first trike

[big mick]

i am about to embark on my first trike building journey. i have 25years engineering experience ie machining, welding, fabrication, so i hope my construction problems will be limited however i do have questions to ask. i have a 900 diversion motor 1.whats the best rear end i can use that has half shafts.2.i intend to mount the diff central in the frame which will mean the prop will be at an angle what is the severest angle i can have before i over stress the ujs.3.i like swedish style trikes which means long forks,whats the longest set of forks i can get away with so it will handle at low and high speeds incorperating rake andtrail calculations if possible 4.i plan to use cds round tube to make the frame i have access to a mig welder or should i tig it i can`t make up my mind.

[Alik Windrush]

Wow, questions questions. What I say to everyone is just have a go cos in the first two weeks you'll learn 90% of all you'll ever need to know about building a trike......... Trouble is that by then it'll probably be too late and you'll have to start over..!!
Bike props really don't like being run at steep angles. They are designed to run almost straight and you may find you'll need to 'ease' out the UJ with a grinder to achieve the angle.
To avoid this (if you really don't want to off-set the diff) try aiming the prop flange toward the bike engine driveshaft. You can probably win an inch without anyone noticing the diff aint quite straight.
CDS is lovely..... If you have a mandrel bender.
TiG is prettier
Long forks will give crap handling and an element of 'Flop' over-centre but look fantastic.
Springer forks (with a bottom rocker wheel mount) can help with handling probs but not as pretty as tele's.
Forkin' by Bob in the USA is the guy for extreme over length tele's.
Or just built something cheap and easy as practise. Good luck.

[Blackjack]

1.whats the best rear end i can use that has half shafts.

All rear axles have half shafts. Do you mean an independent set up? Presumably by "best" you mean readily available, cheap and with a wide range of diff ratios? Then Sierra is probably the answer. Small and light? Something like a Suzuki Balero (Small 4 WD saloon version of the Swift hatchback) rear diff might appeal if the ratio you needed was available.

2.i intend to mount the diff central in the frame which will mean the prop will be at an angle what is the severest angle i can have before i over stress the ujs.

No cut and dried answer to this one, depends on the joint as they vary quite a lot. It is possible to relieve the yokes to get a bit more travel on some of them and if you're planning on using the bike one on the front then measuring the angle the swing arm travels through from full droop to fully compressed will give you a good idea of what's sensible for that particular joint.

3.i like swedish style trikes which means long forks,whats the longest set of forks i can get away with so it will handle at low and high speeds incorperating rake andtrail calculations if possible

Define "handle". Especially in the context of a Swedish style trike. You'll be lucky to get a turning circle measured in metres and not kilometres let alone anything else! Big back tyres? Skinny front one? Lots of rake? It's going to turn in like the Exxon Valdez. Trikes put an entirely different set of forces through a pair of forks, and big long ones bend. Trikes steer like a car and not like a motorcycle, which means the steering axis needs to be fairly upright. Once you start kicking the front end out, the trail becomes irrelevent, it ain't going to steer.

4.i plan to use cds round tube to make the frame i have access to a mig welder or should i tig it i can`t make up my mind.

Makes no odds. I'd argue MIG is preferable, given that you have somebody competent welding it up. TIG weldors tend to get overly obsessed with tiny beads, often to the detriment ot the actual strength of the weld.

If I can throw in an observation at this point, you're labouring under a bit of a misconception. Your construction problems begin with the design, having the skills to execute a job only means the problems don't become apparent until you start riding the bloody thing!

[Blackjack]

...........
Forkin' by Bob in the USA is the guy for extreme over length tele's.
........

Frank?????

And if you're running UJ's the flanges really ought to be parallel because that and correct phasing is what they rely on to work properly. Driveline shunt, which sounds like a German insult but is what you get if your flanges aren't parallel and your yokes are out of phase.

[Alik Windrush]

1: Your right.. Forking by Frank, ta
2: What are you doing up at this time of night.?

[Blackjack]

Mostly taking the piss......

No. I'm usually up at this time of night. I'm crap at going to sleep, though once I'm started I'm world class at the actual sleeping bit.

[Alik Windrush]

Sleep is what I do between about 3 am and 10 am. Tinned beer tastes better at this time of night.

[Sir Ewok]

Was still at work, while you lot were playing.... :rolleyes:

[Mad Dog]

An idea for the offset problem:-

If you get hold of a 4 wheel drive diff, then knab the transfer box as well. Or just get a transfer box anyway, coz they do this rather well with a bit of jiggery pokery.