The benefit of wings fixed on thesuspension [Archive]

Dunk Mckay

11-28-2012, 02:43 PM

I think the case of unsprung vs sprung aero is far more critical in the case of under trays and ground effect devices than it is with wings.

With a sprung undertray/front wing you are moving towards and away from the ground, so your static position needs to be higher up so that you do not stall when things approach the ground. In doing this you compromise on the maximum downforce you can get at normal ride height. Other complications from one side of the undertray/front wing being lower/higher than the other are also a concern.

With fully unsprung undetray/front wing in ground effect yuo can put them as low as you want for maximum aero (minus a few mm for tyre deflection maybe) without worrying about the above problems of ground proximity causing stalling/imbalance. The difficulty with th is is mounting everything to you're uprights and maintaining stiffness in your aero devices, good packacking, etc.

With wings you are merely talking about loads path to the wheels and having more stable loads on the tires, yes this is also important but imho probably less so for aero loads.

In short if you have the time and resources to do it properly, then the pros of unsprung ground effect aero definitely outweigh the cons. With rear wings less so, but if you can think of a way to do it easily and without compromising any other systems or vehicle reliability then it is probably marginally better. More often than not however, it is likely that you could better use your time and resources developing another area of the car first.

old soldier

11-29-2012, 12:01 AM

It seams your last sentence give me some inspiration?I will compare these two kinds?thank you ?
Originally posted by Bemo:
If you don't know why it should be better why do you want to do it? Think about what the differences between the two concepts are. What are the advantages and disadvantages of attaching the wing to the suspension?

And if you choose to do this, make sure you don't use your rear wing as an incredibly stiff anti roll bar...

old soldier

11-29-2012, 01:52 AM

OK?I will try this way

Originally posted by Lorenzo Pessa:
Try to sketch a "force path" from wing to tyres in each of two cases.

old soldier

11-29-2012, 01:56 AM

In the plan?the rear wing will provide 2000N downforce at 80km/h ,sounds a little big.So I will think about other factors,thank you for reply!
Originally posted by cal_len1:
Im assuming that you are comparing unsprung aero vs sprung aero. The question that I would have is how much downforce are you making? Would it require such stiff springs that would compromise other aspects of the car? If that is the case maybe you need to think about wings atttached to the a-arms.

old soldier

11-29-2012, 02:03 AM

Wow?Such a big reply.after reading it,I got a lot of information,But "this is also important but imho probably less so for aero loads",perhaps my english is so poor,Im confused,can you explain more about it? Next I will carefully analysis the load's effect on our suspension,thank you a lot!!!
Originally posted by Dunk Mckay:
I think the case of unsprung vs sprung aero is far more critical in the case of under trays and ground effect devices than it is with wings.

With a sprung undertray/front wing you are moving towards and away from the ground, so your static position needs to be higher up so that you do not stall when things approach the ground. In doing this you compromise on the maximum downforce you can get at normal ride height. Other complications from one side of the undertray/front wing being lower/higher than the other are also a concern.

With fully unsprung undetray/front wing in ground effect yuo can put them as low as you want for maximum aero (minus a few mm for tyre deflection maybe) without worrying about the above problems of ground proximity causing stalling/imbalance. The difficulty with th is is mounting everything to you're uprights and maintaining stiffness in your aero devices, good packacking, etc.

With wings you are merely talking about loads path to the wheels and having more stable loads on the tires, yes this is also important but imho probably less so for aero loads.

In short if you have the time and resources to do it properly, then the pros of unsprung ground effect aero definitely outweigh the cons. With rear wings less so, but if you can think of a way to do it easily and without compromising any other systems or vehicle reliability then it is probably marginally better. More often than not however, it is likely that you could better use your time and resources developing another area of the car first.

RobbyObby

11-29-2012, 03:51 AM

Originally posted by old soldier:
...the rear wing will provide 2000N downforce at 80km/h...

Holy downforce Batman!!!

If you can design a rear wing to pull that much downforce at that speed, what the heck are you still doing in school and why the heck aren't you working for Adrian Newey?

Seriously, set some more realistic aero goals. And if you really do insist on unsprung aero devices, after doing every analysis previously mentioned, do some research on the University of Maryland and South Dakota School of Mines and Tech. They have both ran unsprung aero within the past year.

Bemo

11-29-2012, 07:49 AM

It's not that hard to design a wing giving that downforce at 80km/h. Just use something very heavy to make sure the wing weighs 200kg - there you go. And the best is that you don't have the downforce at 80km/h but at all speeds http://fsae.com/groupee_common/emoticons/icon_biggrin.gif

But to get serious, you should really use a more realistic number, otherwise you may come to the wrong decision as the pros and cons of sprung/unsprung aero change with higher downforces.

Owen Thomas

11-29-2012, 08:57 AM

Oh man, guys... I just had the best idea for a new FSAE event (http://www.google.ca/imgres?um=1&hl=en&sa=N&tbo=d&rls=com.microsoft:en-us&biw=1280&bih=856&tbm=isch&tbnid=d2hl5XQ_0p21LM:&imgrefurl=http://www.hotwheels.com/toys/mega-loop-mayhem&docid=LoCiuhHyJUi5gM&imgurl=http://www.hotwheels.com/files/toys/toys_detail_boosted_Super_loopz_w3411_.jpg%253F134 4460777&w=660&h=340&ei=0pK3UJ2CFcPi2gXutICYBg&zoom=1&iact=hc&vpx=920&vpy=247&dur=844&hovh=161&hovw=313&tx=205&ty=105&sig=101200677995261509798&page=1&tbnh=108&tbnw=210&start=0&ndsp=25&ved=1t:429,r:11,s:0,i:121) for aero teams.

Racer-X

11-29-2012, 09:13 AM

If the aero teams need to do that then the non aero teams need to have a donut cook off.

Dunk Mckay

11-29-2012, 04:57 PM

Originally posted by old soldier:
Wow?Such a big reply.after reading it,I got a lot of information,But "this is also important but imho probably less so for aero loads",perhaps my english is so poor,Im confused,can you explain more about it? Next I will carefully analysis the load's effect on our suspension,thank you a lot!!!

I was simply talking about how you make design decisions for your entire car based on tyre loads. This is very important and TTC data along with a good understanding of vehicle dynamics will help you with this.

However the difference to the performance of the car between sprung and unsprung aero due to this is probably less important than the difference in peak downforce you can get from an sprung or unsprung undertray. This is only from what I have read so I may not be 100% accurate (engineer) I've not yet had the chance to gain first hand experience of this, although I hope to soon. Perhaps someone who has can back me up or shoot me down.

Bemo

11-30-2012, 12:39 AM

I guess the major problem is that an unsprung undertray is much harder to design than an unsprung rear wing. If you want your undertray completely unsprung (which makes sense due to the reasons you mentioned) you would have to attache it to the four uprights an to nothing else. That is no problem as long as all four wheels are in one plane. But if one wheel is going over a bump it wants to leave this plane. I don't see a solution how it should be possible hat one wheel is moving upwards without highly influencing the other wheels (but I have to admit that I only thought about it for a minute http://fsae.com/groupee_common/emoticons/icon_wink.gif)
Also it has to be very stiff, to make sure it isn't whobbling around under the car. So I guess the major reason why you never see this solution (at least I have never seen it) is because it will be very heavy and the negative impact on the suspension behavior is to big

Markus

11-30-2012, 01:43 AM

Weight of the undertray shouldn't be a problem while using geometrial stiffening where possible and core material wisely. It should result in something reasonable, i.e. around 5 to 10 kg.

Sliding mounts with springs could be an option, if you get the spring rates and modal frequencies of the tray right. You could also use some damping to reduce unwanted reactions. I'd maybe try use something similar to these:

http://www.rc-area.co.uk/blog/wp-content/uploads/2009/03/big-bore-shock-kit-for-slash.jpg

Reducing the effective wheel movements would also help a great deal. I think around +-15mm of movement would be enough.

But the impact on suspension might possess a bigger problem. I'm quite sure you could work your way for a good setup with this "4-corner-antiroll-bar" but some unforseen complications are probably encountered. With heavy downforce (>500N @ 60km/h) it could be worth it, so a failed undertray design would quite easily result in ditching it alltogether.

Dunk Mckay

11-30-2012, 01:46 AM

Someone more experienced than I in these matters has kindly pointed out to me that excessive suspension travel (bottoming out) due to high downforce loads is another reason to mount unsprung aero. The quick solution to this of using stiffer springs will then have a direct (potentially negative) affect on vehicle performance.

As mentioned above it is a heck of a lot easier to mount wings unsprung. In the case where bottoming out is your main issue, then mounting wings upsrung to reduce the aero load transmitted to your springs may be a good solution, especially if you are struggling to come up with a reliable, reasonably lightweight solution for mounting a stiff undertray to your uprights.

With regards to the one wheel bump problem, Bemo, I would question how often you are going to encounter this case. It will mostly depend on the tracks that your car is going to run on. If it's a rare occurrence then you might consider how important it is over the other gains. However if you're bumping up apexes (apii? :P) every other corner then you should probably look into it a lot and either keep things simple and mount your UT sprung, or try and figure out a really clever way to have it mounted to all 4 uprights, but if one wheel starts acting different to the other it only has a small or now effect on the position of the UT. I'm sure them some solution for this, even if it depends on lots of fancy electronics. You just have to decide how capable you are at working al of this out and applying a solution.

Personally I'd keep things simple. If your team have not run aero much before then go sprung for ease of design and manufacture. If you have then you should be able to identify the limitations of your existing designs and how going unsprung would likely affect you performance.

Bemo

11-30-2012, 01:57 AM

At a track like at Hockenheim I'd say you really should consider the bump problem. All I wanted to say is that in such a case you have to consider carfully what impacts such a design has on the suspension behaviour. It will link all four wheels somehow and it will have some effect.
The question you have to ask yourself is how much will downforce increase compared to a sprung undertray and if it is worth it to design such a system.
Another design difficulty not mentioned yet is that you have to attach the undertray to the front uprights in a way that the aren't affected by steering. It would be propably easier to attach it to the outside point of the lower A-arm. With all the packaging constraints you usually have there that's not the easiest task.
I don't say it's impossible, but quite a lot of pain in the ass you have to consider.

old soldier

11-30-2012, 04:16 AM

sorry ?it's wrong?I type 200N wrong to 2000N,such careless?
Originally posted by RobbyObby:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by old soldier:
...the rear wing will provide 2000N downforce at 80km/h...

Holy downforce Batman!!!

If you can design a rear wing to pull that much downforce at that speed, what the heck are you still doing in school and why the heck aren't you working for Adrian Newey?

Seriously, set some more realistic aero goals. And if you really do insist on unsprung aero devices, after doing every analysis previously mentioned, do some research on the University of Maryland and South Dakota School of Mines and Tech. They have both ran unsprung aero within the past year. </div></BLOCKQUOTE>

old soldier

11-30-2012, 04:18 AM

sorry for my carelessness?it's 200N
Originally posted by Owen Thomas:
Oh man, guys... I just had the best idea for a new FSAE event (http://www.google.ca/imgres?um=1&hl=en&sa=N&tbo=d&rls=com.microsoft:en-us&biw=1280&bih=856&tbm=isch&tbnid=d2hl5XQ_0p21LM:&imgrefurl=http://www.hotwheels.com/toys/mega-loop-mayhem&docid=LoCiuhHyJUi5gM&imgurl=http://www.hotwheels.com/files/toys/toys_detail_boosted_Super_loopz_w3411_.jpg%253F134 4460777&w=660&h=340&ei=0pK3UJ2CFcPi2gXutICYBg&zoom=1&iact=hc&vpx=920&vpy=247&dur=844&hovh=161&hovw=313&tx=205&ty=105&sig=101200677995261509798&page=1&tbnh=108&tbnw=210&start=0&ndsp=25&ved=1t:429,r:11,s:0,i:121) for aero teams.

old soldier

11-30-2012, 04:18 AM

sorry for my carelessness?it's 200N
Originally posted by Racer-X:
If the aero teams need to do that then the non aero teams need to have a donut cook off.

old soldier

11-30-2012, 04:46 AM

We have use aero for two years?last year we mount front wing and undertray on Monocoque?half monocoque? ?and rear wing on rearbox ?when we went to FSAE Japan?I saw lots of them use unsprung rear wing?so when we begin 2013?we want to use unsprung but without certain reason just folow the trend.Forgive my ignorance.by the way,if there is some papers talk about this theme?

Originally posted by Dunk Mckay:
Someone more experienced than I in these matters has kindly pointed out to me that excessive suspension travel (bottoming out) due to high downforce loads is another reason to mount unsprung aero. The quick solution to this of using stiffer springs will then have a direct (potentially negative) affect on vehicle performance.

As mentioned above it is a heck of a lot easier to mount wings unsprung. In the case where bottoming out is your main issue, then mounting wings upsrung to reduce the aero load transmitted to your springs may be a good solution, especially if you are struggling to come up with a reliable, reasonably lightweight solution for mounting a stiff undertray to your uprights.

With regards to the one wheel bump problem, Bemo, I would question how often you are going to encounter this case. It will mostly depend on the tracks that your car is going to run on. If it's a rare occurrence then you might consider how important it is over the other gains. However if you're bumping up apexes (apii? :P) every other corner then you should probably look into it a lot and either keep things simple and mount your UT sprung, or try and figure out a really clever way to have it mounted to all 4 uprights, but if one wheel starts acting different to the other it only has a small or now effect on the position of the UT. I'm sure them some solution for this, even if it depends on lots of fancy electronics. You just have to decide how capable you are at working al of this out and applying a solution.

Personally I'd keep things simple. If your team have not run aero much before then go sprung for ease of design and manufacture. If you have then you should be able to identify the limitations of your existing designs and how going unsprung would likely affect you performance.

jordan.k

11-30-2012, 05:53 AM

With the integration of an unsprung undertray and wings attached at the lower A-Arm, it sounds very similar to a twin chassis. Very similar to the Lotus 88 and the 2012 SDSM&T car.

https://plus.google.com/photos/105516328773229091928/albums/5740743675929579153/5740748734888514450?banner=pwa&authkey=CLPOzumippS9jgE

jlangholzj

11-30-2012, 06:47 AM

As much of a push as it was to get there, SDSM&T had a relatively successful season with an unsprung aero package. I can't attest to any of the gains in running suck a package but it is possible. I think they had a showing of 4th in auto-x at michigan.

old soldier

11-30-2012, 07:02 PM

I think fix the aero on upright is such a difficult thing for us?I just want to fix the rear wing unsprung?thank you for your advice
Originally posted by Bemo:
At a track like at Hockenheim I'd say you really should consider the bump problem. All I wanted to say is that in such a case you have to consider carfully what impacts such a design has on the suspension behaviour. It will link all four wheels somehow and it will have some effect.
The question you have to ask yourself is how much will downforce increase compared to a sprung undertray and if it is worth it to design such a system.
Another design difficulty not mentioned yet is that you have to attach the undertray to the front uprights in a way that the aren't affected by steering. It would be propably easier to attach it to the outside point of the lower A-arm. With all the packaging constraints you usually have there that's not the easiest task.
I don't say it's impossible, but quite a lot of pain in the ass you have to consider.

Dunk Mckay

12-02-2012, 02:39 PM

Ok, taking all other ideas and variations out of the equation then...

I think you just have to consider how much more complicated and costly it's going to be to design and built uprights and connected supports that you can mount your wing to. Uprights are relatively small so you're going to end up with a fairly high bending moment at the base of the support arms seeing as you can't triangulate very much. This can be designed for of course, I'm not sure about semi-unsprung wings, I guess you could have a longitudinal 'tether' to the back of your roll hoop and "vertical" struts down to the uprights and eliminate this problem while still sending all you downforce straight to the uprights.

It's mainly going to be the complications in the upright, keeping them stiff, packaging properly, etc. If you've got 13" wheels this should be a lot easier.

Bemo

12-06-2012, 06:24 AM

Just saw on the FS Total Facebook Page that UWA is running an unsprung undertray this year. Definitely nice work. Taking a look at that pic you can see, that it is definitely not that easy.
I hope they'll come to Hockenheim with that car next year. I'd really love to see it running first hand!

Zac

12-06-2012, 07:01 AM

Originally posted by Bemo:
Just saw on the FS Total Facebook Page that UWA is running an unsprung undertray this year. Definitely nice work. Taking a look at that pic you can see, that it is definitely not that easy.
I hope they'll come to Hockenheim with that car next year. I'd really love to see it running first hand!

Also looks like a space frame this year.

Lorenzo Pessa

12-06-2012, 02:10 PM

Really few pics.
It's a little bit unusual the solution they use for cooling. the fan is mounted at the beginning of the radiator inlet duct.
We have to wait few days for competition pics.

rjwoods77

12-06-2012, 06:18 PM

Just some notes to gleen if you were to do it. Notice the watts link for the struts....

http://www.rotaryeng.net/Chaparral-2F.pdf

MCoach

12-07-2012, 02:04 AM

As everyone is discussing unsprung aero of the new UWA car, I would just like to ponder how they control roll stiffness front and rear with the wheels basically bonded to a sheet of CFRP like that. Typically this is done through tire, spring, and ARB adjustment, but that seems to be a moot point when your wheels are fixed to each other...

It may do some odd things, and I'm hoping they've had enough time to do lots of test and tune on it to dial it in.

JWard

12-07-2012, 03:01 AM

Originally posted by MCoach:
As everyone is discussing unsprung aero of the new UWA car, I would just like to ponder how they control roll stiffness front and rear with the wheels basically bonded to a sheet of CFRP like that. Typically this is done through tire, spring, and ARB adjustment, but that seems to be a moot point when your wheels are fixed to each other...

It may do some odd things, and I'm hoping they've had enough time to do lots of test and tune on it to dial it in.

The "w" shaped piece of steel looks to be the component to control heave/ pitch. I imagine they have multiple versions cut from various thicknesses of steel. (spring steel?)