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Dash
07-29-2009, 06:01 PM
Hello all,
I ran across an article talking about Flexure joints the other day, and have sense been trying to find sources to read about them ( seeing as they look pretty cool). Just curious if anyone might have a source of information about them in general.
Dash
07-29-2009, 06:01 PM
Hello all,
I ran across an article talking about Flexure joints the other day, and have sense been trying to find sources to read about them ( seeing as they look pretty cool). Just curious if anyone might have a source of information about them in general.
exFSAE
07-29-2009, 06:09 PM
Not much to them.. just a strip of material that flexes. Idea is to use that instead of a bearing for a pivot.

Can be metal, can be composite, can be whatever so long as it holds up to the static and fatigue loads.
Dennis Seichter
08-01-2009, 10:46 AM
Check for example the cars from Darmstadt and TU Wien, they both use flexplates.
Yellow Ranger
08-02-2009, 09:58 AM
lehigh university use them as well
Zac
08-02-2009, 10:58 AM
UWA is also using them on their current car.
Drew Price
08-02-2009, 04:44 PM
Don't forget TU Graz's titanium flextures!


Best,
Drew
Mike Macie
08-03-2009, 02:31 PM
Does anyone know how much flexures affect your wheel rate. I know it will vary by each design. Just a discussion i always wanted to have with a flexure team.
Drew Price
08-03-2009, 05:46 PM
Aah, from memory, it was pretty small numbers, 5-15 lbf/in or so depending on lots and lots of things, the tricky part is that it changes as a function of suspension displacement from static.

Should be essentially linear.

For a 2" suspension travel or so, I bet a really really clever engineer could probably even get the uppers and lowers pre-loaded against each other and do some cancelling each other out, but that comes down to your assembly and manuf. tolerances for the whole suspension and frame system, since corner-weighting the car will put all 4 corners displaced a little.

This part of the reason for very small rate addition from the flexture.

Best,
Drew
Tim.Wright
08-04-2009, 01:11 AM
I belive UWA's was strong enough to act as the primary spring when their pull rod broke at FSAE-A last year.

Tim
TimR
08-04-2009, 05:06 AM
I'm from the Sydney Uni team and currently investigating these. Currently I'm investigating spring steel couplings as our budget didn't stretch to the kevlar composite ones I've seen on the UNSW car and others.
Who else, besides UWA, is looking at using CF driveshafts/flexible couplings?
Adambomb
08-04-2009, 11:06 AM
TimR, are you talking about flexures in place of CV joints? That sounds pretty wild. Now you've got me thinking...

We're also considering steel flexures on the a-arms. If nothing else because I know we're good with steel, but I still lack some confidence in our CF manufacturing. As for the wheel rate effects, I'd say look at force vs. displacement, and throw that in your "total" wheel rate calculations. Drew's idea of cancelling forces sounds pretty cool too, wouldn't be too hard to figure out the necessary preload I imagine.
Zac
08-04-2009, 12:37 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Timo:
I belive UWA's was strong enough to act as the primary spring when their pull rod broke at FSAE-A last year.

Tim </div></BLOCKQUOTE>

I could be wrong, but doesn't UWA use torsion springs instead of coil-overs?
Tim.Wright
08-04-2009, 10:22 PM
At the back I'm not sure. They definately had them up the front. What ever they had at the back it was pull rod operated.

Tim
TorqueWrench
08-04-2009, 11:32 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Adambomb:
TimR, are you talking about flexures in place of CV joints? That sounds pretty wild. Now you've got me thinking... </div></BLOCKQUOTE>

I wish I could find my notes from that Rutgers seminar about now. Steve fox showed pictures of a team that used a rubber donut-type flexture in their driveline as a replacement for CV joints. I seem to remember him saying it didn't end that well for them that year, but thats not saying it can't be done correctly.
Peter
08-05-2009, 12:50 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by TimR:
I'm from the Sydney Uni team and currently investigating these. Currently I'm investigating spring steel couplings as our budget didn't stretch to the kevlar composite ones I've seen on the UNSW car and others.
Who else, besides UWA, is looking at using CF driveshafts/flexible couplings? </div></BLOCKQUOTE>

Delft (and I remember an other team as well) used this from 2003 to 2006:

http://dutracing.nl/wp-content/gallery/dut06/0080.jpg

Be aware of the effect on the wheelrate, as for the light Delft cars this effect was notable.

Peter
Delft 04UK, 06FSG