Hi guys, am just finishing the exterior part of my 914-6 project, and am a little confused about chassis reinforcement. I have come across two kits that seem to vary quite differently in their layout. One is from patrick motorsports.
http://www.patrickmotorsports.com/part/586/
The other two from engman, a 'long' kit
http://engmanparts.com/innerlong.php
http://engmanparts.com/hellholekit.php
What do i need for adequate reinforcement before adequate track work. I have done a lot of work already to tie the rollbar into the shock towers, and
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Full Version: Confused about body reinforcement
some pix of the cage/ rollbar
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It ties into the longitudinals in with bolts in the front and rear of the longs
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It ties into the longitudinals in with bolts in the front and rear of the longs
I think with a cage, you don't need the "long" kit. (I have the long kit)
I can't see where the rear of you cage goes, so not sure if the chassis kit is necessary either. Others can probably answer...
I can't see where the rear of you cage goes, so not sure if the chassis kit is necessary either. Others can probably answer...
That is looking good. Nice work.
Thanks, here's a thread of th build.
http://forums.pelicanparts.com/showthread.php?t=395856
The cage basically ties into the body and rear tranny mounts, which is reinforced by the eye-bolts you see going into the aluminum panel mounted on the rear of the tranny. I'll try to get some better pix over the weekend. I am worried about the hell-hole area, which has rusted away to expose the chassis beam which runs dow the right side of the car. will send pix soon.
http://forums.pelicanparts.com/showthread.php?t=395856
The cage basically ties into the body and rear tranny mounts, which is reinforced by the eye-bolts you see going into the aluminum panel mounted on the rear of the tranny. I'll try to get some better pix over the weekend. I am worried about the hell-hole area, which has rusted away to expose the chassis beam which runs dow the right side of the car. will send pix soon.
I would go with the Engman kit, he will work with you on special mods.
Send me the Patrick stuff and I'll turn it into a boat anchor, if he has your money it's the last support you'll ever get.
Send me the Patrick stuff and I'll turn it into a boat anchor, if he has your money it's the last support you'll ever get.
Hmmm, just notices that performance products has a '914 chassis stiffening kit' in their catalogue. Anyone used it?
Looks to me you've got it covered as far as stiffening already, the suspension ears are something you should if you haven't already reinforce.
QUOTE(cobra94563 @ May 9 2008, 02:34 PM) 
I think with a cage, you don't need the "long" kit. (I have the long kit)
I can't see where the rear of you cage goes, so not sure if the chassis kit is necessary either. Others can probably answer...
excuse me, but i don't see a "cage" ...
all i see is a roll bar and some tubing going to the rear shock towers, or so it seems ...
the weakest part of the 914 is right in front of the seats and this car does not seem to have any additional support there.
you'll either need to get a full rollcage (that's what i would do) or at least install the engman long kit.
otherwise, as soon as you start to apply torque or lateral Gs, the chassis will twist like a bungie cord ...
Andy
yep, agreed. There was a real scientific study done and printed in the Up Der Fixen Porsche series, book three, last few pages.
The guys put a 914 chassis in a vibration testing lab and found the weakest point was in the longs....drop a string from top of the windshield to the longs....that is the spot that cracks.
McMark has some pics here of the cracks ...good to know that you cannot see them with all the undercoating in place.
If you are racing this car, a cage that ties into the longs at that spot is paramount to keeping the chassis from twisting, cracking and flexing alot.
Looking at your build its really cool.
These chassis's where built with 165/15 tires in mind...not 1 foot wide slicks...that is what will pretzel yours...
Rich
The guys put a 914 chassis in a vibration testing lab and found the weakest point was in the longs....drop a string from top of the windshield to the longs....that is the spot that cracks.
McMark has some pics here of the cracks ...good to know that you cannot see them with all the undercoating in place.
If you are racing this car, a cage that ties into the longs at that spot is paramount to keeping the chassis from twisting, cracking and flexing alot.
Looking at your build its really cool.
These chassis's where built with 165/15 tires in mind...not 1 foot wide slicks...that is what will pretzel yours...
Rich
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Chap, Andy, Rich, thanks. I researched this forum before building my 'semi' cage, running the front braces from the roll bar forward to the maximum point on the longs, where they are bolted. The roll bar is bolted just rear of the seats, and then tied in to the rear strut brace, and then back to the tranny mounts and rear of the car. I was hoping this would be adequate to reduce torsional flex. These pix are not great, but all i have at the moment taken from early in the build. Do you think i still need to reinforce the longs?
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Chap, Andy, Rich, thanks. I researched this forum before building my 'semi' cage, running the front braces from the roll bar forward to the maximum point on the longs, where they are bolted. The roll bar is bolted just rear of the seats, and then tied in to the rear strut brace, and then back to the tranny mounts and rear of the car. I was hoping this would be adequate to reduce torsional flex. These pix are not great, but all i have at the moment taken from early in the build. Do you think i still need to reinforce the longs?
I used this pix from a previous thread as a model for tying in to the shock towers
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So these 'engman' plates just get welded to the inside of the longs, across the 'weak' point as it crosses the plumb-line droped from the windshield? Will welding some steel plate across the weak spot accomplish the same thing?
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So these 'engman' plates just get welded to the inside of the longs, across the 'weak' point as it crosses the plumb-line droped from the windshield? Will welding some steel plate across the weak spot accomplish the same thing?
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Yes, that's where it goes. No idea if just a small scab plate would be an adequate reinforcement; but it stands to reason that the larger area and longer section of the Engman kit would hold up better and be at least a bit stiffer.
Note that this is only really adding another thickness of metal to the original structure. To really make it stiff, you will need to put something across the door opening above the level of the long--and the higher, the better. (Like the top hoop of a roll cage, for instance.
)
The Perf Products stiffening kit is the same (more or less) as the Patrick one. As is the kit that we sell.
Brad Mayeur, and others, sell a "clamshell" or outer rocker reinforcement/replacement. It doubles up on the outer wall of the longitudinal, similar to the way the Engman kit doubles up on the inboard wall of it. Harder to install, though, due to the other reinforcements on the outside there.
--DD
Note that this is only really adding another thickness of metal to the original structure. To really make it stiff, you will need to put something across the door opening above the level of the long--and the higher, the better. (Like the top hoop of a roll cage, for instance.
)The Perf Products stiffening kit is the same (more or less) as the Patrick one. As is the kit that we sell.
Brad Mayeur, and others, sell a "clamshell" or outer rocker reinforcement/replacement. It doubles up on the outer wall of the longitudinal, similar to the way the Engman kit doubles up on the inboard wall of it. Harder to install, though, due to the other reinforcements on the outside there.
--DD
i've never been a fan of bolt-in cages and rollbars. i think you'll be adding a lot of strength if you weld in good sized scab plates and weld the tubing of the rollbar to that.
as for the longs, i think DD is right, the larger the patch welded on the better. the engman kit ties the whole long together and does a good job in stiffening up that part.
think about it. open the doors on your 914 and look straight through from side to side right about where the front edge of your seat is. there's nothing holding the chassis together at that point besides the longs.
any triangulation there will help the stiffness immensly ...
Andy
PS: keep up the good work!
here's a pic of my cage being welded in at TC Design. the small door braces you see are just to prevent the car from shrinking while tony was welding the cage.
even thought i didn't opt for the full "race" X-brace on the doors, the amount of stiffness compared to a stock car is amazing ...
as for the longs, i think DD is right, the larger the patch welded on the better. the engman kit ties the whole long together and does a good job in stiffening up that part.
think about it. open the doors on your 914 and look straight through from side to side right about where the front edge of your seat is. there's nothing holding the chassis together at that point besides the longs.
any triangulation there will help the stiffness immensly ...
AndyPS: keep up the good work!
here's a pic of my cage being welded in at TC Design. the small door braces you see are just to prevent the car from shrinking while tony was welding the cage.
even thought i didn't opt for the full "race" X-brace on the doors, the amount of stiffness compared to a stock car is amazing ...
Yes, amazing.....and no "stiffening kits" here.....unless you wanna count my own.
JP,
I like the little lower tube supporting the inner suspension.
Did you do anything similar on the outer one?
Adjustable I assuem, and can you post a pic please...
Rich
I like the little lower tube supporting the inner suspension.
Did you do anything similar on the outer one?
Adjustable I assuem, and can you post a pic please...
Rich
No, I didn't.
It's a good idea, tho. I've never had trouble with either the inner or outer. The inner reinforcement was something I'd been thinking about for some time and finally did this last winter. A failure there would ruin my day. The car has held up remarkably well, considering the abuse it gets...2 drivers, all metal suspension, stiff springs, 10 inch slicks and our gawddamn venue is a rough cob. It held alignment pretty well last season before the inner mod.
Before the tubes to the suspension towers (2 winters ago) I was bending the chassis....or so the alignment changes told me. Also had some minor cracking (if there is such a thing) at the base of the rear towers/longs.
If the outers ever move I have a plan.
Brant has a good set up.
It's a good idea, tho. I've never had trouble with either the inner or outer. The inner reinforcement was something I'd been thinking about for some time and finally did this last winter. A failure there would ruin my day. The car has held up remarkably well, considering the abuse it gets...2 drivers, all metal suspension, stiff springs, 10 inch slicks and our gawddamn venue is a rough cob. It held alignment pretty well last season before the inner mod.
Before the tubes to the suspension towers (2 winters ago) I was bending the chassis....or so the alignment changes told me. Also had some minor cracking (if there is such a thing) at the base of the rear towers/longs.
If the outers ever move I have a plan.
Brant has a good set up.
A better look during fabrication.
I had the motor out for a rebuild.
I had the motor out for a rebuild.
Im talking about a heim jointed tube that will HOLD the alignment...and also make it alot dame easier to change...Im old...the BFH thing is stupid...a nice heim joint tube, fastened to the long further up...I saw that somewhere...maybe brant...dunno..
Rich
Rich
Ayup, that's what Brant has.
NOTHING will hold alignment if you have rubber...or plastic for that matter....bushings. You may have it in static, but that goes out the window as soon as you accelerate, corner, or brake. The only rubber in the suspenders left on my car are the upper & lower rear shock mounts. Everything else is mono ball or needle bearings.
Old are you? Welcome to the club.
I'll be 63 in a couple months....God willing & the creek don't rise.
NOTHING will hold alignment if you have rubber...or plastic for that matter....bushings. You may have it in static, but that goes out the window as soon as you accelerate, corner, or brake. The only rubber in the suspenders left on my car are the upper & lower rear shock mounts. Everything else is mono ball or needle bearings.
Old are you? Welcome to the club.
I'll be 63 in a couple months....God willing & the creek don't rise.
Thanks for all the input guys. this board rocks! 
I hear what you are saying by way of full tied-in cage, but am headed toward the 'Engman Solution' as i want to maintain the aesthetic look of the 908/3 rollbar for my project.
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I feel that with the longs reinforced, in addition to the forward bracing, I will be ok, at least at the present power level.
The car is a long-term project, meaning that as i add power, (3.2-3.6 or turbo motor, i will concurrently 'beef up' the rigidity of the frame. As to how old, just turned the big 40.
I hear what you are saying by way of full tied-in cage, but am headed toward the 'Engman Solution' as i want to maintain the aesthetic look of the 908/3 rollbar for my project. Click to view attachment
I feel that with the longs reinforced, in addition to the forward bracing, I will be ok, at least at the present power level.
The car is a long-term project, meaning that as i add power, (3.2-3.6 or turbo motor, i will concurrently 'beef up' the rigidity of the frame. As to how old, just turned the big 40.
I have been watching this project on both boards and I have to say "it has style".
Love the nose......excellent! The profile of the roof line is perfect in proportion to the rest of the car. The center locks and Panzer wheels just add to it. Just knowing that open motor is right behind the driver sucking cabin air get's my adrenaline going. I salute you.
My own take on reinforcing the tub........I would install the Engman Kit and
an 8 pt cage. I would also tie the rear rails to the shock towers top and bottom. Easy to do and worth it. Cage tied into the front strut towers.
With what this car will become you will not regret it. Once you go into heavy spring rate country something is going to give. If you are considering a fat displacement torque monster in the future reinforcement is not an option. Better over engineered than under. As far as the outer "GT Kit". Well it can't hurt but I think better way's of strenghtening the outer rail/suspension console area are found. Running a tube from the outer console upward into a cage tube are more effective at controlling "rail roll". Adding tube's on the inner console upward and forward add considerable strength to the control points and minimize camber and toe changes under load.
A lot of debate exists on reinforcing a 914. What many do not understand is these tubs have already experienced about a "couple zillion flex cycles" already in life with a 100,000 miles on the clock. Then we get a hold of one and double or triple the stress's on the tub via our performance modifications. Hummm?
Someone above mentioned look at the inner long directly below the top of the windshield frame. I can't agree more. If you put a straight edge on the inner long about a 8-12 inches behind the front heater tube you will notice a ripple in the sheetmetal. It's usually not much. I have not found a 914 yet that does not have this. It is visably noticeable from the opposite side of the car. This is a result of a life of flex cycles or "the paperclip syndrome" (metal fatigue and work hardening). Some 914's this area cracks. I have even seen it on 911's on both sides that have had hard lives. Especially on the drivers side because of the E-Brake notch on the 914. The notch does not allow energy to travel beyond that point and fatigues to the point of fracture. The passenger side usually does not crack as it has no notch to stop this "flex wave" so energy spreads farther forward all the way up to the front wheelhouse (without cracking) spreading the load futher within the metals elasticity limits. Look at a long span highway bridge and you will picture this better.
With the addition of wide sticky tires and fat displacement motor is going up the lateral and torsion/twist loads on the chassis. This should also be addressed with reinforceing of those suspension areas that want to give/fatigue along with stout longitudinal enhancements. Longs can be strenghtened via truss (cage) or doubleing up (Engman) on the sheetmetal as an added layer. Twist can be controlled with diagonal bars (side to side & diagonally across the chassis). The wider the tire you go the less body roll and camber/toe changes you will want to achieve. Fat wide tires do not like big axis changes.
Bottom line is is the chassis is going to flex no matter what you do to beef it up. How much it it flex's depends on what you intend to do with it both driving and modifying it. The yellow car above has a very well designed cage both for safety and rigidity. I bet if he added a tube going upward from the inner console to the diagonal cage tube would make a huge difference in controlling camber changes during lateral loading. Whoever did that cage knew what he was doing. Well thought out!
(hey Chris! How's my cage coming?)
Love the nose......excellent! The profile of the roof line is perfect in proportion to the rest of the car. The center locks and Panzer wheels just add to it. Just knowing that open motor is right behind the driver sucking cabin air get's my adrenaline going. I salute you.
My own take on reinforcing the tub........I would install the Engman Kit and
an 8 pt cage. I would also tie the rear rails to the shock towers top and bottom. Easy to do and worth it. Cage tied into the front strut towers.
With what this car will become you will not regret it. Once you go into heavy spring rate country something is going to give. If you are considering a fat displacement torque monster in the future reinforcement is not an option. Better over engineered than under. As far as the outer "GT Kit". Well it can't hurt but I think better way's of strenghtening the outer rail/suspension console area are found. Running a tube from the outer console upward into a cage tube are more effective at controlling "rail roll". Adding tube's on the inner console upward and forward add considerable strength to the control points and minimize camber and toe changes under load.
A lot of debate exists on reinforcing a 914. What many do not understand is these tubs have already experienced about a "couple zillion flex cycles" already in life with a 100,000 miles on the clock. Then we get a hold of one and double or triple the stress's on the tub via our performance modifications. Hummm?
Someone above mentioned look at the inner long directly below the top of the windshield frame. I can't agree more. If you put a straight edge on the inner long about a 8-12 inches behind the front heater tube you will notice a ripple in the sheetmetal. It's usually not much. I have not found a 914 yet that does not have this. It is visably noticeable from the opposite side of the car. This is a result of a life of flex cycles or "the paperclip syndrome" (metal fatigue and work hardening). Some 914's this area cracks. I have even seen it on 911's on both sides that have had hard lives. Especially on the drivers side because of the E-Brake notch on the 914. The notch does not allow energy to travel beyond that point and fatigues to the point of fracture. The passenger side usually does not crack as it has no notch to stop this "flex wave" so energy spreads farther forward all the way up to the front wheelhouse (without cracking) spreading the load futher within the metals elasticity limits. Look at a long span highway bridge and you will picture this better.
With the addition of wide sticky tires and fat displacement motor is going up the lateral and torsion/twist loads on the chassis. This should also be addressed with reinforceing of those suspension areas that want to give/fatigue along with stout longitudinal enhancements. Longs can be strenghtened via truss (cage) or doubleing up (Engman) on the sheetmetal as an added layer. Twist can be controlled with diagonal bars (side to side & diagonally across the chassis). The wider the tire you go the less body roll and camber/toe changes you will want to achieve. Fat wide tires do not like big axis changes.
Bottom line is is the chassis is going to flex no matter what you do to beef it up. How much it it flex's depends on what you intend to do with it both driving and modifying it. The yellow car above has a very well designed cage both for safety and rigidity. I bet if he added a tube going upward from the inner console to the diagonal cage tube would make a huge difference in controlling camber changes during lateral loading. Whoever did that cage knew what he was doing. Well thought out!
(hey Chris! How's my cage coming?)
Jeff, most excellent points and thanks for the complements!!!!. Your dissertation kinda ties everything together. I have indeed gone over the chassis and notices a few of the 'ripples' you mention. I am ordering the engman plates and will be installing them in the next week or so. I am also planning on tying the front/side rollbar braces into the front shock towers but running tubing forward. Further reinforcement will occur, but i just want to start enjoying the car for a little this summer after working on it for so long. If it looks like chassis flex is still a major issue, so be it, and the hardcore track days will just have to wait until i can reinforce adequately. Thanks to all you guys!!!
QUOTE(juicersr @ May 9 2008, 02:06 PM)
Hi guys, am just finishing the exterior part of my 914-6 project, and am a little confused about chassis reinforcement. I have come across two kits that seem to vary quite differently in their layout. One is from patrick motorsports.
http://www.patrickmotorsports.com/part/586/
The other two from engman, a 'long' kit
http://engmanparts.com/innerlong.php
http://engmanparts.com/hellholekit.php
What do i need for adequate reinforcement before adequate track work. I have done a lot of work already to tie the rollbar into the shock towers, and
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Got to tell you love the look and the work you have done
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