Pauls splitscreen van project: 01/06/2012

I've had the dilemma if I should or how I could shorten the mounting position of the lower shock mount on the front beam lower trailling arms. I've scoured the internet for how to do it, without any luck so here's how I did it.

I could just cut the arm to the length I needed and drill out the existing bolt, but I first wanted to see if I could take the parts apart how they were assembled, and if that doesn't work then cut it up and drill it out. I started with the pin that holds the bolt in place.

Because the trailing arm is such an awkward shape to hold in a flat vice I came up with the idea to clamp the arm in a position between the drill bit and the tip of a bar (ground to a point, allen key pushed into a round lump of ali) using the positions that I centre punched on the pin.

This took a while to set up, I ended up using the cut off pieces of leaf springs from the front beam as spacers to clamp the arm, most importantly to keep the pin square to the drill bit. I first went through with a 3mm bit. this snapped as it tried to break through and left me with a broken bit inside the arm. Not easy to remove!

I then drilled as far as I could with a 4mm bit (the diameter of the pin) this then allowed me to knock the remaining part of the pin out with a punch.

Now onto pulling the bolt out. I first tried to pull it out cold but it didn't want to budge. so I then built myself a little oven at the end of the garden. Then donned my leather attire (I'm also a part time Gimp) and set about becoming a Pyro. I was able to draw the first bolt out with a steel spacer I made and a bunch of washers, this took about 4 attempts of heating the arm up for 3-4 min each time with a butane torch in a brick covered over/hamster house keep the heat local, this also helps saves gas and time.

As I was winding the nut down on the second bolt to draw it up through the spacer and washer under the nut it caught on the shoulder of the bolt, making me sheer the thread of the bolt.

This left the bolt half in the arm with no thread on the sticking out part to help draw it out.

To get around this problem I cut a new thread on the shaft, having first cut the arms of my die holder down so I could get the die to rotate a full 360 deg.

With the nut on the new thread, and a bunch of washers ready I was ready to try again.

Another quick blast in the furnace and a lot of squealing as hot metal graunched on hot metal... like the droid torture chamber under Jabba's palace.

Finally both lower shock mount bolts came out, I made sure I left the arms to cool naturally so they retained their original material properties. If I had stuck them in a bucket of water to cool this would have hardened them but also made them very brittle.

Video of bolt removal after heating

So now with the pins out I can get on with modifying the trailing arms. I started by setting up the arm in the pillar drill using the existing 12mm hole and a drill bit to make sure its square. I then deepened the hole by what I thought was 12mm but ended up 18mm deep, This means the depth of the hole now starts to go into the arm I hope it won't affect the strength.

So I then threaded the hole with a 14x1.5 mm tap using the tap in the drill at first to get me started to make sure it went in square, with the thread cut all the way down I then cut 13mm off the face.

I tidied up the burrs and mating face with a file.

I couldn't use the old shock mount bolts, as I broke one and they would no longer fit in the hole, so decided to make my own

They are 95mm steel rod with three steps 14mm, 12mm and 10mm, length to fit the arm, shock mount and nut. I'm just waiting for a 14mm die to turn up before I can fit the bolts/pins in the arms. I later found out my shock mount bushes are 12.5mm(1/2") holes so I my make another pair if there is too much rattle with the first batch!

So my 14mm x1.5 die arrives and I try to cut the thread in the lathe. This was tough so I tried turning a little more material off the outside diameter I finally managed to get the die to cut but by using the chuck key as a lever. This also caused the smooth face of the shock mount to score from twisting in the jaws.

I screwed in the new bolts in the trailing arms to check the depth of the 14 mm thread I'd cut, it got to the base with 1 mm sticking out but as I pulled it out with a couple of nuts twisted together on the 10mm thread end the bolt started to bind. This was not good.

After a lot of cussing, thinking I'd just scrapped a trailing arm and new home made bolt I tried winding the bolt out jammed in the vice, this lifted the bench off the ground. After shearing the new bolt and a couple of days break, scratching my head I finally managed to drill down the bolt with a 12mm bit, offset from centre close to the tip of the internal thread. This broke the bolt away and with the use of a punch in side holes I got the old bolt out in bits. whoop whoop. happy smily.

This let me to turn down my second set of bolts

This time I started the thread cutting on the lathe with a little bit of taper on the end of the bolt and did the rest by hand. I used a v block and piece of tin plate to protect the shock mount face.

With the new bolt sliding into place I could check the fit with the shock. Not sure if the nut and washer should clamp the bush or allow it to spin?

A couple of pictures of the arms with the bolts

The final stage of assembly and the thread was thread locked with a low viscosity Locktite

I then purchased a set of 120 roll pins from Halfords normally £8 but got then for £4 with a trade card. Anyone need 118 various roll pins?

I drilled through the bolt first with a 3.2mm bit using the bit poked into the other side as a sight guide. Then opened this up with 5/32 bit starting from the opposite side.