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Catch Can

  • wadewilson
    1 month
    So the weather here has been a bit shite the the last couple of weekends and a recent post about catch cans had me thinking about them and how hard would it be to turn one up on the lathe? The other question was "do I really need one?". Well I am sure that we could all debate this ad infinitum but the reality is there is always a small bit of "varnish" build up on the inside of the throttle body at every service and since I had some time up my sleeve why not make one and see how it goes? I fit these regularly to diesel cars and some seem to need them while others seem to be fine without them. Worst that can happen is I have wasted a bit of lathe time and had some fun doing it.

    Had a bit of a scratch around in the steel off-cut pile and found a piece of mild steel about six inches long and two inches across. Perfect. Threw it in the lathe and roughed it down to the approximate size I wanted. Next was to bore out the main body and cut a thread into the base of it to accept the main shaft.

    The main shaft is just a 16mm bolt with the head cut off and bored through the center from one end to the other and then cross drilled for the gasses the flow through. I do not have a photo of the cross drilled hole so you will just have to believe me that I did do this. I then machined the nipple to accept the quick connect fitting. This is not really needed but I have them laying around so why not use them?

    The lid was drilled for the vent holes and bored for an interference fit for the main shaft. The lid was then heated up and the shaft put in the freezer so when put together they had a bit of play but when cooled and warmed respectively they formed a firm joint. This was then brazed just to be sure. I wanted to silver solder it but had none on hand nor did our local tool shop. Brazing gives a good mechanical joint just does not look as good as silver in my opinion so I brazed it on the inside where it will not be seen. I had already machined a chamfer on the inside of the hole in the lid for the bronze brazing material to flow into and give a good fillet all the way around.

    One other thing I did not take a photo of is the O ring around the inside of the lid that the lip on the base seals against to stop any potential leaks down the side that would look unsightly.

    I could not make up my mind as to whether I wanted a polished or brushed finish so I polished the base and brushed the lid. Polish has won and the lid will be polished to be the same as the base. Have also been wanting top try out a metal blackening method using beeswax and linseed oil so this may be the way I go for the final finish.

    Final size is about 1'5 by 2.5 inches plus the nipple for the quick connect fitting. I have made the nipple a little longer than necessary so that when fitted in the bike the hose will run up over a couple of things without having a tight kink in it.

    For a filter material I will be using a sintered bronze material that we use on the inlet of 12 volt compressors. This stuff has a really good filtering capability while still having a good flow rate. This should allow it to breathe while catching the oil, after all that is what this is all about. Had also thought about using stainless steel wool but will see how the bronze works first.

    Anyway, just thought I would share for everyone.