Monocoque Chassis Info Needed

[Peter Kjellbotn]

Hi everyone. I'm from the University of Alberta, and 2007 will be our first year running a carbon monocoque chassis. I'm currently one of four people designing the chassis as a senior design project, and I'd really like to get in touch with some people who have run a composite chassis at competition before.

One of my questions is what methods have been used for mounting subsystems to the monocoque; the a-arms for instance. I've heard of replacing some of the core material with an aluminum insert during layup, and then drilling/tapping that insert so that mounts can be bolted on. Have any of your teams used this method?

We'll be using vacuum infusion to mold our chassis, and we're considering molding it as an upper and lower section. Has anyone tried a multipiece design? and what method did you use to join the sections? We're looking at using a lap joint and structural adhesive.

It'd be great to get some feedback on this subject, and just to find out who has some monocoque experience in this forum. So if you have any experience with composite chassis design, please post your email and we'll be in touch. Thanks!

[Peter Kjellbotn]

Hi everyone. I'm from the University of Alberta, and 2007 will be our first year running a carbon monocoque chassis. I'm currently one of four people designing the chassis as a senior design project, and I'd really like to get in touch with some people who have run a composite chassis at competition before.

One of my questions is what methods have been used for mounting subsystems to the monocoque; the a-arms for instance. I've heard of replacing some of the core material with an aluminum insert during layup, and then drilling/tapping that insert so that mounts can be bolted on. Have any of your teams used this method?

We'll be using vacuum infusion to mold our chassis, and we're considering molding it as an upper and lower section. Has anyone tried a multipiece design? and what method did you use to join the sections? We're looking at using a lap joint and structural adhesive.

It'd be great to get some feedback on this subject, and just to find out who has some monocoque experience in this forum. So if you have any experience with composite chassis design, please post your email and we'll be in touch. Thanks!

[Jersey Tom]

Talk to the guys at Colorado State.

[Erich Ohlde]

We have run a full/half carbon monocoque since 98 and would be wiling to work with you guys

[John Valerio]

Peter,
it's good to hear another team is going carbon, and another canadian team no less. right on.
anyway we're running a carbon monocoque for the second consecutive year and have no complaints about it (except for the cost, that is).
what we do for front suspension is fill (not replace) the Al core with an epoxy-filler mixture to give it buckling strength and then DP460 the hardmounts on to the outer surface, and bolt them through the monocoque.
this method has been quite successful for us. make sure you fill the core under all your glued on stuff (shock, rocker and arb mounts) or the carbon will start to compress under them.
for the layup, we do it all in one mold, we have a fairly simple monocoque shape so we can just use Al sheet as a mold. check out http://engsoc.queensu.ca/formulacar/ to see some construction pics.
it terms of a multi piece lay up, we've never done that so i can't comment. perhaps the ETS chassis people can though, as i believe their 05 car uses a top/bottom construction with the joint doubling as side impact bracing.
hope any of this helps.

[Homemade WRX]

out of curiosity what programs are you guys using and testing your chassis' with?...fibersim? catia?...
you guys are the only ones talking of joining the monocoque category next year... http://fsae.com/groupee_common/emoticons/icon_wink.gif

[Blake_DFSAE]

Just a question (we're not considering a CF monocoque as a first year team) but what's the weight difference between the CF mono and a tube chassis on average?

[Wright D]

A Steel space frame can be very weight effective when done properly. Especially when close outs are used as stressed panels. This blurs the lines between monocoque and space frame.

As an example; our 2005 frame weighted in at 38 lbs of steel tubes, and when the floor, stressed body work, stressed seat, and rear sub frame were added in, the weight jumped up to 48 lb. Thought this weight might seam high, it includes all of the suspension mounting points(a arms, rockets, damper ends, steering rack, anti roll bars...) AND the seat belt mounts, the drive train mounts, the head rest support. Basically, that weight includes everything that gets welded on to the frame.


Pictures of the frame are here. (http://formula.engr.arizona.edu/05pics.html)

[Peter Kjellbotn]

Hi guys,

Thank's a lot for the feedback! I'll be emailing you guys from Queen's and Kansas in the next few days with a couple of questions.

To answer the question of what we'll be using to analyze the chassis: we'll be doing the modeling in Pro/Engineer and solidworks. We'll then import the geometry into ANSYS, create our material model and do all of the analysis with ANSYS.
Last term, I did some composite analysis with ansys mainly using the shell91 element, but I'm not sure if that's the element we'll be using for this analysis.

Peter Kjellbotn

[John Valerio]

Blake, i believe our 05 car monocoque weighed in at 34 lbs, including the rear frame (not the diff box though, but it was really light as it was mostly CF). However, this years car is considerably bigger for ergo and strength reasons, not to mention we've switched back to the CBR600 after a 3 year stint with the suzuki single.

WRX, what do you mean us and kansas and now alberta are the only ones in the monocoque class? there are many other monocoques out there, UWA, RMIT, Delft, ETS, TU Graz, to name a few. And before CF, we had an Al-Balsa monocoque since 2000.

Peter, looking forward to hearing from you guys.

[Homemade WRX]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by John Valerio:
Blake, i believe our 05 car monocoque weighed in at 34 lbs, including the rear frame (not the diff box though, but it was really light as it was mostly CF). However, this years car is considerably bigger for ergo and strength reasons, not to mention we've switched back to the CBR600 after a 3 year stint with the suzuki single.

WRX, what do you mean us and kansas and now alberta are the only ones in the monocoque class? there are many other monocoques out there, UWA, RMIT, Delft, ETS, TU Graz, to name a few. And before CF, we had an Al-Balsa monocoque since 2000.

Peter, looking forward to hearing from you guys. </div></BLOCKQUOTE>
no, I was reffering to how peter was asking as they are looking to go moncoque too...I was stating that they aren't the only ones looking...
I'm just curious as to the software people are using to develope there's.

[L.R. Weidner]

Greetings to all! I commend any team that takes on the added effort and complexity of making a composite car.

I did some of the composites chassis design stuff at CSU (it was my masters thesis topic).

For development and analysis we used legacy information, physical testing and Pro/Mechanica. I found early on that the physical testing is much more relevant than the FE code results because of the limited skill level of the craftsman (me). Especially early on, I rarely had a bonded joint that was as strong in the load frame as it was in the FE code. And those were usually a simple lap-joint.

The car they'll be taking this year is of multi-shell design. Here's a picture I took of it at the unveiling back in January.
Colo State 2006 (http://home.comcast.net/%7Elucasweidner/temp.htm)

If there is anything that I can assist with I'll do my best.

Good luck to all!!

~Lucas

p.s. You'll have the remainder of your lives to get some sleep. This might be your only chance to do well at the FSAE competition!! http://fsae.com/groupee_common/emoticons/icon_wink.gif

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Lucas Weidner
lucasweidner@hotmail.com
CSU FSAE 1999-2003
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[TG]

Lucas,

gorgeous car! Would you by chance have your thesis online somewhere? I'd love to take a look at it.

Also if anybody knows of good composite design papers, would you please share? I know I'm fairly competent with basic composites calculations, just would like to get a better handle on modeling them in finite elements. Thanks.

[L.R. Weidner]

Tim-

Thanks, hopefully it will perform at competition as well as it looks!

I'd love to point you in the direction of my thesis, but as of yet it's incomplete. http://fsae.com/groupee_common/emoticons/icon_frown.gif

I left school after finishing my course work in search of the real world. I found it, and found it to be rewarding and VERY, VERY time consuming! Thusly, I've had considerable difficulty finishing the thesis.

I did publish an introduction to my thesis as a SAE paper in 2002:
A Multi-Shell Assembly Approach Applied to Monocoque Chassis Design (http://www.sae.org/servlets/productDetail?PROD_TYP=PAPER&PROD_CD=2002-01-3360)

That was then the basis for a SAMPE paper by Paul Fuqua (also of CSU): Tooling Development for a Multi-Shell Monocoque Chassis Design (http://www.sampe.com/store/paper.aspx?pid=2486)

My thesis is pretty much <span class="ev_code_RED">due</span> this fall (2006), so I'll post any new information in this tread as it is available.

Until then, please email me or post here with questions and I'll do my best to answer them.

~Lucas

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Lucas Weidner
lucasweidner@hotmail.com
CSU FSAE 1999-2003
"Real World" 2003-present
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