Foaming the chassis
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ichiwan2
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Article from SportCompactCarWeb.com
Foam-Filling the Chassis
In any high-performance car, it is impossible to make the chassis too stiff. The stiffer the chassis, the higher its natural frequency, making the energy imparted to it by bumps less likely to excite the body's structure. A stiffer chassis enables the use of stiffer springs and shocks without hurting the ride. This is because a stiff, non-flexing chassis transfers more force into the suspension where it can be dissipated by the springs and shocks instead of transferring the force to the occupants. A stiff chassis is also more responsive to roll rate tuning for balancing understeer and oversteer. This is one of the reasons why automotive engineers are continually investigating ways to stiffen chassis without adding weight.
In a final bit of reengineering to stiffen the body, we injected the chassis with catalyzed rigid structural polyurethane foam. Structural foam, in the 2 lb per cubic foot density that we used, can stiffen chassis members up to 40 percent.
Higher densities of foam can increase stiffness by up to 300 percent. Since we cannot retool custom parts to redo the Z's body, we figured that this would be an excellent, low-cost way of greatly increasing chassis stiffness. Injecting foam is not a new technique for chassis stiffening. The Infiniti Q45 uses this sort of foam in some of its chassis members to increase stiffness, as do a few other premium cars. In fact, the foam we chose is the foam recommended to repair damaged Q45s.
To get the correct foam for our project, we contacted Art Goldman, Foamseal's automotive product manager and author of an SAE (Society of Automotive Engineers) paper on the use of structural foam for the stiffening of automotive unibody structures. We used Foamseal's two-component foam kit, p/n 11-22 to fill the main members of the chassis. Like we mentioned earlier, Foamseal is the supplier that I-CAR, a national certification group for quality auto repair, recommends for the repair of damaged, foam-filled chassis. The Foamseal kit uses a two-part catalyzed polyurethane foam, which quickly cures into rigid, waterproof, closed-cell foam. To prep the car, we carefully masked off all painted areas anywhere where the foam could drip. As this sort of foam is a thermosetting catalyzed plastic, we realized it could be icky if it spilled on paint or any part of the car's interior. This foam is nasty stuff. It is impervious to all known solvents and cleaners.
Rubber gloves must be worn. Get some of it on your hands and it will stay there for more than 3 weeks--don't ask how we know. Do not get this stuff on your paint. Wear old clothes; we ruined ours while learning how to handle the product. We injected the foam into the rocker panels and frame rails of Project Z through existing bolt and drain holes. When injected, the foam reacts like shaving cream and quickly expands to fill the empty space. You can judge how much foam to add by watching its expansion progress through some of the holes. Once injected, the foam expands and begins to cure in about a minute so you need to work fast and plan how you inject the foam before you start.
The life of the foam kit is limited to a few hours once the seal is broken. We filled all of the Z's unibody frame members using five foam kits. When foaming a chassis, you must remember the wires and other lines that pass through the chassis must be relocated or they will be entombed forever.
We were amazed at how this simple procedure improved the performance of the car. The chassis now almost feels like it has a roll cage. A sloped driveway can be driven up sideways with nary a creak. Even though the Z already has a pretty tight chassis, it feels more solid. The ride has improved and road noise has been reduced noticeably. We bet that the car will be even more responsive to chassis tuning measures in the future. If you are a slalom racer, a road racer, have a lowered car or even just want a smoother ride; foaming is a worthy, easy-to-do modification. Foamseal has foams in densities as high as 10 lbs per square foot if you desire to make things even stiffer.
Do not--I repeat--do not attempt to use cheap, hardware-store canned foam. This is not the same thing, and if injected into your chassis, will form a gummy mass that won't dry. Foamseal foam is a professional grade foam, which although it is a little unforgiving to cleanup mistakes, has superior mechanical properties and catalytic curing so it will dry even in an enclosed space.
These changes are continually improving and refining Project Z as we eagerly await our motor. We still have some more parts that we will install and review in upcoming issues. Stay tuned, the best is yet to come!
Full article at:
http://www.sportcompactcarweb.com/projectc...6scc_proj300zx/
Foam-Filling the Chassis
In any high-performance car, it is impossible to make the chassis too stiff. The stiffer the chassis, the higher its natural frequency, making the energy imparted to it by bumps less likely to excite the body's structure. A stiffer chassis enables the use of stiffer springs and shocks without hurting the ride. This is because a stiff, non-flexing chassis transfers more force into the suspension where it can be dissipated by the springs and shocks instead of transferring the force to the occupants. A stiff chassis is also more responsive to roll rate tuning for balancing understeer and oversteer. This is one of the reasons why automotive engineers are continually investigating ways to stiffen chassis without adding weight.
In a final bit of reengineering to stiffen the body, we injected the chassis with catalyzed rigid structural polyurethane foam. Structural foam, in the 2 lb per cubic foot density that we used, can stiffen chassis members up to 40 percent.
Higher densities of foam can increase stiffness by up to 300 percent. Since we cannot retool custom parts to redo the Z's body, we figured that this would be an excellent, low-cost way of greatly increasing chassis stiffness. Injecting foam is not a new technique for chassis stiffening. The Infiniti Q45 uses this sort of foam in some of its chassis members to increase stiffness, as do a few other premium cars. In fact, the foam we chose is the foam recommended to repair damaged Q45s.
To get the correct foam for our project, we contacted Art Goldman, Foamseal's automotive product manager and author of an SAE (Society of Automotive Engineers) paper on the use of structural foam for the stiffening of automotive unibody structures. We used Foamseal's two-component foam kit, p/n 11-22 to fill the main members of the chassis. Like we mentioned earlier, Foamseal is the supplier that I-CAR, a national certification group for quality auto repair, recommends for the repair of damaged, foam-filled chassis. The Foamseal kit uses a two-part catalyzed polyurethane foam, which quickly cures into rigid, waterproof, closed-cell foam. To prep the car, we carefully masked off all painted areas anywhere where the foam could drip. As this sort of foam is a thermosetting catalyzed plastic, we realized it could be icky if it spilled on paint or any part of the car's interior. This foam is nasty stuff. It is impervious to all known solvents and cleaners.
Rubber gloves must be worn. Get some of it on your hands and it will stay there for more than 3 weeks--don't ask how we know. Do not get this stuff on your paint. Wear old clothes; we ruined ours while learning how to handle the product. We injected the foam into the rocker panels and frame rails of Project Z through existing bolt and drain holes. When injected, the foam reacts like shaving cream and quickly expands to fill the empty space. You can judge how much foam to add by watching its expansion progress through some of the holes. Once injected, the foam expands and begins to cure in about a minute so you need to work fast and plan how you inject the foam before you start.
The life of the foam kit is limited to a few hours once the seal is broken. We filled all of the Z's unibody frame members using five foam kits. When foaming a chassis, you must remember the wires and other lines that pass through the chassis must be relocated or they will be entombed forever.
We were amazed at how this simple procedure improved the performance of the car. The chassis now almost feels like it has a roll cage. A sloped driveway can be driven up sideways with nary a creak. Even though the Z already has a pretty tight chassis, it feels more solid. The ride has improved and road noise has been reduced noticeably. We bet that the car will be even more responsive to chassis tuning measures in the future. If you are a slalom racer, a road racer, have a lowered car or even just want a smoother ride; foaming is a worthy, easy-to-do modification. Foamseal has foams in densities as high as 10 lbs per square foot if you desire to make things even stiffer.
Do not--I repeat--do not attempt to use cheap, hardware-store canned foam. This is not the same thing, and if injected into your chassis, will form a gummy mass that won't dry. Foamseal foam is a professional grade foam, which although it is a little unforgiving to cleanup mistakes, has superior mechanical properties and catalytic curing so it will dry even in an enclosed space.
These changes are continually improving and refining Project Z as we eagerly await our motor. We still have some more parts that we will install and review in upcoming issues. Stay tuned, the best is yet to come!
Full article at:
http://www.sportcompactcarweb.com/projectc...6scc_proj300zx/
MeanStreak
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musclehedz
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ichiwan2
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AutoFoam is flame resistant. Poured petrol on it and lit it up. Fuel burnt off and foam was largely intact, it did not combust, i.e., did not fuel the flame. Also tried battery acid - no effect. It does not appear to absorb water either. (I was there when it was demo'd)
Do this experiment with the foam that you have, inject some of your sample into an empty mineral water bottle (about 1/2 the bottle), leave it to expand and close cap when it reaches the bottle neck.
I suggest that you then drop by at KL Auto Accessories and compare and check out the samples Desmond has of other PU foams.
The Necessary
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Just a thought:
there goes your exquisitely engineered german crumple zones.
Good luck!
there goes your exquisitely engineered german crumple zones.
Good luck!
ichiwan2
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The PU foam is just a rigid foam, it is not as solid/dense as a block of steel. There is air in the foam in closed cells. The rigidity is conferred by the expansion of the foam under sealed environment, e.g., like air in an air mattress. The PU foam is breakable, unlike steel. It does, however, add to the stiffness of the chassis
The main areas of application of PU Foam are in the door sills, B-pillar, C-pillar, A-pillar and certain cross members in the front (like having the strut-bar at the bottom) and rear. Personally, I would prefer to have a stronger passenger cell, which should protect the software of the car, i.e., me and my passengers.
Furthermore, the handling improvements reduce the likelihood of one losing control/traction, which for my humble e21, is very important.
The Necessary
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Sure, if all you do is apply the foam to your A/B/C pillars and central chassis. However, I seem to be reading posts advocating the use of foam in the front and rear chassis sub-sections, which in (more modern cars) is where the crumple zones are.
Sure, the foam is breakable, and it's not as hard as steel. But the same principal that makes it so effective in making the car "stiffer", ie. the spread of incidental force on the chassis across a greater area, is also the same principal that will cause the collasible sections to deform in a way not intended by the designers/engineers.
Of course, how that impacts on the passenger "safety cell" is open to debate, but, when it comes to the lives and safety of you and your loved ones, should there even be cause for a debate?
Sure, the foam is breakable, and it's not as hard as steel. But the same principal that makes it so effective in making the car "stiffer", ie. the spread of incidental force on the chassis across a greater area, is also the same principal that will cause the collasible sections to deform in a way not intended by the designers/engineers.
Of course, how that impacts on the passenger "safety cell" is open to debate, but, when it comes to the lives and safety of you and your loved ones, should there even be cause for a debate?
i think most modern cars wont benefit much from foaming. my friend did it on his 156 and didnt notice any difference - noise or handling - from it.
and mind you, the 156 isnt exactly the most well insulated car out there.
the older bimmers might see some gain from it tho.
redd
and mind you, the 156 isnt exactly the most well insulated car out there.
the older bimmers might see some gain from it tho.
redd
Lee36328
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I don't hear anyone talking about crumple zones where antiroll bar and struts bar are concerned...
Yes, the engineers made the car with certain parameters in their calculation and doing anything to the car will alter those parameters.
The same can be said to :
1. changing the airfilter
2. changing the engine
3. changing the suspension
4. changing the brakes
5. changing the exhaust
6. driving with a bad mood
7. ad nauseum
In short, if you alter anything, the calculations are out.
Secondly, I would be mightily impressed if the lowly foam is stronger than steel to the extent that the crumple zones are shifted inwards, in which case, I would feel safer, since I've effectively strengthened the passenger compartment by foaming the A and B pillars...
For the aggressive driver, an foamed car will actually need the crumple zone less since foaming helps with handling.
In the case of the Alfa 156,
1. insulation is not the main benefit of the foam. If you foam a noisy lorry, you will unlikely to notice any improvement in noise insulation
2. I don't drive a 156. It worked beautifully on my e36 though...
Sit in two cars of the same model, foamed and unfoamed. Beats hearsay and imaginative theorising anytime for accuracy.
Cheers!
