1938 Le Super Triporteur Cyclauto

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I came across this which got me thinking along these lines:-



Key
Yellow = steering tube
Red = sprocket
Blue dotted = chain

Make it all much lighter and a decent seat. Get the gears in the proper positions on the handlebars rather than as suicide shifters and you can add any rear end of your choice. If it's a bit tall for you (20" wheel = backside at 25"ish) you could even add a step on the front of the cargo area. You could also lower it by starting off with a higher rake on the forks and bringing the bottom bracket lower too. The biggest limit would be the bars have to be able to turn well like a Pashley style trike does which will limit the recline of the seat. The front steering tube could be angled back slightly taking a liberty with the chain as derailleur gears do to assist in keeping the steering twistable. You could even make different rear ends and swap them on a couple of bolts and quick detach cable connectors.

The big plus of this system is the rider pivots with the front so no python hip dislocation. This thing could even turn in it's own length. The big drawback would be steering chain failure though I'd think it unlikely a chain would fail in such light use.
 
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Radical Brad

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It's a clever design! No induced pedal steer, no chain interference, and can use 26" wheels for most riders.
The only change I would make is to use a triple tree fork. A lot of stress will be put apon the fork crown, where the tem is welded to the fork.

Brad
 
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Interesting, but perching my 180# on top of a swiveling turntable just feels "dodgy" and my hip joints are screaming "Please Don't do this, if it comes off and you fall we will be broken!".
 
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Lay the forks back and you reduce the riders height and you also get a measure of lean into the corner. The lean is fixed to the angle of turn so is not an independent choice.



You can also have USS. The bar holding the lower bottom bracket passes through the chain. Here you are limited to the amount of turn generated by the width of the bars as eventually they foul on the chassis to the rear. It still generates a lot of turn though. Rods and rod ends can always still be used instead of chain similar to the 1938 original. Rods will limit turn over chain but on this latest design that would be unlikely to be limiting.

 
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One interesting point regarding laying the forks back that has just come to me is that the more laid back the forks the greater the self-centring effect as the riders weight is effectively brought to the lowest level without input which is front wheel straight ahead. Turning the bars raises the rider as the wheel turns. In effect this is the same phenomenon as a python but without the hip twisting and without the pedal steer effect. If you go too far in lowering the forks not only do you loose steering but you also have to raise your bodyweight further with the same leverage. Just as with a python there'll be an optimum balance between centring effect and effort to turn. This will not be a fixed optimum as per the python but will vary according to the lard and strength of the rider (weight and strength generally go togther within a variation). The optimum balance will also be decided by the typical speed and corners the cycle is used for as you'd want to balance the lean into corners to work on an average. Slower corners would want to ease you to the lower side and faster ones the upper. It would be better if the lean was not a tied factor but it'll hardly be worse than being thrown to the side on a std non-leaning trike in a corner.

The more I think about it this is indeed a very workable system. In particular the latter one with USS. I'd use rods instead of a chain to take any slack out and it'd also be easier to build with rods. Use wide bars and keep the distance between steering tubes small to maximise turn and I think you get a 26" wheel or even bigger in there as the bottom bracket can always rotate nearer to the seat if needed and all you'd need is sufficient inside leg to get over the wheel and an inch or so of steel. A bit of ingenuity and the bottom bracket can be made adjustable to rotate as needed, sliding around the top curved mount. So long as the deraileur rotates too adjustment could be huge. If the derailleur doesn't move there'd still be a fair amount of scope to swing the BB within the scope of the derailleur's ability to cope. Better still use an IGH and swinging the BB is a doddle. I think this latter USS version balances ease of mounting, a comfortable height and still sufficiently low to be stable. Stability would of course be much better due to the lean factor over a regular delta of the same rider height. Front end grip in a corner should be much better than most deltas too as your weight is over the wheel. The biggest drawback I can see to such a design is that you are ripping up the chassis rulebook on triangulating. In fact you're giving it to the dog to savage and then flushing it down the pan. The connection from the front BB to the rear chassis is used in beam though no worse than a Warrior but the seat mount is going to need to be substantial. In my case more substantial than most and the steering tube passing through is going to need to be beefed up too. It's more than possible that steering bearings won't hold up and a pukka bearing system is likely to be needed like Danny's PPP.
 
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A bend in the bars to bring them forward allows more turn and suspension in the middle which as well as comfort goes some way to destressing that joining beam. Short as a python, without the quirks yet with decent size wheels and off the floor. I was going to pause on building after the Drypod but this has got me quite excited. I'd better go lie down. The python is dead, long live the reheated 1938 design! I'll call it the Twister.


 
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Taking Brad's point about a triple tree, I've moved the seat forwards so that extra long forks can come straight through the triple tree to make the mount for the seat. This will reduce stress and weight accordingly. It does mount the rider higher but not by much. The chassis is now a flatbed made to a size convenient for a large storage box or two. Boxes to be easily mounted / dismounted as needed. I have a triple tree set from a Kawasaki 900 that will only require an outer casing making for the headstock bearing. I doubt the fork inners are long enough but they can be extended if needed for the seat mount.

 
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I recall from the old forum someone visiting, in the states, a small manufacturer of a similar cargo trike.
It was a cargo box with the rider high over the front wheel.
It was probably 3-4 years ago.
Someone else remember this?
 
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I was looking at that one recently whilst thinking about the 1938 design. This one is slightly different and indeed quite a few designs use the same system. This one is a 45 degree or so pivot with fixed bars quite wide apart so you turn by pulling / pushing on the bars and you roll towards one or other bar as you turn. The bars must be wide spaced to allow the room for that rolling action. It's in effect a simpler but similar design. I do wonder about it's self-centring* though as the rider is at the highest point straight ahead and any turn lowers them. There is a small amount of self-centring in the riderless design but adding a rider would appear to more than offset that. I suspect that it'll be fundamentally unstable unless balanced. That's not to say it would be any harder to ride than any regular bike. I simply don't know the answer to that one but it wouldn't come to a stop and keep you upright without some pressure on the bars holding you in place.

The biggest difference in the 1938 rehash is that the bars behave like regular USS bars do and if I sort out the issue below will be balanced at rest.

* I have just realised I have designed out the self-centring in my last design by lifting the rider forward of the forks. Some design work still to do. The second to last design had the centre of the riders weight below the pivot so at rest the rider keeps the wheel dead ahead and so the trike is stable whilst stationary. I've lost that in the last design and need to move the rider back somewhat in relation to the pivot.
 
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