Rotoflex . Tools to make replacement easy.

[Seveneer]

Elan Rotoflex Tools

There are two problems with the Rotoflex

1 - the first problem is that the Rotoflex does not match the diameter of 96mm of the Elan tripod, as specified in the product catalog of Dunlop Metalastik part 21/967/1. The parts that I received are a bit too small with a diam of 94 mm only ! Having called Trelleborg, who seems to be the current manufacturer, I was told that no one ever complained and that they had no plan to change the manufacturing process! So I decided to make some tools to fix that.

One way to solve this is to take away the steel band, allow the Rotoflex to expand, then compress it back to the correct size using hose clamps. Unhappily, while doing that, you will find that the Rotoflex rubber seems to be alive, and that it is very difficult to adjust all 6 holes to the correct position. So I developed a simple tool to adjust the Rotoflex.

It is a steel plate with 6 holes diam 13mm drilled on a 94mm diam circle. Also, 3 washers of 3.2mm thickness. The Rotoflex, as received, is bolted to the plate, using six 7/16" bolts and the three washers to keep the Rotoflex flat. The steel band is then taken away, and replaced by a very strong hose clamp diam 130-140 mm. Leave the clamp a bit larger, then loose the bolts and allow the Rotoflex to expand into the clamp. Please note that when the 7/16" bolts extend into the 13mm holes, they will be on a 96mm diam circle. Eventually, you can check the size using the tripod you dismounted.

2 ? The second problem is that, as fitted in the Elan, the Rotoflex work under a slight axial compression, which means that a flat Rotoflex is too wide to fit into its space. Be careful to check that the steel guides into the Rotoflex are not symmetrical, and that the longer ends must fit on the tripods. Once the first Rotoflex is placed near the disk, there is not enough length to insert the second one near the diff. So I developed some tools to increase this space. These tools are a plate and six bolts that fit on the first Rotoflex, pull the tripod into the Rotoflex, bends it, and increases the space to allow the second Rotoflex to be inserted easily.

The complete tool kit looks like this :

Expansion tools
- two large hose clamps : diam 130 to 140 mm
- one expansion plate : bored with six 13 mm holes on a 94 mm circle
- three 3.2mm thick washers

Compression disk
- one pressing disk : outside diam 125 mm, inside diam 42 mm, 3x 12mm holes on 96 mm circle, one slot 38.5 mm wide to allow inserting the disk on the shaft.
- six tubes : length 25mm drilled for 7/16" 20UNF bolts

The bolts used in the process are the 7/16" bolts used for the Elan. You may need washers to adjust the lengths.

Using these tools, changing the Rotoflex becomes more easy.

I work on a pit, which allows me to move the car back and forth, so I can locate the bolts easily to fit the wrenches. There is not much room there under! The rear axle should be aligned, so I put four 25kgs bags of sand in the trunk.

First, dismount the Rotoflex diff side. Then dismount the Rotoflex disk side, leaving the 3 bolts from the disk in place. Pull out the tripod and the old Rotoflexes.

Using the tools as described above, prepare the 2 new Rotoflexes.

Insert the 3 screws in the first Rotoflex, then set the Rotoflex on the disk side, then the tripod. Because the Rotoflex has been properly adjusted, all fits easily, like magic!

Fit the six tubes on the 7/16" bolts. Then insert the compression plate on the tripod against the 3 tubes. Fit three bolts through the plate, into the 3 other tubes. By tightening these 3 bolts, you will push the tripod into the Rotoflex and increase the available space for the second Rotoflex at the diff side. See picture above.

Before inserting the second Rotoflex, don't forget to fit the 3 screws going into the tripod from the diff side. Only one shown on the picture ! Else, there will be no room to enter them !

Once all the bolts are in place, take away the clamps and tighten the nuts.

Don't forget to drop the bags from the trunk, enjoy a good beer, and you are ready to roll !

More info ? [email protected]

[Henry VIIII]

A brilliant idea, but you will find that if you make up a compression band from 3 smaller jubillee clips, the fact that you have 3 adjusting points means that it isn't really very difficult to line up the holes to match the spider.

[elansprint71]

Welcome to the forum; you are Keith Frank's offspring and I claim my ?5.

[alexblack13]

A brilliant idea, but you will find that if you make up a compression band from 3 smaller jubillee clips, the fact that you have 3 adjusting points means that it isn't really very difficult to line up the holes to match the spider.

Exactly how I do it too. I have an old driveshaft to check the lineup.. tiss very easy.

Well done and a big thank you from the Forum for your very worthwhile efforts.

Alex B ......

[Spyder fan]

Louis,
Very good pictures and information on your tools and method of changing rotoflexes. I wasted many hours in the past changing these awful pieces of metal and rubber until I came up with my own solution as mentioned by others to use 2 or 3 large jubilee/hose clips to deform and compress them to fit.

Your tools would probably have commercial success if there was a wider market for them, it's inspiring to see the level of innovation from Elan owners around the world.


Regards


Alan

[Bruce Crowthorne]

Ditto the jubilee clips.
My only addition is an old bolt of the correct diameter with the end of the bolt ground to a taper. I use that to help / check the alignment as I adjust the jubilee clips. Then the real bolts just slide straight in.
Bruce

[Henry VIIII]

Can I suggest that you make a second set of 6 holes in your flat plate, this time at the radii needed for the actual Elan. Then after you have used the first set as above to control the rotoflex when you break its supplied strap, after you have fitted the adjustable compression band, you can use the second set of holes to pre-set the rotoflex on the workbench to the correct size so that you should not need to do any further adjustment while under the car.

You can do this pre-set of course using the spider on one end of one of the shafts, but it is probably more precise to do it with all 6 bolts instead of just 3.