The first 4wd FSAE car revisted

[clausen]

http://fsae.com/eve/forums?q=Y&a=tpc&s=763607348&f=125607348&m=1716064943&p=1

So isn't anyone going to say 'I told you so'?

Regards

Paul Clausen
Uni of Adelaide

[clausen]

http://fsae.com/eve/forums?q=Y&a=tpc&s=763607348&f=125607348&m=1716064943&p=1

So isn't anyone going to say 'I told you so'?

Regards

Paul Clausen
Uni of Adelaide

[PatClarke]

Absolutely not Paul, and I am disappointed you mentioned it.
Dare I suggest the Novocastrians learned more over the last 12 months than you did? Sure, their car didn't get on the track, but remember the event is supposed to be an educational exercise, and for those guys it certainly was.
Sure, I advised them against it in the beginning, but they were well aware of what they were embarking on, and certainly got no more flack from me....rather a quiet respect for a team with a huge project in front of them.
Were I asked, I would again advise them against such a project for your first FSAE car, but will respect that the final choice is that made by the team....and they didn't do a half bad job when you think about it.
Bravo Newcastle!
PDR

Rudeness is a weak mans imitation of strength

[All Wheeler]

I'd like to thank everyone at the FSAE-A competition who supported and helped us. For a team that didn't get on the track, we left the event feeling that we had earned a respect that we otherwise may not have. Alot of people at the event were disappointed that we didn't compete in the dynamic events, and it would be true to say that our static event efforts suffered as a result of the workload. But nobody can be more disappointed than we are right now. Despite this we are left with an odd sence of satisfaction. We hadn't expected to leave the competition with anything, and ended up taking the best endeavour award. Today we are holding a forum at the University between this year's team and the carry over team (of which, two members are of this year's team). We will hopefully be discussing a two year rotating design and build process.
From this experience it is clear now, that all wheel drive in the configuration seen at Tailem Bend may not have had the desired effect. In the last few days, a whopping 30kg or more was added to the vehicle just from poor (and shoddy) interfacing and bracketry. We intend to finish the 2003 vehicle for the sake of data aquisition and finalisation, and look forward to letting you know the results.
I still believe in terms of system design-an all wheel drive with symmetrical half shafts, no straight line shaft angular offset, outer cv centre of rotation on the king pin axis, minimal king pin offset, all wheel steer inversely proportional to the dynamic weight transfer, Low in additional weight , with small transmission losses, would be of advantage. If there are no (or minimal) torque steer effects, small weight penalties and minimal transmission losses, I don't see how AWD can be a bad thing. The challenge lies in incorporating all of the above mentioned into the one design.
Cheers,
Doug

[Sam]

Great effort guys. We at UQ would like to thank you gents for that solenoid valve you lent us. Couldn't have made it without your help..

This kind of sportsmanship is what makes the event great.

p.s. will be in the mail soon guys!!

Sam Graham
Engine Group Leader 2003
UQ Racing

[awhittle]

What is snip <<no straight line shaft angular offset>>

Has anyone posted pictures yet?

AW

[All Wheeler]

Sorry, poor description.
When the wheels are straight, both half shafts share a common axis http://fsae.com/groupee_common/emoticons/icon_smile.gif

[Ben Beacock]

What was your wheelbase and weigh distribution? I noticed the front diff was ahead of the feet in the center to accomplish the no angular offset deal. We can't do this because the front axle is below our legs, but we are trying to minimize torque steer as much as possible with the suspension geometry.

Ben Beacock
Co-Manager
2004 Gryphon Racing - University of Guelph (http://www.soe.uoguelph.ca/uogracing)

[Denny Trimble]

Ben,
Interesting 4wd design you have there on your website. What are you using for a center diff, or is it locked?

University of Washington Formula SAE ('98, '99, '03, '04)

[Ben Beacock]

The center diff is an electronically controlled limited slip clutch from Haldex. We send it data from our engine ECU via a CAN bus and tune its ECU to adjust the torque transfer based on the data.

Ben Beacock
Co-Manager
2004 Gryphon Racing - University of Guelph (http://www.soe.uoguelph.ca/uogracing)

[Denny Trimble]

Sweet! Good luck getting it all up and running, that's a big project but it has great potential. I bet you'll be praying for rain in Detroit http://fsae.com/groupee_common/emoticons/icon_smile.gif

University of Washington Formula SAE ('98, '99, '03, '04)

[awhittle]

Ben

Are you going to have enough room on that right front corner to package the inboard and outboard cv's, caliper, disk and get some wheel travel say three inches into the room that is left when the front dif is that far to one side? What type dif would you use in the front dif(torsen,clutch-pack,viscous...) Would you want front wheel drive until slip...rear wheel drive until slip...50-50 split until ???

Just thinking out loud.

AW

[Ben Beacock]

The packaging is mostly worked out, and the upright is being designed now to accomodate it all. I thought about inboard brakes, but there were a few problems: a) there wasn't a strong place to mount the caliper b) if the AWD system is removed, there are no front brakes, and c) the safety is more difficult to deal with when brakes are that close
So the result is that the brakes are mounted to the outer CVs on the inboard side of the upright. This allows us the low scrub radius/KPI we need to reduce torque steer.

The AWD system is permanently RWD with a maximum transfer of 50% to the front (full LSC lock-up)
The front diff is a cam and pawl type, the same as the rear.

BTW we're praying for snow but I think 139 teams are doing the opposite, so we MAY be outnumbered. I'd settle for some rain.

Ben Beacock
Co-Manager
2004 Gryphon Racing - University of Guelph (http://www.soe.uoguelph.ca/uogracing)

[All Wheeler]

We had a 1800mm wheel base, not quite sure about the track width (1300mm I think). We ended up weighing in at a massive 320kg indicating that we gained around 30kg of mystery mass in the lead up to the competition. Our static weight distribution was quite poor due to the location of the front differential and driver. I believe it was around 39%:61% which effectively would have made all wheel drive redundant if you do the acceleration calcs. It had been recommended to us that the front diff be put in that location to minimise the angle of incidence to the driver in the event of diff/CV failure, but when we got to the design event the judges grilled us saying that we mustn't have trusted our design by not placing it beneath the driver's knees. Looks like you've made a good choice with the longitudinal location of the front diff, but I'm not too sure about running an LSD on the front. There are plenty of people who are for and against an LSD on the front, I'm one of the later. If you can manage it, I would have a backup open diff for the front incase testing with the LSD doesn't go too well. The reason for this is that when you corner, under high load the inside wheel will invariably spin LSD or no LSD. If you run a torque biasing centre diff, it will bridle any unbounded slip to either of the front wheels anyway. With an LSD on the front, if the inside wheel spins faster than the outside, you run the risk of diverting torque to the outside wheel promoting front end slide. The torque steer from uneven shaft lengths (ignoring differing shaft angles under steering) can be approximated from the proportion of maximum energy that can be stored in the shorter shaft, and the maximum amount of energy that can be stored in the longer shaft. You can try and energy match by using different shaft geometry on either side. There is a good article on the web posted by the Ford motor company by Jens Dornhege. I think its called 'Torque steer effects on front MacPherson struts....' Not sure, you might have to do a bit of searching for that one. For your centre diff, you may want your torque bias to the front to be proportional to your dynamic weight distribution. You've probably already thought about that, but it's not likely that you'll have more than about 25% mass on the front under full load anyway. Incorporating your brakes into the CVs is a great idea, so too is the electronically controlled centre diff with permanent RWD. I haven't looked at your vehicle, but it seems as though your layout has been well planned. You're in for a big year and I wish you all the best. My email (atleast for the next couple of months) is douglas.teyhan@studentmail.newcastle.edu.au
If you need a hand ,not guaranteeing that I know anything that you don't, let me know and I'll see what I can do.
Doug

[All Wheeler]

Just had a look at your 2004 sneak preview. Is your rear transfer case a chain drive?
Also, this diagram may just be a schematic, but unless you are using a large diameter hollow shaft to the front, you may be dangerously close to a transverse mode of vibration in that bypass shaft at higher speeds. Placing a self aligning bearing along the shaft may not solve that problem either, and you may have to use a uni joint or go to a different shaft geometry. The front diff does look offset pretty hard core, but there would be nothing stopping you from running your left CV suspended such that your shaft assemblies are symmetrical. Looks impressive, hope you guys can pull it off

[Ben Beacock]

Yes, the LSC will be chain driven. The shaft in the drawing was just for positioning, the real one will be larger in diameter and hollow. We're still debating running another u-joint in the center, but regardless there will be a hanger bearing of some kind there.

As for the front shaft, we're making an extension out the to opposite side so that the angles on the shafts are roughly the same. This also means that the shaft doesn't move underneath the legs, which would require more clearance.

Ben Beacock
Co-Manager
2004 Gryphon Racing - University of Guelph (http://www.soe.uoguelph.ca/uogracing)

[All Wheeler]

Sweet. Sound like you've got your stuff sorted. I am delighted to see another team giving AWD a crack. I don't see any logistical reason why your system wouldn't function the way you want it to. Make sure that you get the car built early enough, and that the drivetrain develops in tandem with the rest of the car though. When we tried to put the drive system in our car, it was the last thing to go in. The spaces where things were supposed to go were non-existent and we had big interfacing problems in the front end. Due to time constraints, the front end was assembled so poorly that if I weren't so damn tired I would have been ashamed. http://fsae.com/groupee_common/emoticons/icon_frown.gif Once again, good luck.
Doug

[Daves]

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>So the result is that the brakes are mounted to the outer CVs on the inboard side of the upright. This allows us the low scrub radius/KPI we need to reduce torque steer. <HR></BLOCKQUOTE>

U. of Guelph, do you have any photos of your 2003-04 car's brakes? Also, what size are the front and rear brake rotors? Are you using all wheel drive again?

[Ben Beacock]

Hi Dave,

Here are some photos of the front (cant find any of the rears yet)

http://www.vwot.org/community/modules/Gallery/albums/albuo79/PICT2303.sized.jpg

http://www.vwot.org/community/modules/Gallery/albums/albuo79/PICT2304.sized.jpg

As you can probably tell, we had problems with the CV boots leaking onto the rotors. I beleive the front rotors are 240mm OD and the rears are 175mm OD

We are using AWD again this year. The front upright design is completely different to try and minimize the distance from the CV joint rotation axis to the steering axis. It was 42mm last year, and should be at 8mm this year using a hubright design with the cv joint as the hub. This means the brakes will be back on the outboard side of the upright. We should hopefully have another 5-10 deg of steering angle each way as well.

Ben

[Daves]

Ben,

Thanks for sharing the photos and information. Yours is the first implementation of this type of mounting I am aware of in FSAE. Did your team give the placement any kind of a special name (it's kind of inboard, but kind of outboard)? Our team is using similarly-mounted front and rear rotors (6.5" (165mm) front and 7.25" (184mm) rear rotors. I think our smaller front rotors are to accomodate the steering tie rods.http://www.letu.edu/_Academics/Engineering/engineering/student-projects/formula/images/ani_INBOARD_BRAKES_t.gif

[PowerStranger]

Hello U of Guelph, what is the steering angle? also, what kind of CV joint did you guys use on the front?

[Ben Beacock]

Wow, long ways back. I seem to remember 35 deg as the max angle in 2005 on the inside wheel.. In '04 they were Suzuki atv front outers, but in 05 were custom made by RCV performance and were able to get a bit more angle. At least the 05 car has never had a problem with turn radius.

Cheers,

[PowerStranger]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Ben Beacock:
Wow, long ways back. I seem to remember 35 deg as the max angle in 2005 on the inside wheel.. In '04 they were Suzuki atv front outers, but in 05 were custom made by RCV performance and were able to get a bit more angle. At least the 05 car has never had a problem with turn radius.

Cheers, </div></BLOCKQUOTE>

Thanks Ben for replying. Are they easy to get? We are building a 4WD Formula Hybrid SAE car right now http://fsae.com/groupee_common/emoticons/icon_smile.gif

[BMEP]

Your answer is a search away on Ebay for a used front driveshaft from a polaris,Honda, etc. quad.

[TMichaels]

@PowerStranger:
Just use in-wheel electric motors and get rid of the drive shafts http://fsae.com/groupee_common/emoticons/icon_smile.gif

Regards,

Tobias

[Adambomb]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by TMichaels:
@PowerStranger:
Just use in-wheel electric motors and get rid of the drive shafts http://fsae.com/groupee_common/emoticons/icon_smile.gif

Regards,

Tobias </div></BLOCKQUOTE>

Big +1 on that one. That's how I'd run hybrid, overall simpler than any other setup and you happen to get 4WD as an added benefit.

[cvargas]

God an AWD FSAE car would be awesome. I can't imagine how difficult it would be to make that.

[bob.paasch]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Adambomb:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by TMichaels:
@PowerStranger:
Just use in-wheel electric motors and get rid of the drive shafts http://fsae.com/groupee_common/emoticons/icon_smile.gif
</div></BLOCKQUOTE>
Big +1 on that one. That's how I'd run hybrid, overall simpler than any other setup and you happen to get 4WD as an added benefit. </div></BLOCKQUOTE>

Hybrid is dying, and Electric at Nebraska in 2013 will be the coup de grace. IMHO. http://fsae.com/groupee_common/emoticons/icon_smile.gif

I suspect we will see front wheel motors implemented in FSE within the next year or two. The efficiency advantages of front regenerative braking are too large to pass up. Plus you get 4WD.

[PowerStranger]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by bob.paasch:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Adambomb:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by TMichaels:
@PowerStranger:
Just use in-wheel electric motors and get rid of the drive shafts http://fsae.com/groupee_common/emoticons/icon_smile.gif
</div></BLOCKQUOTE>
Big +1 on that one. That's how I'd run hybrid, overall simpler than any other setup and you happen to get 4WD as an added benefit. </div></BLOCKQUOTE>

Hybrid is dying, and Electric at Nebraska in 2013 will be the coup de grace. IMHO. http://fsae.com/groupee_common/emoticons/icon_smile.gif

I suspect we will see front wheel motors implemented in FSE within the next year or two. The efficiency advantages of front regenerative braking are too large to pass up. Plus you get 4WD. </div></BLOCKQUOTE>

In fact, there was one FHSAE car implemented the 4WD with two independent front wheel motor drives and for independent wheel motor drives.

http://formulahybrid.iit.edu/cars.php

[TMichaels]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">I suspect we will see front wheel motors implemented in FSE within the next year or two. The efficiency advantages of front regenerative braking are too large to pass up. Plus you get 4WD. </div></BLOCKQUOTE>
UAS Zwickau built AWD FSE cars in 2010 and 2011.

Regards,

Tobias