T-bar instead of U-bar

[Aaphree]

Hey everyone, I am trying to design a T-bar ARB. Our team wants to move away from the U-bar, but I am having some difficulty getting started. Any tips/advice on where to get started? Any help would be greatly appreciated

[Brett MacPherson]

Why?

10 char

[Simactive]

Why?

10 char

Why not :)

[Pat Clarke]

Aaphree,

Who are you? What University do you represent? It is rude to anonymously barge in and ask blindly for 'advice'!

Secondly. what is 'different' (better or worse) about either of those anti roll devices? Both are fundamentally torsion springs that resist roll.
They are not the only solution and there have been very many successful FS/FSAE cars that have no such devices at all!

So, tell us what research you have done, what your chassis/suspension design is like, why your team wants to 'move away' from a 'U' Bar?

Then you might get some sensible answers!

Pat Clarke

[Aaphree]

Aaphree,

Who are you? What University do you represent? It is rude to anonymously barge in and ask blindly for 'advice'!

Secondly. what is 'different' (better or worse) about either of those anti roll devices? Both are fundamentally torsion springs that resist roll.
They are not the only solution and there have been very many successful FS/FSAE cars that have no such devices at all!

So, tell us what research you have done, what your chassis/suspension design is like, why your team wants to 'move away' from a 'U' Bar?

Then you might get some sensible answers!

Pat Clarke

I am a student at Penn State, and am on the suspension team for FSAE. This is my second year participating, and first time actually designing anything for the car.

Previously I modeled the A-arms in Solidworks and machined some parts, but this is the first time I've had a major job to do for the team.

The suspension team leader told me he wants to go to a T-bar design instead of our U-bar which we have used in the past. He didn't give many reasons as to why, and he is always in a rush when I catch him,
so I haven't been able to get any specific reasons out of him.

The little information I have been able to gather is that the T-bar is easier to tune, and potentially could lead to more aerodynamic suspension setups...although I'm a bit skeptical on that last one.
Also, they can give a lower antiroll rate than a conventional setup with the same bounce rates. Beyond that, U-bars seem to be more reliable and require less maintenance, and are more common and potentially easier to design.

I don't have the specifics on our entire setup, I missed our meeting this week due to an exam, but that is essentially all I have to work with at the moment. Assuming we use a similar setup to last year, our dampers in the front are
mounted parallel to the ground and the length of the car.

I apologize for just barging in without giving any background information.

[JulianH]

The suspension team leader told me he wants to go to a T-bar design instead of our U-bar which we have used in the past. He didn't give many reasons as to why, and he is always in a rush when I catch him,
so I haven't been able to get any specific reasons out of him.


I don't have the specifics on our entire setup, I missed our meeting this week due to an exam, but that is essentially all I have to work with at the moment. Assuming we use a similar setup to last year, our dampers in the front are
mounted parallel to the ground and the length of the car.

I apologize for just barging in without giving any background information.

Well, to be honest, I'm a bit speechless.
I expected to hear a story from a first year team from India/China/Africa but not from a team that is around "forever".

If you are responsible for the ARB, why is he telling you to do this or that design? Isn't it your goal to learn the design process as well?
It's not like a "well we don't have money for a new engine, we will have to stick to the old one". It's a cheap detail solution...

Look at the big picture: Is maybe a T-Bar necessary due to space issues? If not, than make your own research: Why should I go T-bar? There are a lot of books out there which give you at least a hint.
If you come to the same conclusion (In the design event, it helps to say "I want the T-bar BECAUSE XY" not only "Yeah T instead of U for the win") than do it your way. If not, than you go to him and ask what his deal is...

In the end, Pat is right. They both do the same, you can make fast adjustable solutions for both designs or even win FS Germany without them (Delft 2013).


Good luck!

[Pat Clarke]

Aaphree,
Like Julian, I am shocked. I would have bet money you were from a new Indian team! Your apology is certainly accepted.

And again I agree with Julian. How many points do you think you will get in Design when the judge asks you about your decision to use a 'T' bar and your response is 'The Suspension Team Leader told me to'?

Your statement "Assuming we use a similar setup to last year, our dampers in the front are mounted parallel to the ground and the length of the car" has me wondering how you can go about designing an anti-roll system anyway? What roll are you trying to 'anti'?

Cheers

Pat

[Claude Rouelle]

"The suspension team leader told me he wants to go to a T-bar design instead of our U-bar which we have used in the past. He didn't give many reasons as to why, and he is always in a rush when I catch him,
so I haven't been able to get any specific reasons out of him"

That is so surprising that its is very funny!

So you expect the readers of this forum to be more available than your own suspension team leader? So you look for answers outside because you are not able to get answers inside, correct?

This is not design judging but, as design judge, I can't help to think this reflects poorly on your team organization and coordination.

OK here is the answer: It is because "T" comes before"U" in the alphabet! :)

More seriously and maybe some answer: weight, packaging, manufacturability, accessibility, adjustability...? But seriously speak to your team member(s) first.

A far as Delft winning FSG 2013 they did not win "because" they did not have any ARB! You guys are reversing the arguments. They won for many other good reasons, the main one is that that were able to modifying their yaw moment by distributing their 4 tire Fx with the torque vectoring of their 4 electrical engines instead of changing the Fz of their tires with ARB (which in turn do influence their tires Fx and Fy, traction ellipses shape).

I still believe a team has an advantage to independently tune its front and rear heave and roll (and ideally pitch) stiffness and in a perfect world independently its front heave, roll and pitch damping. Even with a 4WD and good torque vectoring.

[Aaphree]

In response to Claude,

I don't expect the people of this forum to be more readily available than my team, I only wanted some outside thoughts into this issue. Obviously I need to discuss this more in depth with the team, but since I am on my own at the moment I wanted to try and get as
much info as possible (including opinions of others). I apologize if I made it sound like I am asking the forum instead of working with my team (obviously that isn't proper teamwork/organization!). I appreciate everyone's input, whether it's critical or supportive. I have a lot to learn, and all of this is feedback is quite helpful.

Hearing from a design judge has made me see some things that we can improve on (communication). Thanks for your feedback!

[Aaphree]

Pat and Julian,

Thanks for the tips, having never been to a competition, I didn't think of all of the things that the judges would be looking at. Based on everyone's responses, I have a better idea at what I need to look into to go about this design.

Thanks everyone for your feedback. If anything, it's given me some insight into what needs to be done before even trying to design this ARB.

[Claude Rouelle]

Aaphree,

Form follow functions. The question you need to answer is what are the functions that the ARBs are supposed to fulfill. The anti-roll stiffness is one of the main functions but not the only one. I have seen in FSAE / FS many ARBs which did achieve the given goal of anti-roll stiffness but where incredibly big (and therefore heavy) and did induce compliance on their drop link attachments points.

If you push yourself to some attractive and creative thinking, thinking about the functions before thinking about the drawing, the answer could come easier. Start with a list of these ARB functions.

[Drew Price]

Aaphree,

My advice would be that it's extremely important that you go back and forth with the other people designing other parts of the suspension (I'm assuming your group has not frozen the design yet), and not just your team captain. Having multiple people simultaneously designing parts that must integrate with each other is easy to screw up if you don't work with each other. This happens in the professional world more than most people realize.

One design or the other (or even something completely different) should be chosen based on it's advantages. U or T ARB's tend to be more or less compatible with different suspension setups, it's your job as a designer to pick the best solution for your particular setup given what the design philosophy of the suspension is.

That being said, sometimes there are people in a team in a position to dictate tasks to the rest of the team, whether they are good or bad ideas, and sometimes you just have to go with that. But use it as a learning experience anyway. Like Bill said, there will always be zealous prima donnas who want everything their way just because.

:)

Don't forget that this competition is also supposed to be fun. That's easy to do.

[Aaphree]

Alright thanks. I think that I am done for now with this thread, I know what I need to do, so now it's time to actually do it. Thanks for all of your input!

[Brett MacPherson]

I apologize if I set this thread off in a different direction than you were expecting, but we wasted a great many hours last year trying to design a T-bar style anti-roll system. We would have been much better off spending half those hours polishing the system we already had, or improving other lackluster systems. I'm just trying to save you from suffering the same fate.

While I completely appreciate the "cool" factor in FSAE, in my experience (which maybe should not count for much), it's a recipe for disaster, and generally not worth the extra hours spent trying to make it work. But if you feel that's where the greatest amount of learning occurs, and it fits with the goals of your team than I vote to go for it. What do you have to lose?

[Claude Rouelle]

Brett,

What was so difficult in the T bar design compared to a U bar design?

[Brett MacPherson]

For us, the packaging was an absolute nightmare. I should clarify and say that we weren't attempting to replace a U-bar with a T-bar on a reasonably sorted suspension, we were trying to design a monoshock front suspension that relied on a T-bar. The frame wasn't designed with that in mind, we were just trying to graft it on. Our design was pullrod actuated with everything mounted below the driver's knees.

[Bemo]

Sounds like a very bad idea. But from this you can't derive that T-bar ARBs are harder to manufacture or to package. If suspension and frame design don't go hand in hand you will be always in trouble, no matter which particular concept you choose. There were some cars from our uni which had T-bar ARBs. The major reason was that with the suspension systems of these cars a T-bar was easier to integrate in terms of packaging than a U-bar. Choose of concept has always to be done with the big picture in mind, so a general statement wether T-bar or U-bar ARBs are easier to make is just not possible.

[Claude Rouelle]

Maybe this will lead this tread in a different direction but I would like to share the following...

I am teaching vehicle dynamics to top engineers in OEM and on Motorsports department of big companies to people who are several times more qualified than I am...in their specific domain but who can't speak to each other.
Just as an example in one F1 team I know there is a real "god" in tire modeling who has been working for 8 years in that F1 team and who has not seen the wind tunnel yet. If the team win they all think they are gods. If they lose, aerodynamic engineers will blame the engine guys, the engine guys will blame the chassis guys who will blame the tires guys who will blame the management who will blame the aerodynamic department ...so the loop of blame is now closed

The world need specialized people, not specialists. Specialized engineers are people who have a good idea of the large picture and then specialize in CFD or traction control or FEA or simulation but they don't fall from the moon is somebody speaks about brakes or differential in an engineering meeting.

Similarly, the issue faced by the team which thinks about a T ARB and very appropriate Bemo's comments make us think, again, that everything in a race car is intriguingly related. You can't draw any ARB without speaking to several other guys starting with the chassis designer. That ARB will need "some" anchorage points....

Than being said, if a team know what it is doing, I do not see more complication in the design of a T ARB than a U ARB if it is integrated from the beginning of the chassis concept.

Same comment for a mono shock: there are a lot of advantages to build a suspension with mono-shock, especially for a FSAE/FS where weight and packaging are big issues. In fact there could be a tremendous advantage of having a SEPARATE control of heave and roll stiffness AND DAMPING. A few FSAE / FS teams tried that in the past. Their concept was pretty good but the manufacturing and the implementation was pretty bad so it did not work. That is because they mostly copied what they saw on other professional racing cars without first putting down the FBDs and equations on paper. They tried to make the function following the form instead of the form following the functions.

If team members understands what they do I am sure it is possible to make a very good, stiff, light, cheap, reliable and quick FSAE / FS car with T bars and/or mono-shocks. In fact I can't wait to see a team making that innovation working in both simulation and on the track: it is very possible and it will give a lot of advantage.


It is all about a choice between taking the risk of innovation or staying in the comfortable zone of "classic" cars. It about defining what you are afraid of and also if you can put the means and the goals together....

[DougMilliken]

Hi Claude,

The buzz word you didn't use is "interdisciplinary." At least in my college days this was like poison to most of the academics--they wanted to specialize. Your example F1 team sounds pretty academic too(??)

On a personal note, we were surprised that RCVD was picked up as a text book, we just hoped it would be used by engineers in pro racing (a very small market). As it turned out, students like it because it cuts across several disciplines, but I imagine that some faculty members are not so pleased when they have to think outside their specialty.

-- Doug

[Claude Rouelle]

Doug,

Henry Kissinger said" Academic politics is the most vicious and bitter form of politics, because the stakes are so low"

Some companies, including in motorsport are not very different.

Thank God there is FSAE!

:)