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

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To avoid building any frame forward of the rear axle to mount trailing swing arms you could modify the rear cargo carrying part to mount leading swing arms instead. With the swing arm pivot to the rear of the wheel you generally want a more solid pivot to handle forces trying to move the wheel sideways (a bottom bracket ought to be ideal) and you want the pivot slightly lower than the wheel axle to encourage the wheel upwards on hitting a bump. Without this you're trying to force the wheel into whatever it hits. This has the advantage of the chassis doubling as the cargo area floor thus saving weight. The shocks would still be mounted at the wheel axle or could be moved towards the pivot as needed. If you use the ex i-lean with a piece of anti-roll bar you could also use that in a leading rather than trailing set-up.
 
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Clarke if you spent less time looking out the window and picking your nose ?
Yes, I saw that, but I have also seen your carpentry skills, therefore....... ;)
 
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To avoid building any frame forward of the rear axle to mount trailing swing arms you could modify the rear cargo carrying part to mount leading swing arms instead. With the swing arm pivot to the rear of the wheel you generally want a more solid pivot to handle forces trying to move the wheel sideways (a bottom bracket ought to be ideal) and you want the pivot slightly lower than the wheel axle to encourage the wheel upwards on hitting a bump. Without this you're trying to force the wheel into whatever it hits. This has the advantage of the chassis doubling as the cargo area floor thus saving weight. The shocks would still be mounted at the wheel axle or could be moved towards the pivot as needed.
You are right , also I think version 1 should avoid trying to be clever and:-
1) looking cool
2)saving weight
3)to full of tech !

Version 1 just needs to work and prove to me I need suspension ?


If you use the ex i-lean with a piece of anti-roll bar you could also use that in a leading rather than trailing set-up.
Sadly I think in it's current form the iLean is a no go ? it is quite a bit narrower than I remember and narrower the Mk1 rear axle beam :-



I was going to remove these wheels clamp the iLean beam to this and make some trailing arms , I think the track will be much to narrow to try and ride it ...?
 
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Yes, I saw that, but I have also seen your carpentry skills, therefore....... ;)
My display of carpentry skills to you was purely a consenting adult affair and NOT for discussion on a public forum......
 
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My display of carpentry skills to you was purely a consenting adult affair and NOT for discussion on a public forum......
Ohh...
I am still removing the splinters after all this time.
 
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For what it is worth, a simple rig for testing: Two bottom brackets and two pedal arms. Fix one pedal arm to each of the bottom brackets, drill where the pedal normally resides (if you have to, not sure of your axle bolt size) to take a mounting bolt for the wheel. Fit your shock wherever on the pedal arm and to the body rear and you can muck around with positioning/angling (looks fishy) without much effort, time, or destruction.
 
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Sadly I think in it's current form the iLean is a no go ? it is quite a bit narrower than I remember and narrower the Mk1 rear axle beam :-
Remove the bottom brackets and weld in the right length of anti-roll bar to get the right track. Test it by putting one crank arm in a vice and applying all your weight to the other. If you get 2 inch of deflection or so you then need to make the chassis so it mounts the bottom brackets and a central tab. If you get just under the amount of deflection desired then place a piece of pipe over the free one to simulate longer arms and try again. If you get nothing like the deflection you want you either need a different rate "spring" or it's a no-go idea. I genuinely think that such a system is by far the best idea being both anti-roll and also rising rate in that it gets harder as it deflects more.

The better way to put the anti-roll bar in would be to weld the appropriate crank square taper to each end of it and bolt the BB shells to the chassis via the expedient of welding a tab on them and the chassis. That way the bottom brackets would dissassemble for servicing. I do appreciate though that finding out if it will work will involve the expense of a scrapyard anti-roll bar and some effort. Other solutions may cost less with more guarantee of success for less work.

I am even considering this approach for my current trike at the front. On that the arms would need to be leading.
 
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There's a nice torsion bar to spring rate calculator here. Don't forget to half the actual bar length as it needs to be centrally fixed. It'll help you make the best bar diameter vs arm length choice. If I were to use it I'm looking for a half inch diameter bar and 11 inch arms "ish".
 
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There's a nice torsion bar to spring rate calculator here. Don't forget to half the actual bar length as it needs to be centrally fixed. It'll help you make the best bar diameter vs arm length choice. If I were to use it I'm looking for a half inch diameter bar and 11 inch arms "ish".
Yes found that and used it , came from link I posted to someone using a socket set extension bar and grinding it down to 1/2" and mounting it parallel to the suspension with an arm at right angles to it very neat and compact.



I have not dismissed torsion bars and it would not be to difficult to slightly stagger the mountings and have the bars the full chassis width doubt if it is even worth making one arm shorter to compensate as the difference in wheel base between the sides would be no more than 2" ?
However anti-roll bars are difficult to source ?
a) yes they are available on Ebay however they are usually just listed for a specific car and not by length and diameter ?
b) some of them are very complex shapes and so hard to find 2 straight bits long enough.

c) as far as I am aware no scrap yards around me allow you to wander around till you find what you want ? So that would entail a lot of research on my part to identify a suitable candidate and then hours on the phone trying to find one in a yard locally then going and fetching it ...

Still open minded ..
 
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Some have a diameter listed with them on ebay as the more sporty models would get a thicker one than the regular models. You could use pillow bearings insted of BB shells. This would have the advantage of getting a full width of anti-roll bar and not loosing the width of the two bb axles to it. The arms could then be welded on box having been drilled to slide on the anti-roll bar and welded both sides. Even then you'll likely need not much more than 2.5 foot of straight bit.
 
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I've also been reading up on recommended sag when you climb on which should be in the region of 20 to 25% of total travel. I've been working on twice that so a 350lb spring mounted at the wheel at 45 degrees would work each side if using "regular" units. In other words you are looking for 1/2" of sag at the wheel to generate 2" of travel.
The disadvantage of torsion bar suspension is you can not dial in any preload to them unlike regular units.
 
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I've been playing with the calculator and have come up with this for my current trike project front suspension. I was going to go beam suspension but will try this method first.



Looking at your Python with it's lower weight per wheel you could do this.



Take 8" or so of 12mm anti-roll bar, mount one end to the chassis and then through a pillow bearing. Attach a box section trailing swing arm of 10" pivot centre to axle centre length by drilling a 12mm hole in it and sliding it just over the anti-roll bar, then welding both sides. You'd be looking to make the distance between the unfixed / unwelded parts of the bar 6 to 6.5" to give 0.5" of sag which ought to give about 2" of "normal" suspension though in reality it's unlimited up to the point the bar or chassis snaps. Repeat in reverse at the other side, so two separate ARBs. 44 lb/in would give a 1" sag. I would think better to err too stiff than too soft to controll lean and allow for luggage but that's only an oppinion and I suggest an aim of a half inch sag is the target. This requires chassis only under or above the ARB fixed point and pillow bearing. No chassis is required above that to mount a traditional shock to. This assumes the online calculator is correct and the ARB behaves as expected. Anti-roll bars can be welded as a previous neighbour used to (probably still does) have a pukka Mk1 Escort RS2000. He had it from new! It was heavily modified and one of Fords own rally tricks applied to it was to weld a second ARB below the first attached by 2" posts to double the roll resistance.

I've already found and ordered an ebay 12mm ARB with lots of straight on it so if you want some I can pass some on.
 
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Take 8" or so of 12mm anti-roll bar, mount one end to the chassis and then through a pillow bearing. Attach a box section trailing swing arm of 10" pivot centre to axle centre length by drilling a 12mm hole in it and sliding it just over the anti-roll bar, then welding both sides.
Thanks for looking at this for me , it's interesting.
However I would not be confident the trike was safe with the trailing arms welded directly to the ARB ?
Surely doing that the upward forces of the trailing arm would be trying to bend the ARB upwards between the trailing arm and the pillow bearing ?
Are you sure the ARB will be made ' round ' enough to work with pillow bearings ?
I though using trailing arms on a tadpole introduced camber changes and worse castor changes to the front wheels ?

I've already found and ordered an ebay 12mm ARB with lots of straight on it so if you want some I can pass some on.
Not ready yet , can you tell me which one you bought , I have identified a couple that may do ?

Is the length of the trailing arm important to how it works ? or just a variable in the calculations ?
Is the length of the ARB important to how it works ? or just a variable in the calculations ?
 
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You could always devise a clamp system from the swing arm to the bar if not happy welding.

You'd want the pillow bearing as close to the swing arm as possible to ensure all upward force was transmitted to the twisting of the ARB rather than trying to bend it. The cast ones are very tough (I wouldn't use a stamped one) and ought to withstand any such force IMO. They also come in varying degrees of extra strength though I doubt they would be required. You can also run the arm through two or more pillow bearings should you wish. I suspect that would be extra weight for no gain. The fixed mount required could again be a bit of box drilled and slipped over the end and welded then bolted to the chassis. The idea would be to keep the ARB horizontal.

Round enough? - no idea at this stage but almost every cheap bike I've ever bought has had more slop in it's head tube bearing than I'd expect to find here. I have some shim steel so can add to the thickness to a degree and the bar must have been manufactured to some degree of roundness at the foundry. Many Pillow bearings have grub screws which would nicley take up a minor bit of play. As to whether a 12mm ARB really is 12mm or is actually 1/2" but someone didn't think the difference mattered I shall find out the hard way.

Zero camber changes with swing arms. It's swing axles that have that where the pivot is central between the wheels and the whole half axle pivots around that. Trailing swing arms are one of the best systems you can employ here. I can't think of any better system for the job in terms of geometry and weight. Every system that moves has some issue but with a 10" swing arm it's utterly ignorable. There's just over 1mm of fore and aft movement of the wheel as the wheel proscribes 2" or so of it's arc (assuming a swing arm largely parallel to the road) but there's absolutely no chance of that being any issue at all.

Bought this one. Be aware that different variants of the same car may use different thickness bars though.

The longer the swing arm the better from the point of view of the arc it travels. Think of a ridiculous 1" swing arm then move the wheel axle 2" around that - it's doing the best part of a circle. Now expand that to the 10" I suggest and that 2" movement around the arc is almost in a straight line. Now from the point of view of leverage against the ARB, the longer the swing arm the greater the leverage and the fatter and/or shorter the ARB you need. Going longer on the arms will make it softer with the same ARB and shorter will be stiffer. In other words you really want a long (10" or so) arm for the geometry of the suspension if you have room and you then work out the correct thickness and length of ARB to suit. If space is a major issue I'd suggest you could go as low as 6" and then use a thinner and/or longer ARB to suit.

The length of the ARB is vital to it's effective spring rate. A longer piece will give softer suspension. It's exactly like a coil spring. If you take a biro coil spring and feel how easy it is to compress 1cm then cut it in half and to get that same 1cm squash you need twice the effort. Longer and/or thinner = softer. Shorter and/or fatter = harder. If you play around with different values in the rate calculator you'll see that just adding or removing 1" to the swing arm or the ARB can have a sizeable effect.


There is a downside to welding the swing arm and the fixed mount to the ARB in that the bearing can not be removed for replacement. I'd get a pillow bearing with a grease nipple so it can be kept lubed and should replacement ever be necessary I'd grind the fixed mount off then weld a new one back on.
 
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I find this most interesting.
To save weight, why not use a PTFE bearing as the pillow bearing?
They can handle about 400kg dynamic which should be ok.
It's also split so it might be possibly to replace it without grinding the fixed mount off.
I understand that the dimensions of the ARB are more critical with a sleeve.
But it worth a investigation.
 
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An interesting thought. What would hold a split PTFE bush in it's tube though? Usually a bolt goes through them so there's threads and a nut available. Not so here.
 
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Hi all

Yes thanks to Popshot and VK3CKC there is a lot of useful stuff on this thread...

However reality rears it's ugly head ? the current Python is in bits and currently unrideable needs fixing for the winter ?



Vertical frame has been shortened to allow clearance for brake arm , allowing brakes cable to come in from the front and NOT be stood up vertical collecting water !

Frame also now has tabs on to allow rear rack to be bolted on when needed.



It's amazing how much paint it missing from any of the frame facing forwards despite none of it being near the rear wheels and the front wheel having a modest mud flap , seems it needs to be bigger.

So frame now in house , paint warming on radiator and brush in hand ....
 
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So frame now in house , paint warming on radiator and brush in hand ....
Have at it! You know much indoor painting and repairing is appreciated. ;)
I hope you get the improved cable runs & brake operations you are seeking.

I am afraid my trike will need a complete back-to-bare-metal repaint job with all the tweaks and changes I have made.
 
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I hope you get the improved cable runs & brake operations you are seeking.
Apart being weather affected , rain ingress , they had actually become acceptable perhaps took longer to bed in that expected ?

I am afraid my trike will need a complete back-to-bare-metal repaint job with all the tweaks and changes I have made.
Been there , more than once , have the tee shirt AND washed it to death....

I did ride the Mk1 through it's first winter sans paint , not to be recommended.
 
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