Hello... and Some Custom Coilover H-Beam Questions!

[scootz]

Hi guys and girls.

I'm building a reverse-trike in the UK... two wheels at the front and one at the rear. Imagine that a BMW HP2 Sport motorbike has ran into the back of a Formula Vee single-seater racing car and youll get the general idea!

The 'thing' will be used on the road and occasionally on track.

I hope to keep the finished weight below 660lbs (300kgs), so it will be a real lightweight.

The chassis tub is a carbon-fibre monocoque and because it was designed for the Formula Vee series, it makes sense that I run the VW front-end that it was constructed for.

I'd like to make the suspension a wee bit more modern though, so would plan to delete the torsion-leafs and have thru-rods instead so I could use coil-over shocks.

I have to admit that I know the square route of nothing when it comes to the VW beam, so I'd be mighty obliged if you could help out a complete n00b!!!

I want to keep things as light as possible, so I guess the first question is... is there any reason why I shouldn't use an aluminium beam (Jamar or similar) in conjunction with a thru-rod / coil-over set-up (please bear in mind that the vehicle is featherweight and will not be subjected to off-road loads)?

Is there a brand of arm that is particularly light, but strong?

Is there someone (preferably in the UK, but anywhere else on the planet is cool), that could build me a complete aluminium coil-over beam, arm and upright package to my specifications?

Thanks in advance!

Here's some pics of what I'm up to...

[bruces]

looks like a motorised bobsled ,very awesome .

[scootz]

[greg mgm]

That's looks great so far. I'll be following this thread. Post Lots of pics!

[BL3Manx]

This place in the UK makes A-arm (wishbone) suspensions that bolt directly in place of the VW beam.

http://www.red9design.co.uk/

[MOON BUGGY]

another one.



http://www.eyeball-engineering.net/a-arm.html

[scootz]

Thanks guys.

I had a look at the Red 9 wishbone set-up, but its a no-go as my tub is a carbon-fibre monocoque and the 'hard-point' for attaching the front axle is the footwell bulkhead. Here's a few pics of the tub to help you visualise...





And here's a couple of pics of a completed carbon-tub in it's normal Formula Vee format (using leafs)...

[BL3Manx]

[scootz]

I'd need to know how it attaches to a bug / bus before I could really comment. It also looks like quite a heavy piece of kit. I'll give them a buzz in the morning to find out more.

I should also add that it might be advantageous for the front end on a reverse-trike to lose some grip as body-roll increases. Too much grip up there and it could very well flip.

[BL3Manx]

Skidding probably would be better than rolling, but staying in control and upright would be best. This article give a pretty good over view of the process.

http://www.rqriley.com/3-wheel.htm

http://www.rqriley.com/images/fig-3whl.gif

[scootz]

Thanks for the links.

[scootz]

I've decided that I will be sticking with a beam up front. The chassis was designed for a beam, so a beam it shall have!

I've consistently read that a ball-joint set-up is the way to go for highway use, so will buy stock BJ (why am I smiling like a naughty schoolboy) arms and spindles.

I want to keep the weight down, so I'm seriously contemplating making an aluminium beam. As I said in an earlier post, the finished weight should be under 300kg, so it will hardly get a tough time! I will however be abandoning the plan to run coil-overs as I don't think an ally beam would thank me for subjecting it to the constant stresses. So torsion leaf's and un-sprung dampers it is

I was going to buy an old rusty (and cheap!) BJ beam to get the sizes, but I guess I could save a bit of cash by just asking the question... does anyone know the inside diameter of the top and bottom torsion tubes??? I have tried searching, but nothing doing (or I'm doing it wrong! ).

Thanks in advance!

[BL3Manx]

Any improvement in handling of ball joint vs. link pin probably wouldn't be worth all the effort to lengthen the distance between the upper and lower tubes if you used an aftermarket aluminum beam, especially if the link pin was fresh and correctly set up.

The adjustable beam is stronger because its reinforced in the center where other non-adjustable aluminum beams have broken. Use a quality billet beam like Jamar, not a Chinese cast one.

http://www.pacificcustoms.com/mm5/merchant.mvc?Scr...ange_high=

With your light weight you could get away with just running a single stack of torsion leaves in one tube and a Formula Vee type internal sway bar in the other.

[scootz]

Thank for that.

Unfortunately the Jamar and JT ally beams are too narrow for my trike (I need a wide track), so I'll be making my own beam. This is another reason why I'll design it with BJ's in mind.

I just need a good reference for tube ID's and placement.

[scootz]

PS - That's a good call about deleting one set of the leaf's and running a sway bar in it's place!

[BL3Manx]

They also make longer trailing arms which would also widen the front track

http://www.woodsoffroad.com/Arms.html

[scootz]

Unfortunately the steering-rack location and the tie-rod apertures were pre-determined for a standard length arm.

So I guess I'll have to gain the track-width through the beam itself.

[didget69]

There's no reason why you couldn't build a front suspension like a newer Formula Ford or similar chassis, but attach it to a shear plate that bolts to the tub front bulkhead - make a square-tube structure that is welded to the flat plate

http://www.race-cars.com/carsold/vandiemn/v92016/v92016pd.jpg

Bryan
_________________
Internet listed credentials impress no one but Mom...

[scootz]

The tub is a two-skin carbon fibre monocoque and has metal inserts at the front to take the VW axle.

Trust me, I've thought LOTS about the possible ways to fit a double-wishbone suspension (and spoke to the tub builder), but the only solution would be to fabricate a secondary bulkhead to support the rearwards a-arm pick-up points.

It's certainly do-able, but it would cost a fortune!

[BL3Manx]