Making a sliding boom Python ? how ?

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Feb 7, 2008
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Hi all

I really want to get away from having an adjustable seat on the python trikes I ride.

Making the pedals move would be very difficult and heavy especial as there is so little space at the front with 20" wheels and my current design.

Then whilst fighting the ' tilting seat brackets ' it dawned on me I could make the rear frame telescope between the front seat mount and the pivot , it would be the same as having the pedals move just further from them ?

So how can I achieve that and have something that won't seize up if it has been left a year or two before it is used ?

I prefer square tubing Mk1 is 1.5" square Mk2 is 1.25" square and seems to be holding up well.

Paul
 
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Hi Paul I thought we discussed this when you were looking at storage options?
One way looked like this, where the actual boom was a central beam held between 2 others.
Not as nice as telescopic Square tube, but more readily available.


OR:
When I made the rear trike rack for the car I used 2 sizes of tube that fitted (telescoped) really well.
While the "inner-tube"[sic] was quite small in size it was VERY THICK and this might be ideal for your application.
The inner/thicker piece attached to the Python Pivot would still have around 4" of weld seam (fairly unbreakable I would think).
That should allow you to create static front/rear sections that are themselves able to be moved apart/closed-up.
Another benefit might be that the "halves" could them be individually altered in design for differing purposes (local/touring).
 
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Joined
Dec 29, 2016
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Lanc's, England
Hi Paul
You have all you need already.
Make the python into 3 parts.
Cut the rear boom in front of the rear axel so you have a straight tube from the pivot point
If you attach the seat and the rear axel to your original seat clamp instead of the rear boom you end up with a adjustable seat/rear axel.
This is the plan for my next phyton project, but I will use round tube .
 
Joined
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Messages
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Hi Paul I thought we discussed this when you were looking at storage options?
One way looked like this, where the actual boom was a central beam held between 2 others.
Not as nice as telescopic Square tube, but more readily available.
Much to much tube drilling and inner sleeving in my view ?

OR:
When I made the rear trike rack for the car I used 2 sizes of tube that fitted (telescoped) really well.
While the "inner-tube"[sic] was quite small in size it was VERY THICK and this might be ideal for your application.
The inner/thicker piece attached to the Python Pivot would still have around 4" of weld seam (fairly unbreakable I would think).
Now we are talking so what sizes did you use and where did they come from ?
 
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Messages
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Hi Paul
You have all you need already.
Make the python into 3 parts.
Cut the rear boom in front of the rear axel so you have a straight tube from the pivot point
If you attach the seat and the rear axel to your original seat clamp instead of the rear boom you end up with a adjustable seat/rear axel.
I have always had problems with the clamp bolts that have to go under the trike :-



Look at the state of this after riding over a winter !

Also on the Mk2 I am having a lot of trouble with the mounting tabs ?



It is possible I have the bolts to low , maybe they need to be as close to the frame tube as possible ?

What happens is they have to be done up so tight the tabs bend inwards and then if you take the bolts out the tabs have to be straightened before you can either move the seat up and down the main frame or lift it off.

So I am after tube in tube and bolts running in tubes across the frame for the clamping ? unless someone has a better idea ?

I have 1.5" and 1.25" tubing for a DIY solution I wondered if welding 4 say 0.5" x 0.125" strips length wise down the middle on 4 sides of the 1.25" then lightly grinding till it was a snug fit would work ? it could be liberally coated in grease where it is inside the 1.5" to keep corrosion at bay ?

Any lots to ponder...
 
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As a rule pinch bolts ought to be as close to the tube as possible but their very nature will try to bend the tabs. Looks like you need some better quality paint or better still a trip to a local galvanizers.
 
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As a rule pinch bolts ought to be as close to the tube as possible but their very nature will try to bend the tabs.
If as Brad does you use them at the beginning of the build to figure out seat pedal length etc they work fine :)
If you want them to work as adjuster-able always or for component removal not so fine :(

Looks like you need some better quality paint or better still a trip to a local galvanizers.
A side effect of the frame being 5" from the ground.
I hope the next trike will sit higher in an attempt to keep me and it cleaner
 
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Now we are talking so what sizes did you use and where did they come from ?
Well, mine came from www.metals4u.co.uk
The pieces I used were:
  • Outer tube was 30 x 30 @ 2mm wall (chunky in its own right),
  • Inner was a 25.4 x 25.4mm @ 1.6mm.
Having 0.6mm clearance (OD of inner-tube to, ID of outer tube in both AXIS) means it usually slides without fouling on the ERW weld seam of the outer tube.
If you weld nuts on the outer tubes face, then short bolts can be used to clamp the tubes at a set relationship to one-another.

The rack is solid, I can sit myself on it (200#) without mishap.

I believe other gauges may be available.....
For example:
https://www.metals4u.co.uk/mild-steel/c6/box-section/c49/30mm-x-30mm-x-2.5mm/p2298 would yield an ID of 25mm, but you might snag on the erw weld seam, but it can be removed.
https://www.metals4u.co.uk/mild-steel/c6/box-section/c49/25mm-x-25mm-x-2.5mm/p2296 Is a chunky boom insert that you would struggle to twist I think.

Hope this helps.
 
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