Homemade Shifter Kit?!

[DIYMark]

So Ive installed my 66cc HT, modified it, and rode it.

One problem is I live in a Hilly area so a single speed drive train as the intentions of the manufacturer is pointless because you need a low gear to get up the hill and a high gear to go down (well you could roll but that's kinda lame)!

So this is my dilemma, my modded HT (with custom exhaust and more) has LOADS of torque. It literally pulls like a tractor! I can go up hill, through the bush, over rocks and roots....skipping over gutters and trenches - at 38KM/H.

And then on the flat, tar road I can get to 40KMH and any more and the engine will almost self destruct - why? My guess it because there is load going up the hill which essentially "holds" the piston down where on the flats it pretty much flaps around. So up hill can go 38KM/H and then on the flat I go 40KM/H.

So from this I reckon that on the flats I have HEAPS of extra power (and torque) its just that well, the engine over revs very easily - I can pedal take off and reach redline in ~3 seconds (40KM/H). So with all this power I need gears I'm thinking!

So as my name suggests, I will try to make my own shifter kit...but I was wondering if anyone would be so kind as to run me through how one works :shifty2:

From the picture It looks like the crank spins the engine (to start) and the rear wheel to drive the bike forward. So with this dedicated drive...and the average HT pulling 7000RPM at redline, are you trying to tell me the cranks are spinning at approx 200RPM? What do you do with your feet then?

lol I'm pretty sure Ive got the wrong idea of how a shifter kit works (Im thinking that there would be like a freewheel ratchet on the crank or something).

So could some one please enlighten me

 

[bluegoatwoods]

Yup, the free-wheel on the crank saves you.

I admire the DIY attitude, but you might be better off just buying the kit from sickbikeparts. they've already worked out the bugs for you.

I've never ridden one. they're fairly new. But they already have a good reputation, it seems, around here. there's at least a few members here who have one. Maybe they'll see this thread and put their two cents in.

 

[QuadManiac]

The kit does include a freewheel for the crankset/chainwheels so the engine does not turn the crank but the crank will turn the engine (to start).

Have a couple of hundred miles on mine, it works GREAT!

 

[DIYMark]

I'm guessing you also loose the use of the front derailleur and front 2 sprockets? Or with the SBP Shifter kit you keep the them?

 

[QuadManiac]

The kit comes with a full set of shaft, freewheel, cranks and front chainrings. The large chainring is driven by the jackshaft, the small drives the rear cassette. The chainrings are tied together but one-way freewheeled to the crankshaft/pedals so pedaling both propels the bike and turns the engine over for starting.

So, yes, you lose the use of your front derailleur, but no real loss. I find with my 7 speed rear cassette that shifting 2 gears at a time (1-3, 3-5, 5-7) gives me effectively a 4 speed tranny with great RPM spacing for the engine. In first (32 tooth) I can climb any hill without pedaling and in 7th (18 tooth) I top out around 35 mph on the flat.

I think, with a little ingenuity, one could add a third chainring to the front, and still use the front derailleur to shift between two of the three to drive the rear cassette. But I don't see the value unless hill climbing is still desired (with the smaller of the two rings) with more top speed available using the larger of the two. The fundamental issue is interference between the jackshaft to large chainwheel chain and the small chainwheel to rear cassette drive chain where the two cross (a bit behind where the front derailleur would be)... work that out, and you'd be good to go.

 

[DIYMark]

Thank you for the detailed explanation.

For now it looks like im going to have to find some sort of freewheel. I might try the tip first

 

[QuadManiac]

Cyclone ( http://www.cyclone-usa.com/store.php?crn=203 ) sells the front freewheel, needed cranks and chainrings for a total of around $100, but you can't beat the Sick Bike Parts kit for all it comes with for $200.

 

[Technocyclist]

I have the shifter kit... but it can be a pain if you try to use cartridge bottom brackets... You'll need 125 mm or longer... The chain line is critical for the shifter kit. Also, install that aluminum thingy on the right side bearing plate. The engine has a tendency to rotate sidewards to the right. That aluminum thingy stabilizes it...

 

[DIYMark]

Ive been thinking some more (Whoa look out lol) and, if I were to make a shifter kit with ONE jack shaft it I would need a free wheel on the crank. This brings up some problems.

Firstly I need to buy new cranks (Trails cranks are the ones with the threaded "freewheel crank").

And then Ill need to buy a new bottom bracket as my current one is worn out and I don't want to put brand new cranks on a worn bottom bracket. Or even still, the trails cranks may need something other than a IS-IS splined shaft.

Finally I'd have to buy a freewheel sprocket to use as the freewheel.

And even still after "Investing" all that money I will still have problems as the BB shaft that comes in the kit is some what extended.

SO, my idea was to use 2 jack shafts lol.

Now I can place the free wheel on the jack shaft and not worry about the lack of room between the crank and BB shell. So far, for tis set up I plan on using these ratios. Engine to 1st JS is 10T->22T, 1st JS to 2nd JS is 11T->10T. Now on the second jack shaft will be a free wheel and on here will be 2 gears. A 11T one that goes to the Cassette and a 22T one that goes to the crank.

This set up including the engines gearing has a final ratio in 1st gear of ~24:1 which will take me up to 30Km/H a tad before redline. And the highest gear has a final ratio of ~8.2:1 which will take me up to 88Km/H a tad before redline.

My bike has a nine speed cassette so there is a fair few gears to play with, and If I use the afore mentioned ratios it will be the same as having a stock setup but with a 58 tooth sprocket at the back to take off with (1st gear). But then later on you can change it to have the same effect as a 20 tooth sprocket!

Now I'm going to start designing some jack shafts (gotta love Alibre Design!) after I grab some measurements from my engine!!!

Oh yea almost forgot - this 2 jackshaft method will only cost me $30 - that is, the cost of a new shifter (Shimano RapidFire or perhaps a SRAM one IDK, I will definitely need indexed shifting) other than that (chains, shafting, make sprockets) is in my shed.

 

[Large Filipino]

Just to throw this out,my Trike is currently a single speed but I can make it a 3 speed with a 3 speed 20 inch wheel and a 20 tooth jack shaft sprocket.
Here's my thread:

http://www.motoredbikes.com/showthread.php?p=171398#post171398

If you DIY your engine up front this simply does away with messing round on the back wheel. You'll still have your working pedals no matter what you do up front. In theory I could even chain up a 5 speed derailier up front and I'll have myself a 5 speed but I don't like that bike chain as thin as it is and may throw off the jackshaft gear alignment. But a 3 speed hub would be cake walk. A Nuvinci hub even better if I had the $$$$$.