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:

Close up

Brake caliper weld fixture

Ooops, that's the trailing arm weld fixture.

Andy

Now, the brake caliper weld fixture with parts in place

Another shot.

The bearing carrier, fits late 911 bearing

damn andy...that looks great

funny how the fixtures take more time and material than the parts

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"

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

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

damn andy...that looks great funny how the fixtures take more time and material than the parts

Mike,

AMEN!!

Andy

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

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.

that's friggin' awesome!!!

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!

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

that's friggin' awesome!!!

-Ben M.

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

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.......

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...

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.

You do know some one will see this and rip off your idea whoops thats another thread. Looks sweet I like them a bunch

Didn't that Brad R. guy post a picture of a unassembled trailing arm kit a while back ?
What happened to those? oh and that Brad Guy?

Need pictures of the rest of the Car , gonna be nice

Parts look great. Aren't CNC machines great. Yes you really should set up the calipers for a 3.5 or 5.25 caliper spacing. Then you could use EX Nascar parts. If you are going to built new trailing arms you really should build the upright on the end of the trailing arm so that you can adjust camber and toe without changing roll center location. You could also lengthen the trailing arms to help control wheel base changes.

Are you going to use round tubing for the main body of the trailing arm?

Jigs look good.

Hi Andy:

I was VERY interested when reading about your custom 914 swing arms!

-I also have a 914-V8 and have had rear bearing failures and would love to go to a bigger bearing.
-I question the strength of the original unit that was designed for 100 HP and I am pumping nearly 500 through mine.
-It would also be nice to know that there was somewhere to go to FIND a replacement swing arm.

With the professionalism of your fixtures, it looks as though you really know what you are doing!

Any chance you would consider building a set of Swing Arms for me?

Terry

*You do know some one will see this and rip off your idea*

Let 'em rip........there's a ton of work to getting all the data and numbers just right; that's the hard part. The tooling fab is time consuming, but straight forward.

*Parts look great. Aren't CNC machines great. Yes you really should set up the calipers for a 3.5 or 5.25 caliper spacing. Then you could use EX Nascar parts. If you are going to built new trailing arms you really should build the upright on the end of the trailing arm so that you can adjust camber and toe without changing roll center location. You could also lengthen the trailing arms to help control wheel base changes.

Are you going to use round tubing for the main body of the trailing arm?*

Brett, no CNC.....this was all done on manual machinery. I considered fully adjustable stuff, but at this point I wanted to merely replicate an existing trailing arm, even with all it's inherent issues. An upright and all would be nice, but not just yet. I'll be posting pic's of the main arm portion as I progress.

Andy

I've seen a lot of assembly/mock-up jigs working at Boeing [McDonnell Douglas], and I must say you've done a VERY nice job with your trailing arm jig! You should definitely get the results you're after!!

QUOTE (Terryst1 @ Jun 20 2005, 03:11 PM)

Hi Andy: I was VERY interested when reading about your custom 914 swing arms! -I also have a 914-V8 and have had rear bearing failures and would love to go to a bigger bearing. -I question the strength of the original unit that was designed for 100 HP and I am pumping nearly 500 through mine. -It would also be nice to know that there was somewhere to go to FIND a replacement swing arm. With the professionalism of your fixtures, it looks as though you really know what you are doing! Any chance you would consider building a set of Swing Arms for me? Terry

Terry,

It was nice seeing your car at WCC05. It looks like Chris is making major engine mods, can't leave well enough along.

I'll bet Andy has lot's of inquires including mine. The good thing is he's building fixtures which allows the option to duplicate. I agree, they look and should work great...

Quick update......left side nearly complete.

Andy

I love it! Great Work!!!

DAMNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNN

ooooh I want a set! Very nice work!

Wow. I'm in for a set if they ever go to production.

awesome man!!!

i am speechless

this is real art!!

How's the weight compared to stock? I wonder if I could talk Dad into doing a finite element analysis on your design, but using aluminum.

-Ben M.

QUOTE (airsix @ Jul 13 2005, 12:16 PM)

How's the weight compared to stock? I wonder if I could talk Dad into doing a finite element analysis on your design, but using aluminum. -Ben M.

Ben,

I started thinking in steel, went to aluminum, then back to steel. I got cught up with the aluminum version mainly due to the weight advantage, ease of machining, and went forward with less than adequate data. I bought all the proper aluminum materials. I even machined up the bearing carriers. In parallel, I was persuing data on aluminum welded (suspension) structural requirements, only to find in the end that it would require extraneous post weld treating (read $$$). Even with that, there would remain some degree of doubt without a proper testing regime (fatigue life, sudden failure, and so on). It just wasn't worth the risk. So, my decision was simple; make them from steel, and rest at ease.

The weight of these trailing arms is basically the same as a stock trailng arm with a stiffening kit installed. Unseen in the pic, is a structure buried inside that adds considerable strength.

Below pic is of two nearly completed aluminum bearing carriers/paper weights

Andy

You've got some mad design/fabrication skills Andy. I love it!

Hmmmm.......suspension consoles and outer ears to match your wicked swing arms?

Hey 914ners:

Andy will probably get mad, but I'm going to tell you a little about him:

He a graduate Mechanical Engineer who's job it FULL TIME
materials and process research! The wall in his office is covered with patents. He KNOWS materials!

He is also an excellent machinist and has run a machine shop.

He is a total car guy and is building his own 914 V8 conversion as a fun hoppy after retiring from 20 years of GO-KART racing. Needless to say, his Kart had the TRICK SETUP and blew off the competition.

Andy has offered me some tech help with my 914 V8 and
getting working right for Road Racing. HE IS SHARP!!

If you know engineers: he won't do it unless it is PERFECT!

Grins,

Terry

QUOTE (Terryst1 @ Jul 13 2005, 02:51 PM)

HE IS SHARP!!

Of that, there is little doubt!

QUOTE (Terryst1 @ Jul 13 2005, 05:51 PM)

HE IS SHARP!!

DUH!

this is painfully obvious by this thread...

Cool.

Yes. I have/had jigs/fixtures for a 5 inch round chrome moly control arm using a 911SC wheel bearing. Just like the ones on Roger Sheridans car.


B

So when are these going to be available for sale, and how much?

Unreal work, fantastic!


M

QUOTE (andys @ Jul 13 2005, 01:34 PM)

QUOTE (airsix @ Jul 13 2005, 12:16 PM) How's the weight compared to stock? I wonder if I could talk Dad into doing a finite element analysis on your design, but using aluminum.  :idea: -Ben M. Ben, I started thinking in steel, went to aluminum, then back to steel. I got cught up with the aluminum version mainly due to the weight advantage, carriers/paper weights Andy

I think your kicking some serious butt on this issue.

Since I work in a fab/machine shop,I've entertained the idea of making a prototype set for my car.

However,I've been leaning towards doing them out of full titanium.

I couldn't see making the necessary fixturing for a trailing arm set,unless the final product reduced some serious unsprung weight.

I've used a place out Michigan,Tico Titanium for several parts Ive' designed and lasered out for my 6r,so I know it's cost versus weight trade off.Cost is currently about 15.00 a lb.

However,all that being said,if you've already done all the hard work,and all your jig measurements are correct,you may wanna think about capitalizing offa your efforts.

Maybe professionalize a drawing for your jig to sell,or maybe out right sell jigs to others.

I know I'd be interested in drawing plans.

Drawings would take the guesswork outa the whole setup.


Way to go.

Ron

QUOTE (Brad Roberts @ Jul 13 2005, 06:05 PM)

Cool. Yes. I have/had jigs/fixtures for a 5 inch round chrome moly control arm using a 911SC wheel bearing. Just like the ones on Roger Sheridans car. B

Brad,

Are these the one's you're speaking of? Hope the file size is not too large...........

Andy

Hmmm, file format problem.......Anyway, they are the assembly three large tubes with a provision for camber adjustment, right?

Andy

QUOTE (RON S. @ Jul 14 2005, 05:42 AM)

I think your kicking some serious butt on this issue. Since I work in a fab/machine shop,I've entertained the idea of making a prototype set for my car. However,I've been leaning towards doing them out of full titanium. I couldn't see making the necessary fixturing for a trailing arm set,unless the final product reduced some serious unsprung weight. I've used a place out Michigan,Tico Titanium for several parts Ive' designed and lasered out for my 6r,so I know it's cost versus weight trade off.Cost is currently about 15.00 a lb. However,all that being said,if you've already done all the hard work,and all your jig measurements are correct,you may wanna think about capitalizing offa your efforts. Maybe professionalize a drawing for your jig to sell,or maybe out right sell jigs to others. I know I'd be interested in drawing plans. Drawings would take the guesswork outa the whole setup. Way to go. Ron

Ron,

Titanium should be a viable alternative from a material properties perspective, but the costs would be quite high. Using your $15/lb pricing, the billet for the bearing carriers alone would cost about $360. The weight advantage of titanium over steel is not huge (about 60% the weight of steel), and depending on which alloy you choose you may find you need added thickness to get the strength (when comparing like designs). Ti CP grade I, has a tensile of anbout 35ksi. CRS (cold rolled steel) is about 60ksi. You'd have to go to Grade III to get comparable properties, and that would likely drive the cost up even more. Do you have the price for Grade III? I suppose if you want to spend the money for your personal project, then that is certainly your decision. Sure would look zippy if they were polished. Have you checked on welding? From past experience, few weld shops have adequate Ti welding experience, but that is not an issue if you hold that particular skill. I have experience with EB and Laser welding Ti, but have never TIG welded Ti myself. Like aluminum, Ti has a high CTE, so you'll have to pay real close attention during welding, as things will move around a lot.

For titanium money, I might be inclined (maybe) to go with aluminum for even greater weight savings (about 30% the weight of steel) and use those dollars for *proper post weld treatment*.

I don't know if I want to put in the effort to make proper detailed drawings of my weld fixture at this time. It would be pretty time consuming.

These arms are for a street application, and have durability and adequacey as a focus.
If I were doing a track car suspension, I think would have approached the design a lot differently.
Here's a simple basic guide for design considerations with useful links to freeware:
http://www.gmecca.com/byorc/designstrategies.html

BTW guys, I appreciate the comments.

Andy

QUOTE (andys @ Jul 14 2005, 09:51 AM)

Hmmm, file format problem.......Anyway, they are the assembly three large tubes with a provision for camber adjustment, right? Andy

Your trailing arms look good Andy....I'm too much of a hack to show pictures of anything I've done, hence the piss-poor camera phone to mask my butchery

Correct on those tube weldments, the biggest change is making them a true trailing arm instead of semi-trailing like the stock 914 is....not an easy task on a bone stock 914....I know someone on this site was supposed to be building a 914 race car with relocated mounting mounts (not just "up", but so that the axle is perp. to the chassis centerline)

Have you seen Armandos 914/6 GT buildup??

His rear trailing arms are pretty trick, just a few hours worth of work put into them

Rear trailing arms with spherical bearings


Now you are going to powdercoat your new trailing arms correct???

The latest pic's to update my progress. The trailing arms are assembled, but not placed on the car. That will follow sometime later when I fit the flares to the (wider) wheels.

Bottom view of left side:

Andys