FORWARD weight transfer under acceleration (go-karting)?

[West]

My friend is having trouble on corner exit with a go-kart. He claims that once he gets on the gas, weight is being transferred FORWARD. I don't think this is possible in reality, but I can't offer any solutions. Maybe go-karters can chime in on this.

Here are the specs on his cart:

Chassis: Emmick Eclipse 2009, 32mm Tubing, 50mm Axle. 9 Bend chassis, 5 rear axle bearing, CRG VEN08 Brake, Duracon Wheels, MG Grey tires, tire pressure hot 32psi, Rear axle Duracon, Stiff, 48mm axle. Seat Ribtect Euro Spec, engine is Mike Wilson 125cc. 50mm is the front axle size, rear is 48mm.

[Belatti]

Is he driving in reverse?

[donskar]

Is he driving in reverse?

The answer is obvious -- sprung wheelie bars!

[Jersey Tom]

Don't think he's quite got it right.

But in any event. Has problem on corner exit... with what?

[West]

Don't think he's quite got it right.

But in any event. Has problem on corner exit... with what?

I'm sure he knows weight transfer thing is incorrect... but he says the rear end is lifting when he gets on the gas out of a corner. This isn't possible so I am trying to get more info from him.

PS:

"Ok without over complicating the problem, here is the main issue that I’m facing.



Exiting a hair pin corner, or any corner that requires heavy braking beforehand. As I reach the apex, apply throttle and unwind the steering wheel. Both rear tire will lift up, the kart essentially will be driving on 2 front wheels for a second or two, I can hear the engine spinning up rapidly because of this. The track is quite flat with no bumps.

Track is flat asphalt. Yes I’m sure it is flat as I’ve walked the track many time before morning sessions. This has never happened before with my other karts, something about this chassis with 48mm rear axle, and 5 rear bearing supports

I can physically feel the rear end of the kart getting higher, than dropping down. It’s as if I hit a bump, but there’s no bump to hit, and also the sensation is very smooth lift up, not an abrupt one when u hit a bump."

[Jersey Tom]

Sounds more like he's just lifting the inside rear.

[Ciro Pabón]

Wow. That I've never seen. JTom theory is no good: karts have no differential, for the engine to rev, it has to lift both wheels.

I'll call Dr. House and will be back. I love misteries. It has never happened to me, but it has to have a reason. I would love to make a few phone calls and google as mad, but I'm mighty busy.

[rjsa]

Might be too obvious, but is the frame intact? No undesired torsion or bending? No cracks?

Seems like something is snapping and outer rear gives up and then it falls back with the two rears on the ground.

[sticky667]

Why is he running 5 bearing supports? seems like the rear is way way too stiff. On corner exit, the weight transfer would be on the rear axle combined with the weight of the engine and the driver, he shouldn't be lifted off of the circuit at all.


Also, kart tires don't like 32 psi normally. usually less than 20psi is optimum. I'm a head mechanic for an 100cc Tony kart team and we normally run no more than 14-16psi hot on all four corners at places like Grange, Adams, CalSpeed

[Jersey Tom]

Wow. That I've never seen. JTom theory is no good: karts have no differential, for the engine to rev, it has to lift both wheels.

I'll call Dr. House and will be back. I love misteries. It has never happened to me, but it has to have a reason. I would love to make a few phone calls and google as mad, but I'm mighty busy.

Don't be too quick to judge. Diff doesn't matter. For the engine to rev, it just needs to start to break traction. If it's tight enough corner with enough gearing and lateral load I wouldn't be surprised if leaning on 1 rear tire you could get the thing to spin up/slide

If 5 bearing supports is super stiff as rear "suspensions" go, the inside lifting makes a lot of sense along with it FEELING like the rear end is coming up.

[Belatti]

The lifting feeling is just that: a feeling.

He has incorrect tyre pressure and a very very stiff rear.

The pressure for MG greys (HZ if I recall) is 14psi.

More tire info here:
https://www.mgtires.com/site2008/com/index.php?request=produtos_detalhes&valormenu=stop&id=4

Just let 3 bearings, the one in the middle unbolted.

[Scotracer]

Is he driving in reverse?

Oh oh oh oh where can I get a reverse for my kart? It would make those parallel parks much easier!

[West]

Thanks for the answers, but we've all been had:

"Yeah I’ll try them in my dream, if I ever dreamed of this happening again.



Hahaha go karts only have 3 bearing max dude ,and axle size is either 50mm or 40mm, wth is a duracon? Mike Wilson engine? Loll"

I don't know what's more annoying... taking time to create this thread w/ some realistic replies, or the fact that he spent his time making this sh*t up.

[epitaf]

While it's pretty fun playing House with the go kart, an obvious solution is to physically look at what's happening when he has troubles, as the majot sticking point is that we can't determine what is actually happening...

*puts on house hat* He might be shifting his bodyweight forward when he moves the wheel back, a person's bodyweight is pretty significant compared to a cart

[Jersey Tom]

Thanks for the answers, but we've all been had:

"Yeah I’ll try them in my dream, if I ever dreamed of this happening again.



Hahaha go karts only have 3 bearing max dude ,and axle size is either 50mm or 40mm, wth is a duracon? Mike Wilson engine? Loll"

I don't know what's more annoying... taking time to create this thread w/ some realistic replies, or the fact that he spent his time making this sh*t up.

Well he can --- himself then