Are there any reverse-direction gearboxes available?

[5-7HEAVEN]

I'm thinking of installing a rack-mount-type engine in a frame-mount position. HOWEVER, the engine's drive sprocket will be on the right side, in line with the bike's 3/7/21-speed gears. The bike's derailleur will do its normal job of selecting gears and maintaining proper chain tension.

Gears will be shifted when engine is idling, to maintain "mechanical integrity" and not severely abuse the multispeed cassette.

I DO realize that the engine spins counterclockwise, thus making it impossible to drive the gears in this position. THEREFORE, I'm looking for a reverse-rotation gearbox with gear reduction that the engine can bolt on to.

I know that STATON has a chain drive gearbox WITH a reverse-direction sprocket on its outer face. It also has 5:1 gear reduction, which would handily provide proper gear reduction for the engine's optimum range. With a 9t gearbox sprocket and 34t rear sprocket(the biggest one in the cassette), this 3.78:1 gear ratio multiplied by STATON 5:1 gear reduction equals 18.89:1 final drive. This is equivalent to happy time engine and 46t rear sprocket, and is an excellent starting point.

To set up this engine drive, the chainwheel must be moved to the left side, and in line with a STATON 16t left-side freewheel sprocket. The 36t chainwheel and driven sprocket must be matched to use the same chain. It will also be geared to provide 1:2 ratio, which is typical for a single speed cruiser.

Soo, does anyone know of any reverse-direction gearbox, besides the STATON gear chain drive?

Also, let's hear your opinion if this idea will fly. Any helpful suggestions will be appreciated.

I've played "devil's advocate" here, and discouraged/shot down a few members' ideas. Here's your chance to shoot holes in my sails.

Myron

 

[MtnGoat]

What about the 3 to 1 China gearbox that Zomby Builder posted? He says it reverses the drive to the right side, but I don't understand how, or even what that means (direction of drive or side of engine?). Looking at the pictures it seems to just bolt on to the left side without changing anything, which of course isn't what you are looking for.
http://www.motoredbikes.com/showthread.php?t=7624

The problem with all these scooter and pocket bike part sites that have various gearboxes, trannies, etc., is that they post almost no information about the product beyond the title description. Makes it hard for someone like me who is not already familiar scooters or pocket bikes, etc., to adapt these parts to a motorized bike application.

As far as opinions about the feasability of taking over the bicycle drive train with the motor, Zomby builder gave up on his similar project. See his post in 3 speed motorized bike experiment: http://www.motoredbikes.com/showthread.php?t=4273&page=5

I'm speculating that the bicycle chain probably is strong enough (especially if using a 3/32 bmx rated chain) going from drive sprocket to fixed driven sprocket. But when you start jumping the chain from one cassete cog to another, problems arise. I know you are planning to shift when the engine is idling, but if you have a centrifugal clutch and a freewheel cassete, the chain will not be rotating when you shift, and the chain will not change cogs untill you engage the clutch again. I'm afraid when you do you'll run into the chain problems that Zombie Builder did. Perhaps if you are careful to ease into engagement. I guess whether that is practical depends on the clutch.

 

[5-7HEAVEN]

The 3:1 gearbox alone is too high for my needs, unless I could find a 6t for the engine. With 34t driven sprocket, this would compare to happy time engine and 41t sprocket.

Off the top of my head, a 5:1 gearbox with 8t/34t would be a good start off. This compares to happy time engine and 52t rear sprocket. STATON has that box, but i'm looking for a cheaper one.

MtnGoat, those chinese gearboxes bolt into the engine's clutch housing and reverse engine shaft direction. Most popular engines turn counterclockwise. The chinese box literally reverses engine direction, which means that your engine's clutch and drive sprocket would turn clockwise and align with the 7-speed cassette.

Reminiscing on middle-school physics, when a second gear meshes with the main gear, this second shaft attached to the gear will spin the opposite direction of the mainshaft. If a third gear meshes with the second gear, that third gear will reverse direction again, which will be the same direction as the original mainshaft.

The STATON gearbox has 3 meshing gears. This is for gear-reduction purpose, and to maintain the same crankshaft direction.

MtnGoat, you're correct in saying that the chain will not shift gears with engine idling. Maybe the simple solution would be to raise rpm slightly and allow the centrifugal clutch to spin the chain. That would allow the derailleur to shift gears smoothly.

All this is theoretical, but I'm positive that a few members would be able to make it work.

In fact, I wouldn't be surprised if MANY people have successfully done so. Since they don't visit this forum, we are just not aware of their success.

Now if I can just find a 4:1 or lower gear reduction box, this compares to happy time and 41t driven sprocket. This would fit me needs well.

Still looking.

Myron

 

[MtnGoat]

...
MtnGoat, those chinese gearboxes bolt into the engine's clutch housing and reverse engine shaft direction. Most popular engines turn counterclockwise. The chinese box literally reverses engine direction, which means that your engine's clutch and drive sprocket would turn clockwise and align with the 7-speed cassette.
Myron

Ah, now I understand. So you mount the engine so the output shaft is on the right side of the bike, and reverse the direction with the Chinese 3:1. Now you are driving forward from the right side.

Too bad 3:1 isn't enough. The price is right. Still it's better to pay for the 5:1 Staton box than get into the complexity of building a jackshaft in order to reduce the gear, imho.

 

[5-7HEAVEN]

MtnGoat, using this particular STATON gearbox has many advantages and options.

http:www.staton-inc.com/Details.asp?ProductID=3239

1. You can use it to reverse direction and for gear reduction on the bike's right side.

2. You can flop it to the other side and use the box's inside sprocket and have 18.75:1 gear reduction. Slip an 18t onto the box's drive shaft, run a chain to link a 16t freewheel sprocket on the left-side hub and have 16.67:1 drive. This is equivalent to happy time engine and 41t sprocket.

3. Mount this gearbox at the rack mount behind the seat and drive the 16t left-side hub.

4. Mount this gearbox at the rack mount behind the seat and drive the right-side NuVinci hub.

5. In every position, the gearbox's spare drive shaft can be used to drive an alternator for your electrical system. It can also drive the alternator to power up a front electric hub motor.

For an extra $60, STATON'S 5:1 reverse-direction gear reduction is a valuable option.

Still looking for a less-expensive reverse-direction box with 5:1 gear reduction.

Myron

 

[5-7HEAVEN]

Happy Time 4.1:1 gearbox

In another thread, someone suggested using the bottom end of a happy time engine as a 4.1:1 gear reduction box.

After mounting an 80cc Chinese engine onto my 1976 SCHWINN HEAVY DUTI cruiser frame, I took some measurements. With a smaller diameter chainwheel, the engine sat lower. HOWEVER, there was only 8.5" clearance from the engine's clutch housing to the top frame tube. This was due to the extra BULK/SIZE/MASS of the happy time "gearbox" residing below, where the engine would normally be placed.

Now, the only engine short enough to mount in MY spacious frame would be my pocket bike engine. No other engine fits in the frame with this "gearbox". No happy time, no HONDAS, ROBINS, MITSUBISHIS, chainsaws or weedwhackers.

That is, unless I enlarge the frame height-wise, build a custom-frame or believe in Santa Claus.

This "gearbox" also has a mechanical clutch. Since my engine has a centrifugal clutch, the manual clutch would be a liability which serves no purpose and eventually needs replacement. This clutch could probably be disabled by tackwelding the disc to the shaft.

The position of the pb engine's 6-tooth drive sprocket in relationship with the gearbox's 12t crankshaft sprocket would seem to be aligned. The "gearbox"'s drive sprocket would then align with the left-side rear sprocket.

HOWEVER, in order to align the sprockets, the pb engine's bulk would shift to the right side of the bike and not be centered with the frame.

Multiply the 2:1 gear ratio from the 6t/12t engine-to-"gearbox" by 4.1:1 happy time ratio. That product multiplies the 10t/36t rear sprocket to arrive at final gear ratio of 29.52:1. This is equivalent to happy time engine and 72t rear sprocket, which is very good for pocket bike or chainsaw engine's 8,000rpm/11,000rpm torque/power range.

I take that back. Chainsaw engines won't fit in my old, large cruiser frame.

Hmmm, provisions would have to be made for the "gearbox" to accept a drive sprocket at this crankshaft. I believe that most of the project's cost would be in fabricating/machining/finding a crankshaft/sprocket adaptor. It might be simple and inexpensive, or it might cost a lot.

All this is GREAT, except that this happy time "gearbox" has now REVERSED the engine's crank direction!!!

This reversal makes driving the left-side rear sprocket impossible without another BULKY component to convert the drivetrain back to counterclockwise direction.

Of course, you could always extend your frame, custom-build your frame, believe in Santa Claus, then add ANOTHER happy time gearbox in series.

HOWEVER, this makeshift reverse-direction gearbox is EXACTLY what I was looking for. My original intention was to find a cheap, reliable reverse-direction gear-reduction gearbox. This was to link my pocket bike engine to the bicycle's 7-speed cassette and derailleur.

At 4,000rpm/8,000rpm,11,000rpm, speeds with a 34t rear sprocket would be 11.4mph/22.8mph/31.4mph.

With 28t second sprocket, it's 14mph/28mph/38.6mph.

With 24t third sprocket, it's 16.2mph/32.4mph/44.5mph.

With 22t fourth sprocket, it's 17.6mph/35.2mph/48.5mph.

Of course, now I have to reverse-mount the gearbox UPSIDE-DOWN. This is so that the gearbox's 10t sprocket faces the bike's 7-speed cassette.

And of course, the happy time's mounts don't align with the frame, so that's another issue to contend with. It is do-able, not impossible. The mounts aren't critical, since happy time is no longer a vibrating engine.

And here it is...my inexpensive, high-quality reverse-direction gear reduction box project. by swapping the happy time's crankshaft sprocket, gear ratios from 18.59:1 to 41.82:1 are attainable. This is equivalent to happy time engine with easily-replaceable sprockets, from 45t to 102t.

I don't have to extend my frame, I don't have to build a custom frame, and I don't have to rely on Santa Claus.

Thanks for the ideas, fellas.

Myron

 

[srdavo]

HOWEVER, this makeshift reverse-direction gearbox is EXACTLY what I was looking for.

I'm glad you've found what you were looking for. I hope we get pics, as your project continues.

 

[5-7HEAVEN]

Thanks, Dave.

I just bought a dead engine, and will keep you guys posted on my progress.

Myron

 

[5-7HEAVEN]

Mating an 18t sprocket to a "Happy Time" crankshaft

I'm doing preliminary measurements and calculations for my "RODGER Box".

"RODGER Box" means Reverse-Of Direction/Gear-Enhancement-Reduction Box.


This gearbox has room for a 2.5" diameter sprocket. This is after the magneto is removed and the box's face is machined flat.

The "RODGER Box's" 10t output sprocket's teeth may need 1 mm narrowing to fit the existing bicycle chain.

I need to do more empirical(actual) work on the project. Too much hypothesizing.

Myron

 

[Alaskavan]

Sounds like a good deal Myron. Keep us posted. And....... pictures?