MC Pherson --suspension

[iansen]

hey,

i have just one question
Why doesn't anybody drive with a Mc Pherson suspension strut?

If you would do that, you don't need Linkages and rods

Thanks a lot

[iansen]

hey,

i have just one question
Why doesn't anybody drive with a Mc Pherson suspension strut?

If you would do that, you don't need Linkages and rods

Thanks a lot

[acedeuce802]

Have you ever seen a camber curve for a strut type suspension?

[Dash]

Correction: You wouldn't need as many linkages and rods.

Also, where do you plan on connecting the spring/damper?

[iansen]

now i have found a diagramm http://fsae.com/groupee_common/emoticons/icon_wink.gif

looks bad http://fsae.com/groupee_common/emoticons/icon_wink.gif

[iansen]

i have seen this?
what do yo th ink about that, dash ?!http://www8.pic-upload.de/thumb/14.11.11/f4up2gs4dalb.jpg (http://www.pic-upload.de/view-11993687/Mc-Pherson.jpg.html)

[iansen]

don't worry, it is not our car http://fsae.com/groupee_common/emoticons/icon_wink.gif

[Dash]

That's not a McPherson strut. Although, with that angle and how the chassis is shaped its probably going to end up being not very pretty.

[JWard]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Dash:
That's not a McPherson strut. Although, with that angle and how the chassis is shaped its probably going to end up being not very pretty. </div></BLOCKQUOTE>

"like"

[AxelRipper]

Maybe someone has a shot of UofM Dearborn's car from a few years ago. Its mounted on the wall of their garage for everyone to see (and for Mr. Royce to point out when he does the SAE talk there). 4 wheel McPherson Strut.

Also, shock angles like what iansen posted are still being used. We have one in more of a strut-type setup. On our pit cart.

[Drew Price]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by iansen:
hey,

i have just one question
Why doesn't anybody drive with a Mc Pherson suspension strut?

</div></BLOCKQUOTE>



Three reasons:

1) Weight

2) Stiction

3) BENDING (reason 3.5 would be load paths, but bending implies inefficient load paths in general [usually]).



BTW that photo is NOT of a McPherson strut suspension....

[PatClarke]

Drew,

There are several more reasons you have not mentioned. I can think of at least three biggies.

Lets hear some suggestions?

Pat

[CameronBeaton]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">McPherson strut </div></BLOCKQUOTE>
Cost and less unsprung weight must be two of them.

Pat, have you ever seen a team with McPherson strut suspension?

[PatClarke]

Yes Cam, I have.
In Michigan about 10 years ago. I cannot remember which team it was but the car was yellow and had strut suspension at both ends. I think they are called McPherson struts (after Earl McPherson a legendary GM engineer) when they steer and Chapman struts (after Colin Chapman of Lotus fame) when used at the rear. The car was big and ugly and inneffective and may well be the one pasted in the workshop (see post above) to remind the team of their past sins.

Cost and Unsprung weight are NOT two of my three 'biggies' important though they are.

Seriously. A team could probably make a case for a strut type rear suspension if they could overcome the camber gain issues and used inboard brakes.

Pat

[acedeuce802]

We got a chance to see University of Michigan Dearborn's early 2000's car with a strut suspension at each corner at the FSAE Workshop they hosted.

[Tom Wettenhall]

Well, to run Mac struts on an open wheeler you'd need either outriggers or truly incredible KPI, wouldn't you? Sufficient caster to deal with the camber issues that creates would make the steering a bit difficult, and there'd be some fun problems with diagonal load transfer perhaps. I don't like the bump steer implications of the wheel paths much either.

Brake torque is liable to create some pretty impressive stiction. Is that why you suggested inboard brakes for a strut rear end?

Coil torsion with steering is also going to hurt the steering effort a bit, although putting one end of the coil on a thrust bearing or even just a nylon washer would probably alleviate that.

There are other problems, like the aforementioned camber control, hefty weight, time and money cost of damaging a strut and so on, but I can't think of anything really huge apart from the steering and braking.

I've got another question if I may; Have you ever seen power steering on an SAE car, Pat?

[PatClarke]

Thats better Tom, the huge KPI causes steer camber issues and the brake torque is reacted in bending in the strut. Both those things would be very difficult to justify to the judges.

And no, I have not seen a car with power steering assist. Nor do I want to! If a 250kg car requires power assist, there are some very basic errors in design.

Pat