Sunday, 29 January 2017

The XS Triple Sidecar - Sidecar brake (part 3)

As you may remember from the end of the last post, there wasn't exactly a whole lot of meat left in that swingarm. So a new insert had to be made on the lathe, tapped to M16x2 on the inside, so if I ever bent the axle I could (relatively easy) make a new one on the lathe.

Now this time I played around with some Sandvik inserts I bought a while back and honestly the first attempts to work with them were disastrous. After reading their speed and depth of cut requirements, I was shocked, bearing in mind that my old Matra MDR2A is a plain bearing lathe from the 1950ies and was never meant to be run above 1200rpm for a prolonged time and only shortly above 1500rpm, which is why I decided that 1800rpm should be doable with some good modern oil and a bit of "force feeding" and guess what...

... like a hot knife through butter. The results are amazing: The surface is almost mirror-polished, chip-breaking was nothing to write home about, but I guess that's due to the fact that I was still running on the lower limit of what the inserts are made for. I really have to try one of these inserts on my mate's industrial lathe, which can spin to almost 2000rpm.

This also reminded me, that I still had a MT3-TPUN-something-something holder for the mill and as I wanted to get the wheel as close to the swingarm as possible some 10mm had to be taken off the old axle mount. Being smarty-squarepants junior, I decided to read up on the specs of the inserts and guess what, full throttle and pretty much 10mm in one go at 1mm feed was (again) the lower limit.

The chips had a beautiful straw colour and it was a matter of seconds. I've had a harder time milling through some tin-can-grade aluminium in the past. 

The only real failure of the day was the moment when I tried to press in the new axle holder into the swingarm and I had to ask round for favours and press it in with a hydraulic press. A bit of will (and a good vice), you can create up to nearly 5T of pressure in a normal vice.

That's the unthreaded axle poking out of the wheel...

... and that's literally 20 minutes of manually tapping a M16x2.00mm thread. (I really have to fix the power-feed and thread cutting facilities on my lathe...)

The finished product: An axle that can be swapped out, whenever you feel like it and pretty much all ready to go back in.


  1. The Matra's are a class lathe, we had them at school, I preferred them to the old Bridgeports we used to run. What oil are you running? Your low shed temperatures are going to have an effect surely? What cutting oil do you use Greg? Must say I prefer the more modern aerosols to the old water-mix sud's, better finish I reckon........

    1. I run the Matra's gearbox on 20W50, which appears to be thin enough in Winter so the motor won't bog down, when it spins up. In Summer I used to run it with some 75W140 gearbox oil that was left over from my Jawa days. But as it's not leaking more with the 20W50 than with the transmission oil, I just use that one all year round.

      For cutting oils: I use diesel (or red) for aluminium and also for light-duty work on steel. Heavy duty stuff I do with a 50:50 mix of water and waste oil. When working with inserts I found them to produce the nicest finish, when used dry especially as the Sandvik inserts are really, really susceptive to temperature shocks and will then fracture immediately.