Electric Power Assisted Steering

[tom shaughnessy]

I just returned from the SCCA June Sprints where I drove my Formula 500. I was eating lunch with some FSAE graduates and discussing the simularities between our two cars. I am in the process of adapting a electronic power assisted steering system to our chassis.
Problem- I can not find a compact unit that will fit into our car. It would be fantastic to see some of the FSAE technology incorporated into SCCA F-500. If anyone has ANY information on a electronic power steering unit, please respond. thank you tom

[tom shaughnessy]

I just returned from the SCCA June Sprints where I drove my Formula 500. I was eating lunch with some FSAE graduates and discussing the simularities between our two cars. I am in the process of adapting a electronic power assisted steering system to our chassis.
Problem- I can not find a compact unit that will fit into our car. It would be fantastic to see some of the FSAE technology incorporated into SCCA F-500. If anyone has ANY information on a electronic power steering unit, please respond. thank you tom

[Drew Price]

Tom,

Are you talking electric actuation, or an electric fluid pump?

Electric actuation on small-ish road cars that come to mind are new Minis, and the Prius.

Electric pump conversion that seems semi-popular (and cheap) comes out of some of the MR2's.

I think there are some racing specific ones that have come out semi-recently, but I remember them being EXTREMELY expensive, but haven't really been looking for the last 6 months or so, could be something new on the market for this season.

Maybe calling up some of the fab companies and see if you can get any leads?

Best,
Drew

[Adambomb]

Well, I know Saturn used electric power steering for a few years in some of their more "bread and butter" cars. Even then when you consider that you must ADD a heavy electric motor to the system compared to an already heavy and complex engine-driven system, it would be prohibitively heavy and complex.

I can say that in the rare occasion a race car will have power steering (IMCA Hobby Stock comes to mind), the lightest setup is generally a combo of a late-model FWD pump and the existing power rack. Both of which are made for a 3000+ lb car. In fact, most people building race cars from street cars will scour junkyards for parts to convert to manual steering, as it is lighter and doesn't suck power.

As long as you don't plan on having 8 year old girls or 98 year olds driving the car, power steering is, IMHO, an abortion in a racing car. Biceps are lighter than hydraulic systems, if you have a problem steering I'd work on those first http://fsae.com/groupee_common/emoticons/icon_wink.gif

Combine all that with the generally "almost adequate" charging systems in FSAE cars, and now you have another problem.

You can lighten the steering considerably by getting the kinematics right, that would be an infinitely better approach. Not sure how much room the F500 guys have to play with kinematics, but ditto on that too.

[tom shaughnessy]

These units are electric motors that attach to the steering shaft and bolt to the frame. They have a ECU with different settings. I found one unit in England -3.5 kilos but overall too big in size. Yes they are rather expensive-$4000. I've heard some of the FSAE teams are using something similar to these units but can't find any information on them. http://fsae.com/groupee_common/emoticons/icon_smile.gif tom

[rjwoods77]

They are putting them on quads now these days but I would suspect they aren't that light since in the commercials show big fat out of shape rednecks struggling to hold them up. RX-8's currently have electric assist steering as well. No redneck commercials on that though.

[Zac]

I know GM is using electric power assist on a lot of their smaller cars (cobalts and the like). I have no idea about size and weight though. I also don't know how independent the system is from the rest of the cars electronics.

flaming river also has a turn-key system for street rods but it is expensive and probably heavy.

[Drew Price]

Tom,

Do you have hydraulic power steering on the car already?

I was blanking earlier and couldn't remember that Woodward Precision Steering (http://www.woodwardsteering.com/index.php?option=com_content&view=article&id=647&Itemid=544) was the company I was trying to think of. There are some new offerings recently (saw an ad in RCE), and they have very compact adjustable hydraulic units that I believe meet your 3.5kg quote from above and are very compact.

And who doesn't like that anodized red & blue on racing car plumbing bits????? (I know I do....)


Best,
Drew

[Drew Price]

Post coming, I linked to Woodward Steering website, so it's getting moderated, but check that out in the mean-time.

Best,
Drew

[CB23]

I also own an F500, set up for autocross. I have always said - well, since the new front end geometry - that the only limiting factor for me in slalom is how fast I can turn the steering wheel. And I do strength train for this.

I have been curious about this for some time, but it isn't on my primary wish list. Many of us already need to ballast up, so the weight, even for a larger battery, isn't that hard. No alternator, but I have a DC-DC charger that I use in grid, between runs.

Chris

[tom shaughnessy]

I've talked to Woodward and their unit is much to big- also $6000+. The size of the 4-wheeler unit is what I'm looking for. It might work for autocrossing but I want something designed for the track. tom

[Drew Price]

I'm not familiar with the F500 rule book, are there limits on front suspension or steering kinematics then?

What are they?

Best,
Drew

[CB23]

Very few limits. Must be independant suspension, no sway bar allowed, limit on track width (55"), must use only a single rubber hocky puck as your only damper (shock). edit: per corner

Essentially everyone has rack and pinion steering, most cars have "rear steer" (the rack attaches to the rear of the upright). All have disk brakes, nearly all inside the 10" wheels.

Chris

[Drew Price]

Are 10" wheels required?

Are everyone's cars that hard to steer? Seems like you should be able to get trail and to a lesser extend scrub radius down, get the camber curves happy, and find a steering pickup lever arm length / caster angle / rack ratio / steering wheel dia. that works for you, and I bet it would still be cheaper than trying to add power steering, less potential failure points, less maintenance, etc.

Without knowing much about the series yet are those things everyone has worked to sort out yet? I don't know how far into it you guys are, and don't know if you've looked into any of those things yet....

Enlighten me?

(I am graduated and seeking employment if it's just time and energy to make the necessary modifications!)

Best,
Drew

[Adambomb]

Yeah, I'm still not convinced that power steering is necessary. Although these electric-only systems do sound interesting. Lots of new power-assist systems out there, sort of reminds me of my co-op at Mercury Marine where they were working on a power-assist tiller handle for outboard motors. I still think Americans are just getting too lazy though http://fsae.com/groupee_common/emoticons/icon_biggrin.gif

Should be able to get it where you want it with kinematics...although I can understand what a PIA it is to try to change those on something that already works.

One other thing to consider is the often overlooked factor (in FSAE at least) ergonomics. Our '07 car was an absolute bear to steer. Used to have to use breath control and bite down hard to get through a slalom fast, and about 10-15 minutes of fast driving is all anyone on the team could take before their arms turned to mush.

We added a 2" spacer behind the wheel, bringing it closer to the driver, and that completely changed the feel of the car. Not only is it a ton easier to steer, but now your arms don't get tired, your side muscles do (but only after a long day of autocrossing).

[CB23]

10" wheels are a requirement.

I have been told by "a race car suspension design group" that I need to reduce my scrub radius, but that seems quite difficult to do. Though perhaps easier than power steering! (I have kinda hijacked Tom's thread, but the same topic) My uprights are large blocks of machined aluminum, as are the steering arms. Both very stiff, overbuilt.

Most F500's are hard to steer (in autocross), though some aren't. Most of those that aren't just push. . .

In my car, as in most, the steering wheel - 10" diameter - is the maximum size to keep my knuckles from brushing the roll cage. And if I move it any closer to me, then I bump my elbows. This can be fixed, but I'd need new fiberglass. Which again, might be cheaper than power steering. . . http://fsae.com/groupee_common/emoticons/icon_biggrin.gif

And one of the reasons that power steering hasn't been on my list is that I really only want it in slaloms. http://fsae.com/groupee_common/emoticons/icon_smile.gif

Chris

[Drew Price]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by CB23:
I have been told by "a race car suspension design group" that I need to reduce my scrub radius, but that seems quite difficult to do. </div></BLOCKQUOTE>


No, that's the easy one to change, you just go to less offset in the wheels provided that the inside of the wheel doesn't contact the suspension links (in which case you could always go to a slightly narrower wheel).

Changing trail is the hard one. The spindle has to be moved relative to the upper and lower balljoints, which almost certainly means new uprights. It changes the steering geometry some too.

Are your outboard steering pickups bolt-on pieces, or are they integral to the upright? It might be possible to retrofit longer / adjustable ones if the whole thing is one piece, especially if your steering rack has adjustable mounts inboard to keep or even tweak the steering.

Do you know how much scrub and trail your car has now, or do you have a photo?

Best,
Drew

[CB23]

Here are some links to some photos of my front end. Sorry, Tom, I seem to be hijacking your thread even more. . .

edit: two of the links didn't work, have fixed them.

http://i420.photobucket.com/al...500FrameJan04013.jpg (http://i420.photobucket.com/albums/pp290/carf500/F500/F500FrameJan04013.jpg)

http://i420.photobucket.com/al...500FrameJan04009.jpg (http://i420.photobucket.com/albums/pp290/carf500/F500/F500FrameJan04009.jpg)

http://i420.photobucket.com/al...500FrameJan04011.jpg (http://i420.photobucket.com/albums/pp290/carf500/F500/F500FrameJan04011.jpg)

Chris

[tom shaughnessy]

The main reason I'm lookong for power steering is age and injuries. The young kids coming out of karts love the set up. I've been racing these cars for over 30 years and need the power steering to continue. tom

[Drew Price]

Perfectly reasonable Tom! I think that's about all I know about it for now, keep us updated if you find anything.

Chris, I can see what they mean by asserting you should reduce your scrub radius! It looks tricky to do with your setup, but it does look like a re-designed steering pickup might let you tuck the upright into the wheel a little bit, but probably wouldn't gain you much.

Have you tried just going to a slightly slower ratio rack and see if you can get away with it? That might be the easiest thing to do, it looks like you'd have to mess with lots of different components to have a significant effect by doing any of the things mentioned above.

Best,
Drew

[Kirby]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Drew Price:

Chris, I can see what they mean by asserting you should reduce your scrub radius! It looks tricky to do with your setup, but it does look like a re-designed steering pickup might let you tuck the upright into the wheel a little bit, but probably wouldn't gain you much.

</div></BLOCKQUOTE>

Not an option in this case. Using my laser eyes it looks like hes in the vicinity of 6+" of scrub. Bringing in his steering arm is not a possible redesign, not only will it make it harder to steer, his ackerman would go out the window.

Tom,

I've been looking at Electronic Power Steering (EPS) for my own car (260z) as the engine mount interferes with the location for the hydraulic pump. There are a few options (i've attached a link, it will show in due course): http://autospeed.com/cms/title..._110661/article.html (http://autospeed.com/cms/title_Electric-Power-Steering/A_110661/article.html)

I think in "our" case, FSAE/Formula cars in general, electronic/hydraulic hybrids are out, as are electronic "boosted" racks (toyota). The most common swap I've seen in regular cars is using the power-assistance motor that uses a worm drive to your steering shaft.

There are a variety of options; Mazda2, Holden Barina (Opel Corsa), Chevrolet Cobalt, etc. I once knew a grad student that was working on one of these from a cobalt. With a little weight reduction you would be under 3kg for the unit, especially moving to a lighter shaft. The benefit of the units that have contained Steering Control Units, is that they are tunable: http://autospeed.com/cms/title.../A_2390/article.html (http://autospeed.com/cms/title_Modifying-Electric-Power-Steering/A_2390/article.html)

By adjusting the gain on the torque sensors you can adjust how much power is 'added'.

Here is a small unit from a FIAT that looks reasonable (if you don't mind bringing it from O/S): http://cgi.ebay.com.au/fiat-st...8|301:1|293:1|294:50 (http://cgi.ebay.com.au/fiat-stelio-2004-electric-power-steering-column_W0QQitemZ220429166491QQcmdZViewItemQQptZUK_ CarsParts_Vehicles_CarParts_SM?hash=item33529a279b&_trksid=p3286.m63.l1177&_trkparms=240:1318%7C301:1%7C293:1%7C294:50)

I don't know if its possible at all, you could also reduce the size of the driving motor.

[Adambomb]

Hmmmmm, this is a tricky problem. Looking at rack placement, I can't come up with a good way to play around much with kinematics without risking completely spoiling steering geometry. Doesn't look like you have a boat load of caster either, so another simple solution out the window.

I will agree the scrub radius looks quite large though, may well be the best route to take. Aside from changing the uprights, would it be possible to run a narrower rim/tire with the same backspacing? That's the easiest way I can see to reduce it without adversely affecting everything else. Would probably want to scale the rear tires down proportionally to keep it balanced.