FNR gearbox breakdown/dumb idea

[karl]

I know documentation is limited on this type of chinese thing, but does anyone have a parts breakdown for a ebay/ chinese buggy forward-neutral-reverse box?

Mine is cozy in it's home, and just wanted to see if I could debunk a dumb idea of mine

Mainly is reverse just a chain? , and the dog selects between gear set for forward and chain for reverse?

I want to see the feasibility of converting one into a 2 speed gearbox, before going deep and ordering a sacrifice.

 

[Budget GoKart]

Wouldn't it need a type of clutch? Have you seen rather b weldings two speed I don't think he had a clutch but it sorta worked just not easily.

 

[karl]

Yeah , the plan would be to use a normal centrifugal clutch , chain drive into box.

Let off gas to shift.

Ideally , I would buy a donor gearbox, and remove its foward gears, and install them in place of reverse, backwards to provide overdrive.

I would rather build a better 2 speed automatic box if going the exposed route.
And this could fit a minibike.

 

[itsid]

sorry, but that sounds like a brainfart..
since when does flipping a gear around reverse the rotation?

'sid

 

[karl]

sorry, but that sounds like a brainfart..
since when does flipping a gear around reverse the rotation?

'sid

It changes the gear ratio and replacing the chain with gears will make "reverse" a forward gear of opposite ratio to first

 

[itsid]

huh? I think you need to draw me a picture
flipping a gear cannot change gear ratio either (swapping two might, flipping one cannot)

what chain?
I doubt there is any chain involved inside your FnR gearbox.. it'll be spur gears all the way.
if you have one, crack it open and take a look..

I'm fairly certain -just by the image of the FnR you posted- I know what's inside.
one spur gear on the input shaft
meshed with a floating spur gear on the output shaft (reverse)
next to that floating gear sits a slightly smaller gear also floating of course,
in turn meshed with a small gear on the helper shaft (see the protrusion above the in and output shafts in the case?)
when shifted that small gear is brought into mesh with the input shaft thus driving the output shaft forward.

'sid

 

[karl]

Mainly is reverse just a chain? , and the dog selects between gear set for forward and chain for reverse?

That is why I asked this.

And Its common sense turning around a straight cut gear makes no difference.

I think I explained it pretty straight foward, but yes "swap"

You said flip, not me, I said install them in place of reverse, backwards to provide overdrive.

First gear = small gear + big gear
Second gear = big gear + small gear

The box provides around 15%? reduction, so double that , would be the sepration between gears.

Thanks for the insight on design of the box. I thought it would be like a mower transaxle (peerless 700, ect) that used a sprocket set/ chain for reverse.

I remembered why I dont ask questions on the forum, carry on nothing to see

 

[itsid]

Look what I found online..
quite baffles me, and I'm not exactly sure it's the same style gearbox at all
but that one DOES HAVE a chain!
(picture from a cycle kart forum)

So you might be lucky..

So as I understand you now want the two visible spur gears removed
and replaced by another sprocket chain set?

might indeed work *shrugs*

'sid

 

[karl]

Much thanks, and yes that is the concept. It makes sense the chain is forward, IDK why I thought it was the other way around

And that makes it much easier/ more possibilities / feasible if indeed that is the same gearbox.

Ill keep a lookout for the cheapest one I can find