Custom Trailing Arms, A Progress Thread Options

[andys]

Though it about time I start a progress thread on some custom trailing arms I am designing and fabricating.

First, a little background: My car is a planned LS1 V8 conversion that will use an Audi/Getrag 6 speed transaxle (which I already have). From this, two things result; 1. The drive flanges are placed wider then on the 914, and are assymetric to the centerline. 2. The drive flanges will require adapters, as the bolt pattern is outside of the CV. The 911 axles I intend on using are shorter than the 914, but not enough to provide room for the flange adapters. The motor/transaxle will be placed off-center in order to get symmetry of the drive flanges.

By fabricating the trailing arms, I can accomplish a couple of things. First, I can position the bearing carrier further outboard to get the additional space for the flange adapters. This will also help keep wheel spacers from being so thick. Second, I can use the larger (+5mm dia and 5mm wider) late model 911 bearings, along with the late 911 wheel drive flanges. Third, I can adapt any brake caliper I want, which will be an '89 Carrera to start with since I already have it. It is not my first choice (heavy!!), but it will do for now. I will employ the Wilwood mechanical spot caliper for the parking brake. Fourth, this custom fabrication allows me to create a structural part suitable for V8 power, and yet meet a target weight comparable to a stock trailing arm. Fifth, I can make provision for the pivot shaft bearing of choice. Though I considered the needle bearing setup, I will start off with Weltmeister Polygraphites' (I do have some other polyurethane material that I may try later as well).

So why go through all the trouble? Because I can, is my best answer. Being an engineer, I just can't resist! Also, I have the equipment to do all the machining and welding. Now having said that, I don't think I would start a project like this again, considering all the research, design, fabrication, etc.....takes waaay too much time; time I don't really have.

Ok, enough of all that! I'm sure you'd rather see the pic's, then read all the blather......

This pic is of some of the parts I've made up so far; Pivot shaft housing, pivot shaft bushings to be welded in, bearing carrier, caliper mount, and the large axle tube. I'll add more parts as we go along:

[andys]

Close up

[andys]

Brake caliper weld fixture

[andys]

Ooops, that's the trailing arm weld fixture.

Andy

[andys]

Now, the brake caliper weld fixture with parts in place

[andys]

Another shot.

[andys]

The bearing carrier, fits late 911 bearing

[Mueller]

damn andy...that looks great (IMG:http://www.914world.com/bbs2/html/emoticons/pray.gif)

funny how the fixtures take more time and material than the parts (IMG:http://www.914world.com/bbs2/html/emoticons/smash.gif)

[andys]

Assembly weld fixture with stock trailing arm. The stack of plates on the bearing carrier can be changed to accomodate the stock bearing position and stock bearing, 911 late bearing, and any outward offset to about 2 1/2"

[andys]

The weld fixture can do both right and left sides. Since there is 1 1/2 degrees of camber built into the trailing arm, the fixture adjusts for this. Additionally, I can add yet more camber (+ 1 1/2 degrees) for a total of 3 degrees. Oh, I can lower the shock mounting point up to 1.200".

Andy

[andys]

QUOTE (Mueller @ Jun 20 2005, 12:01 PM)

damn andy...that looks great (IMG:http://www.914world.com/bbs2/html/emoticons/pray.gif) funny how the fixtures take more time and material than the parts (IMG:http://www.914world.com/bbs2/html/emoticons/smash.gif)

Mike,

AMEN!!

Andy

[TravisNeff]

I dunno what is cooler, the fixture or the trailing arm!

[ClayPerrine]

You should consider making the mounting tabs and fixtures for the calipers to accomodate a 3.5 inch caliper spacing. You could sell those separately to people wanting to upgrade their rear brakes.

[Jeroen]

that's friggin' awesome!!!

[nocones]

So what are you saying here Andy, ...now that you've put in all the time and leg work for R&D will you be up for building control arms for some of us V8 guys?

Really nice work! (IMG:http://www.914world.com/bbs2/html/emoticons/pray.gif)

[airsix]

QUOTE (Jeroen @ Jun 20 2005, 12:26 PM)

that's friggin' awesome!!!

(IMG:http://www.914world.com/bbs2/html/emoticons/agree.gif)

-Ben M.

[andys]

QUOTE (ClayPerrine @ Jun 20 2005, 12:25 PM)

You should consider making the mounting tabs and fixtures for the calipers to accomodate a 3.5 inch caliper spacing. You could sell those separately to people wanting to upgrade their rear brakes.

Clay,

Near as I can tell, the 914 bearing carrier is a forging (anyone?). If this is in fact the case, then perhaps one could cut off the existing caliper mounts and weld on a new one with 3.5" spacing. The caliper weld fixture is reasonably simple. This wouldn't however, solve the parking brake issue. If it's for a track car, then it's a moot point. As I progress with the parking brake design, then perhaps I can configure a solution.

Andy

[Mueller]

QUOTE (andys @ Jun 20 2005, 02:08 PM)

QUOTE (ClayPerrine @ Jun 20 2005, 12:25 PM) You should consider making the mounting tabs and fixtures for the calipers to accomodate a 3.5 inch caliper spacing.  You could sell those separately to people wanting to upgrade their rear brakes. Clay, Near as I can tell, the 914 bearing carrier is a forging (anyone?). If this is in fact the case, then perhaps one could cut off the existing caliper mounts and weld on a new one with 3.5" spacing. The caliper weld fixture is reasonably simple. This wouldn't however, solve the parking brake issue. If it's for a track car, then it's a moot point. As I progress with the parking brake design, then perhaps I can configure a solution. Andy

i have a pair of rear trailing arms at home with I think 3.75" spacing for 944 turbo calipers, I'll post pictures once I take a few...yes, the brackets are custom welded on....to be used with 911 internal parking brakes.......

[Jeroen]

maybe a little late, but how about one of those trick set-ups Brad mentioned
Where you can change the toe/camber settings at the hub instead of the mounting point of the arm...

[ClayPerrine]

QUOTE (andys @ Jun 20 2005, 03:08 PM)

QUOTE (ClayPerrine @ Jun 20 2005, 12:25 PM) You should consider making the mounting tabs and fixtures for the calipers to accomodate a 3.5 inch caliper spacing.  You could sell those separately to people wanting to upgrade their rear brakes. Clay, Near as I can tell, the 914 bearing carrier is a forging (anyone?). If this is in fact the case, then perhaps one could cut off the existing caliper mounts and weld on a new one with 3.5" spacing. The caliper weld fixture is reasonably simple. This wouldn't however, solve the parking brake issue. If it's for a track car, then it's a moot point. As I progress with the parking brake design, then perhaps I can configure a solution. Andy

Lots of people here just don't run a parking brake. Others have worked out ways to use a 911 park brake or a spot caliper.

Making a jig and a mounting tab for a caliper is beyond the average 914 owner's ability. Someone who has some machine shop experience could do it, but most of the folks here would not attempt it.

By making the parts available, the average 914 owner can take them to a local welder and have him weld the new tabs onto his trailing arm. You make money and we get the ability to put bigger brakes on the back of our 914s.

The reason I ask this is that I see lots of 914s running around with huge front brakes and stock /4 solid disks and calipers in the rear. It looks really odd that way.