A python trike is born...

Trickytrike

Trickytrike

Hi first thanks to all for inspiration and sharing on this forum and of course to Brad for creating all this i would not have attempted this project otherwise.

I have been tempted by a python trike for a long time because it is unconventinal, compact, the drivetrain looks efficient, it looks great for cargo...

I must say the " life with python trikes mk 1 2 3 etc" on this forum has been inspiring and encouraged me to get started

So i built this contraption out of old bikes, and steel tubing for the back.
I found a mtb with the steering tube at 62 degrees from the beefy bottom tube, which is the recommended steering pivot angle, on the original openbike python collaborative webpage started by jurgen mages the python inventor.

Please dont mind my far from perfect tig welds, hoping to get some feedback from the experienced builders, thanks
 
You need to host the pictures on a hosting site such as Imgur. You then get a link to them to post on boards such as this. In Imgur's case you want the "Direct" link. Once you have the link you click the icon above that looks like a mountain and a sun and paste it.

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My TIG weld need to improve, with a bit of patience...
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The fishmouth - sorry I had to make this stupid joke
 
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This is more obvious with this one that we have a frankeinbike, before the different organs from various "donor" bikes ( uh not sure I got there written consent nor checked they were fully out of order before proceeding ) were covered up by blue paint
 
So now I am trying to tame the python, it is a bit special to say the least... tight turning and fun to steer with the legs but any downhill on our montain roads it very scary even going slow.. any advice from the senior atomic zombies who survived the python experience greatly appreciated
 
Nice ride, thanks for sharing!
I have seen steering dampers used on DIY rides of the snake variety.
They look like the air springs in a car hatch, just smaller.
Also found a set on a large motorcycle that was scrapped.

Brad
 
Thanks I could do with one of these to make it safer.

I bought the story of the self centering effect of the python it works indeed at low speed,
and it can make very tight turns.

But i have the impression going faster the negative trail creates instability.

Also if the road camber or bumps makes it turn...
 
I had to put one on my tilter. It was fine below 25mph ish but above that it went into a tank slapper I couldn't recover from and spat me off. Fortunately I'd got it down to about 15mph or less when I did my superman impression. The steering damper is really a sticking plaster over a compromised design though. In my case I couldn't see an engineering solution to the problem and concluded that it was simply inherent in the design so the sticking plaster it was. If you go for one look at the leverage that it is designed to operate with and the amount of throw it has then look at the amount of leverage you can give it on your application and how much throw it will need there. You are using it outside it's designed application so need to consider these things. In my case I needed a lot of throw and have it turned up to almost it's max resistance. It doesn't get in the way of using it and does tame the effect.

As with my case I am unaware of any design trick to make a python stable at speed. Paul (stormbird) will know much more than me about that though.

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Hey thanks for taking the time to help with the damper, indeed hiding instability under the carpet but at least staying in one piece.

I guess that was the Alan Maurer style trike you built, congratulations on that one I was fascinated by this variable lean steer design, far from my ability but very elegant.

You are right I will need to figure out damper throw, résistance and leverage it may not be in the normal operating range, some trade off between resistance to turning and prevention of wobble or random turning at ( not so ) high speed.

Reading back the 70+ pages long story of the various « stormbird » trike designs I see two reasons why his worked better
- shorter wheelbase so he stays inside the stability triangle ( one obvious flaw I should have figured out about a python trike is that pivot behind the wheel means the contact point of the front wheel moves out while the driver stays in the middle.. )
- various tilting mechanisms with rubber blocks somewhat original compared to the flevo trikes were tested, I am not sure to understand if it helped a lot with cornering and bump steer but definitely interesting

So thanks again for sharing the damper ideas and experience… still some work to do…
 
Sorry not seen this post before , good looking trike and looks very useful.
DannyC of this parish also built a Python which had a nasty habit of climbing camber and trying to put him head on with oncoming traffic ?
There is an old Python mailing list still used by the diehards and I asked why it might be doing this , the only suggestion was maybe it is linked to it's length [ although there are several in the Projects page of the Wiki same length or longer ]
I also altered one of mine to be as long as DannyC's and it did not do that ,

DannyC shortened his and it was better however he never really pursued the envelope with it to see what it did/did not do.

Pegasus also build a Python and we met at York cycle show he complemented me on how nice mine was to ride [ very relaxing ] as his was a handful , it turned with the slightest provocation , just looking over your shoulder could get it to move out of like 3-4ft ! must have tiring to ride.

The rubber blocks were in answer to the ' tilting hysteria ' that seemed to grip home builders on both side of the Atlantic ;)

It was a learning curve and for me was an attempt to allow the Python seat to be high to get out of the mud/wet & dirt and allow a narrow rear track 24" in fact.
There are negative aspects to tilting I have never seen discussed , in my implementation [ and many others ] it free tilts with no correcting mechanism.
If you attempt to employ titling [ in most designs ] it tilts ALL the time , whether you want it to or not so in an urban environment going up and down or cross slopes affected the trike , this constant tilting meant YOU were the computer controlling the amount of tilt and trying to stay upright when the trike underneath you was rocking from side to side.

Eventually you get tired of this and remove the tilting only to find dropping the seat height a little [ removal of tilt mechanism ] a 24" track id actually quite safe as long as you treat it with respect.

The racer had only and 18" track and seat height IIRC about 4-5" and it was perfectly safe at racing speeds if the turns are gentle.

My Pythons have never had bump steer , cornering nah just a little body English should I lift a rear wheel , IIRC wheel base started off at 36" and moved out to I think currently 40" +- a bit.

What is you pivot angle ?
Ok I see you say 62' that is usually suggested for 2 wheelers , however for trikes 56' is recommended , this information is not in my thread as the original Python build was a very very long time ago on a version of this form which has not had all the electrons recycled !
Python trike Wiki my first one was an almost direct copy of Triked Python from the USA , I currently own 2 front ends [ a new one on the blocks ] and 3 rear ends with a 4th cut up.

Pivot is it stiff ? does the front end flop over when you get off ?
Mine is generally to stiff for the front to rise when I get on it , not deliberate just dirt and weather abuse in the rod end bearings :)
Easiest thing to try is fasten some bungee cords to the front end , get it as stiff as possible and see what affect it has ?

Please report back it may help others going down this road Paul [Python Pilot of this parish ]
 
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Hello thanks for taking the time to summarize your python experience, it is quite unvaluable as you are one on the few originals still going around on such an unusual trike.

I looked up the wiki python at openbike.org and a builder from tcheck republic had made a python with 63' pivot angle and a huge trailer so a long wheelbase.

In retrospect what you are reporting makes more sense to me now.

You have a pivot angle of 56' corresponding to the max seat raising vs angle effect according to the python pages, and rod end bearings seem to provide useful friction.
I have put in lovely well greased bearings so the slightest leg movement makes it turn.

Your wheel base is 40" mine 48" so you have more weight on the back wheels and center of gravity better located in the 3 wheel triangle.

As for " turning into camber or bumps " that happens with this one so I guess it is due to the CoG close to the pivot, itself too vertical with negative trail, so if there is lateral slope the trike just wants to fold around that hinge with centered weight and pivot, hence turning the wrong way.

I understand the tilting in any shape of form will add an extra degree of freedom to the already untamed trike and require extra control, so i will refrain from attempting that, thanks for saving me time and limbs with this advice.

I think I will try a few things now :
- damper ( bungee first then proper one )
-load the back with cargo
-lower the seat ( 1" ... marginal ? )
-install back brakes
-shorten the wheelbase ?

I will indeed report on the outcome to share with ohers who might build this peculiar trike.

I feel the handling is disappointing so far but there may be a learning curve, and the direct front wheel drive, compactness and cargo space make this really apealing.

If the mailing list of the "python die hards" is still working I would be happy to exchange through this channel too.

Thanks again for sharing the ecperience
 
Good man keep at it , mine was ridable almost from the start , and I have gone down different avenues trying things , with not everything being a success ;)
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So similar however can you see my front chain ring almost touches the tyre and yours is further forward ?
Now if you removed your front left crank and chain rings I reckon you could make a BB that clamps in the gap
left but much closer to the wheel ? It would not affect your current frame but could be made strong enough to
test to see if it made any difference ?

Yes as you say would be easy to add some load and see what happens , mine above carried all my camping gear however that
only amounts to about 12kg just bulky.

I found brakes on the front on gravel surfaces or in the winter to be dangerous , you could easily lock up the front wheel and
stood a very good chance of sliding to the scene of an accident :)

Now all those theorists will tell you rear brakes won't work they will just lock up the wheel , probably the same theorists that tell
you front wheel drive is also bad , no traction etc etc.

Now these ' can ' happen however how often ? well I ride in all weathers through out the year and they are negligible.
I have 2 slopes around here I cannot get up , one it is just to steep for almost all my recumbents so I don't try.
the other can be ridden assuming it is dry and/or minimal leaves - live with it !

A strange handling effect [ most are with a Python ] with individual rear brakes say you are turning right so braking with the left hand
[ please put each brake on a separate lever ] you slow the left rear wheel down so the rear end turns slightly to the left however due
to the pivot the front end then turns gently right ! actually a good effect ?
Also of course you are increasing your braking force as you now have 2 tyres doing the braking and if one locks nothing bad happens
and having a break on each lever you can just ease off and unlock the wheel.

Traveling with other trikes is interesting , the Python can out turn any tadpole and is the equal or better than any delta trike so
urban maneuverability is excellent. being able to ride along whilst using a phone , eating , reading a map or taking on/off a sweatshirt
is all possible with feet steering and a little practice :rolleyes:

See you have a nice bit on the front for lifting it and getting it round when you cannot ride it.

python@freelists.org and here freelist python not been on the web site for a while as I get a email digest and browse that occasionally.

Have you found this ? german cargo delta with virtual pivot it had some promise I though just needed rebuilding to strengthen some areas ?

Keep the questions coming and ask if you need more pictures.

Paul
 
So idea prop up the front wheel so it is vertical and can't turn.
Then add packing under the rear wheels and measure the pivot angle.
When you have something near mine make some rear drop out extensions [ they could just be bolt on ] and see what happens the the handling ?

Paul
 
My Python is currently "rusting resting" in my shed.
It was an interesting experiment. I was able to ride it "hands-free" in empty car parks and do figure of eights etc. with no trouble.
On the road it was a different matter. The smoothness of the pivot I made interacted all too well with the road's camber and I often found it trying to cross the road as the trike bent in the middle.

Going downhill at speed was "scary" to say the least. ;)

I shall probably recover the useful parts and scrap the frame to make room for....... ?
 
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