Who here would want something like this? (Idea)

[christeeezy]

Hey guys, I've been thinking about various products to make to generate some side profit. I have one idea for kart building. BTW I know a lot of you know about the couple points I'm about to say already, but I want to be thorough, so bear with me.

So I'm sure you guys have all seen a bicycle freewheel hub before. That is the hub on the rear bicycle wheel that makes the little clicking sounds if you pedal backwards. Obviously, the reasoning behind the clicking is that the hub is allowing the chain and therefore sprockets to "freewheel" in that direction. Once you start pedaling the normal way, the ratcheting system locks, allowing the foot power to be transferred through the hub, wheel, then ground.

Now think about live axles and keyed wheel hubs. The upside to using a live axle and keyed hubs is that you get power to both wheels, therefore allowing for more traction. Two big downsides though:

1. It's a LOT harder to turn left or right, even marginally.
2. You wear through your rear tires a lot faster.

Reasoning behind those two facts is that the live axle is keeping both tires spinning at the same speed during turns, resulting in the outer tire being dragged (naturally the outside tire wants to turn faster in a turn due to the larger radius).

So on to my product idea:

Imagine a sort of beefed up freewheel hub on both sides of the live axle, that the wheels are mounted to. The inner races are keyed, while the outer race allows a lock in one direction, and freewheeling in the other direction.

Imagine going off in a straight line. Both hubs are tightly locked, transferring the power through both wheels as normal. Going into a turn, the outside wheel is freewheeling, while the inner wheel is still locked and transferring power. Again, the outer wheel is freewheeling because it is turning at a faster rate due to the larger radius. After the turn is complete, both wheels are turning at the same rate and are both locked once again.

---
So, best of both worlds: traction of a "live axle and keyed hub" combo, with the tire saving and easier turning properties of a dead axle configuration.

Any thoughts on this go kart freewheel hub idea?

-Chris

 

[ML-TOYS]

Basically its a differential to me

 

[klicky96]

This could be something. It really could. your gonna need someone to machine this for you, but it can be done. There will be like 6 bearing but it could work. It will be a lot of trial and error to figure all of this out but you can do it if you set your mind to it.

 

[christeeezy]

Haha I was expecting that answer.

The characteristics of a differential is completely different from what I described

 

[christeeezy]

This could be something. It really could. your gonna need someone to machine this for you, but it can be done. There will be like 6 bearing but it could work. It will be a lot of trial and error to figure all of this out but you can do it if you set your mind to it.

Thanks for the input klicky. I am drawing up some plans to bring to a machinist.

 

[souperman000]

I would at least experiment with your idea, if you can get it produced and sold on the cheap, then I at least might be interseted in trying it out. Just to see how it works if nothing else

 

[Doc Sprocket]

What you are describing exists in the offroad world. It is known generically as an "automatic locking differential". Here is a branded example- http://www.jegs.com/p/Powertrax/Lock-Right-Automatic-Positive-Locking-Differential/745940/10002/-1

Your design (one way ratchet) has two drawbacks- 1) Reverse won't happen 2) Engine braking won't happen. On a go-kart, this is not much of a problem. On a truck, it is- so the manufacturers found a way to make it bi-directional. Basically, instead of one side overrunning, it uses the driveshaft's torque to tell it when to engage. As such, you have to coast around corners. If you hit the gas, it locks up.

Knowing what I know about the various types of limited slip, and manual- and- automatic locking differentials (toystory_ 4wd), I would LOVE to see this for kart/buggy applications.

 

[klicky96]

Thanks for the input klicky. I am drawing up some plans to bring to a machinist.

Okay, big tip here. Build all the gears first out of wood or something and see how your idea plays out before you go to a machinist.

 

[CAPTAINCAVEMAN]

if it was in my price range I would buy it in a hart beat mostely because I hate to where out tiers and I think it would prevent the original slip therefor improving handling and allround offroad preformance
GREAT IDEA
two people posted while I was writing ha

 

[christeeezy]

What your are describing exists in the offroad world. It is known generically as an "automatic locking differential". Here is a branded example- http://www.jegs.com/p/Powertrax/Lock-Right-Automatic-Positive-Locking-Differential/745940/10002/-1

Your design (one way ratchet) has two drawbacks- 1) Reverse won't happen 2) Engine braking won't happen. On a go-kart, this is not much of a problem. On a truck, it is- so the manufacturers found a way to make it bi-directional. bBasically, istead of one side overrunning, it uses the driveshaft's torque to tell it when to engage. As such, you have to coast around corners. If you hit the gas, it locks up.

Knowing what I know about the various types of limited slip, and manual- and- automatic locking differentials (toystory_ 4wd), I would LOVE to see this for kart/buggy applications.

Thank you toystory.

So there is my first hurdle. If engine braking, or just braking, the axle will lock up and the wheels will continue to spin. I would need the brake rotors to be attached to the outer race of the hub bearing, or wheel, similar to the brake setups on race kart front wheels.

Either that or the hub mechanics will have to get a lot more complex.

 

[r97]

I'm still thinking there is something I'm not seeing, but I think it could work very well assuming the bearings are up to the task.

Unlike a differential, this provides a free wheel for coasting downhill (but consequentially removes engine braking). Also, when in low traction conditions, both tires will spin at the same speed, regardless of which has more traction.

The bearings you are looking for are one-way bearings, they are available at mcmastercarr.com, vxb.com, and several other stores. They are available in either needle bearing, or ball bearing styles.

To choose the bearings you must figure out how much torque is going to the rear axle, and make sure the bearings supporting just one of the wheels can handle a good bit more than that figure. Also make sure the bearings are rated to handle the radial and thrust loads that apply, OR have extra support bearings to handle those loads while the one-way bearings only transfer torque.

As far as securing bearings to the shaft and hubs, an interference fit may work, although (as already mentioned) some type of key, or splines would be much better. Each wheel will also need brakes attached to the hubs, two brakes if you want both wheels to be stopping you.

http://www.mcmaster.com/#one-way-clutches/=hgac1u

http://www.vxb.com/page/bearings/CTGY/One-Way-Bearings

These could work extremely well, you would need to get some more specs though (e.g. Key-way dimensions, maximum radial & thrust loads).
http://www.vxb.com/page/bearings/PROD/One-Way-Bearings/Kit10971

EDIT: jeez, I guess I took to long typing that!

 

[crazyman]

Don't discount using a ready made sprag... basically using the same principle, but without the clickety. found in every automatic transmission.

Good thinkin.

 

[porsche930dude]

its a fine idea and would probrobly work good. but complicated and so will cost alot to build. i dont see making money off of it. if its money your after you are much better off making repro parts of vintage karts and minibikes. atlest to get you started making parts and see where it leads you. Iv been doing it for years with old jeep parts and a few minibike parts. Its profitble but the key is to find a way to mass produce the parts as easy as possible

 

[porsche930dude]

there ya go one way bearings! just figure out how to tightly fasten them to the wheels and axle and your done except for the brake

 

[christeeezy]

Don't discount using a ready made sprag... basically using the same principle, but without the clickety. found in every automatic transmission.

Good thinkin.

Right. I was going to model it after the sprag clutches found in transmissions. The one way bearing packs that r97 gave a link to would probably work just as well.


The biggest thing now is the brake issue. I thought up this hub idea to possibly save people money on a differential while offering better performance, but if the brake issue can't be resolved mechanically, I don't see this option being cheaper.

 

[christeeezy]

Actually --

I think it would be viable that the outer race of the hub (that contains the wheel lugs) also extends to the other (inner) side of the wheel, holding a brake rotor. So basically like I said earlier, just like the front brakes on race karts.

 

[r97]

Adding brakes to hubs will be easy, Simply weld some tabs for a brake rotor/drum on each hub, then bolt up the parts! This idea probably would not be a big savings(Maybe more expensive), but would most certainly be nifty and better than a diff (for our application, e.g. no reverse or engine braking as toystory_4wd mentioned).

The bearings could be simply press fit, or secured with keys.

 

[christeeezy]

After some more thinking: To combat the price, brake, reverse, and engine braking issues, one could use a regular keyed hub on one side of the axle, and the one way bearing hub on the other, no?

This will allow dual wheel traction in a straight line, and allow the wheels to turn at different rates throughout the turn - the two things I was trying to solve. When using reverse or engine/axle braking, the regular keyed hub will do the work.

Edit: I already see the problem with that setup. Turning in one direction would allow for the wheels to turn at different rates, but the other direction would lock up the one way hub and the whole axle assembly would essentially behave like a normal live axle setup.

 

[fowler]

Also if u stall going uphill
U are buggered
Unless u sort out the brakes and make them good

Surely investing in building a decent priced chain drive diff would be better
Really there are only crap converted mower ones or hardcore offroad ones
Less moving parts, a lot simpler and safer

 

[christeeezy]

I don't know if creating a differential similar to the one toystory linked to would be simpler to make as opposed to a couple of hubs and rotors fabbed to a one way bearing.