Grimsdale
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| posted on 2/7/19 at 07:38 AM |
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quote:
Originally posted by coyoteboy
6082 does have a huge specific strength penalty though, I guess it depends on whether a race vehicle will see significant corrosive environment. And
whether he plans to heat treat after machining or before?
SCC isn't in my day to day, I'd be interested to see some of the automotive failures if you have any links to study?
A corrosive environment to me is any contact with water. If it's an f1 car that's going to live in air conditioned luxury with only
occasional wet uses before the part is replaced, it will of course be fine. Stored in a garage with a little condensation for years would be less
ideal.
It's a shame it's much stronger in comparison, but I don't see 7075/any copper containing Al alloy to be an option.
Heat treatment before or after machining might affect residual stresses (which can drive SCC on their own).
I don't have any examples i can share in any detail. I have seen similar examples of corrosion based failures of aluminium alloys in aircraft
seat rails (which generally live in a dry environment, apart from occasional cleaning and spilt drinks), cheaply manufactured lorry wheels etc.
quote:
Originally posted by mi2jaca
I will have to look into the material selection and SCC. Can proper surface treatment help? Anodizing?
I've just completed a failure investigation of a 7075 component that was anodised. Whilst the anodised layer isolates the aluminium from the
environment initially, you are totally reliant upon the layer staying intact. It will certainly slow the rate of failure, but any minor damage such as
a stone chip, or even from tightening a nut against the material will cause small defects, which allow moisture to penetrate and initiate
corrosion.
Here is an image of a cross section through the failed component showing SCC initiation from defects in the anodised layer, approx 25x magnification.
The component did not appear visually to be excessively corroded, although there were some white whisps of corrosion product on the surface.
[Edited on 2/7/19 by Grimsdale]
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JAG
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| posted on 2/7/19 at 10:06 AM |
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5 Million cycles is just vertical loading of the Knuckle - suspension movement up or down. Other types of loading have different profiles and total
counts.
There are lots of other load cases (Steering inputs, Cornering forces, Kerb strike force and Pothole impact etc...) that we consider. We have a huge
list of 'load cases' and the actual loads vary as they're almost all driven by the vehicle weight and tyre/damper/spring tune.
We calculate the loading to enable parts to be designed and manufactured. Once we've built some prototype cars we collect actual
'road-load' data to compare and confirm our designs are safe or revise them to make them safe.
I imagine that this design is going to be validated more by very rough calculation and then empirical testing.
Justin
Who is this super hero? Sarge? ...No.
Rosemary, the telephone operator? ...No.
Penry, the mild-mannered janitor? ...Could be!
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Mr Whippy
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| posted on 3/7/19 at 07:00 AM |
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as before, just use something tried and tested from a production car, you will have zero risk of failure
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mi2jaca
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| posted on 3/7/19 at 09:04 AM |
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quote:
Originally posted by Mr Whippy
as before, just use something tried and tested from a production car, you will have zero risk of failure
As before, that was not part of the question. Nothing for you to see here, please move on 
Carl Blomén
Writing from Gothenburg in Sweden
When in doubt - Go fast
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Mr Whippy
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| posted on 3/7/19 at 09:53 AM |
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quote:
Originally posted by mi2jaca
quote:
Originally posted by Mr Whippy
as before, just use something tried and tested from a production car, you will have zero risk of failure
As before, that was not part of the question. Nothing for you to see here, please move on
 LOL what an attitude
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mi2jaca
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| posted on 3/7/19 at 10:19 AM |
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quote:
Originally posted by Mr Whippy
quote:
Originally posted by mi2jaca
quote:
Originally posted by Mr Whippy
as before, just use something tried and tested from a production car, you will have zero risk of failure
As before, that was not part of the question. Nothing for you to see here, please move on
LOL what an attitude
Sorry, not trying to have an attitude. Sorry if I came out a little too harsh.
I have been looking at production car components but I just can’t seem to get the geometry that I want.
Once again sorry, I’m not trying to be a prick.
Carl Blomén
Writing from Gothenburg in Sweden
When in doubt - Go fast
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mi2jaca
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| posted on 3/7/19 at 10:59 AM |
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To get back on the subject I think I will have to go with a 6xxx series material instead, I will see what I can get my hands on.
In my latest revision you might have noticed that I added a second hole for the lower ball joint to make for some caster on either side of the car.
I am also wondering if I could/should use these uprights on all four corners. With different brackets (there we go again!) that would be a
possibility. Maybe I am just over-engineering things now?
Carl Blomén
Writing from Gothenburg in Sweden
When in doubt - Go fast
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coyoteboy
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| posted on 3/7/19 at 08:59 PM |
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quote:
Originally posted by Mr Whippy
LOL what an attitude
To be fair, I was thinking the same as him - he's already stated multiple times that he doesn't want to, drop it
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Camber Dave
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| posted on 4/7/19 at 07:36 AM |
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I've been following this thread with interest.
You did ask for a critique but personally I found some comment unhelpful despite the highly qualified authors.
I would narrow the lower ball joint area to give more room for the lower arm, caliper mounting and rim clearance ect.
Your design (also as used on the Elise) permits 'in paddock' camber change without causing toe/tracking change.
Ideal for optimising Tyre temperatures.
For a project I speculated about using a Water jet cut blank similar to the Elise alloy ones. It would have had a double row ball bearing retained by
a bolted ring that also formed the caliper mount (Using a radial bolt caliper).
quote
"I am also wondering if I could/should use these uprights on all four corners. With different brackets (there we go again!) that would be a
possibility."
From the first instance I thought this was an obvious application. For the rear turn the item upside down and replace the steering arm with a
'Dogbone ' bracket to take 2 rod ends from the lower arm.
There was a design shown at Stoneleigh show in 2006 that used exactly what you are thinking of.
A google search failed to find more info but U to U me with your email so I can send you my pics
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mi2jaca
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| posted on 18/7/19 at 06:16 PM |
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Still tinkering along with this project. I have modelled a possible brake disc and realised that I only have 3 mm clearance between disc and upright.
Could this be a problem? I suppose I will use a shield of some sort on the inside of the brake disc so maybe it isn’t a problem regarding sticks and
stones getting in there?
 
Upright2_rev0_20190718
I also humoured myself with using Shape Generator in Autodesk Inventor
(https://knowledge.autodesk.com/support/inventor/learn-explore/caas/CloudHelp/cloudhelp/2018/ENU/Inventor-Help/files/GUID-D74F47F3-FE22-44EF-85BE-7C6B
1F56DCF9-htm.html) to see what it could come up with. Would you trust these uprights?
 
Upright Shape Generator
Carl Blomén
Writing from Gothenburg in Sweden
When in doubt - Go fast
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coyoteboy
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| posted on 18/7/19 at 09:10 PM |
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https://pdfs.semanticscholar.org/15e1/6bc007369b4e1933a000daa0226652197e45.pdf
3mm wouldnt bother me at all.
Is that a student license or a subscription you're using for shape gen. I've fancied using shape gen for fusion 360 but the price is vast.
Another route to the same answer is doing it manually - start with a block of metal with rigid entities at faces you need, clearance where you need,
load it, mesh it, solve it, then use the FoS clipping to refine a bit. We do this a lot when we need to really pare down mass.
[Edited on 19/7/19 by coyoteboy]
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mi2jaca
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| posted on 19/7/19 at 02:46 PM |
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quote:
Originally posted by coyoteboy
https://pdfs.semanticscholar.org/15e1/6bc007369b4e1933a000daa0226652197e45.pdf
3mm wouldnt bother me at all.
Is that a student license or a subscription you're using for shape gen. I've fancied using shape gen for fusion 360 but the price is vast.
Another route to the same answer is doing it manually - start with a block of metal with rigid entities at faces you need, clearance where you need,
load it, mesh it, solve it, then use the FoS clipping to refine a bit. We do this a lot when we need to really pare down mass.
[Edited on 19/7/19 by coyoteboy]
Thanks for the link! I see that they are using 7075-T6, they are not concerned about SCC? From other FSAE papers I have seen that 7075 seems to be the
preferred material but I guess their life-span calculations are rather on the short side.
We have a subscription for Autodesk Inventor at work that I have free access to but we never use the Shape Generator so I am just playing around with
it. Your way of doing it manually sounds like a far better solution for most cases.
Carl Blomén
Writing from Gothenburg in Sweden
When in doubt - Go fast
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coyoteboy
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| posted on 19/7/19 at 04:36 PM |
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Yeah 7075 isn't a problem for a race car, and I'm not aware of SCC being brought up in the design judging, but because the brief is a low
cost, short run race - only car, many areas are neglected if they are not immediate failure risks. Tends to yield fun innovations.
https://images.app.goo.gl/ipnJy3XEoBagVZip8
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mi2jaca
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| posted on 6/8/20 at 04:04 PM |
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I am resurrecting this thread, much to the amusement of Mr Whippy I hope
Life gets in the way, tumors and stuff, you know the drill - but I haven’t given up on this idea, at least not as an exercise for the mind.
Actually I managed to get a prototype 3D-printed so that I could make a test fit of the hub and other details but of course I ran into trouble
directly, Doh!
Will have to make adjustments and maybe trim down the size somewhat. It’s always one thing to see things on the screen and another in real life
Carl Blomén
Writing from Gothenburg in Sweden
When in doubt - Go fast
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steve m
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| posted on 6/8/20 at 05:31 PM |
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My comments will seem a tad harsh, but along with Mr Whippy, and a couple of others, Re inventing the wheel is not the way forward
Its taken you 14 months from design to a pre production plastic item, that as you say, doesn't quite fit, and that is about 0.001 % of a
completed car, especially if you plan on re inventing the wheel with every part "that you feel does not work" your car will never roll out
of the garage, as fossil fuel will of all been used
There is a lot of joy in building a car from scratch, and I have done it, so know the drill, mine took two years, from start to on the road. others
have done it in 6 months, some on this site started building in 1999 and still havnt finished and never will!!
Building a car from scratch has its own dilemma's to deal with on the way, and some serious head scratching moments, along the way, but re
inventing the wheel on some serious critical components, like uprights, Imho unless you have some form of very high standard in metal science and
engineering, please leave it to the professionals who have since the first car ever drove, enhanced the components to an incredibly safe area
As said, just my humble opinion, and its your build, car and life
steve
[Edited on 6/8/20 by steve m]
[Edited on 6/8/20 by steve m]
Thats was probably spelt wrong, or had some grammer, that the "grammer police have to have a moan at
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Theshed
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| posted on 7/8/20 at 11:49 AM |
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I respectfully disagree with you Steve.
I have been building my car for 18 years and it has given me a huge amount of pleasure. I make just about everything myself including my bolts. Along
the way I have learned so much. The journey is as important as the destination for me (although sanding down GRP is wearing a bit thin). Perhaps the
OP feels the same way. It is a matter of choice really.
The design of these uprights looks perfectly conventional and IMHO preferable to those lethal looking mushroom inserrts that some uprights use.
I have bolt on brackets on my uprights as do many endurance cars. Of course stress points and corrocion need to be addressed but that is no big deal.
When you look at the horrendous welding in the picture gallerys in this site it puts worrries about a thick upright cracking into perspective.
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HowardB
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| posted on 7/8/20 at 12:01 PM |
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quote:
Originally posted by Theshed
(although sanding down GRP is wearing a bit thin).
Howard
Fisher Fury was 2000 Zetec - now a 1600 (it Lives again and goes zoom)
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SJ
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| posted on 7/8/20 at 12:33 PM |
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quote:
quote:
Originally posted by Theshed
(although sanding down GRP is wearing a bit thin).
Just done exactly that on my boat and got a hole as a result
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mi2jaca
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| posted on 10/8/20 at 10:19 AM |
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@steve m No problem! Thanks for the input.
I am however not building a car at the moment, just designing an upright and that was what I was looking for input on. I realize that with my current
rate of progress it would take me several hundred years to build a complete car. But I think that I will complete the rebuild of my motorcycle and
maybe the scratch build of a single cylinder engine before I dig into the car project for real
I have a rule against too many projects at once that I try to keep. Barely…
@Threshed That is a completely opposite view as you say and maybe takes us into a bigger discussion about project management(?) maybe, progress and
the question of when to build and when to walk away. How much energy do you want to invest in a project? For me it is as much (if not more) the
journey as the end result that counts.
I know that I read a great discussion on the subject a while ago but can’t remember where it was. Will see if my memory comes back to me later
maybe.
Cheers for the input again but at the moment I think I will just clench my fist in my pocket and not post more here for the time being.
Best regards,
Carl Blomén
Writing from Gothenburg in Sweden
When in doubt - Go fast
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Mr Whippy
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| posted on 10/8/20 at 01:38 PM |
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The interesting thing I take from this thread is the reality that designing a car completely from scratch is really really complicated and easy to
underestimate the shear amount of engineering and material science that has went into every single part of even the most humble production car.
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MikeR
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| posted on 10/8/20 at 01:59 PM |
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On a tangent, if you're not racing it, you'll need something to cover the wheels to go on the road / normal track days. These often mount
from the hub at the front.
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