Human Powered Vehicle [Archive]

Erich Ohlde

01-23-2006, 06:32 PM

Spy photo's of KU's latest creation
eohlde.portstorm.com/IMG_0278.JPG (http://eohlde.portstorm.com/IMG_0278.JPG)
eohlde.portstorm.com/IMG_0279.JPG (http://eohlde.portstorm.com/IMG_0279.JPG)
eohlde.portstorm.com/IMG_0280.JPG (http://eohlde.portstorm.com/IMG_0280.JPG)
eohlde.portstorm.com/IMG_0281.JPG (http://eohlde.portstorm.com/IMG_0281.JPG)
eohlde.portstorm.com/IMG_0282.JPG (http://eohlde.portstorm.com/IMG_0282.JPG)
eohlde.portstorm.com/IMG_0284.JPG (http://eohlde.portstorm.com/IMG_0284.JPG)
eohlde.portstorm.com/IMG_0285.JPG (http://eohlde.portstorm.com/IMG_0285.JPG)
eohlde.portstorm.com/IMG_0286.JPG (http://eohlde.portstorm.com/IMG_0286.JPG)
eohlde.portstorm.com/MVI_0283.jpg (http://eohlde.portstorm.com/MVI_0283.jpg)

Erich Ohlde

01-23-2006, 06:32 PM

Jersey Tom

01-23-2006, 09:11 PM

I ride my bike

conekilr

01-23-2006, 09:37 PM

Haha, I thought you guys just left me in the courtyard when I was stuck headfirst in the chassis.

Chris Allbee

01-24-2006, 07:12 AM

Erich, you look like you're enjoying your new chassis. We've got one too. Made of metal. Chafes less as you wear it in http://fsae.com/groupee_common/emoticons/icon_wink.gif

Didier Beaudoin

01-24-2006, 08:22 AM

I would like to know about the technique you used to build this chassis. Did you lay all the fibers from the cockpit opening and by the nose? Is that prepreg? What kind of core did you use?

Thanks
(nice job, by the way)

Erich Ohlde

01-24-2006, 09:17 AM

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Chris Allbee:
Erich, you look like you're enjoying your new chassis. We've got one too. Made of metal. Chafes less as you wear it in http://fsae.com/groupee_common/emoticons/icon_wink.gif </div></BLOCKQUOTE>

Does yours way 36 lbs? =] Wait till you see what we have for next year's chassis, we are looking to shed 12 lbs.

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Didier Beaudoin:
I would like to know about the technique you used to build this chassis. Did you lay all the fibers from the cockpit opening and by the nose? Is that prepreg? What kind of core did you use?
</div></BLOCKQUOTE>

We made a high density foam buc, took carbon molds, and layed up. The molds bolt together to form one piece. We did have to lay all the carbon by the nose opening, driver opening, and rear opening. All done with prepreg weave and uni-reinforcement and aluminum flex core

Didier Beaudoin

01-24-2006, 04:46 PM

Thanks for the information. I'm looking forward to show you pictures of our carbon monocoque, but it's still far from finished. http://fsae.com/groupee_common/emoticons/icon_wink.gif

Did you get a polished finish on your mold? It seems like the surface finish of your tub is a little bit raw.

Erich Ohlde

01-24-2006, 07:20 PM

yeah, since we do a structural pre-preg layup there isn't much extra epoxy to form that nice (and heavy) mirror finish.
We just use a very very small amount of bondo to fill in and then paint.

Next year we are hopefully going to be trying something a little different that will give us a mirror (literally) finish without extra epoxy weight

Do you have any pics of what you guys have now? What core are u guys using and what type of mold process do you use?

Didier Beaudoin

01-25-2006, 05:43 AM

We're still in the process of building the molds and testing our method. It is our first experience with a carbon fibre monocoque. At first we wanted to use pre-preg, but it wasn't possible to find any at a reasonable price, so we are now going to use infusion. Because of this, we have to use a closed-cell foam as a core because we don't want it to get filled with resin. So far, the tests have given good results.

The molds should be sent to machining in about 2 weeks, and then the fun part will begin!

Ohttp://www.etudiants.polymtl.ca/fsae/gallery/albums/construction2006/DSC01594.sized.jpg http://www.etudiants.polymtl.ca/fsae/gallery/albums/construction2006/DSC01593.sized.jpg ur molds right now:
http://www.etudiants.polymtl.ca/fsae/gallery/albums/construction2006/DSC01592.sized.jpg

the core:
http://www.etudiants.polymtl.ca/fsae/gallery/albums/First-infusion-test/IMG_2025.jpg

Infusion
http://www.etudiants.polymtl.ca/fsae/gallery/albums/First-infusion-test/IMG_2045.jpg

The result of the first test, a few weeks ago
http://www.etudiants.polymtl.ca/fsae/gallery/albums/First-infusion-test/IMG_2078_1.sized.jpg

I'd love to see pictures of your process also!

Erich Ohlde

01-25-2006, 06:30 AM

What are you guys going to do about bolting through the carbon? I'm sure you and your team already know this but don't use any type of fastener through core! I'll see if I can find some good pictures of our process.

I'm curious about the infusion method, have you found any good sources of information on doing a layup with infusion?

Didier Beaudoin

01-25-2006, 07:10 AM

We are actually in the process of testing different fastening methods. We are thinking of using aluminium plates bonded on each side of the laminate to take the shear forces, and to spread the normal forces. We have to test it first though, as I am not 100% certain the bolt won't crush the foam as we tighten it. The foam may look soft, but it's really hard. It's made especially for infusion and it is used in high-technology marine industry. IF it doesn't work, we're going to use inserts.

About infusion, there's a guy in our team that's doing his final project on the infusion process (I'm not the composites guy on the team, I can tell him to reply to the thread if you want more info) and he's gathered information from various industries, and he's being helped by the high-performance composites research department here at Polytechnique. They have lent us all the equipment needed.

But infusion is all about experience, so we're doing lots of tests to get the right method to be able to infuse our chassis.

Care to share pictures of your process? (mold, layup, etc?)

Thanks

Didier Beaudoin

01-25-2006, 07:26 AM

While I'm thinking about it, what the advantage of having to put a layer of bondo instead of having a mirror resin finish? Is there really a weight advantage? Or is it just less complicated to do?

leclercjs

01-25-2006, 07:36 AM

Hey Everybody,

kudos for you guys at Kansas!

I'll be really interesred to know how you gonna shave 12lbs on next year's car?

For the infusion part, there is no documentations that say step by step how to do infusion. You can find on the Internet a lot of info on the basics of this method, but no '' How to make an Infusion for a dummy" (I would have buy this book if it had existed ;-) )

Results are pretty good with the first experimentations we carried out, we need more practice on large scale mold to really have the confidence and practive before doing the tub.

Cheers!

Erich Ohlde

01-25-2006, 07:43 AM

We just use the bondo because we can't get a mirror finish with our carbon.

As far as the 12lbs weight loss goes, we are looking at a different carbon weave that should be just as strong but lighter, the only downside is its going to be a bitch to layup, we are thinking of doing the car in halves next year and then gluing the completed halves together.

If all goes well next year we are going to try to make two tubs so we can carry one into the design tent and show it to the judges. That would be kinda fun.

When do u guys plan on having your tub finished?

Travis Garrison

01-25-2006, 09:44 AM

There actually are some good sources for infusion "how to's"...

Check out http://www.vat19.com/dvds/andre.cfm

Not free, but probably worth it if you've never done infusion before as there are some good tips in there that will save you time. Nothing beats getting your hands dirty of course...

Jayhawk, why can't you get a paintable surface right off the mold? Is that a peel ply surface? Tool side is typically ready to paint...

Or is it a function of doing the entire layup in one step and not getting even pressure on the tool side due to the honeycomb core? How much weight do you typically put on in paint & bondo?

Erich Ohlde

01-25-2006, 11:05 AM

We do the layup in several steps, (1) outerskin, (2) core, (3) innerskin, (4) edgewrap,seatback,firewall.

We don't get a paintable surface because we use a perforated release cloth with an absorbing matte, this helps ensure even vaccuum across the part and it pulls any extra resin into the cloth. We pull vaccuum through the whole cure cycle since we don't have an autoclave big enough and when the resin starts to flow it tends to get pulled toward the release cloth surface.

Our inner surface has extra resin and it looks great after a light wet sanding/polishing.

Next year we are hoping to get some autoclave time and we should have a much better surface finish.

Travis Garrison

01-25-2006, 01:39 PM

So your layup, going from tool outward, is:

tool
breather/bleeder cloth
peel ply
laminate
peel ply?
more breather bleeder?
bag

Just curious becuase I've always done something more like:

tool
laminate
peel ply
breather bleader
bag

If you keep peel ply on your outer surface an autoclave isn't going to make much of a difference in surface finish.

Didier Beaudoin

01-25-2006, 03:21 PM

If your tub is done the way Travis has detailed, how can you have a good tolerance on the chassis dimensions? The breather/bleeder doesn't seem to have a very precise thickness.

Dr Claw

01-25-2006, 03:47 PM

I've been infusing racing seats/bodywork at LTU for going on 3 years now, if you have questions on infusing, i'll be glad to try and help you http://fsae.com/groupee_common/emoticons/icon_smile.gif.

Fiber Glast has a decent Walk through (http://www.fibreglast.com/contentpages-Vacuum%20Infusion-316.html) here, I'd also suggest signing up for their forum, but i heard most of the good info was perged due to bad buisness decisions. dont take it to heart though, i do all sorts of things differently than they do...

The best advice for infusing though, you gotta have a CLEAN work area. Random sharp edges, little grains of sand...they can ruin everything. Wash your hands too...I cant tell you how many times a dirty finger print is the source of a leak in the bag. That, or fibers cross the sealant tape! rookies i tell you http://fsae.com/groupee_common/emoticons/icon_razz.gif

nick roberts

01-25-2006, 03:54 PM

Not quite...

The layup process for the first few layers goes like this:

Tool
Carbon
Peel-ply
Breather
Bag

So Travis was correct...

The material that we use for the outer layer is not an epoxy rich material like typical tooling carbon. It isnt designed to have excess resin in the fabric which would give a finished surface; only enough for it to cure properly. I guess what most of you are asking about is why use bondo to fill in imperfections in the outer layer when you could just use a material with more resin in it. One reason is that with the peel-ply/breather cloth laying on top of the carbon during a cure cycle and the way we use only a vacuum bag and no autoclave, it naturally absorbs a lot of excess resin. This being the case, even if we did have a resin-rich material, it wouldnt help all that much. In the end, it isnt enough bondo to change how we do things or go to the trouble of sourcing additional carbon with more resin just to do the outer layer with. Especially if we do manage to take 12 lbs off the car next year with our "mystery layup".

-nick roberts
University of Kansas

Didier Beaudoin

01-25-2006, 05:16 PM

Okay, I understand now. It sounds weird though because I've already made parts using prepreg and vaccum bagging and I've never had a surface finish like this one. Maybe you should try adding an adhesive film layer between the tool and the carbon, to be able to sand it and get a good finish?