Planning/Imminent build of 4x4 kart

[itsid]

there's a huge problem in using worm gears...
they simply do not move when there is no active rotation on the input shaft;
they simply lock up on you.
Say the engine is off, clutch disengaged.. and you still cannot even roll the kart.
Engine is running at idle, clutch disengaged, you're going downhill all wheels lock (or teeth will shear)
with an engaged clutch the wheels still cannot move faster than the engine speed (since the wheels cannot transfer rotation back to the engine)

10:1 isn't a problem, it's the worm itself making it impractical.
think of the worm as a screw or bolt... no matter how hard you press it'll not unthread...
very same physics apply to a worm gear.

so you'd need one way freewheeling clutches on every wheel; and in a way that your disc brakes are still able to stop the wheel of course...

'sid

 

[bread]

ok so changed design to 17 in tires, shorter stance
red=gearboxes
green=DS

itsid, what you have said is one of the biggest reasons I chose worm gears.
I never mentioned my plan for brakes!
being so slow and light, braking was not a huge issue anyway, but basically when the clutch is not engaged, full "braking" is

when I drive my gator down hill, engine compression brakes for me, this kinda similar, however in order to move at all, the clutch must be engaged. so imagine full throttle down hill, the worm gears will move only because of the clutch. in other words, sitting on a hill, the kart wont move

this means the drive train is truly locked/not influenced by terrain, etc

also, when I say trailing, I don't mean rock crawling.


skidoo, these are not diffs, and the jackshaft setup you have drawn is to be used for a rwd kart. goals of this project are 4x4 + using the 5hp

still, if these worm gears prove to have too many issues, does anyone have ideas for another light way to get power from a longitudinal shaft to the axles?

 

[itsid]

Well.. you can give it a try (should indeed..)
but while you're still in the planning phase, just quickly make a backup plan, since I assume you're going to need it and being prepared is a good thing when it comes to disappointment
A standard RAGB can do that.. personally I'd go for some sort of differential..
something beefier than a ride on mower but smaller than a car diff *shrugs*

Good luck though,
maybe I'm just misjudging your intention and that's exactly what you want..
in any case.. I look forward in seeing a test drive video

'sid

 

[SkidooTNT]

You know what I meant.
The jack shaft design isn't mine it's Jrgunn5150, he's trying to talk me into axels. I just don't have the money for them.

With the right axels you could definetly modify the jack shaft design to give you 4X4.
I just don't think the plastic worm gears will hold up at all. Climbing rocks will put a lot of sudden loads on them they are just designed for. Maybe if you pulled them out of 20hp snowblowers it might work.

Also for the braking. This thing is just going to be dangerous like that. Doing rock crawling your going to get bounces around a lot and there will be a lot of times your foot will come off the gas. It'll stop you dead. In my experience you always need forward momentum. I just thing you'll regret usin worm gears down the road.

 

[bread]

You know what I meant.
The jack shaft design isn't mine it's Jrgunn5150, he's trying to talk me into axels. I just don't have the money for them.

With the right axels you could definetly modify the jack shaft design to give you 4X4.
I just don't think the plastic worm gears will hold up at all. Climbing rocks will put a lot of sudden loads on them they are just designed for. Maybe if you pulled them out of 20hp snowblowers it might work.

Also for the braking. This thing is just going to be dangerous like that. Doing rock crawling your going to get bounces around a lot and there will be a lot of times your foot will come off the gas. It'll stop you dead. In my experience you always need forward momentum. I just thing you'll regret usin worm gears down the road.

thanks, I'll give em a try but I have backup plans too
they are not plastic, and again, I'm not rock crawling

 

[SkidooTNT]

Sorry. Saw the conversation about tires and kind of just put that together with 20 inch suspension travel to get rock crawler.

Might be ok with metal gears. My experience is one plastic one metal gear in something like that.

 

[chancer]

So is it a Rock crawler?
Sorry couldn't resist!! Carrry on

 

[bread]

would this clutch hold up to the torque of low gears?

http://www.ebay.com/itm/Go-Kart-Mini-Bike-Centrifugal-Clutch-1-Bore-40-41-Chain-14T-Tooth-Heavy-Duty-BH-/111843003242?hash=item1a0a5ccb6a:g:ADcAAOSwAKxWZCt6&vxp=mtr

would a torque converter be the way to go?
this was really the other "big" concern of the whole plan

 

[SkidooTNT]

Because you would be gearing down after the clutch the torque created by the gearing isn't a factor on the clutch.

That said a torque converter is your better bet. The way you'll be geared for torque with a clutch you'll be very very slow. You still won't be that fast with a torque converter but you won't be bored out of your mind driving between spots you need the torque.

 

[bread]

thanks, I hadn't seen it that way, I'll go with a TAV

 

[bread]

there's a huge problem in using worm gears...
they simply do not move when there is no active rotation on the input shaft;
they simply lock up on you.
Say the engine is off, clutch disengaged.. and you still cannot even roll the kart.
Engine is running at idle, clutch disengaged, you're going downhill all wheels lock (or teeth will shear)
with an engaged clutch the wheels still cannot move faster than the engine speed (since the wheels cannot transfer rotation back to the engine)

10:1 isn't a problem, it's the worm itself making it impractical.
think of the worm as a screw or bolt... no matter how hard you press it'll not unthread...
very same physics apply to a worm gear.

'sid

I just found out that I can turn the gear side of the gearbox one way (happens to be forward) and the worm side spins as well...

I thought it wouldn't work either, but I think with the gears properly greased, etc it can, but only one way

 

[itsid]

I just found out that I can turn the gear side of the gearbox one way (happens to be forward) and the worm side spins as well...

I thought it wouldn't work either, but I think with the gears properly greased, etc it can, but only one way

I hate to rain in your parade, but
that's incredibly bad news...
that means the teeth of the cogwheel are almost certainly mostly gone.

Those cogwheels are typically made of brass and even just moving the snow blowers auger they tend to wear pretty quickly;
and the more worn out they are the faster they wear (less contacting surface and such)

Anyways, even trying to roll down a street or pushing that kart in your garage an inch forward,
will effectively remove all remaining teethstumps.

Since it's higly unlikely (nearly impossible) that your wormgear has a steep enough angle to be moved by the cogwheel when in full contact. (since if, it'd work in both directions)

Only way to find out is to pop open that gearbox and see for yourself;
I'm almost sure you'll find a metric ton of brass shavings and a cog with caries.

'sid

 

[bread]

I hate to rain in your parade, but
that's incredibly bad news...
that means the teeth of the cogwheel are almost certainly mostly gone.

Those cogwheels are typically made of brass and even just moving the snow blowers auger they tend to wear pretty quickly;
and the more worn out they are the faster they wear (less contacting surface and such)

Anyways, even trying to roll down a street or pushing that kart in your garage an inch forward,
will effectively remove all remaining teethstumps.

Since it's higly unlikely (nearly impossible) that your wormgear has a steep enough angle to be moved by the cogwheel when in full contact. (since if, it'd work in both directions)

Only way to find out is to pop open that gearbox and see for yourself;
I'm almost sure you'll find a metric ton of brass shavings and a cog with caries.

'sid

the snowblower is brand new, been used maybe once
I had already opened to gearbox and found no shavings, just happy greased gears

I think the reason I can turn it has to do with the fact that there is no load on either side of the gearbox. The analogy you said about a bolt, I don't think is quite accurate because load (pressure) on a bolt. I do think that the gears will be subjected to immense pressure when the kart has forward potential energy. Too bad there is such a grey area with worm gears, maybe there's a reason

Although, lets say the 250 lb kart with 130 lb driver is sitting at the top of a 30 degree hill. If the kart rolls forward without the clutch engaging, it means that the gears are turning the worms like I can do now with it. If I can turn it by hand, the force of tires rolling/weight should be sufficient to get it rolling w/o clutch engaged. Does this mean that rolling it forward in garage, etc wouldn't be harmful at all?

 

[itsid]

New.. nice!

but in that case.. -and looking at the lead angle of the teeth- you cannot have turned that inputshaft by just spinning the output. maybe you cheated unwillingly..
it's hard to believe that any -especially non Moly- lube is able to reduce friction enough.
Again, new out of the box, it doesn't matter if you spin the cogwheel forward or backward;
the result will be the same.
Which again leads me to believe you unwillingly helped the input to turn in some way.
(say just grabbing it to see if it wants to turn)

Anyways, you're convinced it'll work, I'm convinced it'll fail in very short order.
You have it already to test, so please do.

Oh on a side note:

The analogy you said about a bolt, I don't think is quite accurate because load (pressure) on a bolt.

I wasn't refering to a tightened down bolt to fix anything in place.. I was asking you to try to push a bolt through a nut you hold in your hand (screw it in a few threads deep, then try to push it out with the tip of a ballpoint pen [to reduce friction and allow the bolt to rotate])
tapping might work (to break the friction and rattling the bolt free) pushing will not.
and the same thing is true for your wormgear (somewhat similar lead angle)


As I said, please do proceed, just keep in mind that you'll need a backup plan eventually

'sid

 

[bread]

Anyways, you're convinced it'll work, I'm convinced it'll fail in very short order.
You have it already to test, so please do.



'sid

that is not true at all, what reason would I have to convince myself it would work? I am still planning this creation, meaning I'm still open to suggestions. I was thinking further about why I can turn the output only the one way. I think it has to do with the bevel of the gear, but I entirely see how it would fail in the kart.

What is an RAGB? If I was to use a diff, what type would be small/light enough for this application?

I found these on ebay, but seem pretty expensive

http://www.ebay.com/itm/1-1-RIGHT-ANGLE-GEARBOX-32-HP-3-KEYED-SHAFTS-13-1423-3K-/271758992945?hash=item3f46192631:g:GkYAAOSwa39Uy54Y

 

[mckutzy]

A RAGB... Is what you have posted...Right Angle Gear Box.
That is actually a good deal for that type...
But it'll be heavy...

 

[bread]

A RAGB... Is what you have posted...Right Angle Gear Box.
That is actually a good deal for that type...
But it'll be heavy...

wow i feel dumb

I figured it'd be heavy, but I can't think of/find a gearbox other than the worm that is both light and has reduction

atv diff?

Wait just a minute, because I'm still in the planning phase, I can still change my design! I can't believe I hadnt thought of using solid axles and leaf springs. This would mean I wouldn't have to build a complex and expensive independent setup.

ideas?

 

[chancer]

Yeah solid axles.
If it is NOT a "rockcrawler" Do you really need 4 wheel Independent suspension.
Why not live axles and universal joints.

 

[mckutzy]

Why not get a 4WD ATV and modify that...

 

[Denny]

Actually worm gear rear ends are quite popular on heavy duty OTR heavy haul trucks, and earth moving equipment. On the lighter side of things Cushman golfcarts, haulsters and trucksters still use them, and yes you can push them quite easily. My 1971 Am General M35a2 6x6has 3 of them and they roll quite well. The weak area on the snowblower drives is the aluminum casting case.

Denny