My life with Python trikes Mk1 , Mk1.5 , Mk2 ?

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While the old saying "a chain is only as strong as the weakest link" is entirely true, it is the discovery of its location that takes the time.

It would appear to have failed at a point where the forces were/are most concentrated.

As you have fixed that, I would look next at the mating parts to this failure and where they attach for any signs of deformation or stress fractures.
Which is why I suggested you had a look at yours ? all that 2mm box and 4mm plate has to end somewhere ?
Unless the whole trike is made of that ?

Paul
 
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Which is why I suggested you had a look at yours ? all that 2mm box and 4mm plate has to end somewhere ?
Unless the whole trike is made of that ?

Paul
Ahhh... but...yes...but...no.
Mine hasn't broken (yet) and yours has; so your situation is the focus of the group attention (and rightly so in my view).

Mine has not done the hard miles that your has done but it has however passed the "Fat-Boy" jumping up and down test. ;)

The 4mm plate "carrier" for the PPP is bolted to the 40 x 40 1.6mm box section of the main keel and that has a 3mm plate insert inside it with captive nuts welded to it.
The 25 x 25 x 2mm box section interface to the PPP sleeve is prevented from deforming/twisting/collapsing with 3mm end-cap inserts welded all around.
I really do think it is probably as robust as I can make it without being "silly" about it.

But following your experience I certainly will undertake visual inspections before every ride.
Our old bones need all the insurance they can get mate, because they take a lot longer to heal than those of the youngsters.
 
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That it stress fractured rather than bent says it's essentially strong enough for the weight it carries. The stress induced fracture says it is subject to intermittent loadings it can't take. This is likely a result of hitting potholes and similar and having insufficient shock absorbing within the chassis. There's no suspension so all that can absorb force is the tyres. What they fail to absorb the chasis must endure. The front wheel is much closer to the pivot than the rears so that is the prime supplier of force. It could be the use of sturdy box tube at the front is able to transfer force to the pivot better than the more flexible rear triangle of the mk1 which would presumably flex better and thus apply less of those short duration jarring forces to the pivot. It would suggest a more flexible chassis is desirable.

It's a bit like a traditional diamond frame road bike in that a rigid aluminium frame feels like riding a jackhammer but a reynolds steel tubed frame feels like suspension in comparison. The flexible frame absorbs the shock but the rigid passes it on to you.
 
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Popshot

thanks for your assessment very useful.

the box was a buying mistakes as I thought I could only find the size I wanted in 2mm wall , turns out I was looking for the wrong thing , so yes front very inflexible.

like my school report most subjects most pages ' Could try harder ' still heart warming to see even 60+ years latter I still can achieve those standards ;)

Paul
 
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Emiel

Nice find , very neat and well built.....
Obviously it is not a Python , however I can't decide whether it is lean steer or not ? a real puzzle.
he has very little damping for his tilting , just enough to keep it upright when he gets off , probably a very lively ride.

Paul
 
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It is no python, but I think that it is something that is close to it and has some nice things to center it.
It feels more a version that is in between a python and a mosquito.
 
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Emiel

Watching the other videos he looks very nervous riding it and like a lot of lean steer it seems to have a very poor turning circle.

Paul
 
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As I look ad it again, he probably added handlebars to keep balance. In an other Dutch video, they talked about that it takes time to learn to ride it without hands.
 
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Ok so ridden it 3 times now and have some thoughts...

Again it is like the curates egg , ' good in parts '

Before I was sat on the 200kg like this :-



and a forward mounted 100kg elastomer was trying to control it pitching forwards and backwards , which was causing the seat to strike the rear rack.
Having moved the rear elastomer back and increased the value of the front one to 200kg I have lost most of the pitching motion [ not measured it yet ].
However I have lost all the unnoticed suspension it provided !
Now I can tell whether the rear tyres are freshly pumped up or not.

Not sure I am happy with that !

Paul
 
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For what I understand, is that even on the Trike in the video, you need to hold your balance as you want to ride without your hands.
 
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Hi all

Time I got back to this ...



Not sure yet how much space to leave behind the seat , however I still need a sort of transmission tunnel to allow the rear seat sub-frame extension to pivot freely so part 1.

What a crap picture , here it is inserted into the floor/sloping front.

Whist it looked big it is surprising how little room it takes up ?



Needs gluing in and the seams given an outside hot glue fillet to stop water ingress.
It has been raining here not stop for over 24 hours now , think I will need mudguards Monday and I am woefully behind...

Paul
 
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I'm very interested in the lifespan of this. If cardboard can survive it opens up a host of bodywork options.
So how long do you want it to survive and be classed as successful ?
I intend PMF on it before I risk it getting rained on , life has got in the way of completing it however that should change very shortly.

Coroplast I have heard is not particular long lasting in the wrong conditions ?
Apparently it goes brittle in low temperatures and prematurely ages with prolonged UV exposure ?

Paul
 
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So how long do you want it to survive and be classed as successful ?
I intend PMF on it before I risk it getting rained on , life has got in the way of completing it however that should change very shortly.

Coroplast I have heard is not particular long lasting in the wrong conditions ?
Apparently it goes brittle in low temperatures and prematurely ages with prolonged UV exposure ?

Paul
As you cover coraplast, than it will hold a long time. But you can also use the transparent version. Some use the 4mm version of that for their caravan and wrap it, so it is covered and you can't look in.

But you can also use xps plates. Isolation foam. 20 or 30mm. You make a box out of it, glue it together and use poor man's fiberglas or fiberglas to make it strong. As you want to ad a lock, best is to use some wood on the other side.
This is where I am making my new caravan from and a box that I can mount ad the back of the quad where we soon start to build on.
It is light, strong and your stuff is isolated. You can paint it in any color you want and it is durable.
 
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I'd suggest if it lasts a year and still functions well then it'd be a success. Few would want to build new bodywork yearly rather than something more permanent once. Though in reality few materials would last a lifetime.
 
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I'd suggest if it lasts a year and still functions well then it'd be a success. Few would want to build new bodywork yearly rather than something more permanent once. Though in reality few materials would last a lifetime.
I am with you on that , if it survives this winter I will be well chuffed.
It seems silly to not build it from wood as I have the wood , however this is a much faster build and a proof of concept/design and much cheaper as I will need to buy the wood the glue and paint and it would need bringing in each time to dry.
I am using contact adhesive for all flat joints and hot glue for sealing all edges and corners , so they set despite the low temperatures.

Paul
 
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So a Blue Peter moment this afternoon when I got the wheel arches built :-



Knocked up a template from some scrap wood and cut out the 2 bases.



Because cardboard bends unlike plywood the upper part can be made from a single piece and glued on with a hot glue gun , seems nice and rigid.



Then I commandeered the wife's pinking shears and attacked an old bed sheet strips 4" wide were cut with a centre line , these will wrap all corner edges before the flat surfaces are tackled.



The complete kit for 2 [ notice I managed to build two handed mudguards instead of two the same side [ that's a relief ]].
I have some Wilko varnish to try as an adhesive and then need to investigate what to paint them with ?
Exterior gloss would be well waterproof if a little brittle ? A kitchen/bathroom emulsion may be better ?

Paul
 
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What about some type of car stone chip paint? Somewhat rubbery with good waterproofing and flexible. Probably not the most bling option though. I'd think gloss too brittle and a water based emulsion too porous but that's only a complete guess.
 
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