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[kakabox]

Rod End Trailing Arms

I installed Energy Suspension urethane rear trailing arm (ta) bushing in the Kakabox a couple of years ago...
http://www.redpepper...e...st&p=241331
http://www.redpepper...e...st&p=264990

I've run them a for a couple seasons and they seems to work ok, at least they don't squeak! However, one thing I do not like about them is they don't allow the trailing arms to rotate freely. The rotation of the trailing arms binds in the urethane bushings. I noticed this when I installed the bushings. The arms did not pivot freely at all; they bind in the attach clevis...and, FWIW, the OEM rubber bushings bind as well.

I don't believe the rear suspension can work optimally w/the control arms binding in their pivots. I think the car's handling is more precise, consistent, and controllable when the suspension doesn't bind and is free to articulate. So as soon as I had installed the ES bushings, I started thinking about a fix for the bind (actually, I knew exactly what to do as I had installed rod-end front and rear lower ta's on my '90 5.0L Mustang).

Then, one day I saw the old 3g Civic Mugen catalog in jsgprod's pic gallery... http://www.redpepper.../v/gprodn/MUGEN [kudos to jsgprod for putting it in his gallery]...I became inspired when I saw this page:

Trailing arms w/rod ends, freely pivoting rod ends! Nice. From looking at the picture, it 'appears' Mugen just cut off the OE rubber bushing and welded in a threaded insert for the rod end. I decided I could do the same and make my own...right in the little 'ole Kakashop!

Here's how I made the Kakabox version:

First I spent $20 and 1 hour at the local Pull-A-Part and pulled a pair of 3g trailing arms from an '84 Civic:


Before I started cutting up the OE trailing arms, I made a simple 'jig' to capture critical geometry. I wanted the center of the rod end to be in the same location as the center of the OE pivot in the fore-aft direction and also in the inbd-outbd direction.


Using the 'D' hole feature which is common for both the lh and rhs arms, I screwed a delrin bushing into a block of wood. That allowed me to located pivot center relative to that feature. I drilled a hole for the OE pivot bolt and shimmed the arms w/wood until level.

I had some OE trailing arm pivot bushing sleeves which I measured to find the centerline of the OE arm pivot bushing. The OE bushing (and hence, the chassis clevis) is ~2.25" long.

The centerline of the plate that makes up the trailing arm at the bushing is one half that...or 1.25"

So now I know the distance from the base of my 'tooling jig' to the center line of the rod end... 1.25"

I've captured the OE trailing arm pivot's fore-aft and inbd-outbd centerline locns w/the jig.

My idea is to cut off the OE rubber bushing and form a "slot" using the existing lightening hole...like I have marked in red here:

I measure the width of the slot at ~1.20". My idea is to 'wedge' and weld in a threaded insert in this slot...threaded for a male rod end. Because I could easily open the slot up to 1.25" across, and because the stiffening pocket in the arm prevented a centered weld on a cylinder, I decided upon using 1.25 x 1.25 square 1018 Mild Steel bar stock. I bought four 1.75" long sections (cut to length) from a local metal store: http://www.onlinemet...amp;top_cat=197


...to be continued...

[kakabox]

Rod End Trailing Arms...continued...

I wanted to use standard, not metric, rod ends as they are more commonly available. The trailing arms on the fwd 3g Civic don't see the same kind of loading as a rwd car; there's no torque input from the rear axle other than the braking torque from the rear brakes (puts the arms in tension).
The rear axle is just being pulled along behind the front. So, typcially the rod end strength requirements for rear trailing arms of a fwd car are not as critical as a rwd car. Even so, the pivots of the trailing arms are mission critical parts of the car; I don't want to break one while under way. So, I used 5/8 bore x 3/4-16 stud, high strength chrome-moly rod ends purchased here: http://www.speedwaym...-Male,1536.html
The 5/8" bore makes stepping down to the OE M12 pivot bolt a little easier than from a 3/4 bore...more on this later.

So now I had to drill and tap the steel inserts for the 3/4-16 male rod ends. I first found the center (as precisely as possible) by scribing across the corners of the square and center punching the intersection:

For a SAE 3/4-16 threads, the required drill size is 11/16" diameter. I first drilled a 1/8"dia pilot hole through the 1.75 long block of steel. Then I chucked up a 11/16 dia drill, geared down the drill press (540 rpms) and went to work boring the hole.

[side note: I think I've found the limit of my $150 5 spd Crapsman drill press...boring a 1.75" deep, 11/16" dia hole in steel, mild or not, was a long tedious process using lots of cutting fluid!]

The first 1/3rd of the hole is not the roundest, but, as the drill bit was stabilized the deeper it went in, the last 2/3rds of the hole were golden! The rod end threads in just short of 2/3rds of the way, so, no worries. Of course, doing this on a lathe is the way to go, however, the Kakashop aint got no stink'n lathe! Cutting the 3/4-16 threads was not a problem. In the end, the threaded inserts turned out quite well:




Next up was cutting off the OE rubber bushing from the arms:

After formerly spending hours burning out the rubber bushings to insert the urethane ones, it was very satisfying just to slice the whole mess off!

With the OE bushing off, I now had a better picture of how the insert was going to be wedged in and welded...



I used a hand file to open up the 'slot' to 1.25" wide and tapped the insert in using a hammer. Placing the arm in the tooling jig and using the pivot locator hole and spacers, I located rod end bore center in the same locn as OE. Now mocked up in the jig, the insert was ready for welding:




...continued...

[kakabox]

Rod End Trailing Arms...continued...

I fired up the welder and welded the insert in...welded all edges in contact w/the insert. Then I rounded and smoothed all corners and sharp edges. I put the arm back in the tooling fixture to recheck the geometry...perfect, the geometery hadn't changed!




BAM! Imitation MUGEN trailing arms!

Ok, so now how do I go from the 5/8 rod end bore to the OE M12 trailing arm pivot bolt? Well, w/a bushing insert of course...however, since the Kakashop aint got no stink'n lathe, I had to do some head stratching and lots of measuring to come up w/the soln!

The ID of the rod end is 5/8" or .625. I first measured the ID of an extra set of Energy Suspension rear trailing arm bushing sleeves, I found it to be .480"...the OE M12 bolt dia measured .465"


I just happen to have in my scrap metal box (doesn't everyone have one?), four .75" long cutoff sections of seamless .630" OD x .375" ID steel tube.
Putting the section of .630" x .375" tube in my 'v' block vise...I used a 15/32" drill (.469") to bore out the ID.


As 'ghetto' as it seems, it actually worked out quite well as I ended up w/an ID of .475", or .005" smaller than the ES sleeve. The .475" ID actually is a better fit w/the OE bolt:



However, at .630", the OD was too big for the rod end ID...even for a pressed in bushing. I measured some reduction bushing for rod ends I had and found that the OD of the bushing was typically .002" larger than the ID of the rod end bore they were to be pressed into. So, using a sanding drum Dremel attachment, my drill press, 400 grit sandpaper and oil, I polished the OD of my bushings to .626-.627".


I'll freeze the bushings and press them into the rod ends. I'll cut up my extra ES metal sleeves to make the necessary .688" long spacers (two each side) to go on either side of the rod end to center it in the chassis clevis; same locn as OE.

This concludes the fab of the imitation MUGEN rear trailing arms! And, sadly, it also concludes my Holiday break from my 'day job' as I go back to work tomorrow. But stay tuned...I still have more mods up my sleeve for the new year!

Cheers!

[Christ]

I don't get it. You always come up with something I want to read.. even when I originally wanted to read something else. You've pulled my attention away from an SRT-4/5-speed 2000 Caravan swap. LOL.

Great work on this!

[Henault]

That is awsome make some for resale.

[JMSBND]

"I will just have a look" I said to myself about your build thread.

Now I am back out in the garage measuring up stuff on my 1G CRX. You always give me great inspiration. I will be ready for the "no slop" shift linkage later this week as I FINALLY have 2 weeks holidays myself. You no reach shifter is already in my car and I am working through the suspension now.

Great work as usual!

James

Australia

[wills85]

great work man.. i like this alot

[lxndr]

I see you finally found a use for your Dremel.

Nice work as as usual!

[DEIVIONCRX]

That looks pretty damn good, i never noticed the mugen arms were spherical like that.

[Christ]

Are the spherical rod ends adjustable at all?

Only reason I wonder is for the very short amount of adjustment you'd have then to the wheel base... even an inch or so, not that it would probably do much... but it would be cool to tell people you have an adjustable wheelbase

[OG Wagon]

ha, ha.

...and I was happy to just get my timing right!

We're not even in the same planet.

Incredible. Keep up the innovation!

[kakabox]

Thanks everyone...I knew throwing the word MUGEN in the Update subject line would bring the people in!

I see you finally found a use for your Dremel.
Nice work as as usual!

Thanks...nice to see you in da house!
Actually it's a Dremel attachment...I get more use out of a $3 cobalt hacksaw blade then I do my $100 uber Dremel. What a waste of money.

Are the spherical rod ends adjustable at all?
Only reason I wonder is for the very short amount of adjustment you'd have then to the wheel base...

Yes they are. The other reason I made the rod ended trailing arms is that I plan on using their adjustability to "square" the rear axle w/the front by measuring across diagonals. I built a track 5.0L Mustang w/full race suspension and did this. Easy to do w/plumb-bobs and measuring tapes, but tedious. Like you mentioned, the rod ends allow for minor adjustments to the wheel base.

Cheers!

[Greg Gauper]

An excellant write-up as usual!

I have been looking to do a similar modification over the winter. I thought about using pre-tapped threaded tubing, available from several racecar supply shops (used for custom A-arms and such), but the steel block idea would work just as good.

Rather than reuse the metric OEM bolts and having to come up with custom bushings for the rear trailing arm pivots, did you give any thought to the idea of just cutting off the existing nut and using conventional AN hardware (AN bolts and nuts) so that the bolt size matched up with the rod end diameters, and then you could use off-the-shelf SAE bushing material?

[Maine_Honda_Racer]

If you could fab up a set of these for public sale I would definitely buy them, let me know on price. Additionally, are you still making Kakashifters?

[kakabox]

An excellant write-up as usual!

I have been looking to do a similar modification over the winter. I thought about using pre-tapped threaded tubing, available from several racecar supply shops (used for custom A-arms and such), but the steel block idea would work just as good.

Rather than reuse the metric OEM bolts and having to come up with custom bushings for the rear trailing arm pivots, did you give any thought to the idea of just cutting off the existing nut and using conventional AN hardware (AN bolts and nuts) so that the bolt size matched up with the rod end diameters, and then you could use off-the-shelf SAE bushing material?

Thanks Greg.

I also looked into using off the shelf tapped tubing and weldable threaded inserts. I couldn't find anything geometrically suitable. The lightening hole in the arms are ~1.2" wide. And since it's in an offset stiffening pocket of the arm, I couldn't envision getting a reasonably sized tube to both be in contact w/the edges of the slot (for welding) and position the rod end in the same place as the OE bushing center. With the square block, I was able to do both.

I also thought of centering a threaded tube in the arm slot, and then welding plates to the arm and then to the tube and use offset spacers to mount in the chassis. However, I didn't like that soln as there were too many pieces involved making it an overly complicated design; simple soln are usually the best. I wanted the center of the rod end to be in the exact same locn as the center of the OE bushing...although, I don't know that it really matters.

Yeah, I looked into cutting the OE pivot bolt captured nut off of the chassis clevis and using standard hardware. That was my original idea. I did that for the Kakabox phb brace...

http://www.redpepper...e...st&p=243295
However, there is not a lot of room to get a drill motor and 5/8" bit in there to enlarge the holes in the OE ta clevis. Hence, plan 'B': making inserts for the rod ends.

Actually, making the 5/8" OD x M12 ID bushing was relatively easy. Typically I like to use 'scraps' I have in house, that's why I used pieces of a .630" OD x .375" ID steel tube I had and drilled them out to .475" ID using a 15/32 drill. The bushing fab would of been even easier had I used .625" OD x .459" ID DOM steel tube available here: http://www.onlinemet...p...3&top_cat=0
FWIW, I bought 24" of this tube just in case my bushings didn't work out. However, the .625" OD of this tube does not give me the interference fit I want w/the ID of the rod end.

As far as "SAE bushing material" goes...the OE & Energy Suspension sleeve bushings both appear to be made from mild steel (the ES bushings are actually made from two pieces of seemless steel tube, one thicker wall tube pressed inside another tube that defines the OD). I'm thinking the rod end bushing I made from seemless tube will perform and last similarly. FWIW, I always coat the shank of the pivot bolt w/antiseize to help w/corrosion. I'll make spacers that go on either side of the rod end when installed from extra ES sleeve bushings I have.

Cheers!