Any reason not to tie the shock towers into the cage? Options

[SirAndy]

I know there are certain restrictions with some of the race organizations.

Who and what are they? What are the penalties?

Why shouldn't i tie the shock towers into the cage?

Will it work going *under* the engine lid? Or do i need the angle from up high to be effective?
What about the front?

And how about a removable petty bar?

(IMG:style_emoticons/default/idea.gif) Andy

[DanT]

with the cage Andy, I doubt the Petty bar is going to gain you anything.

as far as the cage extending to the strut towers, that is what all the really fast 914s have. makes the chassis super stiff and allows the suspension to do the work instead of the chassis.

If you never plan on competing W2W I doubt it really makes any difference.
SCCA AX rules may put you in a different class with that modification. Not familiar with SCCA rules.

[J P Stein]

The biggest downside is the door bar. To get support for the roll bar/suspension tubes interface you need to get the door bar up to the level of the towers. That becomes a PITA for ingress/egress. For AX, you need a roll hoop like another hole in the head. With that gone, you can step over the door...when the top is off. Top off used to be worth .5 sec to me back when I had one....no rhyme nor reason for that, it just was. Never tole you that before the shootout......go figure.(IMG:style_emoticons/default/biggrin.gif)

A straight shot tower to tower is not ideal but better than nothing.

[grantsfo]

Andy, From my research it really depends on class and sanctioning body. Non SCCA organizations tend to have some flexibility. Your car in something like ITE would be interesting. Go to SCCA and read ITE rules.

[SirAndy]

If this really only concerns SCCA, then i think i might just go ahead. I have no intensions of running with SCCA ...

(IMG:style_emoticons/default/idea.gif) Andy

[drew365]

Here's a couple of pics:
Upper rear through the window

Front in trunk

[sww914]

The POC used to count through bulkhead bracing as 1 point but they've done away with that point in the interest of safety. It will still bump you up into the V classes (but so does flares) which requires more safety equipment but it's free now. They only run up in the bay area once or twice a year so it may not mean anything to you. As Andy's pictures show, triangles are good. If you look at the pictures of the 917 chassis or any of the tube frame chassis you'll see nothing but triangles.
The nascar boys just use big huge square hunks of iron, but triangles of tubes are lighter and stronger.

[bam914]

You can go through the back window in SCCA. I did this on my IT 914.

[SirAndy]

Thanks guys!
(IMG:style_emoticons/default/beerchug.gif) Andy

[Krieger]

The rear shock towers are only spot welded on 3 of the 4 sides, from what I've read in past posts here. The metal is fairly thin at the shock tower. Why don't you just go to the top of the frame rail where the rear suspension mounts, it is much thicker and seemingly more relevant location?

[SirAndy]

Why don't you just go to the top of the frame rail where the rear suspension mounts, it is much thicker and seemingly more relevant location?

I think there's two separate issues that i'd like to take care of.
first, general body flex, which should be noticeably less with all the points tied in.
and secondly, camber changes due to the top shock towers flexing. for that, i'd think going to the top of the shock tower would be the best approach ...

(IMG:style_emoticons/default/idea.gif) Andy

[J P Stein]

When tying into the towers, I added a 1/8 doubler plate to the towers under the land of the tube. I used this doubler to overlap the long to tower connection.....2 birds with one doubler, eh?
I'll do some pics if anyone wants to see both the front & rear.

BTW, another downside.......the above will raise unholy hell with your paint job.

JPIII

[SirAndy]

I'll do some pics if anyone wants to see both the front & rear.
BTW, another downside.......the above will raise unholy hell with your paint job.

Yes, pics please!

As for the paint job, that was hands down the biggest "throwing cash out the window" expense on my car so far. (IMG:style_emoticons/default/icon8.gif)

$6000 for paint that didn't last 6 month ... I could have had a crappy Maco paintjob AND get a WEVO 915 for the same amount ...
(IMG:style_emoticons/default/headbang.gif) Andy

[Joe Ricard]

I did the same thing with my car as JP did.
Some day my car will look just like the shit box except for bunny ears.

[byndbad914]

Will it work going *under* the engine lid? Or do i need the angle from up high to be effective?

Andy - that ? wasn't addressed yet... don't know about the rules, but just the mechanical side of this. The answer is "it depends". Arguably, the higher the bar ties into the cage the more advantage the bar has to carry the load in compression/tension than in shear at the mount. BUT, the difference is minute so I would say that doesn't matter much IMO.

Now, the real part that does matter IMO is how the load is transferred thru the cage to the chassis. I don't remember your cage specifically, but if you DON'T have a bar running from about left shoulder level down to the front mount point on the long by your left foot (so you would have to climb over it a bit to get in), then go to the top of the cage above the engine lid.

If you DO have some sort of door triangulation, you can run the tube from the rear susp either a couple inches above or below that mount point and tie in there for an "exteriorly" clean look. If you don't have triangulation in an area you run load to, the tube will bend in a serious "event", and especially if it breaks off it will impale you right about neck high.

[SirAndy]

If you DO have some sort of door triangulation

Doors and front ...

(IMG:style_emoticons/default/shades.gif) Andy

[SirAndy]

Rear ...

(IMG:style_emoticons/default/shades.gif) Andy

[byndbad914]

oh, cool Andy.

If it were me (= opinion) I would tie the rear susp support about 2" above the tube you have triangulating down in the door there. I would also tie that lower bar (running parallel to the long to the long) near the center about an inch or so in front of where that down tube ties in. Then everything is tied to the long and all reaction points in a crash are tied directly to structure, not an unsupported section of tubing.

edit - I notice a white mark on the lower tube after posting reply - that's where I would tie a short tube down to the long right there to support that area.
edit2 - aahhhhh. I'm a dork/blind. Saw the passenger side, already tied in! couldn't see it on the driver side, so ummm, nevermind.

Then it would be right up under the engine lid, still "inside" of the car and be really clean. I personally hate to see tubes sticking up and thru the rear window - but that is from a purely visual perspective, not structural perspective. I hate the fact my air cleaner sticks up so high on my car for instance - I would love to run a lid and hide everything.

[GaroldShaffer]

Andy, pictures of my SCCA FP racer I bought last fall. Let me know if there are any other angles you would like to see.

[J P Stein]

Pics of the tie in points.
Front to rear.

This is a modified roll cage. If I was starting from scratch, I'd prolly rethink a few things. I aslo seam welded everything in sight.