What Factors Affect Toboggan Speed?

[aldiver1]

I am competing in a National Toboggan Championship, (2 person division), and need some info on toboggan design. There are three factors that I can control and need some advice on, in laymans terms, please.

1) The sled can be 16 to 18 inches wide. The chute is 24" wide. Which would be faster?

2) The sled can be 6 to 8 feet long. Which would be faster?

3) The sled can either have a flat bottom, or have 3 "extended slats" or "runners". Which would be faster?

Thanks for any help.

Al

 

[JaredJames]

Well a sleek and slender profile would be key. Width should come down to the riders. If you can get away with 16, go with that. For length, again I'd go for 6 if you can get away with it, although that extra two feet might help get a better profile.

I'd try and get it as light as possible.

I'd use slats / runners on the bottom, minimise resistance.

I'd recommend you check up some professional designs as well.

 

[Curl]

If this is on softer snow then you want to maximize the area or else you "sink in" and it increases resistance.

Also do you have to make turns?

 

[JaredJames]

If this is on softer snow then you want to maximize the area or else you "sink in" and it increases resistance.

Also do you have to make turns?

By chute, I assumed it was like the olympic toboggan runs. Not so sure now.

 

[aldiver1]

Thanks for the replies.

BTW The toboggan will run in a 400' long iced chute.

 

[Phrak]

I am competing in a National Toboggan Championship, (2 person division), and need some info on toboggan design. There are three factors that I can control and need some advice on, in laymans terms, please.

1) The sled can be 16 to 18 inches wide. The chute is 24" wide. Which would be faster?

2) The sled can be 6 to 8 feet long. Which would be faster?

3) The sled can either have a flat bottom, or have 3 "extended slats" or "runners". Which would be faster?

Thanks for any help.

Al

First you should see what the winners have used.
Second. To obtain any valid advice on design, you should make the rule book for your competition available to those of us who might be capable of advising. Can you post it?
Third: Suspension is critical to gain an edge.

 

[K^2]

jarednjames' advice is spot on. If you can make it aerodynamic, and get it on descent runs, the rest pretty much depends on the riders. Narrow is good, but not if it compromises stability. Long is good, but not if it makes the thing heavier.

I'm not sure if suspension is a good idea. It would depend on how even the chute is. If the toboggan starts to "jump", it's obviously bad. But if the ride is just a little bumpy, I'd go with that rather than introduce suspension. Suspension is extra weight and it also effectively increases drag due to energy dissipation.

 

[Phrak]

jarednjames' advice is spot on. If you can make it aerodynamic, and get it on descent runs, the rest pretty much depends on the riders. Narrow is good, but not if it compromises stability. Long is good, but not if it makes the thing heavier.

I'm not sure if suspension is a good idea. It would depend on how even the chute is. If the toboggan starts to "jump", it's obviously bad. But if the ride is just a little bumpy, I'd go with that rather than introduce suspension. Suspension is extra weight and it also effectively increases drag due to energy dissipation.

jarednjames' advice is not spot on. Your advice is misinformed.

Weight, in and of itself, has nothing to do with elapsed time. Two rocks dropped off of the Tower of Pisa at the same time drop as fast as a single rock dropped alone. Rethink your premises. This is not rocket science. This is Newtonian Physics predating Newton himself.

Suspension is paramount in considerations to obtain the edge in this sport that measures success vs. failure in parts per thousand.

Weight indirectly effects aerodynamic drag and surface friction. These are the indirect effects of weight. Aerodynamic drag is minimally effected while surface drag is by comparison much larger.

Suspension effects surface friction. Suspension tells you how variations in surface irregularities are either recovered as momentum or dissipated as heat energy. Suspension is king.

 

[JaredJames]

jarednjames' advice is not spot on. Your advice is misinformed.

Weight, in and of itself, has nothing to do with elapsed time. Two rocks dropped off of the Tower of Pisa at the same time drop as fast as a single rock dropped alone. Rethink your premises. This is not rocket science. This is Newtonian Physics predating Newton himself.

Firstly, I never said weight affects the final time in that sense.

I might be thinking of the wrong sport. I figured there'd be some sort of run up (they run, jump on and they're away). So, being as light as possible would be an advantage to get them the best start. At least that was my line of thinking.

If there is no run up, I wouldn't worry about the weight affecting acceleration. You won't save bugger all on such a small scale, although I'm sure every little would help with drag in such a precise sport.

 

[K^2]

Weight, in and of itself, has nothing to do with elapsed time. Two rocks dropped off of the Tower of Pisa at the same time drop as fast as a single rock dropped alone. Rethink your premises. This is not rocket science. This is Newtonian Physics predating Newton himself.
[...]
Weight indirectly effects aerodynamic drag and surface friction. These are the indirect effects of weight. Aerodynamic drag is minimally effected while surface drag is by comparison much larger.

We can't have a discussion if you contradict yourself in one post. I'm wrong that he should reduce weight, but weight is going to increase surface friction which is a big concern?

Yeah, get back to me when you are ready to make sense on the topic of weight. On to suspension.

Suspension is paramount in considerations to obtain the edge in this sport that measures success vs. failure in parts per thousand.
[...]
Suspension effects surface friction. Suspension tells you how variations in surface irregularities are either recovered as momentum or dissipated as heat energy. Suspension is king.

How about considering how the suspension affects friction, eh? If you have a soft suspension with dissipation, the energy dissipated in suspension is kinetic energy lost.

The suspension is king because you want a very hard suspension for maximum speed. The harder, the better. If the surface is smooth, that means eliminating suspension all together saves you most time in the run.