Hypothetical design

DIscuss anything relating to non-standard cycles and their equipment.
Grldtnr
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Joined: 11 Jun 2020, 7:04pm

Hypothetical design

Post by Grldtnr »

I will have to wait for my multi million lotto win to come in, but I would like to build a FWD,steer, braked recumbent tadpole trike, suspension all round, with a tilting facility, carbon fibre chassis is on the wish list.
The tech is out there, one of the simplest cars the 2CV employs the technology FWD ,inboard disc brakes,very pliant suspension, so why can't I have that on my dream machine?
Mike Burrows might be the go to engineer for this imaginery project.
Or is one available already?
A laid back, low down, layabout recumbent triker!
Jdsk
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Re: Hypothetical desigin

Post by Jdsk »

Why FWD, and what are your thoughts about the drivetrain?

Jonathan
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[XAP]Bob
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Re: Hypothetical desigin

Post by [XAP]Bob »

Weight
A shortcut has to be a challenge, otherwise it would just be the way. No situation is so dire that panic cannot make it worse.
There are two kinds of people in this world: those can extrapolate from incomplete data.
Grldtnr
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Re: Hypothetical desigin

Post by Grldtnr »

Jdsk wrote:Why FWD, and what are your thoughts about the drivetrain?

Jonathan


Hypothetically, FWD coz a short chain run, depending on how far the front axle is, it should give traction, and handling,thinking of a differential , Longstaff used to build his own putting 2 freewheel bodies back to back.

Weight shouldnt be a problem if built of Carbon fibre, the drive train probably needs to be metal.
A laid back, low down, layabout recumbent triker!
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Tigerbiten
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Re: Hypothetical desigin

Post by Tigerbiten »

FWD has been tried in tadpole trike but it's never been very successfully implemented.

Back Wheels are easy because they don't need to turn.
Front wheels are much more complex because you need some form of CV joint in the kingpins.
Then you want it to tip which adds at least another set of UV joints to an already complex setup.
Then depending on how it's setup the half shafts may well alter in length slightly, this must be also be accommodated for if needed.
So not simple.

Luck ............. :D
hercule
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Re: Hypothetical desigin

Post by hercule »

Front wheel drive:
http://www.eland.org.uk/s327.html
"Denman" on Bentrider Online also built a FWD tadpole but it never entered production afaik... pictures of it looked really good though

All wheel drive:
https://tadpolerider2.wordpress.com/201 ... happening/

Tilting:
http://www.tripendo.de/galerie

Carbon Fibre:
http://carbontrikes.com (now working with Bacchetta)

As [XAP]Bob says, the more complications you add to the machine the more challenged your 1 human-powered engine will be - by weight and power losses in the transmission. The differential on my Kettwiesel definitely eats up some of my meagre power output, though a straight power side chain line does compensate. My VTX is as simple as it gets and it's a very good (quick, comfortable and light) machine. Though my FS Trice QNT is still hard to beat.

I don't know if the Steintrikes Wild Wave entered production: https://tadpolerider2.wordpress.com/201 ... ing-trike/
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[XAP]Bob
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Re: Hypothetical design

Post by [XAP]Bob »

My assumption is that a dual freewheel should be pretty darned efficient - particularly if designed to be a single unit, rather than needing a jack shaft and three chains.
A shortcut has to be a challenge, otherwise it would just be the way. No situation is so dire that panic cannot make it worse.
There are two kinds of people in this world: those can extrapolate from incomplete data.
Grldtnr
Posts: 233
Joined: 11 Jun 2020, 7:04pm

Re: Hypothetical design

Post by Grldtnr »

[XAP]Bob wrote:My assumption is that a dual freewheel should be pretty darned efficient - particularly if designed to be a single unit, rather than needing a jack shaft and three chains.

It was a particularly smart piece of bodging on Geo.Longstaffs part, he did some lovely stuff,met him briefly.
Anyway, this is all a design exercise, let's just say a bit of navel gazing after a lot of pints of stout, and a plateful of cheese!
I should imagine, the wheelbase could be short, but how far away could the front axle be without making it twitchy? Bearing in mind the requirement of FWD , it may be best not to have the front axle underneath the bum, that might make it nose dive and dump you under harsh braking, that means having disc brakes to simplify things,perhaps inboard .
Unfortunately my numbers haven't come in yet;
A laid back, low down, layabout recumbent triker!
Jdsk
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Joined: 5 Mar 2019, 5:42pm

Re: Hypothetical design

Post by Jdsk »

Would inboard brakes mean half-shafts? Or are you thinking of braking near a chainwheel distal to the freewheel(s)?

Jonathan
Grldtnr
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Re: Hypothetical desigin

Post by Grldtnr »

hercule wrote:Front wheel drive:
http://www.eland.org.uk/s327.html
"Denman" on Bentrider Online also built a FWD tadpole but it never entered production afaik... pictures of it looked really good though

All wheel drive:
https://tadpolerider2.wordpress.com/201 ... happening/

Tilting:
http://www.tripendo.de/galerie

Carbon Fibre:
http://carbontrikes.com (now working with Bacchetta)

As [XAP]Bob says, the more complications you add to the machine the more challenged your 1 human-powered engine will be - by weight and power losses in the transmission. The differential on my Kettwiesel definitely eats up some of my meagre power output, though a straight power side chain line does compensate. My VTX is as simple as it gets and it's a very good (quick, comfortable and light) machine. Though my FS Trice QNT is still hard to beat.

I don't know if the Steintrikes Wild Wave entered production: https://tadpolerider2.wordpress.com/201 ... ing-trike/



AHH ha! Hercule, just read your posting, so it had been done before, I liked the pic's you linked to particularly lusted after the carbon fibre look ones, so it's just now a question of that lotto win!
A laid back, low down, layabout recumbent triker!
speedy7777
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Joined: 24 Sep 2017, 11:20pm

Re: Hypothetical design

Post by speedy7777 »

The velo-tilt ticks several boxes but isnt tadpole. Someone in USA has bought the entire project and is planning to produce them.
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[XAP]Bob
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Re: Hypothetical design

Post by [XAP]Bob »

The disadvantages of a tadpole are basically eliminated by having it as a tilting trike
A shortcut has to be a challenge, otherwise it would just be the way. No situation is so dire that panic cannot make it worse.
There are two kinds of people in this world: those can extrapolate from incomplete data.
StephenW
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Joined: 22 Sep 2010, 11:33am

Re: Hypothetical design

Post by StephenW »

If you had rear wheel steering then you could make the drivetrain simpler. You wouldn't need CV joints any more. This would be lighter and more efficient. It would also allow the width of the vehicle to be reduced, because the front wheels wouldn't need the space to steer any more. This could improve aerodynamics.

You could also get rid of the universal joints if you wanted to - I can think of two ways of doing this:
1. Non-independent front suspension AKA a live axle. This could be suspended either by a five-bar linkage (four trailing arms and a Panhard rod) with coil springs, or with leaf springs. The cassette, derailleur and double freewheel would be in the middle of this axle. I'm not sure if this would result in a higher vehicle overall because the axle would be cutting across at hub height and might get in the way of the rider's legs. In general non-independent front suspension is considered a bad thing, because going over a bump on one side of the vehicle only results in gyroscopic forces from the wheels which are not cancelled out, affecting the steering. But that is with front steering; I'm not sure of the effect with rear steering.

2. Leading arms (like on a 2CV), with a separate chain going to each wheel. There would be a jackshaft (slightly in front of the rider's bottom), with the derailleur and double freewheel in the middle and a sprocket at each end. These sprockets would be connected to the hubs by short lengths of chain, one on each side. Although this introduces an extra stage to the drivetrain, if the sprockets are reasonably large and and positioned so the chain length doesn't change with the suspension going up and down (so no tensioner is needed), the losses might be small.

I reckon option 1 could be fast in a straight line but terrible going round corners or on uneven surfaces.

Also, I think it is difficult to design a vehicle that handles well with rear steering! (But maybe computers could help?)
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[XAP]Bob
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Re: Hypothetical design

Post by [XAP]Bob »

Rear wheel steering is not generally considered a good thing on a road vehicle - partly because in order to turn away from something (say the kerb, or an oncoming lorry) you have to move the rear of the vehicle *towards* that thing.

With a trike that might not be a big issue since the “towards” might remain within track width, but it’s not a given.

I also suspect it’s harder to get a stable and predictable rear wheel steering assembly - though of course the fastest car of all time had rear wheel steering.
A shortcut has to be a challenge, otherwise it would just be the way. No situation is so dire that panic cannot make it worse.
There are two kinds of people in this world: those can extrapolate from incomplete data.
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simonineaston
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Re: Hypothetical design

Post by simonineaston »

Well all I'm saying is that if they can develop cable-free charging for my phone, surely someone can devise a chain-free cycle drive...
S
(on the look out for Armageddon, on board a Brompton nano & ever-changing Moultons)
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