The 2012 Aluminium Racing Toboggan Build Thread (pic heavy)

[OSR]

You could base the seat shape on a horse saddle which would help with the sliding forward:
http://en.wikipedia.org/wiki/File:EnglishSaddlePar...

[joe58]

Just a quick sketch. I understand what you mean about the suspension struts. In this 3/4 sketch it shows the simple concave seat. This will probably need a small skeleton of tubes under it to keep it's shape then the skin obviously.

Shown are the simple singular wishbones(One at each corner) attaching to more the inner edges. Hopefully these could be attached as shown in the red at either end?

The same attachment can be applied to the struts. Hopefully due to the low profile of the sled cycle struts could be used due to length restrictions.

The seat, could you get away will a more dense cushion cut to shape placed nearer the front and in theory leaning forward in you boots if you were skiing. Tried to design the thing as a sit down skier basically. Then you can put your bum up towards the cushion and legs over it, therefore eliminating you sliding forward. Also handles on the top edges of the main seat section will help steer/ carve.

[maser_spyder]

joe58 said:

Just a quick sketch. I understand what you mean about the suspension struts. In this 3/4 sketch it shows the simple concave seat. This will probably need a small skeleton of tubes under it to keep it's shape then the skin obviously.

Shown are the simple singular wishbones(One at each corner) attaching to more the inner edges. Hopefully these could be attached as shown in the red at either end?

The same attachment can be applied to the struts. Hopefully due to the low profile of the sled cycle struts could be used due to length restrictions.

The seat, could you get away will a more dense cushion cut to shape placed nearer the front and in theory leaning forward in you boots if you were skiing. Tried to design the thing as a sit down skier basically. Then you can put your bum up towards the cushion and legs over it, therefore eliminating you sliding forward. Also handles on the top edges of the main seat section will help steer/ carve.

'Quick sketch'? I built the last five of these on less detail than that.

I like the wishbone idea. It reminded me of the old RC car wishbones, with all the adjustable bits, and I don't see any reason I could sort of replicate a similar fashion, to make the angles adjustable for fine tuning.

A bit like these;



but the other way up.

And having thought about it, there's no reason the runners couldn't have handles themselves.

Adding a handle on each runner would give a bit of stability to the rider, something to grab hold of, and would ultimately allow better weight shifting and moving the angle of the runner directly at the same time.

Of course, I have NO idea how I'm going to actually make any of this.

[joe58]

That's why I'm knocking up a Google Sketch up. Here you can see my simple joints. I've oversized the holes of the so you can see the wishbones/ struts meeting up with them. Bolt through and nut on either end. Maybe through a washer in their of course. The struts would be a tricky part. (I've borrowed them from the database by a a guy called Waldo.)

But the Triangular holders with the holes in should be a easy to make and could take in your RC car principle easily.

Also shown is the separation between the black frame and the silver seat sheet metal.

[maser_spyder]

I feel distinctly amateur.

That looks superb.

[joe58]

Well I'm currently waiting for some of my group to recover from going out last night, so we can actually get on with some other design work(automotive design students...). That's why I could spare a morning messing around doing that.

But yeah that's a quick knock up of what I thought might work. I know I've been going on about carving and leaning, but will it turn like I want it to? Your originals have no steering, but only very narrow where as this is designed to be very planted having the opposite affect to agility and therefore steering?

But effectively it has a ladder chassis, which would allow other things to be attached, say a brake to the rear very easily. I have an idea for that too, but I'll let you do it as your versions also seem very good. I wasn't expecting to see all that frame work and suspension when first opening the thread.


I haven't done any research onto what else is out there so something similar may have already been done. It could be worth having a look, but I presume you've already done that.

So yeah my ideas I will let you get on with your own as I have stuff to do.

[tvrolet]

joe58 said:

That's why I'm knocking up a Google Sketch up. Here you can see my simple joints. I've oversized the holes of the so you can see the wishbones/ struts meeting up with them. Bolt through and nut on either end. Maybe through a washer in their of course. The struts would be a tricky part. (I've borrowed them from the database by a a guy called Waldo.)

But the Triangular holders with the holes in should be a easy to make and could take in your RC car principle easily.

Also shown is the separation between the black frame and the silver seat sheet metal.

Neat drawing. Only thing is you're relying on the joints for fore and aft stability of the runners. Can I suggest a small tie-bar from the front joint on the runner to the rear unsprung joint on the chassis.

Another thing that's just struck me (my how the mind wanders) is that folks have naturally assumed that there would have to be the same setup back and front. I was thinking that too for a while as that's how cars work and it's what we're familiar with. But is there a need here for the runners to be independently suspended back and front? Assuming they don't, then you'd only need the double wishbones and spring (or sngle wishbone and spring) at one end of the runner - the other end just needs a tie-rod along the same plane as the fixed length rod at the 'spring' end, so that would simplify things.

Simpler solution again has just stuck me - must stop typing and leave thread....

OK, imagine this - upside down transverse leaf spring attached to chassis at centre and ends attach to runners at front where I guess the weight is? If it's good enough for Corvette etc. At the other end of the runner there's a wishbone style link on the same plane as the leaf spring. So with just this the runners are firmly bound fore an aft, and have up and down suspension but so far their angle is still uncontrolled. So quite separately we have a single upright on the runners with a tie rod to the chassis with adjustable length and mounting holes. Mount the toe rod closer to the runner and there is more variation in camber under load, shorten/lengthen the tie rod to adjust static camber. Make sense?

[King David]

maser_spyder said:

This looks good in principle, but the problem would be actually making the damned thing!

Suspension is quite hard to find, and what's mostly out there is heavy, 700 lb/ft mountain bike kit, which is very stiff, and would allow much movement.

That said, I have a plan forming of a mix of this, and plan A above.

It's all got quite technical. Fantastic.

I should state from the offset that I don't have even the slightest level of engineering knowledge or ability. But have you looked at Mountain Board trucks? They are fairly wide and extremely tough and you can buy different stiffness shocks to moderate levels of lean.

http://www.extremekiteshop.com/kites/mbs-matrix-pr...

[J B L]

maser_spyder said:

So, it's that time of year again chaps, dust off your spikey-heeled shoes and crash helmets, and get ready to throw yourself down a mountain at 40mph on a glorified home-made tea tray.

For those who missed it last year, I had a stab at making what I was too tight to buy, and ended up going a bit OTT....

Yes. Me. Any chance of a link about last year's antics?

(sorry I'm not much of an engineer and can't design stuff.... I'd buy them though )

[joe58]

King David said:

maser_spyder said:

This looks good in principle, but the problem would be actually making the damned thing!

Suspension is quite hard to find, and what's mostly out there is heavy, 700 lb/ft mountain bike kit, which is very stiff, and would allow much movement.

That said, I have a plan forming of a mix of this, and plan A above.

It's all got quite technical. Fantastic.

I should state from the offset that I don't have even the slightest level of engineering knowledge or ability. But have you looked at Mountain Board trucks? They are fairly wide and extremely tough and you can buy different stiffness shocks to moderate levels of lean.

http://www.extremekiteshop.com/kites/mbs-matrix-pr...

I have a mountain board. They're not actually that wide, about 400mm. But they could work in some designs. And you could maybe lengthen the axle further.

[maser_spyder]

J B L said:

maser_spyder said:

So, it's that time of year again chaps, dust off your spikey-heeled shoes and crash helmets, and get ready to throw yourself down a mountain at 40mph on a glorified home-made tea tray.

For those who missed it last year, I had a stab at making what I was too tight to buy, and ended up going a bit OTT....

Yes. Me. Any chance of a link about last year's antics?

(sorry I'm not much of an engineer and can't design stuff.... I'd buy them though )

Here you go;

http://www.pistonheads.com/gassing/topic.asp?h=0&a...

[rhinochopig]

Bin the coil sprung shocks and go for some base model fox floats - they have no adjustability except for air pressure so you can run them very very soft if need be.

They are typically binned soon after purchase on full sus bikes because they lack the pro pedal / damping adjustment of the models higher up the range, and can be picked up very very cheap. Ideal for what you want.

To avoid the complexity of dampers / wishbones have you though about a tri-ski arrangement - similar to a disabled ski-chair. Large single in-line carving blade, which sits under your mass, with two slightly raised out-riggers to allow you lean onto these to turn?

[Life Saab Itch]

I think everyone is getting a bit complicated here.

If it was me I'd be looking to use the frame as it's own spring.

Mount the front and back of the runners to the frame solidly at the bottom (to keep the runner at the right angle, but pivoting at the top, then halfway along the runner, mount a strut with joints on to the opposite side of the base

The effect of this should be that if you lean to the left, the right runner gets pushed outwards in to a curve to turn you left.


This way is very "Colin Chapman" and should result in a light sled.

How much turn you get will depend on how much flex the runners have in them. I'd build them too thin, then if they are too flexible pour molten wax down them to stiffen them up, or something.

This will be a trial and error effort involving lots of lying around on the garage floor on it leaning and seeing if it changes the shape of the runner.

The idea is sound though.

[maser_spyder]

Life Saab Itch said:

I think everyone is getting a bit complicated here.

If it was me I'd be looking to use the frame as it's own spring.

Mount the front and back of the runners to the frame solidly at the bottom (to keep the runner at the right angle, but pivoting at the top, then halfway along the runner, mount a strut with joints on to the opposite side of the base

The effect of this should be that if you lean to the left, the right runner gets pushed outwards in to a curve to turn you left.


This way is very "Colin Chapman" and should result in a light sled.

How much turn you get will depend on how much flex the runners have in them. I'd build them too thin, then if they are too flexible pour molten wax down them to stiffen them up, or something.

This will be a trial and error effort involving lots of lying around on the garage floor on it leaning and seeing if it changes the shape of the runner.

The idea is sound though.

Now this was actually my original plan.

Basically take the 'simple' sled, but make the connection from the uprights to the runners slightly flexible (using car suspension bushes or similar), rather than solid (welded) arrangement. So there's flex, but not 'movement' on the runners.

Then use a fairly simple cross-brace, so that leaning on the left would push out the right hand runner, and basically 'weight' it. If possible, put another simple counter-brace in to un-weight the inside runner at the same time.

As you say, all very 'Chapman-esque', keeping it lightweight and simple.


Actually, I have a feeling the same bloody thing is going to happen as last year. I've already got five home-made toboggans, and that way it's going, I'm going to end up with at least another two or three.


1) Technical, adjustable wishbone type with quad suspension mounts and carving style runners.

+ Likely to be highly effective at turning corners, satisfying build (if it works).

- Difficult to fabricate with my basic skills. Likely to go badly wrong!


2) Basic, Lotus-style suspension design, with simple cross-bracing to weight the opposite runner.

+ Easy build, can probably do this in a day or two. Should be as good as the 'best' one from last year, but with improvements. Not likely to go wrong at all as it's so simple.

- Will still need to use hand/foot brakes to make cornering, to some extent, and hence lose speed.


Oh sod it. I'd better go and order some more aluminium.

[cazzer]

Its been a slow day

[maser_spyder]

King David said:

I should state from the offset that I don't have even the slightest level of engineering knowledge or ability. But have you looked at Mountain Board trucks? They are fairly wide and extremely tough and you can buy different stiffness shocks to moderate levels of lean.

http://www.extremekiteshop.com/kites/mbs-matrix-pr...

Looks great, I was thinking along the lines of cutting the end off, welding a plate on here, hacking a bit off there, then saw the price.

Shame, they'd be near perfect otherwise for a slightly different (number 3) design.

[maser_spyder]

doogz said:

Bit fiddly, and i've not exactly worked it through, but this is the first thing that popped into my head:



Fish plate with cut out to control rotation of upper end of 'leg' with a damper/spring to control compression, and a tie bar to hold it together.

10/10 for ingenuity, looks like a good little system.

But minus several million for seriously over-estimating what I'm capable of fabricating!

Just buying some ally now, tube, flat bar, rectangular tube. That's it.

Assume I'll be making this from Corn Flakes packets, and that would be nearer my level.

[maser_spyder]

cazzer said:

Its been a slow day

Race?

[Mattt]

I agree about junking the suspension, I'd be looking to connect the skis to the tray at the rear, so that when you shift your weight it will alter the angles of the skis.

[chevy-stu]

cazzer said:

Its been a slow day

Pretty much made already. My friends hire these every time we go away as they can't ski... Can be mad and dangerous but great fun..