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Beebo Kanelle
Does anybody anywhere know where to find the torsional rigidity of the 914 with the roof off vs. roof on vs. steel roof (916) ?

Thanks in advance.
Chi-town
I've never seen an FEA of the whole car but I would be interested in knowing also.
mepstein
No difference with the regular top. It's not bolted on. The steel top helps but the A pillars move easily so nothing like a full roll cage.
Dave_Darling
I am told that there actually is a difference with the stock top on. Even though not bolted, it is attached and helps a little bit. Anecdotal evidence: A nationally-known autocrosser lost a half second on a particular course at one point and then got it back later in the day by noticing that one of the top latches had become unlatched and latching it again.

Sadly, I have no numbers to back that up.

--DD
jmitro
that sounds like placebo effect to me.

I have no firsthand or secondhand knowledge, but I would suspect as mepstein said it makes no difference whatsoever with the targa top on or off. Too much slack in the rubber weatherstripping
914forme
The front A Pilars are the same as the 944, pretty much the same setup. Same gauge, same structure, etc.... Difference could be in the base as it attached to the cowl section.

Some of the GTs have bolted down tops, and they added reinforcement to the lower A pillar not the whole thing. these did make a difference.

916 steel roofs made a difference, just like any coupe does.

Nothing will be as good as a proper cage.

In Pano reprinted up fixin' they did do a test of frenquency variations on the 914 chassis. interesting read, I might have to look it up again.
Tdskip
Not what you asked, but bracing the internal core structure of the car the longs and rear firewall is the place to do it rather than the top unless you want to loose the roof and weld the car closed.

Chi-town
A bolt down metal top would make a big difference as it completes the "box" just like in a FRC Corvette or Supra Targa.

Bracing the longs is a band-aid for not having a solid roof structure. The longs flex because there is no top to the "box".

An A pillar to roll hoop brace setup would probably do more and weigh less. The trick would be making a fiberglass top with a metal structure and a way to actually bolt it on.

Of course a full cage takes care of the issue all together but is not feasible for street cars.
mgphoto
The factory 914/6GT’s had steel reinforced roofs, steel rods front to rear and an x pattern left to right.
Mark Henry
I have two 914's here one is rust free ( rolleyes.gif ) unmolested, the other repaired, GT kit and inner long stiffener kit.
Putting my hand flat across the hoop/top part line, pushing the car around, the OG car you can feel the part line wiggle. The car with the inner long kit the part line has no wiggle whatsoever..
ConeDodger
QUOTE(jmitro @ Jan 6 2019, 01:37 AM) *

that sounds like placebo effect to me.

I have no firsthand or secondhand knowledge, but I would suspect as mepstein said it makes no difference whatsoever with the targa top on or off. Too much slack in the rubber weatherstripping


I doubt placebo effect was in play. National level autocrossers are remarkably consistent. They can often predict improvement run to run. Mostly because unlike novice drivers, they know where they lost time. When they lose time, it’s usually spectacular. Ie: they spin...

I have driven my 914 without a top and without a windshield. That window frame wags like a golden retriever when dad comes home! laugh.gif
VegasRacer
Elvira has a cage plus some additional reinforcement.
On the track, with the top off . . . the top corner of the windshield frame will flex almost an inch vs. the corner of the cage. yikes.gif
GeorgeRud
I notice quite a difference between my original -6 with the original chassis and my conversion -6 that has 914Ltd’s stiffening kit installed. Years ago, Bruce Anderson and Garretson Enterprises did actual measurements of body flex.
Dave_Darling
I believe that the guy whose car they tested was actually the same person who told me the anecdote about the latch....

--DD
Curbandgutter
Hello, I did run some numbers on the torsional rigidity of the 914. Here's the link http://www.914world.com/bbs2/index.php?sho...p;#entry2396780

See POST#10

Bottom line is that the stock 914 chassis is very flexible, 3,326’# per degree from my testing. Although I didn't say it at the time, I ran the numbers with and without the doors and found no real difference. From my "door" tests, it's safe to assume that the roof will not be any different. There is too much flex in the hinges, and latches before the roof and doors begin to provide support.

Based on testing, I can say that, other than a full roll cage, that the next best thing is to stiffen the longs. Then, if you wanted more, a welded steel roof like the factory. There is a reason why the factory went with a welded steel roof in the 916.

I'm almost to the point where I can test again with the full roll cage in place. Based on modeling, I'm expecting a 10x stiffer chassis now.

In testing, I found that one of the longs had a stress crack in it. I don't know if that was just mine, or if most of the 914's out there are running around with cracked longs.
rgalla9146
This is a great topic.
I want a 914 coupe.....with AC
Chi-town
I think I'm going to move forward with a bolt on roof frame idea.gif
73-914
QUOTE(rgalla9146 @ Jan 6 2019, 06:14 PM) *

This is a great topic.
I want a 914 coupe.....with AC

It's called a Cayman
Beebo Kanelle
It appears that the 914 has a stiffness of 3,326 '#/Degree

Thanks, that gets me in the ballpark.
Curbandgutter
QUOTE(Beebo Kanelle @ Jan 6 2019, 05:49 PM) *

It appears that the 914 has a stiffness of 3,326 '#/Degree

Thanks, that gets me in the ballpark.


Yes, sorry I should have stated that instead of forcing you to go look for it in the post. I updated my response to show the number. smile.gif
rgalla9146
QUOTE(73-914 @ Jan 6 2019, 08:41 PM) *

QUOTE(rgalla9146 @ Jan 6 2019, 06:14 PM) *

This is a great topic.
I want a 914 coupe.....with AC

It's called a Cayman


Yeah, one of them too. They're beautiful. Make mine a GT4 please.
Beebo Kanelle
This is interesting :
http://youwheel.com/home/2016/06/20/car-bo...rehensive-list/
VegasRacer
2013 Cayman Steel.
Click to view attachment
Dave_Darling
QUOTE(Curbandgutter @ Jan 6 2019, 03:13 PM) *

Bottom line is that the stock 914 chassis is very flexible, 3,326’# per degree from my testing.


We know that is the value in at least one case. It would be interesting to see if that is the same on many different 914s.


QUOTE
In testing, I found that one of the longs had a stress crack in it. I don't know if that was just mine, or if most of the 914's out there are running around with cracked longs.


It is pretty common for the inner long to crack at the recess for the handbrake handle on 72+ 914s.

--DD
mepstein
QUOTE(Curbandgutter @ Jan 6 2019, 06:13 PM) *

Hello, I did run some numbers on the torsional rigidity of the 914. Here's the link http://www.914world.com/bbs2/index.php?sho...p;#entry2396780

See POST#10

Bottom line is that the stock 914 chassis is very flexible, 3,326’# per degree from my testing. Although I didn't say it at the time, I ran the numbers with and without the doors and found no real difference. From my "door" tests, it's safe to assume that the roof will not be any different. There is too much flex in the hinges, and latches before the roof and doors begin to provide support.

Based on testing, I can say that, other than a full roll cage, that the next best thing is to stiffen the longs. Then, if you wanted more, a welded steel roof like the factory. There is a reason why the factory went with a welded steel roof in the 916.

I'm almost to the point where I can test again with the full roll cage in place. Based on modeling, I'm expecting a 10x stiffer chassis now.

In testing, I found that one of the longs had a stress crack in it. I don't know if that was just mine, or if most of the 914's out there are running around with cracked longs.

Was the crack at or near the e-brake mount?
@Curbandgutter
sixnotfour
beefing up the pillar base
Curbandgutter
QUOTE(mepstein @ Jan 7 2019, 08:33 AM) *

QUOTE(Curbandgutter @ Jan 6 2019, 06:13 PM) *

Hello, I did run some numbers on the torsional rigidity of the 914. Here's the link http://www.914world.com/bbs2/index.php?sho...p;#entry2396780

See POST#10

Bottom line is that the stock 914 chassis is very flexible, 3,326’# per degree from my testing. Although I didn't say it at the time, I ran the numbers with and without the doors and found no real difference. From my "door" tests, it's safe to assume that the roof will not be any different. There is too much flex in the hinges, and latches before the roof and doors begin to provide support.

Based on testing, I can say that, other than a full roll cage, that the next best thing is to stiffen the longs. Then, if you wanted more, a welded steel roof like the factory. There is a reason why the factory went with a welded steel roof in the 916.

I'm almost to the point where I can test again with the full roll cage in place. Based on modeling, I'm expecting a 10x stiffer chassis now.

In testing, I found that one of the longs had a stress crack in it. I don't know if that was just mine, or if most of the 914's out there are running around with cracked longs.

Was the crack at or near the e-brake mount?
@Curbandgutter


@mepstein it was actually about 12" back from the a pillar. See POST 193 in the link below for a picture of the crack

http://www.914world.com/bbs2/index.php?sho...6845&st=180
steuspeed
QUOTE(Beebo Kanelle @ Jan 6 2019, 09:06 PM) *



Convertibles consistently about half as rigid as the coupes. My dad raced a Corvair 140 corsa for years. Got his hands on a 180 turbo convertible. Went from first to last in the class. Horrible handling no matter what he did. Turbo lag was no help either.
mgp4591
QUOTE(sixnotfour @ Jan 7 2019, 10:05 AM) *

beefing up the pillar base

Jeff, any special treatment when you weld those up besides the usual "take your time and space the weld points accordingly"?
phillstek
QUOTE(sixnotfour @ Jan 8 2019, 04:05 AM) *

beefing up the pillar base

Have this done on my car after cracking two windshields. Car was lowered with stiff suspension. Haven't had any issues since. I used Armando's pbase site as my template.

rick 918-S
Urethane the windshield to the frame will help also.
Tdskip
QUOTE(sixnotfour @ Jan 7 2019, 12:05 PM) *

beefing up the pillar base


Interesting - I have a '74 where the windshield is loose that I may try this on.
dr914@autoatlanta.com
There is an amazing difference between a 914 top on and a 916 welded top.

When I picked up the 916 in Jacksonville and drove it back in circa 1991, the very first thing I noticed was when going over rail road tracks I can only describe it as the car would go bump only once where as every other 914 I had ever driven (and I have driven thousands) would go bump bump. The car is much more precise and stable like everything is working together rather than having a front half and a rear half. Quite sensational as the car feels like a 914 with its act together. An absolute pleasure to drive at high speeds and around corners.
That car Brutus, with the 2.9 is CRAZY. Both fast and precise, when driving makes one reminisce about what could have been


QUOTE(Beebo Kanelle @ Jan 5 2019, 07:17 PM) *

Does anybody anywhere know where to find the torsional rigidity of the 914 with the roof off vs. roof on vs. steel roof (916) ?

Thanks in advance.
Click to view attachment Click to view attachment
sixnotfour
QUOTE(mgp4591 @ Jan 10 2019, 03:02 AM) *

QUOTE(sixnotfour @ Jan 7 2019, 10:05 AM) *

beefing up the pillar base

Jeff, any special treatment when you weld those up besides the usual "take your time and space the weld points accordingly"?


Ask George AA did it..for Jon Lowe
914forme
John had templates and the parts made, Georges crew welded them in for John, not sure if they did the fabrication or not. Lots of parts on John's "GT" clone where done either by locating the original, or by having them fabricated by various entities that had access to GT parts. Moss comes to mind as a chief fabricator of GT parts including the 100L tank.

Man I miss talking to John, and I miss that car, I found a few NOS parts for that one.
dr914@autoatlanta.com
we spent hundreds of hours on Jon's car making it identical to the original GT. Probably was close as any clone could have ever been. It was quite a while ago though so hard to remember
Jon really lost it after a nasty divorce with Valentine's sister, sold his GT clone for a song and never looked back


QUOTE(sixnotfour @ Jan 10 2019, 12:19 PM) *

QUOTE(mgp4591 @ Jan 10 2019, 03:02 AM) *

QUOTE(sixnotfour @ Jan 7 2019, 10:05 AM) *

beefing up the pillar base

Jeff, any special treatment when you weld those up besides the usual "take your time and space the weld points accordingly"?


Ask George AA did it..for Jon Lowe
914_teener
QUOTE(rgalla9146 @ Jan 6 2019, 03:14 PM) *

This is a great topic.
I want a 914 coupe.....with AC



Buy a Cayman.
Tdskip
QUOTE(914_teener @ Jan 10 2019, 04:49 PM) *

QUOTE(rgalla9146 @ Jan 6 2019, 03:14 PM) *

This is a great topic.
I want a 914 coupe.....with AC



Buy a Cayman.



Hmmmm, wonder if anyone actually did that exact thing?
ChrisFoley
I add a-pillar reinforcements when I build a hard top
Click to view attachment
BeatNavy
QUOTE(ChrisFoley @ Jan 10 2019, 05:22 PM) *

I add a-pillar reinforcements when I build a hard top

Chris, are these something you sell or would be willing to sell? I like the idea of additional structural integrity here. Some of us can weld somewhat competently but can't fabricate very well dry.gif
sixnotfour
QUOTE(dr914@autoatlanta.com @ Jan 10 2019, 01:37 PM) *

we spent hundreds of hours on Jon's car making it identical to the original GT. Probably was close as any clone could have ever been. It was quite a while ago though so hard to remember
Jon really lost it after a nasty divorce with Valentine's sister, sold his GT clone for a song and never looked back


QUOTE(sixnotfour @ Jan 10 2019, 12:19 PM) *

QUOTE(mgp4591 @ Jan 10 2019, 03:02 AM) *

QUOTE(sixnotfour @ Jan 7 2019, 10:05 AM) *

beefing up the pillar base

Jeff, any special treatment when you weld those up besides the usual "take your time and space the weld points accordingly"?


Ask George AA did it..for Jon Lowe .. it is a sad story ..the pca crash legality didnt help..he wasnt directly involed but..


I heard it was forsale ..sent him a deposit asap
pete000
I clearly notice more cowl shudder with the top removed...
djway
What inner structures are found on the steel roofs?
ChrisFoley
QUOTE(BeatNavy @ Jan 10 2019, 05:30 PM) *

QUOTE(ChrisFoley @ Jan 10 2019, 05:22 PM) *

I add a-pillar reinforcements when I build a hard top

Chris, are these something you sell or would be willing to sell? I like the idea of additional structural integrity here. Some of us can weld somewhat competently but can't fabricate very well dry.gif

I'll take a look and see if its something I can make available easily.
strawman
QUOTE(ChrisFoley @ Jan 11 2019, 04:13 AM) *

I'll take a look and see if its something I can make available easily.


Sorry to hijack this thread, but I'd be interested, too. Thanks Chris!
ChrisFoley
I looked in my CAD files for a pattern but we must have hand cut them.
Maybe there's a paper pattern in one of my template folders.
Mark Henry
QUOTE(djway @ Jan 10 2019, 11:13 PM) *

What inner structures are found on the steel roofs?


924 roof
IPB Image

There's a few threads on it being done.

http://www.914world.com/bbs2/index.php?sho...p;#entry1351242

http://www.914world.com/bbs2/index.php?showtopic=104406

http://www.914world.com/bbs2/index.php?showtopic=66687
Mark Henry
AA did a steel roof (links above) and it has a fair bit of structure
For sure it adds stiffness to the chassis.
IPB Image

IPB Image


This looks like a top notch job, but I still like a 914 as a targa smile.gif
dr914@autoatlanta.com
we had our crazy irishmen do it. (crazy=irish?). (before everyone gets mad, I am an Irish catholic so I can say it!! (LOL)


QUOTE(Mark Henry @ Jan 11 2019, 03:45 PM) *

AA did a steel roof (links above) and it has a fair bit of structure
For sure it adds stiffness to the chassis.
IPB Image

IPB Image


This looks like a top notch job, but I still like a 914 as a targa smile.gif
dr914@autoatlanta.com
I will see if I can find headliner shots, here is the old one on Brutus Click to view attachmentbefore removal. notice the wrinkly old seats, and the debris on the headliner


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