Off the wall idea for a quad

stormbird

stormbird

0
So what could DannyC do with this ?
20210123-114254.jpg


Why not turn it into a proof of concept Python type quad ?

So he has already built a 2WD drive unit integrated into a quad rear axle ?

So he makes the pivot on the above trike vertical welds/bolts the 2WD unit in the front frame in place of the current IGH , puts the seat back on and gives it a spin.

Now before all you theorists tear the idea to pieces ...
1) only proof of concept ? the proof maybe ' it's a bad idea '
2) yes it will/may have bump steer ? [ so does MY quad !!! ] can it be lived with or controlled [ bungee , dampers etc ] see 1)
3) he has all the parts ?
4) he looks like a Test Dummy under certain lighting conditions ?

Don't forget in some circles my Python is considered the spawn of the devil and cannot possibly work [ sadly no one told it ;) (y) }
if it could work it would make an interesting pedal car as it removes a lot of the design restraints ie.
a) what to do with the chain
b) no Ackerman or centre point needed
c) race tracks are predominately smooth or very smooth
d) does it need caster ?
e) it could be built VERY low
f) probably short as well

Paul
 
stormbird said:
So what could DannyC do with this ?
20210123-114254.jpg


Why not turn it into a proof of concept Python type quad ?

So he has already built a 2WD drive unit integrated into a quad rear axle ?

So he makes the pivot on the above trike vertical welds/bolts the 2WD unit in the front frame in place of the current IGH , puts the seat back on and gives it a spin.

Now before all you theorists tear the idea to pieces ...
1) only proof of concept ? the proof maybe ' it's a bad idea '
2) yes it will/may have bump steer ? [ so does MY quad !!! ] can it be lived with or controlled [ bungee , dampers etc ] see 1)
3) he has all the parts ?
4) he looks like a Test Dummy under certain lighting conditions ?

Don't forget in some circles my Python is considered the spawn of the devil and cannot possibly work [ sadly no one told it ;) (y) }
if it could work it would make an interesting pedal car as it removes a lot of the design restraints ie.
a) what to do with the chain
b) no Ackerman or centre point needed
c) race tracks are predominately smooth or very smooth
d) does it need caster ?
e) it could be built VERY low
f) probably short as well

Paul
Click to expand...
I shall strip it for parts and post the frame to you. ;-)
 
A. Chain is no real issue
B. Centre point is no issue but Ackerman is. It is for any quad and no easy way of introducing it. The inside wheel will not describe a tighter circle so one or both tyres will scrub in a corner.
C. Smooth will likely be no benefit as a quad python needs some form of front axle swivel as the inside wheel would otherwise want to go down whilst the outside would go up. This would act to keep all wheels down.
D. Interesting question. Probably no more so than a trike python needs an accepted amount of trail.
E. It could be low but so can most layouts.
F. Shorter than some other layouts but a swb std quad design can be shorter as the python quad needs room for tiller steering which a std design doesn't.

The biggest drawback is probably the inner wheel wanting space the legs do because of that tiller steering. A non starter I suspect because of that. And yes I am bored at work tonight to have given this any thought.
 
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Popshot said:
A. Chain is no real issue
B. Centre point is no issue but Ackerman is. It is for any quad and no easy way of introducing it. The inside wheel will not describe a tighter circle so one or both tyres will scrub in a corner.
C. Smooth will likely be no benefit as a quad python needs some form of front axle swivel as the inside wheel would otherwise want to go down whilst the outside would go up. This would act to keep all wheels down.
D. Interesting question. Probably no more so than a trike python needs an accepted amount of trail.
E. It could be low but so can most layouts.
F. Shorter than some other layouts but a swb std quad design can be shorter as the python quad needs room for tiller steering which a std design doesn't.

The biggest drawback is probably the inner wheel wanting space the legs do because of that tiller steering. A non starter I suspect because of that. And yes I am bored at work tonight to have given this any thought.
Click to expand...
Many thanks.

By low i mean a seat height of say 3" at it's lowest point !

making low and chain interlinked problems , on almost all pedal cars the chain drives the rear wheels so must find someway of getting round/under the driver.

Lots of the older pedal cars have no Ackerman although i hear tales of cars ' eating tyres ' I wonder why ;)

It is the short chain almost direct drive and no worry of caster/centre point that appeals , oh and I like odd !

Paul
 
I think the challenge to build a proper "Racing Quad" with proper steering Ackerman, etc. etc. is clearly out there waiting to be picked up.
 
Thinking further about a python quad the front has to have an axle system on a pivot over the pedal boom so the boom rises as it turns. If it doesn't then it has no self centring. This can be done but is getting to be a lot of chassis and much of it getting in the way of other bits of itself as well as legs. The front wheels would not lean but stay upright. It would also kill any hope of sitting low as to have any hope of pedaling it your legs would have a lot to get above and over.

It can be done but shouldn't be is my considered opinion.
 
This reminds me of the ac3 trike i think which was a lean steer design. Essentially the front axle was like a skateboard truck.

Could the "python quad" idea be combined with that ?

So a boom with bottom bracket and pedals on a longitudinal tube frame.
A front axle, mounted on central pivot with some angle, and a central differential ?
The whole axle would lean steer (not sure the chain would twist enough)

The rear axle could have a pivot with inverted angle wrt front as in a skateboard

That would make a front wheel drive lean steer quad.

Probably combines the worst of all but Stormbird has started a " divergent brainstorming " thread
 
Trickytrike said:
This reminds me of the ac3 trike i think which was a lean steer design. Essentially the front axle was like a skateboard truck.

Could the "python quad" idea be combined with that ?

So a boom with bottom bracket and pedals on a longitudinal tube frame.
A front axle, mounted on central pivot with some angle, and a central differential ?
The whole axle would lean steer (not sure the chain would twist enough)

The rear axle could have a pivot with inverted angle wrt front as in a skateboard

That would make a front wheel drive lean steer quad.

Probably combines the worst of all but Stormbird has started a " divergent brainstorming " thread
Click to expand...
You can have a swb fwd quad but not a python pivot type easily. The python relies on the pivot rising as it turns to self centre and that is the crux of the issue. Replicating that action with two wheels is complex, leaving you with tiller steering and no self centring. You can in theory generate a rising pivot, but it uses a lot of extra chassis where your legs need to be and still leaves you with tiller steering. Much better to have std tadpole steering and rwd. The swb can be as short as you like and std tadpole steering keeps the wheels away from the legs easier than tiller steering can.

The set-up you describe would lower the pivot at it steers so would want to go full left or full right permanently, if I have understood it correctly.
 
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