Gt Bicycle It-1 ....possible mid drive prototype?

[Green Machine]

So I am contemplating the idea of some kind of motor in the triangle....a matt dual reduction system...with one chain going from the reduction system to the crank...and another sprocket attached to the freewheel on the reduction system, going back to the chain.

Can you guys help me out with some links if this has already been attempted?

I heard the big drawback to this system is pedal inefficiency...but then i thought of hte GT-it 1...which is able to do this kind of drive, apparently without losing pedal efficency.

SO imagine the pictures below with a matt dual reduction system ending with a freewheel at the connection point of the two chains....

Any thoughts or direction would be appreciated. i am sure someone here has already tried it..so link would also be appreciated.

 

[Miles]

Have a look at this thread: http://www.endless-sphere.com/forums/viewtopic.php?f=28&t=16289 A lot of the pics are still missing, though...

 

[Miles]

Just out of general interest - here are some pics I took, a few years ago, of one of the GT prototypes.

 

[Green Machine]

Your a super hero Miles...

You are literally everywhere...i seriously dont know how you do it.

I think i could just learn from what browser you use..and what system you use in organizing all those links...and all that data...

 

[Miles]

I've almost given up saving links.. I just make a mental note and search when I need the info again.

The GT pics, I took at an exhibition in London. Must have been about 6 years ago?

 

[panurge]

I totally Agree with you, and this is the kind of project I try to build, coming in my mind from the same iT-1 design, and since my build is an Up-Hill/Down-Hill bike, the lost in pedal efficiency (not a lot) is not a big problem. In my mind is for sure less important than have more weight on the rear wheel....but I plan to put a Shlumpf or hammershmidt or a metropolis (fullspeedahead) on the cranck instead of the iT-1's Nexus 8, and use a single speed on the wheel, for the same weight gain and the possibility to use belt or stronger chain. In fact actually in my Dh I use only 3 or max 4 gears......and only one on the cranck.

In my build, the dream is to put the jackshaft on the shock pivot hole and use a centrifugal clutch on the motor shaft but there's a size problem that I have to solve for both.

Another goal that Gt team wanted to solve (in addition to the wheel weight gain) was to eliminate the typical chain movement on a full suspension, above all for the single pivots, I think.

Obviously If the bike is not for a Down-hill use these thoughts are not good...

Jules

 

[Green Machine]

Yes i think doing a hard tail would eliminate a lot of the complexity....

I would go with a hardtail build around a custom frame...this whole idea really makes sense to me.

Thanks miles for the brooklyn link build..i think the brooklyn frame is simpler and more obtainable than the GT.

Its kind of sad that the brooklyn didnt seem the right frame for that builder..so it seems he had to abandon his RC motor aspirations.

I think a hard tail version of the brooklyn would be the sweet spot.

Has anyone else attempted this kind of build?

 

[Miles]

I'm keen on the idea of two independent 2-speed gearing systems. One for the motor, one for the pedals. The one for the motor could be automatic.

 

[Green Machine]

Miles do you have link to your double 2 speed you are thinking about or is it just thought at this point?

I think something real simple would actually work...keeping everything on the right side of the bike.

An extended back frame as in below photo....

a matt dual reduction drive system (preferrably with 2 belts instead of chains for quietness)

And the freewheel on matts system....as seen in below pic would have an extra chain link on it going to the back wheel sprocket. But how could the pedals turn the wheels without cranking the motor...a 2nd freewheel? Would i need a dual freewheel at that point..is such a contraption available or even possible?

What other problem would i have?

The big disadvantage i thought would be pedaling efficiency...but if the GT and brooklyn are proof maybe it is possible to do without losing much....

I think for this purpose keeping both chains on the same side works perfectly since i am dealing with an extra wide bottom bracket (140mm axle width).

 

[Miles]

Miles do you have link to your double 2 speed you are thinking about or is it just thought at this point?

It's just the area that I'm interested in. Still developing the motor gearboxes, at the moment.

 

[Thud]

EGM,

135mm spacing on that bike?
Your proposals are within easy reach...all you need is a pr of White ind. freewheels broached to slide onto a freehub.
no need for the freewheel on the reduction now. (let me know if you need a hook up...I don't know if Luke is still offering the service these days...)

The reduction unit would be geared to power the inside sprocket
The chain would pedal normaly on the outer freewheel.

your limitaions for human gearing would be the 3 chainrings on the crank.
(your motor gearing is set by your wind choice+ voltage & performance goals)

I run most of my bikes with a very simular twin right side drive set up.

I have several 2 speed gear boxes built...allways tweeking the design LOL!

 

[Miles]

From the archive:

http://www.endless-sphere.com/forums/viewtopic.php?f=28&t=12449

http://www.endless-sphere.com/forums/viewtopic.php?f=28&t=13532

 

[Miles]

One of Thud's gearboxes in parallel with your Hammerschmidt.......?

 

[Thud]

hehe just building my post count LOL. (but I like the way you think Miles!)

 

[Miles]

 

[Green Machine]

I could use your guys help on this one...

SO got kit from sick bike parts to do a freewheel crank...supposedly bolt right up right?

So put everything together.

The freewheel scrubs against the frame...as if the axle isnt wide enough...i cant get any wider axle that is already on this thing.

I am stuck...any tips? Grind down the frame?

 

[Thud]

What is your bottom bracket length?
did you get the widest BB from SBP also?

it would help if you laid all the parts out on a table in aproximate sequence to gett a good look at the kit. & then a photo of the bottm backet shell in the frame...is it inset? IF so you have some fabricating to do.

thats as much as i can do form here....

 

[Green Machine]

Here is a picture of the bb...I am not sure if it is inset.

SBP doesnt even have a bb this wide...this is the stock 135mm square tapered bb that choppers usa sells...the widest axle i know of. This is a fat tire sand bike.

Have one more day to have this bike ready for the SF hill climb

 

[Thud]

SBP sells a 158mm BB....but the offset is all to the left....(my favorite!)
http://www.sickbikeparts.com/catalog/product_info.php?cPath=23&products_id=108&osCsid=4abdshe0a8k0vcvoghq5321mt4

& a wider one for cartridge style
http://www.sickbikeparts.com/catalog/product_info.php?cPath=23&products_id=114&osCsid=4abdshe0a8k0vcvoghq5321mt4

what i can't see in the photo's is if yours is a standard bb with adj. cups or cartridge...if its standard, the crank should fit easy....but the rules are not in play on a custome frame like that.....

 

[spinningmagnets]

how deep are the threads in the BB? I suspect they are deep to allow the customer to cut off some of the BB to achieve the desired width...but I could be wrong.

 

[Green Machine]

Sm,

I will take out the axle tomorrow and take a look..

Thud...the first sbp 158 axle you mentioned says it wont work with the hd freewheel which is the one i am using....

Do you know about the wider one ...cartridge style?

Are either worth a try?

Tomorrow we need to decide if we are going to go with right hand drive or just rip off the rear disk brake and go with a left hand drive.

I think also with a different set of freewheel cranks it might work...i am using the SBP cranks...and they seem to take up more space than they could if better designed.

Thanks for all the help guys..really appreciate.

 

[Green Machine]

If you guys were going to take the machining route..is it possible to just grind down the SBP hd freewheeel?

Or go ahead and try chopping that frame?

Heading out to do the dirty deed now....the race is tomorrow...today is our last shot of throwing something together.

Will try to post pics from the shop...

 

[Thud]

you can certainly remove the "tangs" where the freewheel removal tool bites on the unit. that will give you a little room.

Removal after that is a couple dimples with a drill bit & a drift punch tp spinn the body.

 

[rodgah]

thats a completely one off BB on that bike, I noticed it from the other picks you posted on another thread. Its unfortunate that the sickbikeparts cranks dont offer enough clearance, I wouldnt be hacking into a TI frame unless there was no other way around it.

 

[Green Machine]

Yeah we ran into multiple problems and wont have the bike done before race day.

The biggest problem is the matt drive is not configured to run on this wide a frame....so we are going to go with the more long term solution of the double free wheel like this thread started....lt-1 like but with belt drive...but with both chains on the right hand side. The thing that the lt-1 proves is that you can retain peddle efficiency with an indirect chain line....

I wonder if I can do this with belts??

For the short term we are bolting matts system to a beater for the race tomorrow....

Just flew together on the beater.