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Author: Subject: Critique my upright design
Grimsdale

posted on 2/7/19 at 07:38 AM Reply With Quote
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

posted on 2/7/19 at 10:06 AM Reply With Quote
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


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Rosemary, the telephone operator? ...No.
Penry, the mild-mannered janitor? ...Could be!

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Mr Whippy

posted on 3/7/19 at 07:00 AM Reply With Quote
as before, just use something tried and tested from a production car, you will have zero risk of failure
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mi2jaca

posted on 3/7/19 at 09:04 AM Reply With Quote
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

posted on 3/7/19 at 09:53 AM Reply With Quote
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

posted on 3/7/19 at 10:19 AM Reply With Quote
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

posted on 3/7/19 at 10:59 AM Reply With Quote
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

posted on 3/7/19 at 08:59 PM Reply With Quote
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

posted on 4/7/19 at 07:36 AM Reply With Quote
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

posted on 18/7/19 at 06:16 PM Reply With Quote
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
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
Upright Shape Generator






Carl Blomén

Writing from Gothenburg in Sweden

When in doubt - Go fast

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coyoteboy

posted on 18/7/19 at 09:10 PM Reply With Quote
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

posted on 19/7/19 at 02:46 PM Reply With Quote
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

posted on 19/7/19 at 04:36 PM Reply With Quote
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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