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advice on springing a python trike ? long post !!!

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GeoffBird View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote GeoffBird Quote  Post ReplyReply Direct Link To This Post Posted: 25 October 2017 at 11:46pm
You are a perfect student and me a less than perfect professor, Paul. Your trike is obviously very usable in the Real WorldTM and I'm sure an article on how you built it, how you've used it and how you plan to improve it would be of great interest.
Right Time - Right Place - Wrong Speed
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Post Options Post Options   Thanks (0) Thanks(0)   Quote stormbird Quote  Post ReplyReply Direct Link To This Post Posted: 26 October 2017 at 11:13am
Hmmmm.....

Walked into that one , didn't I LOL

There was an article publish a couple years ago covering my build of the first Python trike.

I can write this up also .....

However I am a bit of a butterfly flitting from project to project with far to many on the go at once, the curse of being retired.

So completely unable to meet editorial deadlines , however it does need building and testing thoroughly before next years Holland jaunt in June.

all for now Paul
 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote stormbird Quote  Post ReplyReply Direct Link To This Post Posted: 09 February 2018 at 12:46pm
So this is a mockup of the spring mount.
The joint at the top will not be a 45' mitre joint but trying a sort of lap joint where it is easier to cut and there are 6 welds holding the joint instead of 4 of the mitre joint ?



Like this.

Plan 1

then I need some spring seats/locators to stop spring creeping out of position , probably a washer with a tube welded on that fits inside the spring and the whole lot maintained in place with some 8mm threaded rod and lock nuts ?

or

Plan 2

could the springs be held top and bottom with washers with a slot clamping the outer coils to the frame tubes ?

unsure of stress being put on the retaining rod and whether the rod should be 8.8 hardened ?



So green lines where spring seats will be ?
horizontal cut at blue line
red is where vertical tube will sit [ with notched corner at top ]
purple line show main forces
wonder if I should brace horizontal tube to pivot cheeks light blue lines to stop it bending away from spring caused by vertical forces ?

where the right hand vertical column will be there will be a bracket at the top to take a brace holding the upper seat mount.

regards Paul
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Post Options Post Options   Thanks (0) Thanks(0)   Quote stormbird Quote  Post ReplyReply Direct Link To This Post Posted: 17 February 2018 at 12:30pm
So got a bit further , to much ' honey do stuff ' !!!



So vertical bit of wood to be replaced by steel and welded in position shown ?

Should give me enough room to get in with me ugh torch and clumsy hands.

The surplus will be cut from the top tube.

On reflection this will be a simple 90' butt joint with a piece of 3mm plate capping off the open end , much easier than the notched corner ...

The 3mm capping will be used as a basis for 2 plates overlapping the joint and having a pair of bolt holes in them to mount the bottom of the upper seat mount ?



So blue line 3mm capping plate

red 2 cheeks that will hold lower seat mount ?

green is seat mount - probably a piece of frame seat tube +clamp so piece bolted to seat can slide inside seat tube and so be adjustable ?

It has been suggested that the top tube may bend ? it is 1.25 x 1.25 x 1.5ish ?

regards paul
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Yanto Quote  Post ReplyReply Direct Link To This Post Posted: 18 February 2018 at 7:20am
I would say if you keep that set up you will need external gussets on all corners to try and keep everything in shape.  Without doing the maths (moments) you will not know if the tubing is strong enough, never mind the effects of the welding.

Could you slope the top spring mounting tube to get rid of the vertical tube, then have the seat mount directly above (or just in front) of the the spring? This will require fabricating an internal mounting plate for the spring at angle to compensate though.
Ian, retired.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote stormbird Quote  Post ReplyReply Direct Link To This Post Posted: 18 February 2018 at 12:16pm
Yanto

Yes,  I think it will have to be gusseted it looks far bigger/clunkier than it actually is as the camera was quite close taking the pictures, the vertical tube is only 3.25" [ 8cm ].

Originally the tube was to be sloping however there are lots of problems for me welding it as there would be an internal angle I could not weld up.
Where the BB shell sits is the best place to weld these parts , however the lips of the pivot bracket prevent me getting in to make a good weld.    

Yes the welding is also suspect , only an amateur working at the limit of my skill/experience Wink

regards Paul
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Yanto Quote  Post ReplyReply Direct Link To This Post Posted: 18 February 2018 at 3:04pm
The views/scale are deceiving, it does look bigger.

I wasn't commenting on your welding prowess, far better than I could do, I meant the effect of the heating cycle on the steel.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote stormbird Quote  Post ReplyReply Direct Link To This Post Posted: 18 February 2018 at 4:40pm
Yanto

None taken Big smile

However whilst typing my drivel I had a spanking good idea ?

Realising that if what I was doing looked clunky and crude it probably was .....

I give you the Mk2 rear spring mount ?




As the pink cheeks to the pivot are the strongest steel around why not extend them up to the spring with some 50mm x 3mm steel and add a cross piece at the top to capture the spring ?

This is a mock up from 3mm plywood , the new style mount only needs 3 pieces ?



Plenty of weld area and enough room to get in with the torch :-



For a sense of scale here it is with the seat dropped on :-



and with a wheel also ..



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Post Options Post Options   Thanks (0) Thanks(0)   Quote stormbird Quote  Post ReplyReply Direct Link To This Post Posted: 21 February 2018 at 6:52pm
Ok hardest welding I have had to do to date Jester



had to tack this while it was jigged and clamped to my workmate , this whilst kneeling down and then had to do 6 tacks whilst standing.

these are not normal TIG positions Smile



Then had to weld 2" using the torch in my left hand , not to be recommended !!!



Needs the welds tidying and a bit of fettle.

Those lips on the top were there to stop me burning the edges whilst welding the spring mounting plate , decided to keep them and cut a slot in each one wide enough to allow my small luggage straps to pass through no extra parts and useful.

Found some of my springs came with domed washers so purloined a couple of those for mounting the spring on.

This seems to be bl**dy heavy ! need to weight it and find out.....

Already thinking about springing both rear wheels and making it lighter ..sigh ...
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Yanto Quote  Post ReplyReply Direct Link To This Post Posted: 21 February 2018 at 7:00pm
That looks better than MK1, just what i was trying to explain, I would get this version up and running and used a bit before starting another.
Ian, retired.
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