Interesting idea 2T3 delta trike

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Hi all

The Finnish forum has a couple of interesting delta trikes not seen anywhere else ? they call them 2T3 for 2 tracks 3 wheels

this one ended up with a body

So the idea is the trike only has 2 tracks , must make it easier to find a path on snow covered roads ?



A lower version , interesting as they steer both the wheels on one side !



The top version did acquire a steering damper during development.

drawing wrong way around and I have draw the single wheel in middle rather than nearer seat.

However where is the trike stability triangle [ red dashed line ? ] does not look right ? or does it follow red dotted line instead ?
It almost looks like you are sat alongside a 2 wheel recumbent with the wheel on a side car on the other side ?

Does it really need rear wheel steering ? if not it would be easy to drive both rear[ish] wheels ?
Also then it could be built with 3 x 20" suspension forks and be fully suspended ?

Just curious before I start cutting metal for my delta [ in my head [ there are Python things to attend to first :D]]

Paul
 
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I doubt it needs rws any more than any delta does. The dashed line is right but if you move the single side wheel back to where the examples have it the area then encompasses the rider. They've made the rear wheel steer less than the front by giving less ratio to the the rear on the central steering pivot at the side. It's notable that despite plenty of snow, being Finland, they have prioritised rws over 2wd. How much is 2wd really needed? It's extra weight but is it extra benefit?
 
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It's notable that despite plenty of snow, being Finland, they have prioritised rws over 2wd. How much is 2wd really needed? It's extra weight but is it extra benefit?
I think they all use studded tyres in the winter , 1wd is great till the situation occurs when you need 2wd ;)

Paul
 
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There's only 1 steering lever which equalls one brake lever, though a static mount could be made to mount another. It's interesting that having one lever the rider still appears to reach over to get both hands on it. Those chassis look very flexible!

Having rws does mean a big caster can be used and still get good lock. That high caster front and rear on the steering side does mean some wheel lean which will help the tyres dig in on a corner
 
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There's only 1 steering lever which equalls one brake lever, though a static mount could be made to mount another. It's interesting that having one lever the rider still appears to reach over to get both hands on it.
Possibly a bar end shifter ?

Those chassis look very flexible!
I believe the upper one was made from 25mm tubing and was described as very elastic when being ridden. It had a body and was very portly apparently.





Signs of being ridden



The end !

Having rws does mean a big caster can be used and still get good lock. That high caster front and rear on the steering side does mean some wheel lean which will help the tyres dig in on a corner
I suspect the 2 wheel steering is because the front wheel has limited lock turning right , however for a delta it is quite compact in length.

Paul
 
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Curiouser and curiouser. It should turn left as easily as right as the type of steering employed is no more limited one way than the other. The seat only has lateral support at one side! The rear employs more caster than the front and as such will lean into the turn more than the front. It could be shorter still without the rws but nowhere near as funky. A most interesting trike design.
 
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Hi all

The Finnish forum has a couple of interesting delta trikes not seen anywhere else ? they call them 2T3 for 2 tracks 3 wheels

this one ended up with a body

So the idea is the trike only has 2 tracks , must make it easier to find a path on snow covered roads
There being not many new inventions in cycling, that looks like a recumbent version of a Coventry Rotary Tricycle layout wise. Fascinating to see a over a century later, good find!
 
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Curiouser and curiouser. It should turn left as easily as right as the type of steering employed is no more limited one way than the other. The seat only has lateral support at one side! The rear employs more caster than the front and as such will lean into the turn more than the front. It could be shorter still without the rws but nowhere near as funky. A most interesting trike design.
From the animation it looks like it interferes with the frame when turning right ?
Of course you could build that out anyway.

Paul
 
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There being not many new inventions in cycling, that looks like a recumbent version of a Coventry Rotary Tricycle layout wise. Fascinating to see a over a century later, good find!
yes correct , nothing new under the sun



UK Ebay has some replicas for sale Rotary tricycle original 1839
Paul
 
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So due to the kindness of Dale Rider I have a 20" front suspension bike [ I really only wanted the forks ] I do have a couple of similar frames.

So the mind started to wander and this came to the front...



If I joined both frames together discarding the middle wheel I would have 2/3'rds of a 2T3 trike ? with full suspension ?

The missing piece [ the lone wheel on the other side could also be suspension and would need to be driven from the pedals.

Best guess at wheel base would be 66" as simply bolted through existing axle holes.
shorter by cutting chain stays
to really as long as I wanted by adding a joining piece chain stays to chain stays and seat post to seat post ?

Probably have to be longer a pedals would need to be in existing front place and I need to clear rear wheel [ if it was set up for steering ?

Wondered if bolt through axle holes could be a pivot and spring mounted across seat post enabling it to scissor in the middle ? may not be stiff enough in vertical direction ?

Paul [ mad ideas factory ]
 
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not at all "Bonkers" :) Love it.
 
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not at all "Bonkers" :) Love it.
The current mental stumbling block is only 1 lever for steering , ok for around my local estate however not happy with that for longer rides ?

Need to find a way of having tank steering with 2 levers and not one ?

Or offset the steering at the fork end for a central steering column/wheel [ maybe 2 sprockets and a chain ? ] , then connect front and rear fork together down one side as pictured ?

Paul
 
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I remain to be convinced that the two tracks approach offers any real world benefit over a more conventional design. Interesting for sure but better?
 
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I remain to be convinced that the two tracks approach offers any real world benefit over a more conventional design.
+1 on that ;)

Interesting for sure but better?
Suppose that depends on whether you perceive there to be any problems with a traditional delta ?
it would certainly let you sit at the widest point of the stability triangle , and over the axle of the driven wheel without compromising the luggage space ?

Paul
 
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Hi guys. This seemed to me like a rather awkward machine but maybe the plus points Paul just noted do actually give it some merit ?

I've been looking at the layout of those wheels and trying to imagine cornering and I think the rear wheel steering may be a necessity. Trying to imagine the thing turning without it seems to be likely to produce horrible tyre scrub. I'm not hot on geometry but it lookd to me that because the two 'rear' wheels are so offset one of them would need to travel sideways a fair bit to manage traveling along a curved path. I think the rear steered wheel actually needs to be pointed at an angle to the other side to make a smooth turn?

Am I right? If I'm not it certainly wouldn't be the first time :) I'd love to see you build one Paul. I wonder if it would help getting through those doglegs you need to negotiate?

John
 
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Hi guys. This seemed to me like a rather awkward machine but maybe the plus points Paul just noted do actually give it some merit ?

I've been looking at the layout of those wheels and trying to imagine cornering and I think the rear wheel steering may be a necessity. Trying to imagine the thing turning without it seems to be likely to produce horrible tyre scrub. I'm not hot on geometry but it lookd to me that because the two 'rear' wheels are so offset one of them would need to travel sideways a fair bit to manage traveling along a curved path. I think the rear steered wheel actually needs to be pointed at an angle to the other side to make a smooth turn?

Am I right? If I'm not it certainly wouldn't be the first time :) I'd love to see you build one Paul. I wonder if it would help getting through those doglegs you need to negotiate?

John
John

Good point well made.

As you say maybe someone needs to take one for the team ?

Currently undecided which way around to build it ? 1 wheel on left or 1 wheel on right
and whether to try 2 wheel steering or 2 wheel drive ?

Paul
 
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A review after dismantling was provided:-

Räntis was dismantled in late January 2021, after teaching that:

Rear steering failed. Too big a waste. Without the steering wheel, it didn't work at all. The steering wheel started to wobble from side to side.

The whole device is too heavy. Going electric makes it easier, but the range of the battery is too short.

Z-crankshaft too slack.

A chain that is too long gives a rubber-band-like pedal feel, and when riding on a bike, the chain starts to bounce up and down and eventually leaves the front sprocket.

The attachment of the bench
[ seat ] to one 25mm round tube is bad. The staff [ rider ] always wants to slowly turn sideways.

The roof was missing and there was too little trunk space, otherwise, in such a huge bike.

Well, was it worth doing in the first place? It was really worth it.
The 2T3 is a great design, because the two driving grooves and the overpasses are much easier than a symmetrical tricycle. Sufficient traction with a towing bike, but not too much weight. The puck lasted well.
[ body I assume ]
A covered bike is warm to ride in cold weather.
A lot of understanding came from control geometries.
There were many interested people and even more astonished onlookers.

Would I make an improved version again?
Yes, I could do it someday, but maybe I would leave out the rear steering completely, and battery technology has to develop tremendously before such a heavy bike can actually be driven.


I have highlighted the main bit's and added some comments in brackets in red.
Odd it was to heavy as it was 25mm tubing [ although a lot of it ] and Coroplast body.

paul
 
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Heavy is a relative term and I wouldn't have described the trikes shown as heavy but rather as flexible due too little chassis. Given these were Scandinavian they probably have many hills so any weight above a diamond frame bike is possibly a crippler. The rear steer wobble issue is probably exacerbated by a single steering arm. For me the picture of the rider getting two hands on the one arm is very telling. I suspect that with two handed steering that instantly becomes much less of a problem to the extent it may be controllable by a damper. I certainly wouldn't entertain such a machine without a change to get double handed steering. A simple way to get both hands in play is to use a large U shaped set of bars so both go forward to steer one way and both back to steer the other. Not an ideal but simple and adds little weight beyong the extra piece of handlebar.

The further forward the single wheel goes the more the rear steer becomes necessary and the more it must steer in relation to the front. A traditional delta doesn't exhibit enough tyre scrub to be an issue. Now imagine a taddy with only one front wheel doing the steering - horrendous scrub. Now imagine a taddy with rear steer. Essentially a delta going backwards - no appreciable scrub again. If the single wheel is one third along the wheelbase you want a two to one steering ratio front to back. This is only in relation to tyre scrub and other factors may dictate a change to that.
 
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Nicely explained Darren. Much clearer in my fuddled head now.

I'm sure you and Paul and Danny could come up with a simple double arm steer or handlebar steer as in a 'normal' bent trike.

I also can't see weight being too much for the simple frame in the pics but as you say, flex probably would be. Again experienced builders could sort that out easily enough.

It would be nice to see what you 'old hands' could come up with in building this design just to prove the pluses and minuses of the thing.

John
 
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The steering could be sorted by use of a set of bevel gears.




The top shaft is nothing but a means to hold the gear. The other two shafts counter rotate. Add steering arms to those shafts and you get tank steering. One forward and one back and only one needs attaching to the central steering arm at the side of the trike. The weight of the system will probably be a price worth paying to get two hands on the job.
 
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