intake construction

[swade]

Im working on new construction methods for intake manfolds. I spoke with several teams regauding this subject and one popular technique was cnc wax molds, what kind of wax are you using? Are you makeing parts and pulling the wax out as a solid or are you melting it out? thanks for any help

swade

[drivetrainUW-Platt]

how does the wax hold up to laying carbon fiber or fiberglass? We have done foam and aluminum plugs in the past and havent had the best of luck. Foam melts with chemicals while you are painting/laying up on it and aluminum is a pain to get out.

[Ian M]

I would like to hear of past experiences also, as we are planning on doing a fiberglass intake this year, but haven't decided what to make the mold out of. We were thinking styrofoam or wax though. Any good/bad stories to tell.

[swade]

when you use foam, the resin eats the foam, if you paint it with exterior house paint (containing Aclyn) it creates a barier for the resin, or you can just use epoxy (no reaction), thats how i made body plugs last year, the house paint works well. At formula alot of teams i talked to used cnc wax or hand molded wax but i cant remeber what kind, this weekend im going to run an experiment using candle wax for a mold and then carbon/epoxy and carbon/resin (polyester and vynlester) unless i get some solid information. my goal is to make a solid plenum and melt the wax out in a oven.

[Kenny T Cornett]

Has anyone got any experience withe "seafoam" ??? If you don't know what it is, it's a two part water soluable foam that will NOT degrade under contact with resins. I haven't seen very much done with it but what I have seen has been amazing (carbon intake tubes with complex bends and shapes).

[KU_Racing]

We made our intake last year using blue machinable wax. the stuff is pretty awesome- you can machine it lightning fast to a perfect surface finish, it doenst react to resins, it is non porous so you dont have to treat it before you lay up on it.. I would be careful about melting it out though. It would take a lot of sustained heat to do that, and I dont know how varying composite structures might react. the stuff is a dream to lay up on though- perfect inside surfaces, and to remove parts you just lift a corner and squirt in some shop air, and the parts will pop right off.

[Kenny T Cornett]

Found it! The new line is called "AquaXXXXX". The specific product I was talking about is called AquaCore

http://www.acrtucson.com/products/Aquacore/index.htm

Looks absolutely fantastic. The offer other water soluable solutions for the composites industry.

AquaFill
http://www.acrtucson.com/products/Aquafill/index.htm
Water based smoothing agent (like bondo)

AquaSeal
http://www.acrtucson.com/products/Aquaseal/index.htm
Waterbased sealant for tooling


They also have a castable (sp?) version of the foam.


Very cool stuff

[conekilr]

Hmm, the machinable wax sounds like a very good soultion.

We used aquacore last year to lay up our plenum and over flow containers. It's a great product but also a very timely process. It is quite brittle if not packed extremely well and there is still the chance of loosing your intended shape due of chipping, etc. If you lay up on the aquacore itself, without the sealer or filler, then you will get a very grainy surface finish from resin capturing some of the aquacore and therefore preventing any water from removing it. This stuff is very interesting to work with though because you can't really stab or cut it however, when sheared side-to-side it just falls apart like powder/sand. We don't have experience with actually machining the aquacore (shaped by hand) but I'm assuming it would be tricky to handle and very frustrating if you accidentally chipped a piece while removing material. So to sum it up I would suggest purchasing all 3 of the aquacore products to test with while still looking into other methods such as wax, good luck!

[KU_Racing]

The machineable wax was awesome to work with. Conekilr, do you know how expensive the aquacore material was? they dont seem to have any pricing info on their website.

[Parker]

did anyone perform these machining operations on a simple 3-axis cnc mill?? Im having trouble planning the layout for machining the parts. a 5-axis would be nice...

[Kirk Feldkamp]

Where do you guys buy your machinable wax? The prices I've seen before have been obscene (think McMaster)... so if you have any leads on better prices, let everyone know!

How durable is the machinable wax? Is it what would generally be used for a 'soft tool' for sand casting? How many parts could be made without damaging the surface (assuming you're not using it to make cores)?

Also, any idea how much a 5-gallon bucket of the AquaCore or AquaPour stuff costs?

-Kirk

[swade]

give me till later today and ill have a price list for aquacores product line and ill post it up for you guys. i spoke with them today by email.

chris

[Kirk Feldkamp]

Well? Any updates? http://fsae.com/groupee_common/emoticons/icon_confused.gif

[TG]

I believe the cost for FSAE teams for a 5 gallon bucket of the aquacore/pour stuff is between $80-100 if I remember correctly. They have a standard FSAE discount.

Some of the coolest shit I've heard of is rapid prototyped wax cores. They use it here at ASU for castings, but I would imagine with a proper coating on the surface (maybe you won't even need one) that it would be suitable for composites. I'll have to take a look into that.

[swade]

still wating on the gentleman to get back with me on the price sheet... i spoke with him on friday and seemed interested in helping teams out so hope fully he will email me today.

i didnt get a chance to complete the candle wax experiment this weekend, hopefully in a few days

[Cody the Genius]

Are any of you guys familiar with Z-corp rapid prototyping machines?


That is what we used to make the intake my last year in F-Sae. It uses a flour/ plaster like powder and the equivalent of a printer head sprays out binder to create stacked 2-D profiles. We simply made our intake and then left out the finising processes to make it robust. This way we could lay our carbon directly over the mold and the just hit it with a water hose for a bout 2-3 hours to dissove the mold back out of it. It worked awesome and that's how we made our one piece intake, runners and all.

[Parker]

we would build ours the same way, except the rapid prototyper we have uses ABS plastic. We are still contemplating building the manifold out of it, but it didnt work out so well last year

[KU_Racing]

Sorry for taking so long to reply. The machinable wax is very durable- assuming you dont use and tools to remove the parts (unless you have some huge machining mistake or something, you shouldnt have to- the parts pop right off since the surface is non porous) you could make a huge number of parts from one plug. The was is pretty strong as far as general durablity- unless you drop it or expose it to extreme heat, you wont really screw up your molds. We actually dropped on last year, and were able to repair it by flashing over the broken faces with a torch and basically welding the shards back together.

[RKemmet]

just do it like this:
http://www.u.arizona.edu/~rkemmet/DSCF0393.JPG
and pour it out with water.

[jonny]

Hi RKemmet,

That's a nice pic u have there. So after this process, i assume you would lay some carbon/glass fibre onto the wax. How do you remove the final material as one? I can only think that you could lay one half of the runner( in the axial direction) remove that, then lay the other half and then epoxy the 2 together.
Is there any way to lay the whole piece as one and remove it as well?

[swade]

that mold is made with a water soluble substance. it is laid up as one piece and then water is added, the mold washes away leaving the part behind. good thing is you have a seamless part. bad thing is you can only make one.

[jonny]

water soluble substance?? interesting... whats the substance's name?? is it easy to machine on??

[Hot Rod JayRad]

was this done on a 3-axis? 5-axis? is that the aqua-fill material? can you give some details on how you went about physically making the part and what problems you may have run into.

Thanks!

[swade]

i was merly replying to let you knowthe method, i didnt make that part. the substance is called aquacore. it is machinable but difficult to work with. in order to machine it the rawmaterial has to be pressed and baked. it is very brittle and if not formed properly will chip and crack. we make our intake using an SLA printer. we make several SLA molds, coat them first with superglue to make them hard and then coat them with watersoluble wax. It is then laid up, vacumed and when dry, the part is released from the mold by adding watter. the wax is called optical wax made by freeman.

[KU_Racing]

Water soluble wax!?! That sounds to me like the best of both worlds. What is the machinability like, and how hard is it when finished? Is the mold technique similar to making a machinable medium mold, or is it a casting medium?

[markocosic]

Hand-turned two-piece foam core for the convergent-restrictor-divergent section, hand-finished foam core for the 'cover for a loaf of bread' plenum top. Paint. A fuel-resistant (but only boat grade - cheap) gelcoat, resin and some glass mat. Ali sheet plenum base w/ jenvey intake trumpets. Looks ugly externally perhaps, but is gorgeous internally, robust for the mass and straightforward to do with limited kit.

Most foams will be fine - provided that you can get a good paint base coat on it. Polyfilla (wall plaster/gap filler) over the top of a roughly hacked out open-cell foam, then paint, also works.

Make sure that the foam core is a flexible core - 350mm+ of divergent nozzle around a rigid foam core needs a lot of delicate adjustment tool #43 (club hammer) to remove... http://fsae.com/groupee_common/emoticons/icon_eek.gif

[jonny]

anyone has any porosity issues due to composite intakes?? ie CF is porous and the intake is actually allowing air into the engine even when the throttle position is at 0%...

[Mike Claffey]

Jonny, roughly speaking, if the intake is so thin that it is porous, it will implode when you close the throttle at high rpm.

[jonny]

how do you define thin? we are going for 4 layers of carbonfibre...

[A Richards]

Originally posted by jonny:
how do you define thin? we are going for 4 layers of carbonfibre...

You will probably need to use a core in your intake, four layers would not be enough without one, especially on any flat sections. I've just got back from finishing our new intake moulds. Going be 2 layers either side of a 5mm honeycomb core. We have had trouble in the past with the intake sucking in off the throttle with a construction similar to what you describe.

As for leaking there are many ways to fix that problem if it occurs, which it shouldnt.

A. Richards
DRT Team Manager

[jonny]

5mm core... wouldn;t that make your intake kinda heavy and big?? plus how do you get the core to conform to the shape of the plenum and the radii of bends??

if you'd like to share some pics, my email is jredknapp11@hotmail.com thanks...

[A Richards]

Core weights next to nothing for the extra stiffness that you will get. We had issues with our intakes as described, we are running a single as well which makes its genometry significately different to what most would run. At first we simply added more lays with little effect and the intake was one heavy pig. on tight radius you wont need core, mainly on flat surfaces. As you can see below from the moulds of our new intake we run a monster plenum so the need to use a core is pretty important. However all the trouble that we had was two years ago with a plenum 1/3 the size.


http://i197.photobucket.com/albums/aa249/deakinracetechnologies/Intake.jpg


Your intake maybe significatly different and our experiences may not translate. Give ya something to think about anyway...

A. Richards
DRT Team Manager

[jonny]

thanks A Richards,
Ours is a 4 cylinder.. maybe we do need to add a core at the plenum... thanks once again!!!

[LU-Bolton]

A Richards,
Interesting choice using a core for your intake. However, you don't need one. We've had all of the bad things happen to us with carbon intake manifolds. Too thin leading to intake leaks, too much sanding leading to intake which blew up due to a backfire, etc... This has all been on a WR-426 and WR-450, single cylinder engine also. You can make a very light intake without leaking or stiffness issues with carbon fiber. We've even vacuum infused intakes in the past that worked. First off, your shape shouldn't have any flat surfaces on it. Use a sphere or bulbous-type shape. The curves will naturally be stiffer than flat plates for this scenario. Look at RMIT's or our '07 intake for example(We make them look like this for a reason). Also, use the tightest weave you can find for fabric. Lay it up, leak test it before you EVER put it on the dyno, and run it on the dyno. If it implodes or pulses a lot, make it again with more layers or a new shape. It's pretty simple.

We used a machined wax male mold in the past, wet laid, bagged, and had no issues. It does take a couple tries though to get it right sometimes if you're inexperienced. If you want it to look amazing don't use male molds with a bagged wet lay. Wrinkles form on the outside. The inside however... perfectly smooth. Our moms always told us it's what's on the inside that counts anyways, right? http://fsae.com/groupee_common/emoticons/icon_smile.gif For literal perfection on an intake look towards Purdue's '07 car or Joanneum, for example. Pre-preg, machined female molds, a lot of time and practice, but it looked amazing.

Aaron Cassebeer

[A Richards]

Originally posted by LU-Bolton:

First off, your shape shouldn't have any flat surfaces on it. Use a sphere or bulbous-type shape. The curves will naturally be stiffer than flat plates for this scenario.



Somewhat difficult if you have to put a 7L Plenum into 7Litres of space though that is square





If it implodes or pulses a lot, make it again with more layers or a new shape. It's pretty simple.



Pretty simiple and pretty stupid.
A rather costly and time consuming way if learning what we already know. When your on a Three person team you need to get these things right the first time.




If you want it to look amazing don't use male molds with a bagged wet lay. Wrinkles form on the outside.



Of course im using female moulds. If your making moulds that hard way though you need to make a male mould first.


A. Richards
DRT Team Manager

[Mike Sadie]

So, am i right to assume that you are making the female molds from carbon?

P.S. Aaron was politely giving his opinion, no need to be a dick.

[A Richards]

Nah i made the female moulds from glass.

Is there any great advantages from making carbon moulds?

[Ashley Denmead]

Mike, i don't think Richards was being offensive but merely just having a different opinion to Aaron, no need to call him a dick, i do that enough as it is!

I'm sure you guys must have figured out by now that every car is different and each component may have slightly different design requirements to someone else's, there is no right answer!

One thing i can guarantee is that a cored composite will be more efficiently (weight wise) stiff than a monolithic one, HOWEVER maybe you have other requirements from your design or can get adequate stiffness from using a spherical shape as you've mentioned before. In our particular case we need quite a lot of volume in a small area that is not spherical itself therefore need a plenum shaped something similar to the space it occupies and our stiffness problem is then solved by utilizing a cored structure with somewhat flat sides. Everything is a compromise!

[LU-Bolton]

I agree, there are always different ways to solve the same problems.
A Richards, my first question is why you're using a 7L plenum on a single... seems rather large to me. Of course I'm not an engine guy though, so I'm sure I'm wrong. http://fsae.com/groupee_common/emoticons/icon_smile.gif
Secondly, I was Team Captain, Suspension Team Leader, and Chassis Team Leader in '07. You don't have to lecture me on using time and resources wisely.

Core doesn't make sense to me because I don't think you will get a very good surface finish on the inside of the intake. It seems inevitable. It would be nice to hear your input though on this since I haven't cored an intake.
I'm just trying to give my input based on my four years in FSAE. I saw a lot of intakes in my time. I rarely saw a good one that was cored. It's not that the reasoning behind using core is poor, I think the execution is just more difficult. I think it's harder to manufacture. I think it's probably also easier to make a solid laminate leak-proof intake than a cored one. Unless you are using closed-cell foam, which I doubt you are. Anyways, best of luck. I'm interested to see how it turns out.

Aaron Cassebeer

[jonny]

what is the most accurate way of performing a leak test?? I tried doing something very simple ie blew some cig smoke into the intake and shine some bright light to see for any leaks... but i would think this is a little dodgy...

thinking abt putting the whole system in water but water might not behave as close to air...
thanks in advance

[nickerss]

Turn your engine on and spray carb cleaner/starting fluid anywhere you think it might be leaking. If your idle goes crazy when you spray it, you have a leak.

[Mike Sadie]

Richards, Can you elaborate as to why you are making female fiberglass molds as opposed to just machining your female molds? In my experience, the main reason buck/plug (machined male) molds is to make carbon fiber female molds. The only advantage here is for autoclaving, where the part can be brought up to high temps (>150 C) in the mold. Also with carbon molds, the thermal expansion in the autoclave is not a problem.

I agree that for an intake that requires flat surfaces, you will need some core material. We have made a plenum with no core and it has no problems. I believe it was only 2-3 plys of 3k 2x2 twill.

If you are sure to not make your carbon pieces resin lean, you should not have much of an issue with leaking. If you have the resources, be sure to vacuum bag it. If you bag it, you can make the carbon a little bit resin rich and pull the excess resin into the breather. Having access to an autoclave makes this even more effective.

[A Richards]

I totally agree that CNC'd female moulds are the way to go. The reason that I did it this way is because I was in a massive hurry and didn't have the time to chase up someone with the facilities to machine it and wait for them to get around to it. I needed the mould to be accurate and dead flat so didn't make it out of foam like I initially intended. After I finished the design I saw a nice sheet of steel and proceeded to cut it up and weld the thing together. If the press break in the guillotine didn't try and eat one of my fingers at one in the morning the mould would have been done from start to finish in one night. Yes I agree this is a REALLY stupid way of making moulds, but hey what are you to do? LOL.

http://i197.photobucket.com/albums/aa249/deakinracetechnologies/f1.jpg

http://i197.photobucket.com/albums/aa249/deakinracetechnologies/f2.jpg

I used fiber glass for the mould because I could get a gel coat finish, it's cheap, and can be pulled off the mould in about an hour. It's not going to see an autoclave or temperatures over 40 degrees so should do the job just nicely.

I think that I may have been slightly misunderstood when I used the term ˜cored intake'. I was never referring to having some monster 22mm sandwich panel of an intake, I'm not introducing stressed intakes into SAE quite yet, more so adding a little bit of inertia here and there with 5mm honeycomb. Obviously a certain number of layers are required to make the intake seal. If this and the intakes shape/size alone is going to be ridged enough then core isn't going to be required.

Inside of the plenum will obviously be a peel ply finish, Given the plenums job and the size of ours in particular I don't think that surface finish will be an issue. However it could be in a lot of other intake designs. Obviously very important is the finish inside runners and the restrictor.

The intake will be 3K twill and I wasn't afraid to put a little extra resin in, very important that it seals because a lot of problems will be encountered if it doesn't !!


Plenum size is one of those topics, everyone has their theories, ideas and what works for them. 7 litres sounds like a lot and people will argue that throttle response will go right out the window. Despite this however we have never had a problem with response; I will go as far to say that it is as responsive as any factory motocross bike.
There has been talk of Plenum sizing on 4 cylinder engines having little effect on power output and that it is the length of runners that should be focused on, I also tend to believe this to a degree. On a single however after playing around with various sizes some pretty pronounced changes in performance and the distribution of power become apparent. So different in fact that the car is basically undrivable if you interchange fuel maps between them. To cut a very long story short seven litres of plenum makes more power than a smaller one and shifts the power right up top in the range where we want it, we also have no problems with drivability and have also played with the cam and various other things.

A Richards

[jonny]

hi,
just would like to know whether any one is able to make a fully composite intake inclusive of a throttle body out of composite as well? we have tried it but unfortunately, heat soluble wax doesn;t give good tolerances, ie there will be some leak problem due to dimensional inaccuracies... still unable to find the remedy, currently looking in flanging up an aluminum trumpetw throttle body to the whole composite intake...

[overdrive535]

I believe that SD School of Mines has...out of carbon fiber...I'm not sure how they did it, however...