suspension for hpv thingy

[dutchman]

I am trying to design a steerable front suspension for my home built bike/trike/hpv thingy.
Most comparable hpvs have a McPherson system, but I was thinking double wishbone.
It has to be light, simple to make and with adjustable camber and caster.
It turns out that it is not very simple to design and make. Does anyone have any suggestions or ideas?
I am pretty familiar with math and trigonometry, so that shouldn't be a problem.

Here is an example of a “conventional” hpv and parts: http://www.go-one.us/Maintaining_a_go-one3.html

 

[rusty69bus]

hmm?

 

[piman]

Hello Dutchman,

a simple fix is to find a scrap Triumph Herald\Vitesse\Spitfire and use the complete front suspension. It is a double wishbone system, and as long as you mount the rack at the correct height all the geometry will be done for you.

Alec

 

[Lippyp]

Not exactly light though, having owned and rebuilt a couple of spits.

 

[MrFluffy]

Theres a guy on one of the forums I moderate on who's building a complete hcs front end for a motorcycle from scratch. In fact the entire frame was cnc carved from a lump of alloy. Its amazing but he's been building it for a couple of years now. The geometry was worked out after dissasembling a tony foale designed frame...
If you can make a hcs design, you save half the weight of the front end, but its dependent on getting a suitable hub etc that can be supported in single shear, be light enough for your purpose yet strong enough to survive the bending motion.
If I were in your position right now, Id be looking at the italijet scooter design and seeing if I could use its geometry or suspension components with a larger diameter cycle wheel

The italjet :-

 

[Lippyp]

I know a guy thats making a bike engined rwd mini in a fibreglass shell who's designed his own suspension setup and is machining it from scratch even making the hubs himself. He's a pretty amazing engineer, he even built his own cnc seup for his miling machine from a kit and some odds and sods.

 

[migmag]

What ever you decide to build good solid jigs for eatch side.

This might be use full
http://www.carbibles.com/suspension_bible.html

 

[dutchman]

Thanks for the tips. I’ve been digging into “suspensionology” a bit.
Man, that is bloody interesting stuff. The design, its geometry, the way the wheels move when pushed up, the influences on steering behaviour and handling. Fascinating.
Pretty difficult to fabricate though since a lot of special parts are involved. Might be a bit over the top for a souped up bicycle, but hey… Its fun.
The simplest design I discovered is this flexible wishbone/springarm design, but I also like the formula one system…

 

[dutchman]

I also like this one, but doubt whether I can find the parts i.e. kingpins, balljoints, etc for it...

 

[rusty69bus]

ignore king pins/ball joints, even the invaild cars don't use these. go for rose joints and bolts through tube for the king pin setup

 

[dutchman]

go for rose joints and bolts through tube for the king pin setup

Good one Rusty, Thanks!

 

[peterd51]

Hi,

please forgive the ignorance...

but what's a rose joint please?

Regards
Peter

 

[migmag]

http://cgi.ebay.co.uk/3-8-x-3-8-UNF-Right-Hand-Rose-Joint-F2-kit-car_W0QQitemZ190190849444QQihZ009QQcategoryZ43120QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

 

[rusty69bus]

that's them, basically it's a balljoint with no taper+thread just a hole straight though

 

[peterd51]

Hi,

thanks for that. Actually, when I first looked at the photo I thought it was one big unit...

took about ten seconds to realise it wasn't!

I must find somewhere to use a couple of these...

Regards
Peter

 

[bill_gj]

Dutchman - pardon my ignorance, but what's the advantage with these things over a straight forward bike?
I realise you've got a low centre of gravity and (with a three wheeler) you can't just fall over, but doesn't it all get a bit heavy compared to a bike, unless you have lots of expensive materials?

 

[migmag]

You get more of an advantage with the pedal angle.

On a conventional cycle on the power stroke your relying on the torsional strength in your back shoulders and arms to maintain a rigid base for your leg to push against.

on one of these contraptions you simply push against the seat.

(for every positive action there is an equal re-action.)


I'll be back..........Gotta go.

 

[dutchman]

Another advantage is the much lower air resistance.
If you add a fairing, you will be dry when it rains as well.
I hope to keep the total weight under 30kg

 

[mymini86]

These are pretty heavy though.

And these must be pretty light. Probably you can change the camber by adding adjustable brace into the chassis like these?

 

[chunkolini]

looks fantastic, but it must bump the weight up massively.
I have ridden a couple of recumbent trikes without suspension and wonder if it is really neccessary, a load of work.
Re the wishbone design, with no dampers that could get a bit 'interesting' on surfaces with a bit of a ripple as it starts to resonate.

Keep us posted I love this stuff.

Chunko'.