Suspension

[JD232]

Does anybody know of any team that is not using a double wishbone suspension?

[JD232]

Does anybody know of any team that is not using a double wishbone suspension?

[Brett Neale]

We used a DeDion rear suspension in 2004 and 2005. Combined with the gear drive, it earned us a win in the Design Event in 2004, but just as any big change like that, it needed to be developed further to work well on track.

Big kudos to anyone who steps out of the box, particularly with suspension.

[mtg]

Cal Poly - SLO uses a live axle rear suspension.

Concordia used a "slider" suspension (like what my old Lego cars used) in 2004.

Brown University has also used a live rear axle (2003 - 2004 I'm pretty sure).

This is argueable, but Lehigh has been using flexures on their wishbones, so at minimum it's a non-conventional double A arm setup.

[Chris Lane]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Brett Neale:
We used a DeDion rear suspension in 2004 and 2005. Combined with the gear drive, it earned us a win in the Design Event in 2004, but just as any big change like that, it needed to be developed further to work well on track.

Big kudos to anyone who steps out of the box, particularly with suspension. </div></BLOCKQUOTE>

I think the design win you talk about stems from your justification for that design choice, not the system itself.

You could use the crappiest system ever designed, but if the justification for it is there it will earn you points.

[overdrive535]

Our 07 car (We had the good sense to not bring it to competition) had a swing arm on the back of it. We call it the "Abortion" car. The whole thing was the idea of a deranged engineer who loves the damn things. Just another great example of a person who is good at persuasion getting a crappy idea accepted.

[Pete M]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Chris Lane:
You could use the crappiest system ever designed, but if the justification for it is there it will earn you points. </div></BLOCKQUOTE>

If you can justify it, then how is it crappy?

[Christopher Catto]

lol. i like your comment. you have a point.

but life is full of those circumstances

theoretically an engine BEHIND your rear axle is not a good idea. but hey, it works for Porsche!

ok bad example. ummm, think maybe using i dunno, balsa accelerator pedal. if you can prove that it's safe enough and lighter than carbon fibre and cheaper, then why not...
it would be crappy if failed every second run.

[rjwoods77]

The website will be updated one of these days/years but here is the car we made but finished to late to be comp this year. It will be at VIR and Detroit. Pretty unique rear suspension I will gladly take credit for. Better pics are on the way soon I hope.

http://www.eng.buffalo.edu/Students/Organizations/sae/formula1/index.html

[The AFX Master]

Rob

I can say that's a pretty unique car overall. In fact, i got surprised to see a solid axle (aluminum!) with a briggs + CVT. This is th kind of config popular on Baja but almost rare on FSAE.
the normal questions:

How many HP's do you get out that Briggs?
How much does the car weight?
I didn't understand well you rear susp (isn't clear on the photos at all), is a "live axle" without a diff?
Really did you save weight with the 7075 axles?, the last rare example of thick axles i've seen was the Delph hollow carbon shafts with flexplates as CV's

[rjwoods77]

AFX,

Dearborn got 42hp out of theirs and not being disrespectful but I think ours will do a little better due to a better exhaust design and a slightly better intake setup. Again let me repeat I have all the respect for Dearborn since they were the team that made me think what I was doing was the right direction. I was always planed for a max of 50hp out of the engine with a max redline of 7000-8000rpm and assuming power dropoff at 5500. Our dyno is just about fixed so we will see what they get out of it now that we have a holdable load mechanism.

The car came in at 375 as pictured in the team photos. It was shy some guards so that will add weight but the 9 lbs drop in flywheel weight will more than cover that. Actual competition fighting weight will be 375-385. It is real heavy for what it is in my opinion. The next generation car if the team stays with this concept ca easily drop 30-50 lbs since the car was more of a construction project than an engineering project. This year is about validation of concept and seeing how far off we are from our assumed performance goals. Next car cycle wont be chicken before the egg.

It is a live axle without a diff. Some teams have not run diffs and done very well as Pat Clark talked about in his video. The choice was made for the sake of simplicity and cost report considerations than performance. Our 51 inch, 7075-t56 axle costs 250 bucks and can be shipped to our door in a days notice. Compare that to a set of half shafts and a diff and and the results will make you vomit. The axle weighs 8 lbs and there is a senior design project in the works for a carbon center section axle bonded to aluminum stubs as well as a carbon torsion tube that will drop about 9 lbs from the whole assembly.

In general I think our car is the best compromise between Cal Poly SLO and Dearborn's car. Both were very significant design studies and we feel that ours is the best compromise at least for this generation. Hindsight is 20/20 and improvements are being made but now that our level of understanding is increasing the follow up car should make our current one look like shit. It should be noted that I have graduated and no longer am a official team member but I still make the hour drive most Saturdays to help them with problems and dissemintate the craziness of my head to help them understand what this is all about. I should also note that the car has still yet to run fully under its own power but the team is taking it slow to avoid fuckups to minimize damage to an already fragile budget. I am supremely confident that the end result will be a shocker to FSAE but then again it is all hearsay and bullshit until the rubber rubs off the tires so we shall see.

[rjwoods77]

Overdrive,

The Cal Poly SLO car used a linked rear axle that utilized a monoshock rear and the requisite "shuttlebox". The only thing is they didn't allow any lateral movement of the shuttlebox with bellville washers. The car basically had infinite rear roll stiffness. This turned the rear suspension a pure rotation swingarm in kinematic behavior. 4th in design without paint on their rear subframe and 12th overall in 2006 Formula West. Just because it doesn't look like a stallion doesn't mean it isn't a prize pig.

[rjwoods77]

Overdrive,

I almost forgot. Arkron dropped a 16hp Briggs V-twin in their mini-baja car that had a swing arm and double a-arm front suspension in 1995 and called it the bajamula. It was doing very well. I believe the story goes their were 20th going into the endurance but had a faulty fuel pump and DNF'ed. Granted it was 1995 but still. They then switched the single cylinder briggs back into and went to a baja comp and won. I think 2003 Lehigh FSAE used a swingarm on their car and finished 30th.

[mike86z28]

We (Concordia) used a slider suspension in our 2001 and 2004 cars. The idea was very original and we obtained many great responses from all judges, even Carol Smith!

Although we have now adopted A-Arms to devellope new suspension designs.

Let me knwo if you need any info on them.

Mike
---
Formula Coordinator

[Arjen]

Could you actually run a double wishbone front suspension and a beam axle at the rear?

[Mike Macie]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Arjen:
Could you actually run a double wishbone front suspension and a beam axle at the rear? </div></BLOCKQUOTE>

Yes

[Arjen]

do you reckon it would work as well as an independent double wishbone front and rear ? im doing my final year project now and i have to find out if the beam axle is a possible candidate for the rear.

[Garlic]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Arjen:
do you reckon it would work as well as an independent double wishbone front and rear ? im doing my final year project now and i have to find out if the beam axle is a possible candidate for the rear. </div></BLOCKQUOTE>

No I don't reckon it would, but it's your project and therefore you need to establish some quantifiable criteria and then see if the beam axle can acheive it.