CFFD - Chain Front Freewheel Drive

I've been a v-belt drive kinda guy for awhile now, but then got into friction.
Now I'm onto chain drive & wanted to assemble something quick and easy without spending any new money.
I sheared a drum from its shaft on my Dax friction driver & while waiting for the replacement, decided to slap this thing together.
-Its my old racing MTB (Litespeed Obed titanium frame)
-Spread a cheap cromo fork 20mm's
-Install a rear wheel into the fork (thread-on 34T freewheel)
-Mount pocket bike 5:1 transmission (10T)
-run std BMX chain 1/2" x 1/8" (410)
It freewheels which none of my previous project have done. I think this will be better for the engine (no engine braking) & greatly improve clutch wear & clutch spring failures.
I'm planning another future project that will run a chain from a rear rack mounted engine straight to the rear cassettes' big ring & then another chain from the other 8 shiftable gears to a front freewheel single ring.
Here are the pics
-Lowracer-

 

[BigBlue]

Nice detailed pictures. Hope the gearbox holds up. Thought of the Staton 5:1 gearbox if the China 5:1 doesn't hold up. Definitely an affordable way to go. I have a nice 53cc Goped engine that I would like to mount like this a give me the freedom to mount a rear rack as a power assisted touring bike.

Good Luck,

Chris
AKA: BigBlue

 

[Fabian]

I like the design work lowracer.

Can you please explain how effective your chain tensioner is, and if it makes a difference to maintaining good chain tension?

Fabian

 

[lowracer]

BigBlue,
From what I've been hearing, the 5:1 china gearbox is a keeper. The now out of business 'TheScooterGuy' kit ran the same gearbox & I know of a few members running high power thru this transmission without failures. I topped of the '00' grease today.
Fabian, The tensioner works really well. I took a single speed tensioner & removed the rear derailleur bolt & spring. Then one of the holes already in it fit a 5/16" bolt nicely. The tension is supplied by a heavy duty rubber tie down strap hooked around to the other side of the channel. There is a sliding shaft w/cinch bolt to fine tune the jockey wheel against the chain.
-Lowracer-

 

[Fabian]

@ lowracer

So you would say that not having a chain tensioner could cause problems, and would make life a lot more difficult?

If you didn't have a chain tensioner, can you explain some of the problems it would cause?

 

[lowracer]

Fabian,
The chain slaps around. It would slap enough to hiot the front brake arm & the tire. The non-driven side of the chain becomes slacker than the driven side & can derail as its moving to & fro.
The tensioner not only keeps the chain taught but straight. I wouldn't want to run a chain driven MB without a tensioner.
I do have 2 road bikes. One is a fixie & the other a singlespeed & they dont have a tensioner, but they have nice adjustable track ends with adjustment nuts to pull the chain. I have thrown a chain (derailed) on my road bike coming down a bumpy bridge.
One of my DH MTB's has a tensioner guide jockey wheel under the front chain ring as well as top side guides (walls) on both sides to keep the chain from going anywhere....very effective for bombing down a mountain offroad style...
-lowracer-

 

[Fabian]

Lowracer, can you do me a favour and convey this information about a chain tensioner being beneficial, if not "vital" for the safety and reliability of a chain driven system.

I was under the impression (or was given the impression) that i was the only person who experienced these problems with a chain driven system; which forced me to make my own chain tensioners for the chain driven SickBikeparts shift kit.

I am sure the guys at SickBikeParts would find your information and experience "particularly valuable" (because my product feed back fell on deaf ears); they might even take your advise on board and develop their own chain tensioner mechanism for the shift kit.

 

[lowracer]

I got the chance today to take this new rig out for an extended test drive of 58 miles.
The chain drive performed flawlessly & didnt skip a beat (no pun intended). I got 58 miles on just under 50 oz of fuel (still some left in the tank) so lets say 48 oz.=155 mpg's...Not too shabby considering it was a windy day.
Some observations after todays adventure?
1- I dont like rigid (no suspension) bikes!!! (this rig beat me up unmercilessly especially at high speed & sat on a large leather rear sprung beach cruiser saddle)
2- I like chain drive (even though there is an annoying whine to the 5:1 transmission. Maybe that will go away over time...its still new)
3- I really like freewheeling when off the gas (I know my clutch is loving the freewheel)
4- I want to turn one of my two full suspension DH bikes into a rear chain freewheel drive (possibly a homegrown shift kit, or just a single ratio like this rig)
5- Needs a more power engine (the Tanaka 32cc is ok, but once spoiled by the 40cc & the mojo powerful pocket bike engines, only another 40cc or GP460 will do)
I'm putting a parts order together to turn 'The Beast' (the bike in my avatar) into a rear rack chain driven freewheeler...will keep ya posted
-Lowracer-

 

[BigBlue]

Lowracer,

I've read that even the Staton gearbox whines until it is broken in. Per Sheldon Brown, you can make a custom cassette by disassembling. I could imagine you could install two 34 spoke sprockets on the rear cassette - one for the engine and one for pedaling. Adjust your rear derailleur stop limits, so the two chains don't collide. Also would be wise to have a space between the two sprockets.

Look under, "building Custom Cassettes":
http://sheldonbrown.com/k7.html

Good Luck,

Chris
AKA: BigBlue

 

[lowracer]

BigBlue,
I think I'll put some miles on the 5:1 transmission to see if the whining gets any less. Its not obnoxious, just noticeable.
I have a completely disassembled cassette, but dont think I need a 34 for pedaling. I rarely get out of the bottom 4-5 gears using the 44T front ring for pedal power.
I ordered the parts today to turn my rear friction DH bike into a chain drive. I will still have to figure out if I'll go with shift kit style (rear rack to front chainring) or one ratio (rear rack to 34T rear cassette cog)...Rear suspension is the big deciding factor on which way I go.
-Lowracer-