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raygreenwood
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Joined: November 24, 2008
Posts: 21521
Location: Oklahoma City
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 Posted: Wed Jan 21, 2015 4:40 pm Post subject: |
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| bradself wrote: |
Being lazy here, I think I bookmarked pics from someone's trailing arm rebuild but those are fab'd from urethane rather than glass filled delrin, correct? Do you do top hats, Ray, or similar to your control arm bushings? Just eyeballing the original bushings it looks like a new beefier inner sleeve might be needed to hold up under the 60 #s tightening torque
, the original looks like a big roll pin, actually. |
The inner sleeve is no problem...very high grade steel..in fact I reuse them.
The problem with the 60 lbs tightening torque is not with the original sleeve...it will be with the delrin flange discs that are on each side of the steel bushing.
I used shortened steel sleeves...specifically so that they will not bear against the steel sides of the yoke....because once you put the slot in the subframe yoke to adjust camber.....the steel sleeve will not have as much material to each side to bear against...and it dishes the subframe yoke badly...making it very hard to adjust.
If you want to use a full factory length steel sleeve...it would need to be about .250" bigger in diameter.
Long ago...I machined urethane control arm bushings. They sucked. They get harder every year. In five years they literally shattered. Also....a hat shaped bushing has as much flex....as the original control arm bushings had sleeve slipping issues. They were "hat" shaped with outer flanges...so each bushing was 2 parts. This issues were that the urethane was hard enough for the bushing...but not the hat. And once I shaved off the hat rims and replaced with delrin discs...which helped immensely....the two part bushing would squirm axially in the hole because both directions would try to flex about the center parting line.
Both of these problems....cause excessive misalignment of the radius arm during maneuvering. This wears the crap out of the centering ring and then the radius arm...and eventually leads to ugly vibrations...which is what you get while the radius arm is wearing out the eye in the subframe.
The best way if you are having machine work done is a two part delrin bushing with hat flanges...that are recessed slightly to take a .060" thick bronze thrust washer in the outer faces of each end of the bushing. Ray |
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bradself
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Joined: January 13, 2013
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Location: SF, CA
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| Posted: Fri Jan 30, 2015 7:39 pm Post subject: |
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| The rear wishbones, not the front control arms. |
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raygreenwood
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Joined: November 24, 2008
Posts: 21521
Location: Oklahoma City
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| Posted: Fri Jan 30, 2015 10:56 pm Post subject: |
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The rear wishbones are similar to front, control arms but different in one respect....an important one......the ends of the steel bushings were knurled to bite into the yokes that are bolted to the beam.
What this means is that the rubber part of the bushing that is bonded to the central steel tube bushknh is what flexes and twists as the wishbone moves......a really stupid design....but oddly.....they last a, really really long time. The problem is that as they age and wear the rubber, shears away and the ttailing wishbones slip to one side in the yoke. It screws ip rear geometry.
the easiest way to fix this is just like the front. Solid delrin bushings wrapped around the stock steel bushing tube with steel, bronze or delrin spacer discs at each end. Use the original bushings so that the knurled ends keep the bushing locked in position when you tighten the eccentric bolt. Just leave a little more tolerance between d3lrin and the steel buwhing so that the delrin can rotate around the bushing. It will be a wear item.
or you could skip the delrin and do torlon or bronze.
I can send you a picture in the am of what the knurled end of the rear bushing looks like. Ray |
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bradself
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Location: SF, CA
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| Posted: Sat Jan 31, 2015 9:59 am Post subject: |
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Have spare wishbones and see the knurling--the inner steel sleeve of the bushing must be thicker than I'm imagining, I haven't knocked them out. Which would you surmise wears slower, bronze or delrin?
Torlon??
I wondered about the delrin "washers" on the front control arms being bronze, but again, I've no idea which material would have greater longentivity. |
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bradself
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Joined: January 13, 2013
Posts: 167
Location: SF, CA
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bradself
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Joined: January 13, 2013
Posts: 167
Location: SF, CA
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| Posted: Sat Jan 31, 2015 10:39 am Post subject: |
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| The inner steel bush that looks like a big roll pin is seperate? Curious bushing, I'll have to knock it out and chop it up. Guessing the outer sleeve is press fit, bonded to rubber which is also bonded to the inner knurled sleeve. If it was fabbed of sintered bronze it would likely be sized to slip in the wishbone, slip around to knurled sleeve, and greased, yes? Similar to the front it's hard to figure out how to keep dirt/abrasive from fouling this. A maintenance cost of no longer having the stock bushing available I guess. |
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raygreenwood
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Joined: November 24, 2008
Posts: 21521
Location: Oklahoma City
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| Posted: Sat Jan 31, 2015 11:14 am Post subject: |
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| bradself wrote: |
Have spare wishbones and see the knurling--the inner steel sleeve of the bushing must be thicker than I'm imagining, I haven't knocked them out. Which would you surmise wears slower, bronze or delrin?
Torlon??
I wondered about the delrin "washers" on the front control arms being bronze, but again, I've no idea which material would have greater longentivity. |
Of course bronze would be really good for the washers in the front end.....but also more than is necessary and requiring machine work I cannot do. I could pay for it...but with the number of items I have to pay for to fabricate...its going to get extreme $$$ in the long run.
Also...and here is the important part..... as long as you have wide, proper thickness washers between the control arm bushing and yoke to tightly pack the control arm bushing joint in the yoke....which positively aligns the control arm....and then have proper radius arm GUIDANCE by having a good centering ring bushing between the radius arm donuts at the rear........there will be virtually no wear to the discs you have at the front....so delrin....or even UHMW or polypropylene will work just as well as bronze for the bushing discs up front....and are easy to produce at home.
The problems are this: the main failure point of both the control arm bushing....and downhill because of control arm bushing failure....is when the rubber of the control arm bushing fails...allowing the control arm to slip forward over the sheared bonded rubber....and contact the forward face of the control arm yoke.
100% of all type 4 control arm bushings eventually do this....always. Some sooner than others...but all of them.
When this happens....downstream.... it mis-aligns the radius arm...cocking it...or trying to cock it in the bore. This side loads the centering ring that keeps the radius arm rod centered in its bore between the two bushing donuts.
VW made this centering ring out of rather soft polyethylene or polypropylene. Its in a dirty, gritty spot. It rapidly wears through it....and in many cases literally disintegrates it. For years I never knew in most cars I found that there was a centering ring because most were worn literally away.
This mis aligns the rod causing contact with the metal bore. If driven for long distances it wears the eye oval. It causes really odd vibrations and rattles in the front end...it causes the radius arm donuts to slip sideways and starts wearing them out.
All of this starts...because the original control arm bushings have no flanges to control position of the bushing barrel.
So....how did I get shorter center steel bushings to allow the use of flange discs on each end without the steel bushings contacting the yoke?....I used a pair of steel bushings that I cut/ground the bonded rubber from ....that came from a mark 1 or 2 rabbit sirocco or Jetta.
This is how I figured out the problems in the first place. Back in the late 90s...my bushings were so wasted i had to do something.....so I installed a pair of rabbit bushings. Cheap...well made. But the rubber was easily 30-40% softer than the high compression bonded rubber of the 411/412 bushing.
One trip around the block felt like driving on soup....and the bushing length was about 10mm shorter so I had to put washer spacers between each end of the bushing to keep it centered. Later I ground the crown of rubber down from each end...and put a series of large flat washer shims the same thickness at each end.
This fixed everything. The steering cleared up.....and the control arm yokes stayed centered.
I drove on these for about 15-20k miles before the bushing rubber literally shredded because it was simply too soft. So....I switched to urethane rabbit style bushings with the same washer/spacer mod. They did OK....but within a year in the heat of Texas....they became really hard and just cracked to pieces.
After reading quite a bit of European car as to how the water cooled guys did high performance bushings.....I stumbled upon the fact that all of the high end VW, Audi, BMW guys had gone to Delrin for street use and glass filled delrin for track use.
The delrin washers/discs I made ...were done on my drill press. I used an end mill and a slide table I have to shave a piece of delrin plate I bought at Mcmaster carr down to about 6mm. Then used a bi-metal hole saw to simply cut discs, then drilled a 12mm hole for the bolt...then sanded them smooth.
You can buy 1/4" x 3" wide black wear and water resistant delrin from Mcmaster Carr for about $10 per foot. You can cut the discs with a hole saw. I will measure the diameter and exact thickness for you when I get home.
Sadly they have no 5/16" in plate. The next size up is 3/8" which takes a bit of material removal. But all can be done on a sander before of after you cut too shape.
As for the rear trailing arms....notice from your picture that the inner bushing is a split bushing. Its possible that it can be easily replaced if its worn.
Also....I suspect that the larger steel bushing has a recess ground in it. I have never dissected this part so I will just to see how its made.
I know why VW designed it this way....because I have been agonizing for YEARS...on how I might change the design to make it easily replaceable. Its difficult. If they had made a rubber bushing with a sliding tube inside....meaning no wind up to the rubber.....that sliding tube..say steel center, bronze outer...would wear rapidly. I say the design was stupid but thats harsh. Most all I find except for the side slipping issue...are still functional. With wear though...they tend to droop causing camber issues.
I have also found by looking at other designs....that you could replace the rubber with a solid bush and probably never feel any real vibration from where it is.
The only real function that needs to be added to the stock part is spacer discs to keep the trailing arm from slipping sideways. If your bushings are still in great shape...you could simply add packing discs on each side like I have dont on the control arms.
But....if your rear camber is already excessive.....they are done. I would simply replace. It with a solid bushing. Delrin or Bronze. Use the original steel bushing with the knurled ends. Leave the split inner bush. In that way...these will never wear out. You get movement...simply drive out the inner split bush and replace it.
Betting we can get them here
http://www.cook-leitch.com/pdfs/WJ%20Baker_broch.pdf
Ray |
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bradself
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Location: SF, CA
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| Posted: Sun Feb 01, 2015 12:41 pm Post subject: |
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| What slips in what, or, what's bonded to what, in the rear wishbone bush? I don't know the condition of these other than the rubber is not bonded to the larger outer bush. I assume the outer metal bush is a part of the complete bushing assembly. |
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raygreenwood
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Joined: November 24, 2008
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Location: Oklahoma City
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| Posted: Sun Feb 01, 2015 3:08 pm Post subject: |
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They are made similar to the front control arm bushes or so I was told long ago.....like high school....by the mechanic who worked on my first 411. They should have an outer steel sleeve....visible in the picture. That should be bonded to the inner knurled sleeve by rubber. The inner split sleeve is the actual bearing that rides on the bolt.
I have had rear trailing bushings on two cars that "slipped" on the rubber....just like thr front control arm bushings do. This makes me think they are made similar to the front control arm bushings....only a lower proportion of rubber to metal.
Generally when the rear trailing bushings do slip....they slip outward. It would not take much of a packing ring resting only on trailing arm housing to keep these centered.
One set got really bad where it had slipped back and forth a bit and messed up the rubber so I had a bit of movement in the rear trailing arm.
These bushings last so long that it makes me think that if you could simply replace the split bushing to take up for any wear....and add some shim rings on each side to keep the trailing arm centered......it could give good service for ages.
I have not looked at mine for a long time. I dont know their condition. Also the way its up on blocks right now I cant reach the rear readily. But as soon as the front suspension is back on...the car will swap ends in the garage and I will pull the rear trailing arms and beam to undercoat and install the camber adjustment and will deal with them then.
I do have a pair of trailing arms on the shelf with good bushings. I could press one out to see what gives. Ray |
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Tram
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Joined: May 02, 2003
Posts: 22728
Location: Still Feelin' the Bern- Once you've felt it you can't un- feel it.
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| Posted: Sun Feb 01, 2015 3:42 pm Post subject: |
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| 19super73 wrote: |
| Mike Fisher wrote: |
| vwfye cut his front springs down to level his 412 wagon. |
It actually lowered the front end, not leveled it. Tram bought uncut springs from me to bring it back to stock stance. Then because I wanted the springs back so badly he made me buy the whole car to get them back.
Fye stance.
What it looks like now.
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The car actually rode like garbage- it bottomed out way too easily.
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Немає виправдання для війни! Я з Україною.
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| Just my hands. And a little lube. No tools. |
To best contact me, please use the EMAIL function in my profile |
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raygreenwood
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Joined: November 24, 2008
Posts: 21521
Location: Oklahoma City
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| Posted: Sun Feb 01, 2015 4:53 pm Post subject: |
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Zactly......I actually tried that way back in the mid 90s.....back when I had springs laying around from about five cars. It sucked.
Thats when I realized just how well the progressive springs on these cars were calibrated. Through experimenting with the bump stop spacers while I was looking for a new cartridge I found that you can compress the front spring a little further to allow a small amount of lowering ....about an inch or so to set things level.....without upsetting the balance.....but r3moving coils is a no-no. Not only does it remove capacity.....it does nothing to change the stroke length of the original cartridge. It simply removes load capacity so the weight of the car compresses what is left of the spring....thus making it sit lower.
The problem with that is that when you go over a serious bump....really a dip or hole.....the strut unloads .....the rod extends fully and now there is little or no tension between the top of spring and the top plate. Its a rattly mess. Ray |
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bradself
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Posts: 167
Location: SF, CA
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| Posted: Wed Feb 04, 2015 7:20 am Post subject: |
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Back to the wishbone bushing for a sec: if the rubber has become unbounded from the outer most bush it's basically a goner, si? However it might be schvitzed it seems like movement would then occur at the inner split bush against the bolt and at the outer most surface against the wishbone itself, as well as between the serrated bush and whatever the rubber/outer bush has been replaced with.
OR, if the replacement was made to interference for in the wishbone it would only slip between that material and the serrated bush.
The centering shims would also slip so I wonder if two shims per side would make sense, then slipping against themselves. If they're delrin, unless they're sized with some clearance in them they would suffer under the 60 #s torque--as in the front control arm replacements.
Just thinking out loud here, I ain't no engineer! |
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raygreenwood
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Posts: 21521
Location: Oklahoma City
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| Posted: Wed Feb 04, 2015 11:36 am Post subject: |
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| bradself wrote: |
Back to the wishbone bushing for a sec: if the rubber has become unbounded from the outer most bush it's basically a goner, si? However it might be schvitzed it seems like movement would then occur at the inner split bush against the bolt and at the outer most surface against the wishbone itself, as well as between the serrated bush and whatever the rubber/outer bush has been replaced with.
OR, if the replacement was made to interference for in the wishbone it would only slip between that material and the serrated bush.
The centering shims would also slip so I wonder if two shims per side would make sense, then slipping against themselves. If they're delrin, unless they're sized with some clearance in them they would suffer under the 60 #s torque--as in the front control arm replacements.
Just thinking out loud here, I ain't no engineer! |
Your logic is spot on. Whenever you make a thrust washer...ideally...if space and side loading permits...if you can make it two part washer or even better...a three part washer....you would get rid of more wear and friction. Just like the reason you use three shims on the main bearing.
The serrated bushing runs full width in the yoke. Its designed to center the trailing arm. It is designed to be stationary and not turn with the movement of the arm...for the same reasons why I dont want excessive clamping load on the bushings in the front control arms....because it bears up against an open slot. If the serrated bushing moved....it would wear heavily against the slot.
If nothing is out of sorts or worn on...or un-centered yet on your trailing arm bushings...the best bet right now would be to put spacer shims on each side of the bushing...between trailing arm and yoke...to keep it centered.
There are two things that seem to tear the rubber section up the most.
1. And this one is really important......when you loosen the eccentric bolt or even the non-eccentric bolt on the outer trailing arm yoke...to adjust,....mark the position of the eccentric with a sharpie pen....and then LOWER THE CAR TO THE GROUND BEFORE TIGHTENING THE NUT ON THE ECCENTRIC BOLT......if you dont do this.....the serrations lock the bushing in the fully extended position...and when you put the car back on the ground it puts the rubber under heaving twisting load. On older bushings driving on that tears the rubber up fast.
2. Once the rubber is torn loose inside...it does not mean the bushing is dead. If you allow it to slip sideways until the trailing arm tube contacts the yoke.....now it is dead.
So....if you can bush the trailing arm tube with thrust washers to keep it centered...before it becomes uncentered....your trailing arm bushings can last for eons.
After that.....if you need to make new bushings....I think there are two options....which are really different trains of thought. Both have positives and negatives.
1. Keep the center serrated bushing.....remove the rubber and the outer metal tube.....then make a 1 part surrounding tube bushing....either glass filled delrin, MDS filled nylon...or bronze..... with a centering flange on one end only...usually the outer end because that is the direction of thrust and slip. Make the bushing for the outer yoke of the arm with its thrust on the inner end....so it will keep thee whole arm centered.
Polish the outside of the serrated bush. Make the ID of the delrin flange bushing a dead fit....not interference (I guess it could start out with a slight interference fit).....and press in the serrated steel bush.
The serrated steel bush will lock to the yoke like normal....and the trailing arm and delrin bush will rotate around the polished serrated bushing.
The positives is that this is precise and simple. The negatives is that even wiith good grease....its a wear part. Sooner or later it will wear out. Might be 30k miles ...might be 100k miles. Just unknown.
2. Go with the method I used for the front control arm bushings. Get new steel bushing stock (mcmaster carr and many locations)......and make the OD of the steel bushing smaller than the original serrated steel bushing....probably about 3/16" wall section at the most. This is so you cn have thicker Delrin or bronze around the core bushing.
But make the length of the center steel bushing a dead fit in the yoke. No interference...just within a few thousandths.
Do the flange at one end or both ends it makes no difference...except that a flange at both ends will require it to be a two part bushing and a flange at one end will make it a full width one part bushing.
With this method....The positives: you will use just enough torque on the eccentric bolt to take the slack out of the yoke against the bushing flanges.The operation will be smooth and have virtually no wear....
The negative:....you will need a set screw on the eccentric to make sure it does not rotate.
Ray |
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