Turbo LS3 powered Slingshot

[Denis]

this looks like it could be fun...but kind of a lot of power through 1 tire

http://www.lsxtv.com/news/swap-insan...led-slingshot/

[DGthe3]

A lot of power though 1 wheels, yes. And that gets compounded when you realize that the rear wheel is only supporting some 600 lbs of weight. Less weight = less traction. Wouldn't surprise me if that thing could spin the rear wheel in any gear.

But bravo to them for actually building it. Its not too often that a vehicle gets an engine swap to quadruple the horsepower.

[BAD DAB]

Thats bad@$$

[Denis]

Originally Posted by DGthe3

A lot of power though 1 wheels, yes. And that gets compounded when you realize that the rear wheel is only supporting some 600 lbs of weight. Less weight = less traction. Wouldn't surprise me if that thing could spin the rear wheel in any gear.

But bravo to them for actually building it. Its not too often that a vehicle gets an engine swap to quadruple the horsepower.

oh true, i didnt even think about the weight. sounds like its just going to be a smoke machine

[trademaster]

Originally Posted by DGthe3

A lot of power though 1 wheels, yes. And that gets compounded when you realize that the rear wheel is only supporting some 600 lbs of weight. Less weight = less traction. Wouldn't surprise me if that thing could spin the rear wheel in any gear.

But bravo to them for actually building it. Its not too often that a vehicle gets an engine swap to quadruple the horsepower.

Less weight = less traction, but less weight also = less required force to accelerate at a given rate. Tires spin because there isn't enough traction to transfer the necessary force to accelerate the vehicle at a rate equivalent to the acceleration of the tire's rotation.

F = MA -> A = F/M

If you cut the mass in half, the required force to accelerate at a given rate is also cut in half (less inertia). Really, the biggest difference maker is the weight distribution and contact patch due to the weight. Obviously, this is oversimplified because there are numerous force vectors, but it probably doesn't spin as horribly as you would imagine. It has so little mass to move.

[DGthe3]

Originally Posted by trademaster

Less weight = less traction, but less weight also = less required force to accelerate at a given rate. Tires spin because there isn't enough traction to transfer the necessary force to accelerate the vehicle at a rate equivalent to the acceleration of the tire's rotation.

F = MA -> A = F/M

If you cut the mass in half, the required force to accelerate at a given rate is also cut in half (less inertia). Really, the biggest difference maker is the weight distribution and contact patch due to the weight. Obviously, this is oversimplified because there are numerous force vectors, but it probably doesn't spin as horribly as you would imagine. It has so little mass to move.

I never said it would be slow to accelerate.

To further specify your reason for why a tire spins: its because at that given wheel speed, the torque divided by tire radius exceeds the frictional co-efficient multiplied by the normal force at that wheel.

Since physics is often incomprehensible when its just a jumble of words:

Rear wheel power = torque x wheel speed
Torque = rear wheel power / wheel speed
Torque = force x distance
Force = torque / distance

therefore

Force = (power / wheel speed) / distance

On the other side of things:

Normal force = mass x gravity x % weight distribution
Frictional force = co-efficient of static friction x normal force

The Force at the contact patch =

Torque / radius(tire) = co-efficient of static friction x normal force

Or ...

F= (P/w)/r = mu(s) x N

If the power side exceeds the friction side, the wheel spins. Note that power and normal force are in direct proportion to each other. Consequently, the smaller the normal force, the less power can be used. But the faster you go, the more power you can use.

Since the slingshot is very light, the maximum amount of power that it can apply is fairly low. At higher speeds, more power can be put down. But it could very well be that with the trike being so light, and the engine so powerful that even in 5th gear, the engine might still exceed the friction limit. Hence, my post.


Also ... you didn't fully work out the implications of Newtons second law:

(I'm sick of word equations at this point ... )

(1) F = ma = mu(N)
(2) N = mg
sub (2) into (1)

F= ma = mu(mg)

masses cancel, therefore:

a = mu(g)

When an accelerating force is based solely on contact friction, mass becomes irrelevant.






*edit*
I'm ignoring the effect of inertia & lift/downforce as speeds increase

[shank0668]

Originally Posted by DGthe3

I never said it would be slow to accelerate.

To further specify your reason for why a tire spins: its because at that given wheel speed, the torque divided by tire radius exceeds the frictional co-efficient multiplied by the normal force at that wheel.

Since physics is often incomprehensible when its just a jumble of words:

Rear wheel power = torque x wheel speed
Torque = rear wheel power / wheel speed
Torque = force x distance
Force = torque / distance

therefore

Force = (power / wheel speed) / distance

On the other side of things:

Normal force = mass x gravity x % weight distribution
Frictional force = co-efficient of static friction x normal force

The Force at the contact patch =

Torque / radius(tire) = co-efficient of static friction x normal force

Or ...

F= (P/w)/r = mu(s) x N

If the power side exceeds the friction side, the wheel spins. Note that power and normal force are in direct proportion to each other. Consequently, the smaller the normal force, the less power can be used. But the faster you go, the more power you can use.

Since the slingshot is very light, the maximum amount of power that it can apply is fairly low. At higher speeds, more power can be put down. But it could very well be that with the trike being so light, and the engine so powerful that even in 5th gear, the engine might still exceed the friction limit. Hence, my post.


Also ... you didn't fully work out the implications of Newtons second law:

(I'm sick of word equations at this point ... )

(1) F = ma = mu(N)
(2) N = mg
sub (2) into (1)

F= ma = mu(mg)

masses cancel, therefore:

a = mu(g)

When an accelerating force is based solely on contact friction, mass becomes irrelevant.

Very thankful to be reminded of physics while attempting to relax and disconnect myself from my studies

[DGthe3]

Originally Posted by shank0668

Very thankful to be reminded of physics while attempting to relax and disconnect myself from my studies

You're welcome. I too find classical physics to be relaxing.

On a related note ... I am very glad that engineering is based off of Newtonian rather than quantum mechanics.