mx5 diff problems

[CTWV50]

Originally Posted by PorkChop

On another note, I think people are being too sensitive here. I didn't see Phil criticise any one person. Bear in mind, I've got a SSC based MX5 chassis (well, I have 2) and I've actively contributed to discussions with other builders both on this forum and IRL on different aspects of improving the design. I don't feel offended.

If Phil post was constructive about the possible failures of the Saturn chassis then that would be fine or peoples welding but it doesn't come across like that at all to me. Apparently he can't sleep at night thinking about it's short comings! A bit dramatic. No?

Originally Posted by PorkChop

Phil does have a point though about welding quality. If your welding isn't up to scratch (which is a very real possibility with a home build, not saying anyone in particular is not up to it), then should you really be building a car capable of going over 100mph?

We all know this and it's a good point so do destructive tests on your welds and make sure they're not going to let you down. That's what I did. There's no need to describe possible builders as "a less then proficient person" which is very polite insult to my mind considering the tone of his post.

Originally Posted by PorkChop

An alternative could be to use the adjustable wishbones to set up the car, then make a second set of fixed (or semi fixed) wishbones to those settings. This is what Formula Student builders are advised to do rather than have rod ends acting as outboard ball joints, which usually fail.

Thank you, this is useful information and something I hadn't thought of.

Originally Posted by PorkChop

WRT the rear upper wishbones, I think it will be difficult to find a way around this without redesigning the outboard end of the wishbone a la Johno's latest design. I do think that it should be possible to have an acceptable set up for the rear suspension using the SSC design.

I don't see this as much of an issue and like you think it's a workable design.


With regard to the diff support design, I see this as one of the fun/interesting bit's of the build, something we can all throw ideas around with. I enjoy the discussion. I'd like to avoid solid mounting if I can but if that's what it takes then so be it.

With regards to how solid a rubber mounting needs to be, I can jack the rear of my car up using the nose of the diff (obviously only a part built car at the time)
and it does not move at all in relation to the car chassis but that might change during a hard 1st gear launch, maybe 2nd gear launches could avoid this issue completely which might not be as daft as it sounds considering the weight of the vehicle.

[PorkChop]

Originally Posted by CTWV50

If Phil post was constructive about the possible failures of the Saturn chassis then that would be fine or peoples welding but it doesn't come across like that at all to me. Apparently he can't sleep at night thinking about it's short comings! A bit dramatic. No?

I read the not being able to sleep bit as either tongue in cheek, or he's like me. I sometimes go over what I need to do with this bit or that bit of the build.

Originally Posted by CTWV50

We all know this and it's a good point so do destructive tests on your welds and make sure they're not going to let you down. That's what I did. There's no need to describe possible builders as "a less then proficient person" which is very polite insult to my mind considering the tone of his post.

I remember Albert posting up a youtube vid of someone showing you how to weld, where it was more like how NOT to weld. People may not be as thorough as you are with weld testing etc. And Phil did say 'may' not 'is'.

[CTWV50]

Originally Posted by Talonmotorsport

I have been waiting to get that of my chest for the past 2 -3 years and I will never have any thing to say about the Saturn design ever again. But I will say this to all those that I have had conversations with about it .... see 'I told you so'!

Once again, hugely constructive, thanks Phil!

[TheArf]

So I will make this my last input on this subject (well at least for tonight as the cider monster is taking hold) but Phil have you ever completed the build of a haynes because I have never seen anything posted with a completed car built by your good self if you have I appologise if not don't slagg off other peoples efforts and designs

Good night

Arfon

[Short]

Surley, if there was the slightest doubt in the weld, if someones got any common sense, they will get someone else to weld it. Im no welder - I will openly admit that. I employ 4 of them. I tack it/set it up, they weld it for me. There all coded and I trust them.

As for people questioning the Saturn build guide - ITS A GUIDE!!! Its not a foolproof way. Its a learning curve. That's why im building one. to 'play' and have something worthwile at the end (plus I need an excuse to leave the wife indoors with the 2 toddlers!!)

Im not wishing to call anyone down, and I feel kinda guilty for Phil getting a kicking on a thread I started.

Your all great engineers. You've all got guts to take a project on like this, and I admire the talent that there is. Ive got to admit, ive copied some of your ideas (not saying whos )and theres one or 2 builds that I aspire to challenge. Keep up the great work, ALL of you.

[Numplumb]

Hi everyone I wanted to mount the diff nose on rosé joints with poly inserts,this was the idea but when I mocked up a bracket like Phil's there doesn't seem to be enough room between sb4 to be able to do anything but a solid connection, the drive axles don't come out central between sb1 and d11 they are slightly forward is this correct, I have placed the plates cp26 as per Saturn alterations to the build show with the measurements as shown but I would like to move the diff back a bit to give me room to mount the nose as I wanted to do nothing is welded yet no suspension brackets or the cp26 plates, also my chassis was built as per the book for Sierra donar so top damper mount has to be moved forward so if I could move the diff back it would save me doing that, anyone got any suggestions?.
Regards Mick.

[PorkChop]

Why would you mount the diff on rod ends? I can't see any advantage to doing it...

[Numplumb]

Maybe I've not explained properly not rod ends more like the suspension mounts like Caterham mount theirs but just two not four
Regards Mick.

[skov]

Originally Posted by Numplumb

...the drive axles don't come out central between sb1 and d11 they are slightly forward is this correct

Yes, that's correct. Bear in mind that if you do bring the diff back you might need to make the wishbones longer (which wouldn't be a bad thing as the rear wheels are very close to the chassis on mine).

[StruveD]

I went the route of solid mounting the nose combined with poly diff bushings. I don't know how common it is on your side of the pond, but state side its pretty common to either switch to poly bushings or go with a solid aluminum bushings for the diff carrier, with the only negative side effect being increase vibrations and noise. Also doing either of these is effectively solid mounting your diff. Prior to fabricating the nose bracket I had just the poly bushings installed and was only able to move the diff nose 1mm. So solid mounting the nose would have very little effect on things.