Interior/Exterior Foam injection into frame ?
Foam injection into frame ?
On many cars, one can inject rigid foam into frame members, and get a more rigid frame as a result, with improvements in handling and noise-reduction.
While under my MCS today, I noticed that there are four box-section frame members running fore and aft under the front seating area. These are spot-welded to the floor pan - one on either side of the exhaust-pipe tunnel, and one on either side near the outside of the floorpan, which goes forward and up a few inches into the firewall area.
I'm wondering if anyone else has tried foaming in these hollow frame elements, and if so, what were the results? I realize that the Mini is a pretty rigid structure compared to many cars, but this change would be akin to welding the box section fully, instead of the spot-welds from the factory - a common racing mod.
My plan is to use a two-component urethane foam (Never use hardware store foam-in-a-can for this) and fill each of these sections. I hope to achieve reduction in road and engine noise and vibration by damping the floor pan. (Note: dampening means to get it wet
).
If I were most interested in adding rigidity to the frame, i.e for racing, I'd use an epoxy foam which sets harder, but the urethane foam retains just enough elasticity to act as a pretty good damping material as well.
I'd be really interested in hearing from anyone else who has done this mod on a Mini.
While under my MCS today, I noticed that there are four box-section frame members running fore and aft under the front seating area. These are spot-welded to the floor pan - one on either side of the exhaust-pipe tunnel, and one on either side near the outside of the floorpan, which goes forward and up a few inches into the firewall area.
I'm wondering if anyone else has tried foaming in these hollow frame elements, and if so, what were the results? I realize that the Mini is a pretty rigid structure compared to many cars, but this change would be akin to welding the box section fully, instead of the spot-welds from the factory - a common racing mod.
My plan is to use a two-component urethane foam (Never use hardware store foam-in-a-can for this) and fill each of these sections. I hope to achieve reduction in road and engine noise and vibration by damping the floor pan. (Note: dampening means to get it wet
).If I were most interested in adding rigidity to the frame, i.e for racing, I'd use an epoxy foam which sets harder, but the urethane foam retains just enough elasticity to act as a pretty good damping material as well.
I'd be really interested in hearing from anyone else who has done this mod on a Mini.
From an article at SCC. Find the manufacturer at http://www.foamseal.com/auto_aftermarket.htm
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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.
-------------------------------------------
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.
hmm....seems like there might be a problem with moisture getting trapped in there and rust appearing much sooner than it should.
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MTH Specialist
Joined: Mar 2005
Posts: 739
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From: Houston, TX
Originally Posted by rednwhitecooper
hmm....seems like there might be a problem with moisture getting trapped in there and rust appearing much sooner than it should.
Coordinator :: Northwest Indiana MINIacs
Joined: Nov 2004
Posts: 2,412
Likes: 0
From: Valparaiso, IN
I use a 2 part foam when building rockets. It secures the fins to the motor mount and strentghens the rocket for takeoff. I am level 2 certified TRA #07839 ("1/8A" through "L" impulse) with the Tripoli Rocketry Association.
Foaming is quite common in the "Tuner" world. They gotta do something to stiffen the car after they get rid of all that heavy factory reinforcement braces!
To be quite honest, I figured that everyone here already knew about foam.
Foaming is quite common in the "Tuner" world. They gotta do something to stiffen the car after they get rid of all that heavy factory reinforcement braces!
To be quite honest, I figured that everyone here already knew about foam.
There are certainly other places where foam would be useful, but my goal isn't so much stiffening as vibration damping in the floorpan to reduce the road-roar from our incredibly coarse worn macadam highways in the Pacific NW. I'll be using a 1-3/4 lb./ft. foam.
As to the water-trapping issue, I'm not too worried, because a) BMW does a pretty good job of sealing the underside and inside surfaces, and b) I'll give the car a couple of days in a warm garage to dry thoroughly. I've used this stuff before, and there are holes in useful places, so I expect to get a good fill. The foam will, of course, prevent any moisture from ever getting in there again, and I will use plastic hole-plugs to seal the holes.
I'll report on how it works next week.
As to the water-trapping issue, I'm not too worried, because a) BMW does a pretty good job of sealing the underside and inside surfaces, and b) I'll give the car a couple of days in a warm garage to dry thoroughly. I've used this stuff before, and there are holes in useful places, so I expect to get a good fill. The foam will, of course, prevent any moisture from ever getting in there again, and I will use plastic hole-plugs to seal the holes.
I'll report on how it works next week.
Coordinator :: Northwest Indiana MINIacs
Joined: Nov 2004
Posts: 2,412
Likes: 0
From: Valparaiso, IN
Originally Posted by MSFITOY
Great idea...however, these box rails are so small. Do you think it will help much? How about filling the rockers and A/B/C pillars?
3rd Gear
Joined: Apr 2003
Posts: 219
Likes: 0
From: Atlanta, Ga USA
Great Idea
I am wondering if you can fill the section in the rear behind the battery box that ties the bumber mounts together. This could stiffen up rear flex a bit and could take away significant exaust noise also. I do not know if blocking those two big breather holes would affect anything. I have not been able to figure out if they do anything usefull ventilation wise. Does anybody know? I may stuff mine with fiberglass just to see if it helps with noise.
Keep us informed.
wes
I am wondering if you can fill the section in the rear behind the battery box that ties the bumber mounts together. This could stiffen up rear flex a bit and could take away significant exaust noise also. I do not know if blocking those two big breather holes would affect anything. I have not been able to figure out if they do anything usefull ventilation wise. Does anybody know? I may stuff mine with fiberglass just to see if it helps with noise.
Keep us informed.
wes
I foamed the four frame sections under my floor pan at www.mini-madness.com a couple of days ago, and report qualified success. I used this stuff: http://www.tapplastics.com/shop/product.php?pid=80& I bought two packs, and used about half of the second one.
It was a really easy job. There are 1/2" holes in the right places, and the only prep work I had to do was to put some cardboard down on the floor under the lift. I'd suggest using a lift, as it would be tough to fill the sections while avoiding getting it all over you on a creeper. You do need to plan your route, as the stuff hardens in the nozzle if you pause for 30 seconds.
To avoid the foam coming out on top of a heat-shield, I used some paper to block off two holes under a heat-shield on the exhaust support near the back of the floor pan.
I attached 8" of clear tubing to the foam nozzle, to allow me to get back into the deepest spots at the ends and fill them from the bottom out to avoid voids. Injecting the foam was pretty much a matter of starting at one end of each box-section, and following along as the foam started to come out of each hole as it expanded. The foam takes only a few minutes to harden and stop expanding. You should have a cigar oozing out of each hole onto the floor, which you remove from the car when done.
The results of foaming these four sections were evident, although not as extreme as I had hoped. My car had a bit more engine vibration than most, as I've put firm engine mounts on the lower mount to reduce engine rocking. I've also put Lloyd's heavyweight carpet mats in to soak up road noise. The results I observed were:
- The foam reduced the 4-cylinder buzz from my engine and mounts quite a bit - you no longer get a foot massage at the stop light. I'd say it cut this by half. The car is also slightly quieter, with less engine hum at 60 mph on smooth pavement. I can hear the stereo better at low levels now.
- The foam did not do much to reduce the road roar that you get on very coarse pavement - maybe 2dB reduction. I was a bit disappointed by this aspect.
- The foam did reduce the thump from bumps somewhat, although I'm not the best judge of this - I use 205x55x15 tires. Bott's dots during lane changes excite less protest from the interior plastic bits with the foam. The foam may effectively "soften" the impacts of low-profile tires by stiffening the frame.
- Unexpectedly, the foam seems to have stiffened the car frame as far as torsional flex. The effect I notice is that it seems to track better now during curves, with a bit less bump-steer. This is about the same level of change that I've found when adding a front strut-top brace in other cars.
Bottom line for me is that if I were prepping for racing, foaming the frame would be a no-brainer, although I'd get some stiffer structural foam and would also do the rocker panels and a few other places during a frame-off. If I were trying to mitigate a hard ride, this would also be a cheap thing to try. And if I were working over the car to reduce noise, it would also be on my list, mainly because it is quick and easy - little labor involved.
Is it a biggie? No, but it's a medium upgrade, and it's really easy. If anyone else tries this, I'd be really interested in your results - I don't think I'm imagining the changes in noise and handling, but sometimes it's not easy to be sure, and you can't go back to unfoamed to compare.
It was a really easy job. There are 1/2" holes in the right places, and the only prep work I had to do was to put some cardboard down on the floor under the lift. I'd suggest using a lift, as it would be tough to fill the sections while avoiding getting it all over you on a creeper. You do need to plan your route, as the stuff hardens in the nozzle if you pause for 30 seconds.
To avoid the foam coming out on top of a heat-shield, I used some paper to block off two holes under a heat-shield on the exhaust support near the back of the floor pan.
I attached 8" of clear tubing to the foam nozzle, to allow me to get back into the deepest spots at the ends and fill them from the bottom out to avoid voids. Injecting the foam was pretty much a matter of starting at one end of each box-section, and following along as the foam started to come out of each hole as it expanded. The foam takes only a few minutes to harden and stop expanding. You should have a cigar oozing out of each hole onto the floor, which you remove from the car when done.
The results of foaming these four sections were evident, although not as extreme as I had hoped. My car had a bit more engine vibration than most, as I've put firm engine mounts on the lower mount to reduce engine rocking. I've also put Lloyd's heavyweight carpet mats in to soak up road noise. The results I observed were:
- The foam reduced the 4-cylinder buzz from my engine and mounts quite a bit - you no longer get a foot massage at the stop light. I'd say it cut this by half. The car is also slightly quieter, with less engine hum at 60 mph on smooth pavement. I can hear the stereo better at low levels now.
- The foam did not do much to reduce the road roar that you get on very coarse pavement - maybe 2dB reduction. I was a bit disappointed by this aspect.
- The foam did reduce the thump from bumps somewhat, although I'm not the best judge of this - I use 205x55x15 tires. Bott's dots during lane changes excite less protest from the interior plastic bits with the foam. The foam may effectively "soften" the impacts of low-profile tires by stiffening the frame.
- Unexpectedly, the foam seems to have stiffened the car frame as far as torsional flex. The effect I notice is that it seems to track better now during curves, with a bit less bump-steer. This is about the same level of change that I've found when adding a front strut-top brace in other cars.
Bottom line for me is that if I were prepping for racing, foaming the frame would be a no-brainer, although I'd get some stiffer structural foam and would also do the rocker panels and a few other places during a frame-off. If I were trying to mitigate a hard ride, this would also be a cheap thing to try. And if I were working over the car to reduce noise, it would also be on my list, mainly because it is quick and easy - little labor involved.
Is it a biggie? No, but it's a medium upgrade, and it's really easy. If anyone else tries this, I'd be really interested in your results - I don't think I'm imagining the changes in noise and handling, but sometimes it's not easy to be sure, and you can't go back to unfoamed to compare.
2-3 lbs total weight. You may have to bend back a couple of corners on the cat's heat shield to get at two holes near the front of the inside channels.
As to warrantee, I can't imagine it causing a problem. I looked pretty carefully, and I couldn't find anything inside these frame sections, and it certainly won't cause rust as long as the car was dry when you started. If there were any argument, only the frame sections would be affected, so rust perforation elsewhere would not be related. I'd judge this as lower warrantee exposure than a supercharger pulley.
Let me know if your results agree with mine, mp5999.
Regards,
Rick
As to warrantee, I can't imagine it causing a problem. I looked pretty carefully, and I couldn't find anything inside these frame sections, and it certainly won't cause rust as long as the car was dry when you started. If there were any argument, only the frame sections would be affected, so rust perforation elsewhere would not be related. I'd judge this as lower warrantee exposure than a supercharger pulley.
Let me know if your results agree with mine, mp5999.
Regards,
Rick