Does anyone want a python trike frame?

DannyC

DannyC

0
I built a Python trike to give it a try.
The build was successful, but I decided it was not for me.
Current projects and a grumpy wife mean that it has to go to make room for other things.

So, if there is anyone that would like the frame, they are welcome to it.
It does have suspension at the rear.


20210123-114254.jpg
 
Looks like it is very nicely built, sorry i already have my own python to clutter the garden at the despair of my own wife.

Could you tell more about the geometry and how it handled ?

I would be curious also to know how you built the steering pivot and rear wheels ( SA drum brakes i found only accept 9mm axle )
 
The steering pivot is a 12mm bolt and a set of 35mm Angular contact bearings.
The handling was initially "frightening" because the pivot assembly was/is very smooth without binds. This meant that the centre of the trike was always trying to dive down the camber into the gutter, which meant your FWD was then pulling you out across the road and into oncoming traffic.

Even if you parked it sideways on a slope the centre would fold to place the centre of the pivot on the downside of the slope.

Shortening the trike decreased this alarming tendency to manageable levels. :) On level surfaces with little or no camber it was never a problem.

The SA drum hubs (as in the picture) are on 12mm QR skewers inside 16mm sleeves that bolt through 10mm plates at the ends of the rear cross-member. An interesting feature of rear-braked pythons is that it causes you can get the trike to "Snake" by braking one side only/harder and it makes the centre pivot operate and you change course. It was this sort of unexpected behaviours that made me move on.

TBH if you had a stiffer less fluid pivot, many of the issues would be greatly minimised.
 
Thanks that makes sense to me now.

I have built mine around a headtube and bearings, less robust but equally fluid.

I experienced the same scary tendancy for the trike to go towards the center and wrong side of the road with camber.

This makes sense now, if the slope leans to the right, the trike folds with the weight and wants to turn left.

The "self centering" property of the python compensating for negative trail according to the inventors seems to work on the flat only, and maybe also better for bikes than trikes.

This odd steering behavior can be somewhat dampened by pivot friction as you said...
This maybe why stormbird s trike is better behaved than mine, with rod end bearings ?

Also as you and stormbird pointed out the short wheelbase also improves stability,
I made mine longer to put in more cargo which made handling worse.

Thanks for all the info, there are not many python trike builders around ( who lived to tell the tale )

Having said all that, I still find the python trike is great for carrying cargo on relatively flat roads, very practical compact and nimble.
 
Trickytrike said:
I would be curious also to know how you built the steering pivot and rear wheels ( SA drum brakes i found only accept 9mm axle )
Click to expand...
Probably because yours came out of bikes.

What are euphemistically called ' single sided brakes ' are only found out in the wild on recumbent trikes , a few utility bikes with 3 or more wheels and the very very rare wheel chair.

We have to buy the hubs in parts , so not even a complete kit is available , then spokes and rims and assemble ourselves.

Paul
 
Thanks for the info that makes sense most hubs are for bikes.

I tried to source SA hubs with 12mm axle but could not find any in online shops.

Did you find a source for hubs or do you have to replace the bearings and axles ?
Do you buy hubs in different parts ?
Or go to the extent of modifying the bearing housings with lathe boy ?

The SA XL SD doc mentions 6001ZZ bearings are 12x28x8mm
Found XL FD ( smaller axle ) but not XL SD to buy

Thanks If you have any link to a supplier
 
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SA Hubs come in 2 flavours.
70mm and 90mm
The 90mm ones can have 2 differing axle arrangements.
1. QR axles in M16 threaded tubes that are fitted through the backplate with turned and stepped fittings.
2. 12mm Hardened bolt axles that just go through internal and external spacers.

You have buy style 1 with the main order because they don't sell those parts separately. Or, you can lathe-boy your own parts.

Here is page 37 of their catalogue:
image.png

I get all my SA drum hubs off SJS Cycles here in the UK or e-Bay (If Paul has not beaten me to it).
The thing is that you can convert the cheaper 9mm axled drum hubs from SA to work if you are prepared to make your own parts.
 
Great thanks for the explaination it is much clearer to me now.

I ll try to find the 90mm in mainland europe at least I know what to look for.

I would be prepared to go to great lengths to build a trike but will resort to buying the right parts especially for hubs and brakes.

For the 70mm hubs the SA doc showed 26mm OD 6000 series bearings, I found 12x26x8mm bearings that might have worked but they are uncommon and expensive so I thought I might as well buy the complete hubs if existing.

Thanks again
 
6001 bearings are 12x28x8.
6902 bearings are 15x28x7

With a 1mm thin shim, the 6902 can directly replace the 6001.
 
It's how I adapted "normal" Novatech 12mm Tru Axle hubs to fit the front dropout axles on my trike.
Just replaced the 6001 2RS bearings with the 6902 2RS bearings I'm rolling on for 6000km now.
 
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