Ti Gearbox Case for the Minardi

[desmo]

Here are some images of the new cast Ti gearbox as employed in the Minardi. Although I really fail to see the upside of a Ti gearbox case it is a tour de force of Ti casting, which I understand is tricky business.


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Of particular interest to me is the apparent provision for routing the exhaust through the gearbox into the rear diffuser ala MP4/15.

[Sparky]

These are the missing images...



and


Minardi are obviously trying all they can

And great images Desmo

[desmo]

Thanks, Sparky. I've noticed that the vB format will sometimes add spaces into image URLs for no apparent reason which is what happened here. The URLs were correctly entered. And of course the silly five minute editing timer precludes making corrections...

Anyway, upon reflection the passages through the gearbox dont seem to be ducting for either exhaust or brakes as I cannot see any provision for attaching plumbing to them. Perhaps they're for pushrods or torsion bars for the rear suspension? Guesses anyone?

[Sparky]

Suspension pushrods, almost certainly.

On the second of the pics on your initial post, the holes can be seen to converge above the 'box, in a position where the two shocks would lie.

This theory is re-inforced by the fact that the passages lie between the wishbone mounting positions.

And you're right about the URL entry... We believe you!

[enzo]

I'm not sure about the holes - they look to be way too low and at too steep an angle to be pointing out to the end of the lower a-arm.Also, I don't see anything that resembles a mount for the bellcranks near enough to where the hole emerges at the top. Their purpose is a bit baffling, unless they are trying some sort of combined pullrod-to-pushrod oddity.

[bobdrummond]

Some F1 cars use vertical torsion bars which are positioned alongside the gearbox, or down through the inside (Arrows '98, McLaren & Ferrari, I think). The longitudinal pivot axis for the rocker appears to discount that. Unless, of course, the small diameter shocks are going through the passage, but the torsion springs lie longitudinally. In '99 Gustav Brunner did exactly that, but the dampers didn't protrude from the bottom of the 'box. Look at page 46 of Giorgio Piola's Technical analysis of the '99 cars.

I really like Minardi and it's history of innovation despite their relative poverty. Remember Aldo Costa in the late '80's-Early '90's.

I'd like to see Brunner go to Jordan to replace Gascoyne

It could also be that the passage is for a link to operate a lower rocker which, combined with the conventional upper rocker, would squeeze the damper from both ends giving much sought after damper movement to wheel movement ratios. The more a damper moves, the more effective and controllable it is. Such a setup was used on the Zeus chassis in the early '90's.

Tell me though, where did you get those brilliant photos??

[desmo]

Bob,

The photos are from the website of the firm that cast the gearbox/diff case, here's the URL:

http://www.cevolini.com/

Ah, compressing the damper from both ends. I first recall seeing this idea implemented on Suzuki's excellent Full-Floater suspension used on their motocross bikes beginning, I believe, in the early 80s.

I dashed off a mail to the casting concern asking them about the tunnels in the case. In the unlikely event that they reply with an answer, I'll post it here.

[bobdrummond]

Thanks for the link.

I seriously doubt that the tunnels are to permit full-floating shocks. That set-up would really crowd the critical area at the base of those tunnels.

[Dino IV]

The diameter of the tunnels is indeed too narrow to fit full-floating shocks, bobdrummond.

Great pictures, desmo!
Minardi has some very good mettalurgic specialists working for them, that's for sure. This is the last one in a whole series of great engineering by them over many years. Will Ferrari ever throw away that high hat?

Anyway, it looks like it's either a shock or a damper attached at the holes underneath the side opening of the tube and that it's operated cross-wise by a lever from the pushrod attached to the two 'big ears' on either side.
So with a ltlle text-picturing:
left side of gearbox: wheel+pushrod 0/, lever ^ and damper through gearbox \ like this: 0/^\
Both sides combined: 0/^/\^\0.

Ah I seein bobdrummond's post, the term is 'rocker' not lever. Ingenious system, biggest advantage probably, apart from more rigid rocker system, low CofG.

Some questions:
- where do they attach the rear wing base?
- where are the attachement points for the under wishbone?

[desmo]

Hello Kurt,

Sorry to contradict you but the purpose of these holes is a "big secret".
Actually any expert in suspension design would probably be able to tell you what
they are for but, because of strict confidentiality agreements, we cannot.


We canpublish photos of what we do for MINARDI as we sponsor them but we are
never allowed to get into the technical detail.

Let me know if I can help you any other way.

Regards,

Franco Zucchelli
Export Manager
CRP Technology Srl

[THR]

mmmmmm, this is a little confusing.
this the whole thing? or just the back end and diff?
where is the clever electronic diff?

seems so tiny!

how about one of u lot drawing on one of the pics, where u think the suspension goes. to me there only seems to be a place to bolt the top wishbones too.

[THR]

oh i decided to answer my own question a bit after looking very hard at it.

i think
that the bolt on parts to the casing are the mounts for the suspension
they are bolt on cos they are designed to be sacrifical, upon a prang. to save the box.

something goes in the holes. probs a small shock if u ask me. that bolts to the bolt on bit at one end. so the force must come from above. bell cranked down.
push rods come in at a shallower angle than the holes, so it cant be that.

bell cranks in the big ears on the top?

wot do u lot reckon?

[Marshal]

So Desmo, how much Alpha case do you guys chemi mill off the castings? And which Ti alloy are you using?

Structurally I'd have thought 6-4 might be ok but are there temperature requirements that lead you to 10-2-3 or 15-3-3-3?

I'm also interested in why the split lines on the casing are where they are, is this to improve service ability or is it for casting reasons?

Cheers,

Jonathan Dee,
Metalurgist, BAe Systems Airbus.

[Dino IV]

That's what I tried to text-draw, THR

Considering the width of the big ears, Marshall, they mill a lot off.
I am curious about the split line too, coz the Minardi gearbox was that much hyped because it was one piece.

And still can't figure out the attachement points for rear wing and lower suspension wishbones. Is there some kind of subframe attached maybe?

[bobdrummond]

The lugs at the bottom of the tunnels seem a bit puny to me, seeing as how shock loads are greater than spring loads.

Speaking of shocks, there's a very good interview with Gustav Brunner in the latest "RaceTech" where he confesses that the specification of the damper valving hardly changes from race to race! He's either pulling our leg or else they've got some pretty good dampers on that car.

Last year's Minardi Chassis had unusually long torsion bars positioned along the top of the gearbox. One end was held captive in the rocker pivots, and the other was actually right up at the rear of the engine. At the engine end, a little system allowed the ride height to be altered.

To the casing featured in the pictures, Minardi will attach a long, tapered carbon-fibre crash structure mandatory for a couple of years now.

[desmo]

Let me first clarify that I had no part in the casting of this diff/gear case. If I was forced to guess I'd say that the case is likely venerable old 6Al-4V. It is a well known quantity as a casting alloy, has good thermal properties at the modest temps that a gear case is subjected to, as well as excellent yield strength.

If that is a weld, it's a damn ugly one! Looks like my beginner work.

As for the tunnels, my guess would be that they are to accomidate the torsion bars. The last few MP4s have had their springs mounted in a similar way. There has to be some sort of sub-frame attached to this case, I just dont see enough bosses on it, even if the trailing links/forward parts of the wishbones are mounted on the engine.

[THR]

After careful consideration of all these ideas
i have decided that:

minardi use torsion beam suspension in the rear. one end of the rod going in the angled hole that aims towards the ears.
the pushrod connects to the bellcranks (not shown) which connects to the torsion bar.
the bellcranks also connect to dampers that are mounted in the large angled holes in the casting. these however arent really big enough, so i suggest that the damping is done remotely and in the holes just some fluid displacment is made. (hydralic cylinders). the damping can then be done in a more suitable position. (perhaps closer to the engine, c of g considerations).
four way damping is used on F1 cars, which is all done remotly and i suppose thats the way its done.
with the dampers all linked together to enable roll bars to be uneffective (and therfor not necessary).

the damping will also make all four corners of the car able to work in harmony, which i believe at least the top 5 teams do already.

have u lot read the article on suspension on Gruers site? that talks about this?

anyone actaully know wot the actual travel for a F1 Suspension is? not a guess, an acutal figure? its about 35mm i would say looking at qualifying earlier on today.

also, perhaps the guy who likes metalergy could tell us how the torsion bars are able to stand up to such a HUGE stress for a long time, dont they have a fatigue life? how much do they actually twist? 1 deg? 2 deg? less? is the rate at which a bar twists rising rate?
i would really like to know. as i bet the group would.

thats enough to think about for now!
your turn, wot u think???????

[bobdrummond]

THR, can you post the address of the GRUER site you refer to?

As for 4 way adjustable damping, I believe they've been out of favour for a few years now. They were seen as too complex and what with shock dynos and computer modelling, the adjustability was not required. I refer to my earlier post where Brunner mentioned in RaceTech that damping doesn't change significantly from one race to the next!

I disagree that the tunels are too small for dampers. If you remove the spring-seats and assorted gubbins associated with coil-overs, then I'd say thay'd fit down the tunnels no probs.

The fatigue strength of torsion bars is unlikely to be a problem as they're very old technology and have been used in GP cars since Fangio was a boy. I expect that, in the interests of lightness, the current ones are extremely exotic and lightweight. Titanium maybe? Minardi do seem to have a good source of the stuff.

[Dino IV]

Well it used to be at http://www.gtf1.com but I can't enter it right now, but maybe that's temporarely.

[desmo]

The gf1.com site is down at the moment. Current wheel travel is 25mm front and 80mm rear on the Jaguar. This is probably typical.

[THR]

i still think that the dampers are too large to fit into the holes. well all of the damper anyway. but u may be right.
and i still think that they need the four way dampers to fine tune it.
altho they may not make huge changes in the damping, they will change it from race to race.

[desmo]

Re damper adjustability:

From Race Tech #29:

"...three and even four way adjustment is out of fashion. Seperating high and low speed external adjustments in both and rebound (four way) in theory helps the engineer set up the car in response to driver feedback. However, these days in Formula One teams have such good computer-based simulation programs and rig testing facilities that they can predict with reasonable accuracy the settings required for any given occaision. External adjustment becomes an unneccesary complication, adding unwanted weight."

If you would like a good baseline knowledge of F1 engineering, I highly recommend that you read Race Tech and/or Race Car Engineering. If all posters here read those periodicals, we could avoid alot of the misinformation that is posted here.