credit in my eyes. He's on the "would like to meet someday" person list; just like you are Fred. It was nice of you to acknowledge him. +1
 
#20 ·
A few weeks ago, my friend Gerry (aka Mr. Gizmow) sent me this little jewel of a dual front sprocket assembly (13/15) with all the fixings.
....

Too much... no.. But if I see this on your bike we might have to put you guys in a white jackets with real long sleeves.. :p
Bicycle part Gear
 
#23 ·
#26 ·
Why has no one cut the front cover where the sprocket is and put a screw on access plate? I have considered that just for access to the chain without removing that cover. This would make it real easy for dual front sprocket changes, cleaning etc .
I believe the primary reason that this hasn't been done is that there is an oil supply that runs through the output shaft that feeds the outboard bearing, and then returns to the crankcase as illustrated by the red wire in the picture below.

Auto part Rotor Automotive starter motor Hub gear Tool accessory
 
#28 ·
Excuse my ignorance but how much of a variance could you have in the sprocket combos? Would it be possible to do 12/70 with 15/50, for example?? I can't readily think of a reason why this couldn't be done - assuming different chains, with some kind of quick-connect masterlink system, of course.
 
#30 · (Edited)
Rather than a cover plate Gerry's dual front sprocket installation entails a "V" notch and small hole to "fish" loosened chain from one sprocket to another using "J" shaped and straight rods. With the internal oil chamber there is just not room for a plate as TW-Brian explained.





The brass fittings are oil pick-up and return lines for an auxiliary oil-cooler tapped into the output bearing housing. Before the availability of the LZRDBRTH oil filter cover this was the other known way to do an oil cooler.
That Gerry is one inventive fellow.
 
#31 ·
Appreciate the 'Sprocketiers' willingness to carry the torch in my absence. The front sprocket chain reposition had been pretty straight forward. The "V" in the side case afforded me a better view. With the rear wheel off the ground and free to rotate (Crutch Jack) and the chain slack, a slight push/pull with your fingers to 'MISS ALIGN' while rotating the wheel/chain forward will reposition the chain. Now realize, though simple, practice is a plus. It should be thought of as 'simple and quick'. Many thanks to Brian and Fred.
 
#36 ·
@TW-Brian

So, this may be a stupid question, but how do you change from sprocket to sprocket? Do you just have to remove/reinstall the chain when you want to switch with sprockets you're using, or do you have a way to switch them on the fly like on a standard multi-gear bicycle?

A few weeks ago, my friend Gerry (aka Mr. Gizmow) sent me this little jewel of a dual front sprocket assembly (13/15) with all the fixings.

View attachment 30051



View attachment 30049


I have been running a dual rear sprocket setup for about the last 3,000 miles with various size combinations including 47/50, 47/55 and most recently 55/65. A dual rear sprocket setup just barely fits between the sprocket mounting flange and the swingarm. Gerry's bombproof sprocket assembly has the sister sprocket (13 teeth) mounted inboard from the stock mounting position. Here it is mounted with the chain on the inner sprocket.

View attachment 30050

This got me wondering if a third rear sprocket could be mounted on the inboard side of the sprocket mounting flange. In order to do this, a split sprocket would be required. I remembered that one of Gerry's project had involved a sprocket that he had split in half and I believe he bolted back together. A call to Sprocket Specialists determined that they would be happy to split a 66 tooth rear sprocket for me and they asked me if I wanted a link lock. They explained that with a link lock, they drill holes on either side of the kerf and use a couple of master links to help keep the sprocket halves from flexing. So I said sure, give me the link locks.

Here are the rear 47/55/66 sprockets mounted .

View attachment 30052

It is tight, but there is clearance, even with my ATV rear tire. And the alignment is actually pretty good except for that rubber chain guard thingy that goes around the front of the swingarm. If this proves to be a problem, I may try to mount this guard further inboard, or possibly add a second one inboard of the stock one.

View attachment 30053

Do I really need a TW with 30 different speeds (or 36 if I used this setup on my TW226 6-speed)?

Of course not, but I just wanted to see if it was possible to do :cool:.

(Gerry, thanks again for giving me the opportunity to test out this prototype - it looks like a winner to me!)
 
#38 ·
Hi Tyler,

Changing sprockets is currently all done manually, sometimes requiring the addition or removal of a small section of chain.

It would definitely be nice to be able to change on the fly and I even played around a little trying to use a chain tensioner as a derailleur, but gave up on it as it required too much linkage travel to accomodate the extra chain links needed.

Brian

 
#37 ·
Didn't you see the derailleur on there? :p;):D
 
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#39 ·
I purchased the dual front and dual rear sprocket equipped MrGizmo from Jerry and have never used all 4 of the possible drive ratio combinations. I think about it though when contemplating a longer highway adventure but always end up trail riding where the granny gearing is optimal. So the 15X47 remains available for another jaunt over Tioga and through Yosemite.
 
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