Rear Torsion Tube End Repair Bushing Intallation

[MarkT]

So by popular demand ! I am going to share pictures and words of my torsion tube end repair project:

Starting point:

You need to cut out the original inner quarter ideally no bigger than the standard available repair panel for this area and also taking care not to damage the double skin piece spot welded behind the primary panel ((You will need to salvage this second skin panel as it does not come with the standard repair panel) see image below the salvaged second skin is dry fitted and tacked to the inner side of the standard repair panel and will be plug/stitch welded in place. The weldable threaded inserts in the picture are not the ones that came with the repair panel as I could not find any use for them (to short by about 15mm IIRC) so I purchased standard size weldable inserts which were slightly longer than required and a bit larger in diameter (I'll go in to details in next post) I used the new spring plate bush covers to help align the assembly. Note: mating surfaces were sprayed with High Zinc primer. 

More to follow

Regards

Mark T

[Nige]

And it all looks so easy in the pictures

 

Impressive stuff, I like those clamps where do they come from?

[fat fuchs]

You can buy the repair panel with the 'secondary skin' already in place which saves a good deal of time. Available from restoration design eu for info.

http://www.restoration-design.eu/store/product/PP280R

[Henry]

Thanks for posting , nice reference pics  for those having to tackle this  area. These panels look to make the job a lot easier and not too expensive either ,well the first one anyway.

Edited February 23, 2017 by Henry

[MarkT]

2 hours ago, fat fuchs said:

You can buy the repair panel with the 'secondary skin' already in place which saves a good deal of time. Available from restoration design eu for info.

http://www.restoration-design.eu/store/product/PP280R

FF, 

Nice find, will certainly save time and give others options if they ever tread this path.

For me, at more than twice the cost, I would probably do the same as I have done already, mainly because I do this for a pastime, where cost effective achievement takes priority over speed. The other thing I found, is that the original threaded inserts only have about 5-6 threads, the ones I used (1.5mm pitch, M10, 19mm x 30mm GWR-Motor sport) were threaded over their entire length of ~30mm ~20 threads, so no danger of ever stripping these. Note: the 19mm OD needs to me ground down at one end to ~18mm to fit repair panel holes, this is easily done using a drill, 50mm peice of M10 stud and abrasive paper at one end)

Couple hrs work, think mine (see image below) looks ok and very strong, I'll continue with the topic and post more pics and guidance tomorrow, keep the complementary alternative additions/solutions/suggestions coming, will make the thread all the more useful.

Cheers

Mark T

[MarkT]

10 hours ago, Nige said:

And it all looks so easy in the pictures

 

Impressive stuff, I like those clamps where do they come from?

https://www.amazon.co.uk/d/Clamps/Draper-Expert-Welding-Clamps-Pieces/B00757461A

[MarkT]

The images below show the RH/OS repair panel assembly from the other-side/external, the weldable inserts/spacers (~£1.80 each) are friction fit after grinding/sanding the OD down (remembering the lower rear insert is shorter and has a stand-off spacer, to allow the spring plate to pass through) and with the spring plate cover & bolts in place made it easy to adjust the spacing between the repair panel and the spring plate cover before being tacked in place and re checked before final welding, which in my case was 20.5mm, this may vary from car to car, so do check and allow for paint/under-seal, I would suggest that anything under 19mm you are in danger of the spring plate interfering with the inner wing !

If using the same inserts that I did, you may find that they will protrude from the rear of the internal secondary skin/strengthening panel, this will especially apply to the lower rear insert as this is recessed to accommodate the external spacer/stand-off between the spring plate cover and the welded insert. I found it easier to finish all the welding and trim the internal surplus length with a 4 inch, x 1mm cutting disc in an angle grinder, which can be seen in the previous post in this Topic.

One picture shows together the new repair panel assembly and the original offending panel assembly, by the time I removed the original (Primarily with a air Body Saw 32T) there was nothing left of the bushing cup/end of torsion tube shown in the first post. The holes in the original are from recovering the internal second skin/strengthening panel, discussed in an earlier post in this topic. Note: You need high power on your mig to penetrate the inserts 5.3mm wall thickness (This is possibly why the original inserts/spacers were thinner walled and only had 5/6 threads !), I used 130 amps on my Snap-on Mig 130, I must say it was a little difficult getting the tip around the inserts as the rising sides of the repair panel get in the way.

Other pictures are a) the 2 types of spacers/inserts I have discussed (primarily due to being to short, as much as I tried I could not get the ones supplied with the repair panel to work, they could be used if you did not bother with the internal secondary strengthening skin/panel, makes you wonder !!!, b) Spacer on M10 studding in drill for grinding/reducing the OD from 19mm to ~18mm (only do at one end this leaves you a larger foot print at the insert/spring plate interface end, you could use a lathe but i think overkill, the drill method allows you to do quick checks of the fit in to the repair panel hole and c) the torsion tube end repair bushing (the most significant dim here is the narrower external diameter of the part i.e.74mm, it is this that goes in to the prepared end of the torsion tube that has an ID of ~74mm (Note: From my research & experience, the torsion tubes are not perfectly round internally, they are oval ! by about 0.5mm, which becomes apparent if not by measurement, when you try and fit it, as it will initially only touch in 2 places making it very difficult to install, hence why I developed pull/press tool to do this without overly stressing the Torsion Tube (Pic's to follow)).

More to come, probably tomorrow..........

[MarkT]

So back to the car, the following picture shows what was left of the torsion tube bushing cup after I had cut away the corroded adjoining portion of the inner quarter panel, the area cut away was the minimum that I could cut away without damaging the secondary strengthening skin/panel show in the previous posts of this topic.

You can see that the heater tube has 2 holes in it ! my guess is this is where the original threaded inserts had been stripped/damaged at some time and had been welded up, drilled out to deep and then re tapped !! Note: I have the entire service history 1975-Present for this car and it was only maintained by very reputable (No names) Porsche dealers/specialists makes you wonder !! However easily fixed (see later posting to follow).

I did end up making the repair area larger to take advantage of the new repair panels flange, as the original flange was showing signs of Jacking damage.

As you may of noticed, as some areas can take me weeks to complete, everywhere I clean back to bare metal I treat with Phosphoric Acid and then give it a coat of black 2 pack epoxy, just to ensure I do not get any surface rust appearing until I am ready to final finish a whole section, this may mean removing the epoxy again at a later date (just me, belt and braces / Screw it and glue it}. I only intend to prep the car for a professional spray shop to complete the final finish.

The next image is of the torsion tube cup area cleaned, Phos Acid, and Zinc primer applied, I was fortunate that the torsion tube corrosion stopped cleanly at the inner panel weld line, if the corrosion had gone beyond this point (further along the tube) a more complex scheme would need to have been considered. As you can clearly see I have removed a section of the heater pipe to a) gain clearance to renovate and eventually weld the new repair end/cup to the tube and b) the heater tube at its lowest point was corroded so gave me to opportunity to fix this. Also note at the 1 o/c position further evidence of over enthusiastic historic drilling & tapping of the original threaded inserts. While in this area I took time to tidy and straighten up the mating flanges.

Note: I have seen a picture somewhere where the torsion tube repair end bushing has be welded in with the heater tube still in place however, you can not weld 360 deg you can only get to about 2/3 of the circumference, I wanted 100% 360 deg weld you will see in pics later in this topic.

I bet you are wondering how the hell is he going to weld the heater tube back in.....

The following image is trying to show the final shape of the repair panel I used and using a suitable alignment insert e.g. a plastic jet washer detergent bottle (the white bit in the middle of the torsion tube) with tape around it to get very close to 74mm OD, this then allows the Alignment Insert to friction fit the original torsion tube and the torsion tube repair end bushing (TTREB) cup that are the same ID of ~74mm. so that you can align the original torsion tube WITH the TTREB, WITH the hole in the repair panel.

I hope you can see that I have dry fitted the TTREB INVERTED in to the back of the repair panel taking care that the 2 items are at right angles to each other by ensuring that the TTREB inserted edge follows the repair panel hole edge perfectly, Once you are happy everything is inline, do your final stencilling/marking in order to obtain a perfect fit for the repair panel in to the inner rear quarter panel,

Do not weld the repair panel in yet, you need to fit/press in the TTREB first and then reinstate the heater tube.

Note: Because the original torsion tube will be slightly oval its a good idea to use an alignment spacer (e.g. plastic bottle) that is a little bit compliant.

Pressing in the TTREB next, probably tomorrow morning, hope you think this is helpful.

Cheers

Mark T

[MarkT]

Getting close to the end here,  just to get the TTREB to hold in place, using a rubber mallet I inserted the TTREB in to the torsion tube a few mm.  I then used the now famous  "Mark T Torsion Tube Repair End Inserter "? which I am sure from the picture below you get the idea, if not I'll try to explain it here:

You will need these standard items from ebay:

M20 HEX FULLY THREADED STUD ROD CONNECTOR LONG NUT COUPLER  x 3 (1 at each end and 1 to join the 2 x1m lengths of studding.

M20  ALL FULL THREADED METRIC BAR STUDDING ROD ZINC PLATED  M20 x 2 1m lengths (you will only need ~1.5m.

M20 extra thick steel washers * 2 + a few other larger extra thick washers to build-up the press assembly, the largest washer OD would need to be between 65-74mm in order to fit inside the TTREB, but sit/press on the inner rim.

At the other end (the end you are pulling against), you will need the same washer set-up more for centralising the the M20 bar in the torsion tube and a spreader plate to pull against (see pictures below).

Note: If you need to repair both ends of your torsion tubes, start with the worst one first, giving you the better end to pull against.

 

Complete tool below, but missing the washer set that would centralise the M20 bar in the torsion tube (TT) at the end you will be pulling against, the black covering on the threaded bar in insulating tape just to minimise any damage to the inner TT splines as you pass the bar through the TT:

The 2 long M20 nuts at the pressing end of the bar are there in case you need to stop the M20 rod spinning when you start the pressing of the TTREB in to the TT.

Some more misc pictures below of the  "Mark T Torsion Tube Repair End Inserter "?

The image below: Be better to use a washer assembly to centralise the rod in the TT however, I run out of washers so welded a series of bumps ! that held the spreader plate central in the end of the original TT, keeping the bar central is important as it will ensure that the TTREB is pulled in evenly.

NOTE: DO NOT TRY TO PULL AGAINST AN ORIGINAL TORSION TUBE INTERNAL BUSHING STOP/RIDGE WITH THE WASHER ASSEMBLY (USE A SPREADER PLATE, ACROSS THE FACE OF THE TT & INNER WING) AS THESE ARE VERY WEAK COMPARED TO A TTREB AND YOU WILL ALMOST CERTAINLY DAMAGE IT. ONCE YOU HAVE ONE SIDE COMPLETED WITH A TTREB YOU CAN PULL AGAINST IT WITH a WASHER ASSEMBLY ON THE INTERNAL EDGE/RIDGE. THE DRIP SHAPE OF THE SPREADER PLATE IS TO MAXIMISE THE LOAD AREA.

Before I pressed the TTREB in to the TT, I cleaned and then coated the TTREB and inner TT with high zinc primer and then a film of oil on both mating surfaces (helps with the very high friction between TTREB and inner TT as you press in).

NOTE: You need to ensure that when you press the TTREB in to the TT and before you weld it in place, the outside edge/face of the TTREB ends up in the same place dimensionally as the original outer TT face otherwise if it is not you may not be able to fit/weld the inner TT rear wing repair panel in place and/or your geometry will not be correct. So for me, when I measured both OS & NS original sides from the outer edge of the internal TT spline boss/carrier to the outer face of the original TT it was 43mm both sides. Using the pressing method described here allows very accurate and gradual insertion of the TTREB (keep checking as you go) however, a) don't go to far in, as this will be a pain to try and get the TTREB back out and b) ensure that you have cleaned enough material/weld away from the original TT end to ensure that you can achieve the dimensions required.

I hope this makes sense

Below is what you end up with if all goes well:

As you can see clearly below the inner inner wing is not a 90 deg to the TT hence you will see a run out between the original weld and the TTREB cup edge, this is to be expected.

 

Below: Not a great picture and it did look a lot better in the flesh however, High amp on the mig again and a 306 deg weld (you could not do this with the heater tube in place) of the interface between the TT, TTREB and Inner wing assembly.  In my opinion this is a very strong solution and you end up with a torsion tube bushing cup significantly stronger than the original and you maintain the original TT bushing interface, some solutions I have seen require a custom diameter bushing set made ! 

Below: Again, not a great picture but now painted with 2K epoxy, will show heater pipe rebuild in next post in this topic probably tomorrow.

Cheers

Mark T

[MarkT]

Nearly there, heater pipe welded in, basically I cut the heater pipe through left and right, once I had it out I then cut it through its length ~2/3 at the back 1/3 to the front. When welding the back part of the heater tube in you weld from the inside of the tube and the front part from the outside of the tube.

Then a good clean & Phos Acid and another coat of 2k epoxy, once the car is finished I plan to treat all cavities with Dynax-50 or similar, the heater pipe internal walls will be painted, as I will not want wax oil type fumes coming in to the cabin.

Clean and paint all joints to be welded with high zinc (weld through) primer and stitch weld in your pre prepared repair panel section along with the threaded inserts/stand-offs & secondary strengthening panel. When welding the repair panel to the TTREB I found high power short stitch welds to be the most effective, remembering the wall thickness of the TTREB is 4mm however, spend to long on the stitch and you could blow away the thinner metal of the repair panel. 

Note: I generally treat all newly welded areas with Phos Acid just to make sure any flash oxidisation is neutralised, clean/de-grease then prime.

2K again to preserve the area while I am working else where, will ultimately have 2K primer, Wruth Stone guard and finish colour Black A1A1. 

This is how it all started !!!!!

Hope anybody that embarks on this journey finds this Topic helpful.

Regards

Mark T

[Dr Rock]