12 replies to this topic

[jsgprod]

I've been meaning to make some new front brake ducts for the race car for quite some time now, mainly to replace a somewhat overweight system I made several years ago. I found some stuff that seems to work really well for making fiberglass parts with one-off or odd shapes..flower arrangement foam! It's really cheap ($1 a brick @ wally mart). Actually that's not entirely true, I didn't find this stuff, I have a good friend that owns a custom body shop, he showed it to me a few years ago when he had to make some custom parts for some of his customers. His parts come out looking a LOT better than mine though, without fail.

ANYWAY, I thought I'd take some pics during the process of making the second one (had more time) and post them here. I'll 'splain what's going on best I can .

Here's what I was replacing, aluminum, riveted together 'somewhat' decent intake duct. Pay no attention to the white PVC looking stuff it's taped to.


I start with these green foam flower arrangement blocks, it took two to make one duct.


Any straight cuts I made with an old used up hack saw blade.


It took me a while to figure out the best way to get the blocks and other pieces connected to each other to make bigger, odder complex shapes and still be able to work with it. A friend suggested the hot glue gun...works!


After some cutting, fitting, and glueing, I got to this


More coming...

[jsgprod]

These were the rough shapes prior to final shaping and smoothing, that small gap was filled prior to the final shaping.
-

-

These are the final forms after (literally) shaping with, 1st some rough sandpaper (60 grit), then some finer sandpaper. The finer sanding isn't really necessary, I didn't do it on the first one but did on the second...made no difference in the outcome or the ease/difficulty of foam removal (more on that later).
-

sanding to this shape took less than 25 minutes. Sometimes the glue (from the Hot glue gun) will be outside of the shape where the seams are, you don't want this, I use some sharp, flush cut wire cutters to cut that off flush with the surface.
-

One more to go...

[jsgprod]

Then I just fiberglassed it as smoothly as I could. Not as easy since it is a bunch of compound curves going several different ways. I used the biggest pieces I could that would lay as flat as possible, had to make some cuts in the cloth occasionally to allow the cloth to follow the contour and still lay flat. It's actually several pieces overlayed in different directions to add strength. NOTE, I use epoxy resin! It doesn't cure as fast and gives you enough time to lay all these layers on before it jells...it also doesn't melt the foam! On top of that it's a lot stronger than your general everday fiberglas resin.
The after curing shots:
-
-

Now, how do you get the foam out of the shape so the air can pass through? Ever poured acetone on foam and see what it does? Stuff disappears into nothing! So I poured some into this....NOTHING! it just sits there! So, I went back to the hacksaw blade..and a fat screwdriver, got to dig it out.
-

Gutted
-

Now the air can pass through.
-

I've found that the glue will tend to stick to the resin during the curing, and after all the foam is out you can see and feel it inside the part. Since these are going to be used for air to flow through the inside of the part, I didn't want this. First I tried scraping it off, which will work OK but doesn't always get it all off, then I got out the air grinder and lightly went over those areas, worked really well and even smoothed out those areas a little more.

And finally, mounted back on the car where the original one had been. Notice the lack of the white PVC? Not using it anymore.
-

I did make some new ducts that mount behind the disc/calipers too, just not out of fiberglass...yet.

[NWClassicHonda]

Wow, that looks really good! Great job!

[D Jaws II]

Jay,

You have been busy!

Veddy veddy goot.

Don't tell me, it was again 60-70 degrees today, I see no sleaves in the pics.

Nice job, do you hire out?

What's next?



Donnie

[Vitamin J]

Wow, thats really cool. I'll have to remember that trick.

[kakabox]

Now that is very cool! Well done.
...and you can use carbon fiber cloth too.

Nice write up. Thanks for taking the time to post this along w/the pics. I'm glad you mentioned using the epoxy resin. I've seen this done before but I always thought you just used regular polyester fg resin.

Man, you're giving me ideas again...the first time was when I saw your chassis mounted rear stabar. You saw what happened after that!

Cheers!

[jsgprod]

Just to add the finishing touches to this, here are some pics of the ducting to the back of the brakes. I made these out of some 2.5” exhaust tubing, actually got the idea from something I remember Doodson posting a couple of years ago.

Looking back from the new duct:



From the back side, I trimmed it to fit partially over the back of the brake caliper. That way there will be some cooling to the fluid behind the piston, which is really what we want to keep from getting too hot anyway:



The small Philips screw holding the tab on the bottom in the above pic has since been replaced with an allen ‘button head’ screw, 10/32 size. There’s also one on the top of the spindle that the top strap is held on with. I did this (drilled and tapped those holes) several years ago to hold the previous ducting I had made in place. As long as I don’t over torque them (and consequently strip them) they work really well.

Here’s the duct before I painted and mounted it, the scalloped looking section allows it to ‘just’ clear the CV boot. It can still touch the boot in extreme steering angles but I only get those when moving the car around in the pits/paddock, where the car is hardly moving. On the track it might come close but I doubt it touches.



For those of you that may be looking closely, I took this to show you how I used an old engine part. Ever try to hold short piece of exhaust tubing in your vice to cut, modify, or work on it? Ever notice how easy it is to crush it when you do that? I searched around in the garage during this project looking for something to fit inside the pipe so I could get a good hold on it in the vise. I found this, it fits perfectly inside 2.5” exhaust tubing! It was a little snug, but could easily be tapped in (and out) with the wooden handle of a hammer. Clamp it as tight as you like and you can cut, grind, weld, even shape it a bit with a ball pien hammer if needed (I needed).
Most of you should be able to identify it:



Actually Donnie, I made those a couple weeks ago...you remember, the weekend I told you I was working in short sleeves!

J. I've made a few parts/pieces for the car out of carbon fiber already. My dash and rear hatch/spoiler to list a few. I made a front airdam/splitter out of it a while back but it got a little uuuh, busted up, this past year. I thought about using it for this but it doesn't lay out on compound curves anywhere near as easily as the S-glass I used for this project does. S-glass is a DAMN site cheaper too!

Oh yeah Donnie...it was 43 deg (F) when I got up this morning! It's MUCH warmer now .

Jay

[firstgencrx]

Nice write up Jay!

I am in agreement with kakabox, you have got me thinking about stuff. What is so neat about what you have done is how simple it is! It's always so fun to learn something new that is ACTUALLY very cool.

Take care,

David

[kakabox]

Nice.

Again, thanks for taking the time to post this mod along w/the pics. This one will be 'bookmarked' and I'll print out a hardcopy in color too...just in case the web site goes South again!

Cheers!

[Greg Gauper]

Nice fabwork Jay!
Have you considered working with high density expanded polystyrene and using a hot knife to shape your parts? That stuff would disolve in solvent like you wanted.
Regarding your caliper ducting...
I've tried ducting in two locations:
1) At the caliper like both you and Doodson have done
and
2) Behind the upright, pointing towards the center of the rotor, to force air thru the rotor and out the wheel.

Method #1 is easier, and gives you more room for the ducting with less chance to rub.

Method #2 seems to be more effective at cooling the brakes. I haven't had a problem with cooking the fluid since my old Showroom Stock days when I still ran LMA brake fluid. And keep in mind I used to get Carbotech pads hot enough at my two home tracks to cause the backing plates to soften and bend around the piston (see photos in my gallery). The Raybestos ST41/ST43 pads don't have this issue. I do have issues with my tires rubbing on my ducts when I use a lot of steering angle moving around in the paddock/false grid. Not an issue on the track (and if I do have to use more than 1/2 turn of steering while on track, at that point my brake ducts are the least of my worries...if you know what I mean ) Also, by cooling the center of the rotor, you are getting some cooling air to the hub and bearing.

If I had room, I would run two ducts, one to each location. Bigger is better. That's what the books say, and I've kinda proven that to myself via some quasi scientific tests as a passenger in a car on the highway, holding hoses of various diameters out the window and feeling with my hand how much difference in flow you get from 2", 2.5" and 3" ducts.

I wil say this... the CRX gives you a heck of a lot more space for mounting ducts than the Civic does. I'm jealous. It's a challenge to get decent ducting to fit on the Civic. Still, you've given me some ideas for this spring. I like my current duct locations (picking up air from the front turn signals) but they are just generic off-the-shelf 'circle-track' ducts. They don't seal very well and I think I'm getting alot of air spilling off and bypassing my ducts. I might try your technique to make some custom ducts that seal up tighter to the bumper better for more efficiency. The alternative is to mount them in the air dam, but then you risk ripping them off if you go off track. Edit: Then again, some custom made ducts could be made that are wider yet flatter to get the same amount of surface area, yet provide more ground clearence...hmmm might have to look into that!

I've been playing around with a rear mount bracket design that uses the existing threaded holes in the upright for the OEM dust shield. I would prefer a better method of securing the ducts than my present method, which is to use a ton of zip ties, hoes clamps and safety wire.

Edited by Greg Gauper, 28 January 2008 - 04:01 PM.

[JEM MotorSports]

I just read this post...
now added to my things to do list.
thanks!

[GENONE]

whooooa!

wicked!!! well done!