Pat's design error of the month contest Dec 2008

[DART-CG]

Take a look at the pictures at the end, Pat claims he found at least 18 design errors on that old F1 car

Pat's design error contest (http://www.formulastudent.de/public-relations/fsg-news/news-details/article/pats-column-december/)

Here are the ones I found with a first glimpse:
- scariest ARB-actuation with the longest ARB I've ever seen (at least 5 design flaws)
- steering rod with a huge angular offset for best linear actuation http://fsae.com/groupee_common/emoticons/icon_smile.gif
- mounting of the steering rod to the hub will result in a torsional moment to this odd looking spigot.
- spigot seems to be screwed to the hub. This means that a torsional moment during cornering could unscrew the spigot, hmmmmm http://fsae.com/groupee_common/emoticons/icon_smile.gif
- good old rod ends in bending
- bad vector force load pathes where the heavily stressed lower a-arms are mounted to the chassis will result in beding
- brake lines are carried by a sharp looking metal sheet -> danger of abrasion when moving due to cornering
- mounting of the shock will result in a beding moment to the lower a-arm
- Uhmm, where is the roll center supposed to be?

In addition I don't want to crash in that car http://fsae.com/groupee_common/emoticons/icon_smile.gif The front steel frame will have little effect and supposedly would simply snap away. And the fire extinguisher would be a good slam to the head...

Merry Christmas and a Happy New Year to all of you!

[DART-CG]

Take a look at the pictures at the end, Pat claims he found at least 18 design errors on that old F1 car

Pat's design error contest (http://www.formulastudent.de/public-relations/fsg-news/news-details/article/pats-column-december/)

Here are the ones I found with a first glimpse:
- scariest ARB-actuation with the longest ARB I've ever seen (at least 5 design flaws)
- steering rod with a huge angular offset for best linear actuation http://fsae.com/groupee_common/emoticons/icon_smile.gif
- mounting of the steering rod to the hub will result in a torsional moment to this odd looking spigot.
- spigot seems to be screwed to the hub. This means that a torsional moment during cornering could unscrew the spigot, hmmmmm http://fsae.com/groupee_common/emoticons/icon_smile.gif
- good old rod ends in bending
- bad vector force load pathes where the heavily stressed lower a-arms are mounted to the chassis will result in beding
- brake lines are carried by a sharp looking metal sheet -> danger of abrasion when moving due to cornering
- mounting of the shock will result in a beding moment to the lower a-arm
- Uhmm, where is the roll center supposed to be?

In addition I don't want to crash in that car http://fsae.com/groupee_common/emoticons/icon_smile.gif The front steel frame will have little effect and supposedly would simply snap away. And the fire extinguisher would be a good slam to the head...

Merry Christmas and a Happy New Year to all of you!

[PatClarke]

Hey, thats a good start, keep going.

By the way, you have spotted some stuff that I didn't, so maybe we can find over 20 Design Errors.

Happy Holidays and have a great new year.
I will see you all in Hockenheim in August

Cheers
Pat

[BilletB]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by DART-CG:
Take a look at the pictures at the end, Pat claims he found at least 18 design errors on that old F1 car

Here are the ones I found with a first glimpse:
- mounting of the shock will result in a beding moment to the lower a-arm </div></BLOCKQUOTE>
It will. But is this a design flaw?? How is a control arm mounted push/pull rod any different? We see that all the time and it works well. Mounted away from the center of the control arm's span may not create an unnecessarily large bending moment.

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">
- mounting of the shock itself without a rocker arm will result in huge forces carried by the chassis... </div></BLOCKQUOTE>
Are you saying a rocker arm will reduce loads into the chassis?? I'd say not. A rocker arm creates more points of force application to the chassis, not mention the possible magnification of some of those forces. What are you trying to say? There are no HUGE forces from a direct-to-chassis mounted coilover.

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">
- Uhmm, where is the roll center supposed to be? </div></BLOCKQUOTE>
Who cares?? What difference does it make?? A kinematic roll center means nothing to the handling of a racecar.

MERRY CHRISTMAS ALL!!!

[BenB]

It looks like the spindal is held in place with a nut on the inside of the upright. This should be retained with somthing to keep it from backing off.

The steering links could be mounted in double shear pretty easily. I'm not sure if this is a design error, but its good practice to use double shear.

[DART-CG]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by BennyHL:
[QUOTE]Originally posted by DART-CG:
Here are the ones I found with a first glimpse:
- mounting of the shock will result in a beding moment to the lower a-arm </div></BLOCKQUOTE>
It will. But is this a design flaw?? How is a control arm mounted push/pull rod any different? We see that all the time and it works well. Mounted away from the center of the control arm's span may not create an unnecessarily large bending moment.

-&gt; Hmm, if you can avoid any sort of unwanted stresses without big expenses then you should do it. For sure, rod ends in bending are no deal when you overdimension them. But is it the way to do?

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">
- mounting of the shock itself without a rocker arm will result in huge forces carried by the chassis... </div></BLOCKQUOTE>
Are you saying a rocker arm will reduce loads into the chassis?? I'd say not. A rocker arm creates more points of force application to the chassis, not mention the possible magnification of some of those forces. What are you trying to say? There are no HUGE forces from a direct-to-chassis mounted coilover.

-&gt; OK, my fault. My brain switch the work = force * way in the wrong direction http://fsae.com/groupee_common/emoticons/icon_smile.gif

[Drew Price]

HOLY BUMP STEER BATMAN!!!

1) No free threads above the nylocs on the pivot arms.

2) No captive washers on the free ends of the isngle shear bearings.

3) It looks like the lower damper pivot might even not be aligned longitudinally with the leg of the lower link, so it's actually a bending + TORSIONAL loading. Special.

X) Jam nuts on two of the rod ends I can see are not snugged, but this could just be a during-the-build rollout photo, so I wouldn't count those.

4) A mighty outragious scrub radius. About 5 inches I'd say.

5) What is the brake cooling duct pointingat??

6) Looks like the upper damper pivot and forward leg of the upper wishbone pivot on the same bolt, which gives it a might bending moment, unless there's a third shear separator in there, which I'd wager there is not.

7) I don't see washers under any of the non-counterbored SHCS's like on the lower wishbone pivot.

8) !!!!!! The steering arm spigot is threaded into the upright, and then loaded in bending, and one steering direction will work to un-thread it!!!!!

9) The two arms of the upper suspension link look like they are bolted together by that vertical SHCS, so the loading on the upper arm has the rod end in bending, and the threaded insert in bending.

10) On the frame side, there are lots of triangulations not terminating at nodes, and lots of trinagulating members just stuck in the middle of tubes, like the forward front members, and the support for the fire extinguisher. Looks like the front 'shovel' structure is bolted on, with the bolt guides not axial to the tubes, but stepped off the sides. Which is I suppose not terribly bad since the welds are all nice and long and loaded in shear, but it could be a lot better....

11) The rear wing is not in free air at all.

12) Wing end-plates don't extend nearly low enough for F1 speeds.

13) Semi-radially mounted valve stems might open under high rotational speeds.

14) Front tires look a little low-rider-ish, they're a little narrow for those wheels.

Good call on abrading the rubber brake hoses on the sheet metal DART. With steel braided ones, you'd abrade away the sheet metal guides!!

Best,
Drew

[Neil S]

Is that a fire suppression bottle mounted in the front crush structure?

[Pennyman]

1) From what it looks like, the steering rack retaining brackets are bolted to the bulkhead in close proximity to the holes. This looks like it could flex when large loads are applied.

2) The holes in the front bulkhead have lines running through them, but are not grommeted.

3) The rear ARB (what we can see of it) seems to be mounted to the chassis pretty close to the center of the bar, instead of near the ends. This would cause a bending moment on the ARB along with the torsional moment.

4) Right behind Arno's head seems to be an exposed fuel filler neck with no barrier between it and the driver.

5) The forward link on the front lower A arm looks to have a large tab welded tangent to it, which the shock is then mounted to, as if Arno ran out of space to put a proper bracket!

6) This is a hard one to see, but it looks as if the two legs of the A arms are BOLTED together instead of welded!

[J.R.]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by DART-CG:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by BennyHL:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by DART-CG:
Here are the ones I found with a first glimpse:
- mounting of the shock will result in a beding moment to the lower a-arm </div></BLOCKQUOTE>
It will. But is this a design flaw?? How is a control arm mounted push/pull rod any different? We see that all the time and it works well. Mounted away from the center of the control arm's span may not create an unnecessarily large bending moment.

-&gt; Hmm, if you can avoid any sort of unwanted stresses without big expenses then you should do it. For sure, rod ends in bending are no deal when you overdimension them. But is it the way to do?
</div></BLOCKQUOTE>
</div></BLOCKQUOTE>

Isn't that the exact reason why you have that block of steel in those beautiful wishbones? It would be ideal to mount the dampers directly to the ball joint, but unfortunately impossible with any setup. I would have to disagree in saying that any bending is a design flaw, because it is unavoidable, in any currently feasible configuration. Minimizing the bending is needed, but as far as I have seen, it is impossible to eliminate.

An Australian team just finished 4th (I think) in their design finals with direct dampers, so I cannot see this being one of Pat's chosen design flaws (he seems to like those Australian teams http://fsae.com/groupee_common/emoticons/icon_wink.gif ).

Oh, and I don't see any safetywire on those bolts, IMO, the worst design error of them all! http://fsae.com/groupee_common/emoticons/icon_smile.gif

[PatClarke]

Just to keep the discussion going =]

I don't count the direct acting coilovers as a 'Design Error', after all, that was the way things were done back in those days. There are far worse cockups on the car than D/A suspension, as so many have noted.

I am not sure that their D/A suspension had much to do with the Monash team being 4th in Design in Australia. I think their defence of the design had more to do with it. Whether the Judges like or agree with your decisions is immaterial, they judge on how well you defend your decisions. The racetrack will prove whether the design works or not!

I regularly have Monash team members enthusiastically defend their suspension. But if D/A suspension is so great, why did mainstream race car makers abandon the design years ago?

Firstly, D/A suspension is usually falling rate, not necessarily something you might want, especially at the front.

Secondly. adjustments in ride height, ride frequency, corner weights etc are much easier with pushrods or pullrods.

Ron Tauranac tells that he designed the RALTS with two position bellcranks, so wet setup was quick and easy. Moving the pushrods to a different position in the bellcrank raised the car and softened the wheel rate. Ron had designed many Brabhams, right up to F1 and Indy car champion level with D/A suspension, but once he went to bellcranks, he never went back.

Next thing we will have a team spruiking their revolutionary semi elliptic leaf spring suspension =]

Anyway, Best wishes to all here for the new year, I hope it will not be as scary as some of the pundits fear.

Cheers

Pat

[oz_olly]

Hey Pat,

I just finished reading Brabham + Ralt + Honda by Mike Lawrence. One thing I tried to pay very close attention to was explanations for Ron's adoption of the different design aspect that make the cars resemble what they currently do. Granted you spend alot of time with him (very jealous) and so have probably discussed the matter in great detail, did Ron originally move away from direct actuating outboard suspension to an upper rocker arm/control arm with inboard suspension? My understanding of this was to clean up the airflow for the ground effect cars. The next step he took was to use bell cranks but initially they weren't very good because the motion ratio had way too much rising rate and the suspension would effectively bind. His first cars to use the upper rocker arm were some of the first Ralts ( I think the RT2, the RT1 was an F3 can and still used direct actuating suspension as it was sheltered behind the front body work).

So what do bell cranks give us?
- More flexibility in choice of motion ratio
- Easily achieved rising rate (if you want it)
- Cleaner air flow through the front control arms
- Ability to easily package anti roll mechanism within the body of the car
- More components to design, build and purchase parts for.

So it is reasonably easy to see why bell cranks became the norm in the top open wheel classes where aerodynamics are such a big factor. But in FSAE where we are by no means drag limited and few teams use ground effects why are bell cranks the standard design?

I went to the Top Gear Live show in Sydney on the weekend and there was a really neat live advertisement at the beggining where a small open wheel race cars comes flying out of a van and drifts around the stadium. It looked like it could slip right into FSAE. If anybody knows what this little car was and who makes it please let me know (it had direct actuating suspension).


Sorry for the long post but I don't think this topic has quite been put to bed on this forum.

Cheers

Olly

[PatClarke]

Hi Olly,
Yes, I talk with Ron T at least once a week, though we don't talk much about race cars =]

Your points on push/pull rod suspensions are valid, along with the ability to adjust corner weights without changing preload, tailor rising/falling rates more easily and one Ron is proud of...The ability to rise and soften the car for wet racing by simply moving the pushrod to another point in the bellcrank. A very simple and rapid adjustment when it rains when you are on the dummy grid! Ron was a very practical engineer and many design features were for pragmatic rather than performance reasons.

I didn't get to see Top Gear as I was in Brisbane. I am told they beat the crap out of our i30s and thet the Genisys Coupe was a big hit. Not sure what the open-wheeler was but I will enquire.

Finally, Ron's RALTS were numbered mostly for the formula they were built for. For instance there were several different RT3s built for Formula 3 and ditto with RT4s for Formula Atlantic/Pacific.

By the way, if anyone has a question for Ron, then let me know and I will ask. Olly, is your book autographed? If not email me and I will arrange it for you.

Cheers

Pat

[oz_olly]

I would also like to add that I thoroughly enjoyed reading 'Brabham + Ralt + Honda'. Just ask my wife, for an engineer I am quite a slow reader and I didn't put it down for three days (when I wasn't driving, working etc, I'm slow but not that slow http://fsae.com/groupee_common/emoticons/icon_smile.gif). There are many lessons to be learned from the book that I believe have massive significance to FSAE as our design brief is to build a customer of which we are meant to build 1000 per year. I don't believe Ron ever built 1000 cars in a year but he did do a lot to make his cars easier to manufacture and maintain.

His cars were more popular than his competitors for a variety of reasons but one of the key ones was that he made them easy to set up and tune. He tried to make sure that adjusting one paramater would have minimal effect on another where ever possible. He also made them easier to maintain than his competitors by not sticking important components in hard to reach places.

The book is not a design text by any measure but I think there are many good lessons about how to be successful in motorsport and the value of honesty and integrity, something that has been said of Ron by just about everyone who cared to comment for the book.

The i30s definitely copped a flogging, which made me think in light of Toyota recently pulling all its money out of the Australian Rally Championship. How cool would it be to see a Hyundai backed i30 built for S2000 rules.

If an advantage of push/pull rods is ability to change corner weights without changing preload. Could you not get the same result using direct actuation, setting preload and shimming or adjusting the shock pick up points. I have seen some LMP cars that have shim stacks in the push/pull rods and I assume it is for easy adjustment of ride height and or corner weights.

Cheers

Olly

[Dick Golembiewski]

Pat, That hat looks awfully familiar. I wonder where I've seen at least one other?

[PatClarke]

Dick,
This thread has meandered through a few topics. Which one are you referring to?
Cheers
Pat

[PatClarke]

Quote Oz-Olly
"I went to the Top Gear Live show in Sydney on the weekend and there was a really neat live advertisement at the beginning where a small open wheel race cars comes flying out of a van and drifts around the stadium. It looked like it could slip right into FSAE. If anybody knows what this little car was and who makes it please let me know (it had direct actuating suspension)"

Michael, the car in the Shell commercial is a Jedi. More info can be found at www.jediracingcars.com (http://www.jediracingcars.com)

Cheers

Pat

[oz_olly]

Hi Pat,

I had an inkling that it may have been a Jedi (thanks for confirming it), I did a bit of scouting around the net the other night. I came across the link you gave and unfortunately it is for a site which is under construction. A bit more info and some pics are available here www.formulajedi.com (http://www.formulajedi.com).

Did you get my email? I am not sure if the adress I used was correct.

Cheers

Olly