VR6 Dropped Spindles/hub

[KipVR 1]

As Sam says it would be a much neater job to move the 'spindle' so to speak, but how much clearance is there from the outer CV joint when in place to the underside of the suspension strut mounting lug- 10mm maybe? It doesn't look like there would be much, which means it would be difficult to lower the car by moving the bore through the hub upwards. 30mm would be out of the question.

 

To get that much you would have to reduce the suspension travel (using shorter springs) and then correcting the geometry using the LBJ method- or lower the mount on the cast hub/upright. If you use the LBJ method it would be best to extend the Ball Joint along the KPI to maintain the existing scrub radius.

[Kevin Bacon 5]

OK, so if we have access to quick prototyping and sand casting, the next steps are:

 

1) Figure out how far we need to move the TRE & BJ mounts down. I suggest we use the centreline of the machined bearing hole as a reference, unless there's a better one?

 

2) Cut and shut the required length of metal into a pair scrap bearing carriers and tidy them up.

 

3) Produce a mould of the modded bearing carriers and then go through the sand casting process.

 

Obviously the metal we use is critical. I'm guessing VW used a ductile iron alloy of some kind? Anyone know for sure?

 

Does this seem feasible? Steps 1 and 2 I can see happening for sure, but 3).... I dunno. Could be costly and very time consuming?

 

I think if a batch was run off, there would be enough interest to recoup the outlay. In fact the foundy may insist on a batch of XX, or even XXX being run off anyway?

 

Or does anyone know any Blacksmiths who could do a small run? :D

[poll250 0]

I go away for a few days and all miss all this fun!

 

Boost, if you need access to a lowered VR to take any measurements I'm back in Central Oxford now (Iffley Rd so just down the road from your bro/car).

 

I'd imagine there would be a load of people on VR6OC and CGTi interested if this pans out.

[24V Renshaw 0]

I still need to get out and measured my currently unlowered wishbone angle. Am away on business at the moment though so not had chance.

 

Another option given the small numbers is to machine from billet aluminium like the race car boys do....

 

Jay

[boost monkey 0]

 

3) Produce a mould of the modded bearing carriers and then go through the sand casting process.

 

...

 

3).... I dunno. Could be costly and very time consuming?

 

 

Never fear! Both the protopeople and my casting guy can accept CAD 3D models so no moulding required. If we know (and can measure) exactly how and where the scrap bearing carriers were cut and shut one of us (me/KipVR if he's happy to) can modify the current hub 3D model to match what was done in real life and we can fire that across.

 

I don't recommend proto'ing for metal parts - they build it up in layers of 6 microns, so solid parts end up being incredibly expensive (thousands normally). A plastic proto wouldn't take any of the force or weight but could work for checking geometry? I'm happy to fire off the current hub model to them for a ballpark quote. I'll remove the centre spindle before hand as it will just add £££.

 

Re the foundry minimum order, I'm not sure they will have a min order but the tooling for the casts will be so expensive that you will prob want to get a decent amount of them made just so we're not paying £100 each for a modded hub. Just from experience. Actual casts after tooling seem to cost fook all.

 

---------- Post added at 12:26 PM ---------- Previous post was at 12:17 PM ----------

 

I go away for a few days and all miss all this fun!

 

Boost, if you need access to a lowered VR to take any measurements I'm back in Central Oxford now (Iffley Rd so just down the road from your bro/car).

 

I'd imagine there would be a load of people on VR6OC and CGTi interested if this pans out.

 

Hi Andy,

 

yeah that would be great. Can I come over and pull your hub and balljoint out? ;-) :-D

[KipVR 1]

If you go down the cast steel route, they can use the modded upright as a pattern but they will need one for each side and I'm not sure how accurate the modified parts could be. However they will still need to know all the post machining ops, classification etc.

 

The other option is to model a modified upright, we can rapid prototype from there- but that would be quite pricey but more accurate.

 

Or just model a new upright using the existing scan as a reference, do a drawing, and get some machined from ally, not sure how much that would cost though, if you were to buy the ally for one set, in 7075 it would cost about £150 per side. But it might be much cheaper if you bought enough for 15 sets but I'm not sure.

 

Seems I was replying as Jon was too!

 

Jon/Boost Monkey, there is no point in modelling a pair of modified hubs, you may as well do the modifications in the CAD as it'll be more accurate, I don't mind doing this/you doing this, but others may want to go down a different route of production and i don't want to step on any toes...

Edited November 2, 2011 by KipVR

[boost monkey 0]

Seems so! Lunchtime :D

 

I'm hoping we can just use the mirror feature in CAD to make an opposite hub for the other side. Pikey but should work.

 

How do we feel about fabricating new hubs? Super pikey shellsuit style?

[Kevin Bacon 5]

If the modelling can all be done with CAD, that's even better then :D I'm not used to 'making things' with these fangled computers. I'm a touchy feely man!

 

Jay's idea of CNC'ing a chunk of billet did cross my mind but I personally wouldn't trust it until a full stress analysis had been done, which is more cost!

[boost monkey 0]

You can stress analyse on the fangled computers too which will save cost. They can be pretty accurate too! We can always overengineer / overestimate the forces and then build in a factor of safety so they're completely bombproof.

 

 

@KipVR, sorry mate I see what you mean about the casting people needing an opposite side to take a pattern from. Replied too quick.

Edited November 2, 2011 by boost monkey

[quicky1980 0]

I may be able to get the hubs assessed for their material properties so we could confirm the spec, if needed still?

 

Regards to costs and minimum orders. We can spread out the word to other vr6 owners, at £150 per side I think this is good value.

 

Do we need to carry out stress analysis due to the changes in the mounting positions and the effect it has on the integrity?

[Kevin Bacon 5]

Thread Stickied :D

 

Sam, the stress analysis is more to make sure the material we use is up to the job, I'm just picky like that :D You guys certainly have a good grasp of CADs n things so I'll trust your judgement!

 

Just thinking......if we do CNC from chunks of chunky billet, this would not only reduce unsprung weight, we could also incorporate some other tasty mods whilst we're there, such as mountings for 4 pot calipers, a better way to attach CV grease splash plates and maybe go another 10mm outboard. Widetrack + :D That would then make our ET43 Speedos a nice ET33 effectively, making the arches look better filled and widetrack done the proper way.... spacers need not apply!

 

Although if we don't keep the King ping axis the same, would that fook up the scrub radius? Hmmmm....complicated stuff this....

Edited November 2, 2011 by Kevin Bacon

[boost monkey 0]

KPI is a tricky fella. I can't say I completely understand it so I'll refer to Kip on this one.

Kingpin inclination IIRC is the angle of the line through the top suspension mount (i.e. the 2 holes for the bottom of the damper) and through the bottom mount (in this case the lower ball joint). If this is changed I think the camber of the roadwheel may change when turning? Must get my old textbooks out!

 

*calls for Kip*

[boost monkey 0]

Ok so here's the kingpin on the hub model (attached to forum for Kev!)

 

 

As seen it's the angle through the top mount and the bottom mount on the hub. You continue this line down to the contact patch of the tyre, and the distance between this point and the centre of the contact patch is called the scrub radius (SR).

 

SR allows for easy or hard steering, and determines how well the steering wheel will re-centre itself to straight ahead position after a steering input has been made. Wiki has a good description of it. Search for Kingpin.

 

Hope this helps.

 

Jon.

[Kevin Bacon 5]

Cool, yeah that's my understanding of it although I thought Caster was mainly responsible for self centering? I know scrub radius affects things like tramlining because you certainly get more of that when fitting wheels with less offset!

[boost monkey 0]

The only thing i really know about castor is that more is better from a stability (high speed) point of view.

 

There's a great book called Competition Car Suspension which I leant to Dirtytorque about 3 years ago and have never seen since...!

[KipVR 1]

That tends to happen with books! At least you can remember who you lent it too! Spot on with the kpi etc- edit sorry no the kpi goes from your top mount to your lbj

 

Kev, analysis would be done as part of the design process, especially suspension components!

 

Getting the geometry isn't a problem, deciding on the geometry would be the hard bit. I'm sure people would want different things...

Edited November 2, 2011 by KipVR

[quicky1980 0]

shouldnt the angle of shown above be taken from the top mount pivot point, then to the ball joint pivot point? where you have it now would be OK if we had double wishbones (nows theres a thought....)

http://i74.photobucket.com/albums/i273/Chris_Eyre/Chassis/tn_KPA.jpg

 

---------- Post added at 06:35 PM ---------- Previous post was at 06:28 PM ----------

 

looking at the link where I found the above picture, there is some interesting reading. may be of use?

http://www.clubgti.com/forum/showthread.php?t=228182

[KipVR 1]

Yes it should be to the strut top mount- I'm not sure if that's what he has done though? The wording can be read two ways...

Edited November 2, 2011 by KipVR

[boost monkey 0]

no i took it through the top hole on the hub. My bad!

 

But, using that awesome corrado chassis dimension scan I can redo it as it gives centre of top strut mount from centre line of the car, that just leaves working out the distance between LBJ to the centre of tyre contact patch.

 

Either way, all the design is possible. But as Kip said perhaps people would want different things? I guess we could make "allowances" for 4-pot mounting etc on the new hubs, and then if people don't want them they don't have to have them. I'm sure we could devise a way of fitting removable brackets. Perhaps that is making it too complex though.

[boost monkey 0]

@Sam, I did have a think about double wishbones before! I reckon you could prob mount them directly to the side of the chassis rail (should be strong enough) but nothing really came of it. Just daydreaming really :-)

[KipVR 1]

How far away from the disk guard is the lbj? Is there enough room to move it down in line with the kpi or would you have to move it vertically down?

[boost monkey 0]

I think we need some

 

 

to go have a look. Bonus points to those who know how to use vernier calipers (and have a pair!) :D

[VR6Pete 0]

I am a little confused and lost in all this CAD Jargon..... :)

 

What benefits would fitting these to my Corrado give me?

[24V Renshaw 0]

http://en.wikipedia.org/wiki/Automobile_handling :)

 

Main focus is on roll centre, if you lower the car you want to keep the wishbones pointing up/level by extending the position of the pivot point (ball joint) down.

 

Jay

[Kevin Bacon 5]

In other words, the car will drive like it does on the standard suspension, but XX cms lower :D