Saturday, 30 March 2013

New back axle set-up for 't Kreng

Today I at last found some motivation to take one of my Triumphs out of hibernation, in this case 't Kreng. As she had stood idle for quite a while, it took the fuel pump some time to create enough fuel pressure to get the engine started (almost empty tank), but she did in the end. As she had been sitting outside underneath the car-port since I returned from the 24th edition of the Nachtrit in early November, it came as no surprise that she ran a little rough. The still low temperatures for the time of year didn't help there. But after a few careful kilometres to get everything on temperature she started to behave quite nicely indeed. And with some fresh German 102 RON petrol in the tank I quickly forgot that she hadn't been used for almost 5 months, it really felt good driving the car again.

And that also reminded me of the fact that, as it stands now, she'll be taken apart for the final part of a 15 year upgrade. I mentioned earlier that I have planned some body and suspension modifications, like ditching the horrid sunroof (probably will get a Viking burial!), add a welded in cage, a new suspension set-up front and rear, adding lightness and a new paintjob. And mainly thanks to the rather unseasonal weather (still rather Brrrrr.) I have managed to put some ideas for the back axle on (digital) paper.

As those of you who follow my ramblings on a regular basis know, I have been toying with the idea for a 5-link Panhard rod or a 6-link Watt's linkage set-up for the back axle. So after taking lots of measurements of the back axle and the car and doing some simple mathematic calculations I have decided that the Panhard rod option is the one to go for ...

It is fairly easy to accommodate a Panhard rod with a length of 965 mm (or 38" in old Imperial measurements). Together with my current spring set-up and ride-height the back axle should have a maximum bump travel of 85 mm. Although judging by the markers on the rear dampers 50 - 75 mm of travel is a more realistic figure. And with the mentioned rod length of 965 mm that gives a sideways movement of less than 3 mm, which shouldn't be noticeable when driving the car.

Some other advantages of this Panhard rod set-up are that I only need one fairly simple bracket for the car's body and one for the axle itself. Also this set-up should fit in the original space between the rear of the back axle and the front of the spare wheel-well.
Apart from the very positive fact that with a Watt's linkage there is no sideways axle movement, choosing for a Watt's linkage has some disadvantages. Using the linkage from the Rover SD1 back axle means I have to fabricate two mounting brackets for the body. But I also have to adapt the front of the spare-wheel-well a little to create some much needed clearance. The other option is to fabricate a central pivot point on the front of the spare-wheel-well and add two mounting brackets to the axle. So a lot more work and some extra weight compared to the Panhard rod.

But before physically starting with any work on 't Kreng I first have to finish the DHC ...

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