3 Speed Hub As Jackshaft Question.

cannonball2 · Feb 2, 2015

Contemplating a design to use a 3speed hub as a jackshaft. It requires that the hub be driven from the left side. This means the hubs original driven sprocket freewheels because its basically backwards and as is wont drive anything. However if the driven sprocket is attached to the wheels part(outer) of the hub then then outer hub engages the inner hub driving the bikes original sprocket which in turn would be the final drive to the wheel. Question is will the inner hub now act as the outer hub did when it was used as a wheel and change gearing? Thinking yes.

brown · Feb 2, 2015

I think this page will help if I understand what you want to do correctly.

http://www.pedalchopper.com/3-speed-transmission-system-jackshaft-component-best-thing-ever/

cannonball2 · Feb 2, 2015

Interesting website, thanks for the link. That is what amounts to a shifter kit with just a bit of a different spin. I built one shifter bike and it worked pretty well but the complexity was a bit bothersome keeping it all in sync.

I was kicking around the idea of the hub(there is no spokes/wheel, hub only) being the only additional component in the standard CG drive system. Mounted behind the engine the drive from the engine goes to the outer hub and the original sprocket on the hub drives the rear wheel. Its all on the same side and the pedal side drive is unchanged. No cross over type jack shaft. If the hub will work basically with the drive flow reversed. It would still have three speeds( Im thinking) though maybe the shift pattern may reverse?
In other words the system is driven by the outer hub and the inner hub is driven by it to pass the drive on to the rear wheel.

The only issue if the hub will work that way is that the chains will be some what offset from the normal chain line, and working up the sprocket for the outer hub. The engine would also most likely have use a pull start. The bike will also freewheel like the stand shifter bike with no engine braking.

cannonball2 · Feb 3, 2015

OK heres a visual aid. Maybe my description is confusing. The large sprocket is less than ideal(but it fits so nice!) as it will lower the overall ratio. May be able to make it up in the final drive with a very small sprocket at the wheel, haven't run ratios yet. If this will work it will make a very compact 3sp( or more depending on the hub) shifter bike and there is as said earlier no cross over with the less than ideal driving of the bikes chain ring side.

The large sprocket is to be welded to the outer hubs spoke flange and is the primary drive, the small sprocket is the final drive to the wheel.
Was trying to find out before mocking up if some one has tried this, and/or is my thinking off about the gearing working in reverse.

bowljoman · Feb 4, 2015

it can but I never tested it under load, and models vary how the clutches work. I would not try it with a coaster brake model.

However, there is one hub that will work how you want and should bump start too. fixed three speed.

http://www.niagaracycle.com/categories/sturmey-archer-s3x-3-speed-fixie-hub-kit-36h-120mm-silver

Here are the other options. I use the nexus version. YOu may be able to put the SA sprocket on the S3X spoke flange, however a clamp-mount sprocket might work too.

SA
http://www.niagaracycle.com/categories/torker-tristar-sturmey-archer-3-speed-coaster-brake-hub
Nexus
http://www.niagaracycle.com/categories/torker-tri-star-3-speed-coaster-brake-hub

These f'n hubs ROCK! I power on the right side and removed peddles completely! I use a pull start and Im configured as a 'foot scooter' with flat running board instead

cannonball2 · Feb 4, 2015

Thanks for the reply and the links!
So it appears the hubs in the last two links are similar in operation to what I am wanting to do. The hub I have is a non-coaster older Shimano. I believe the older SA hubs are more robust and are fairly cheap on ebay. Will probably use the Shimano first to see how the theory works out. The CG engine is not a torque monster by any means. Could actually convert it to an auto clutch and make it even easier on the hub, since a pull start would be beneficial/mandatory to use anyway.

Thanks for your input, has been most helpful!

KCvale · Feb 4, 2015

Your engine and back wheel sprockets align.

So what is your plan?
To mount something 3" wide the opposite of the way it was designed to operate in between and offset your engine 3"?

The subject of gearing the left side with existing bicycle parts has been gone over hundreds if not thousands of times.

silverbear · Feb 4, 2015

If you search a bit through the archives we had a member at one time named camlifter. He did what you are proposing and as I recall the results were very good. Somehow or other he was using the 3 speed hub as a jackshaft.
SB

KCvale · Feb 4, 2015

silverbear said:
Somehow or other he was using the 3 speed hub as a jackshaft.
SB

Well sure, very handy if if you have a single speed back wheel but still transferring power in the proper direction on the right side of bike.

The span from left to right is big enough for a 3" wide hub.

My point remains.
You can't insert anything that will change ratio between 2 fixed sprockets already in line with each other without moving something to compensate.

That's why Jim and Paul (now SickBikeParts) came up with the jackshaft and freewheel pedals with dual sprocket chainrings.

If you want to dig in the archives go back to 2009 when they were discussing the their shift kit idea here.

The result is a box of parts that work with bicycle parts.
But hey, power on man, maybe a bigger stick will bring that horse back to life ;-}

cannonball2 · Feb 4, 2015

KCvale said:
Your engine and back wheel sprockets align.

So what is your plan?
To mount something 3" wide the opposite of the way it was designed to operate in between and offset your engine 3"?

The subject of gearing the left side with existing bicycle parts has been gone over hundreds if not thousands of times.

Your not understanding the idea fully KC. Yes Im proposing turning it backwards from its original intended rotation however the chain line is not offset by more than one chain width plus a few mm clearance between the chains. Maybe I shouldn't use the term jackshaft since its not transferring the drive in the usual manner. Concentric transmission suit you better? If this works out it makes in concept(excepting # of speeds of course) a far superior shifter bike than the common version, due to reduced complexity. Not to mention the ease of shifting and the ability to shift from the top speed to the lowest speed while sitting still. Please link me to one of the 100/1000s of threads so I can become enlightened on the engineering of such a system.

cannonball2 · Feb 4, 2015

OK, jut to quell KCs curiosity about my idea, I got the hub out mounted the axle in a vice and marked the hub and a tooth on the sprocket dead even. Turning the hub drives the sprocket at a differential of what ever the ratio of the gear selected is. So by powering the outer hub, the original drive sprocket now drives the wheel at what ever speeds/ratios the 3speed hub has, all from the same side. It is truly a concentric transmission of sorts. It maintains the original chain line except for the distance between the two sprockets, no more than 1/2"
This negates the cross over and the rather problematic derailur system.

BTW KC why the attitude?

silverbear · Feb 4, 2015

cannonball2 said:
OK, jut to quell KCs curiosity about my idea, I got the hub out mounted the axle in a vice and marked the hub and a tooth on the sprocket dead even. Turning the hub drives the sprocket at a differential of what ever the ratio of the gear selected is. So by powering the outer hub, the original drive sprocket now drives the wheel at what ever speeds/ratios the 3speed hub has, all from the same side. It is truly a concentric transmission of sorts. It maintains the original chain line except for the distance between the two sprockets, no more than 1/2"
This negates the cross over and the rather problematic derailur system.

BTW KC why the attitude?

I concur. What's wrong with taking a fresh look at the idea? No reason to get your pants in a bundle even if it turns out to be a dead end. I feel for that horse, by the way.
SB

cannonball2 · Feb 4, 2015

Thanks SB!

I don't know if/or why this wont work. The hub appears to behave the same way as normal when the power flow is reversed. I was mainly asking those that have more hands on with internally geared hubs if this reversing posed any major issues and/or had this been done before with success.
If it will work the conversion should be very simple with a couple of my favorite shaft locking collars, some flat metal, and the hub, extra sprocket and shifter for the basic parts. The hub simply mounts in line with the existing chain line. It would provide a lower gearing, the normal gearing, and an overdrive. I know these hubs are used on the normally configured shifter bike with success, but I never do anything normally.

KCvale · Feb 4, 2015

silverbear said:
I concur. What's wrong with taking a fresh look at the idea? No reason to get your pants in a bundle even if it turns out to be a dead end. I feel for that horse, by the way.
SB

No need to feel for the horse, it's dead already, you know the term 'beating a dead horse' right?

My panties don't get bunched either, I was just trying to save someone from endeavoring on a fruitless costly time consuming venture that already has an eloquent solution.

If you want internal gears change your back hub, you'll be buying one anyway, and it will operate as designed.

silverbear · Feb 4, 2015

I'm quite familiar with the saying "beating a dead horse" and also with the old saying "don't get your pants in a bundle", in other words don't get all upset about something when you don't need to. I didn't say anything about panties. I still don't get all of the emotion invested in this, making it an issue. If a guy wants to try something, let him try and if it works out then great and if it doesn't then so what?
SB

cannonball2 · Feb 4, 2015

OK yall Im gonna have to build this concept to check it out. Wont be real soon as I have things ahead of it. First order of business it to find a sprocket in the 20t range to mod to fit the hub. After that its just mount it and hook up the chains and shifter.

Keep you posted. If it works as thought will be too cool.

bowljoman · Feb 4, 2015

Ignore the non-believers.

If I didnt have my kick bike, I would have already done what you are wanting. Ive built 4 different rides over the years with IGH jackshafts. Very efficient with little overhead, and that is the key to performance with small engines. Less chain weight and 3 speeds is good enough. So maybe you'll have to bump out the china girl engine to the side...

I hit the 40's without any engine mods. It is well worth the effort.

silverbear · Feb 4, 2015

http://motorbicycling.com/showthread.php?t=11499&highlight=camlifter

CB2,
Here is camlifter's thread. Just found it and have not yet re-read it. Hopefully there's something in there of use to you in what you're doing.
SB

cannonball2 · Feb 4, 2015

Thanks a lot SB!
I found it informative in several ways not the least this one. http://motorbicycling.com/showpost.php?p=357412&postcount=96

Bowljoman, What you have is what I am doing except the CG drive is on the left. To make it work Im flipping the sprockets to the left side, inputting the drive into the wheels hub and extracting the drive from the original input sprocket. It will shift thru 3speeds at the former input sprocket. Me and you are on the same page just different sides.

Getting more fired up about this build, may start on it sooner than later.

cannonball2 · Feb 6, 2015

Ordered a 20T coaster sprocket to match a 20t flat plate sprocket I have already. I will machine the center out of it to either weld or bolt to the spoke flange on the hub. If there is room for bolting I favor that method as I can adjust the sprockets close together so as to maintain more closely the original chain line. I see no real issues at this point other than the shift cable may be a little awkward to route, or not.

I have run the ratios thru my gearing calc and I will have my existing ratio in second. My bike will pull away from stop pretty easily, especially with the wet clutch. The under drive will make this nicer, plus I will be able to ride slower as I wanted to do a bit of off roading with this one. The over drive will put the current top speed in a lower rpm range to avoid the max rpm buzz the CGs have plus raise the ultimate top speed of course.

All this on what really amounts to one chain line!

3 Speed Hub As Jackshaft Question.

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