What next?

Hi Kim

I am sure you have tried them but have you looked at the larger pc fans used by overclockers? Such as the YS-TECH FD1238 120mm Fan - 4 Pin (FG-004-YS) these can be puchased from

and have a output of 125CFM. The usual disclaimer.

Stuart

but I am currently veering

Kim, What ever you do please dont make a fan, not only it will it be not much more efficient than the CPU fans, you will need to balance it in two planes and we dont want to read in the papers of a man in the Bristol area with a fan blade in his head do we. Thers got to be a scrap car of 60-70's ilk with your fan on it.

Martin P

Well, that's Sod's Law in operation, isn't it? I had a look at the Vee 4 this afternoon, offering up the Lucas mag to the platform. It is anti-clock at the drive end and would do the job. However, circumstances soon overtook me - scales dropping from the eyes, as it were.

I stripped off the drive components and cast up a drive dog in situ, direct onto the mag drive shaft, trapping a bolt in the plastic metal. You can see the result commencing with

and the next eight photos. It was only slightly more difficult than it sounds. When mounted, the taper on the drive shaft does not drop into the drive dog, the armature bolt head being then in contact with the drive shaft. So it was necessary to cast a dog that was driven by the bolt head. It's not a lot of area, but there's not a lot of torque there, either. Now the first one is done, I might well experiment with a shouldered variant, a bit more tricky to cast, but should be easy enough.

I must own up to dimness as I have come to the conclusion that the engine requires two magnetos of the same hand rotation, both clockwise at the drive end. I stood and stared at it, waving my hands in the air in silent confusion as I ran though it again and again, but there is no doubt. I now feel very foolish and cannot now see, of course, how I came to make the mistake. Both are patently driven from a single vertically displaced bevel gear, so how could they possibly be of opposite hand rotation?

Silly me. Never mind, looking on the bright side, I've restored two other engines whilst I was stalled on the vee4!

As I already have two Air Ministry spec BTH MA2 mags that will fit - one, albeit, sans the proper pick up brush holders, but they will no doubt turn up in due course. I'm amused to note that the pickups that it currently wears are neatly made of wood with glued-in pickups from an earlier age! It has, naturally solved my "What next?" dilemma and I'm now seriously considering the cooling problem. I have a multi-bladed fan from a Land Rover Kenwood set that is a bit too big, but can be adjusted to fit in the space available.

Whilst talking about the magneto drives, might I point out the elegant and infinitely variable timing adjustment. You'll have noticed that the drive dog fits into a rubber collar which in turn fits into a bronze sleeve. The whole assembly is a sliding fit into a steel cup which is driven by the engine. The bronze sleeve is split and a tapered bolt with tapered nut is tightened in order to expand the bronze sleeve so that it grips the inside of the cup like a drum brake.Very pretty engineering - it is this kind of solution to a problem that draws me to aircraft equipment.

Off to cast up another drive dog now - all keen and bushy-tailed!

Regards,

Kim Siddorn

Flicking the mag last night led me to think that one side was not as eager as it might be, so I removed the pick up brushes to find that - as I have often discovered before - that some fool in its past has tried to remove the armature without first taking the brushes out, thus breaking the sides off the slip ring. Flicking the armature made sparks jump to the bearing shim just as I'd expected.

I have no problem with this and have frequently repaired them in the past. I made up a ring of polythene sheet - in this case from the lid of a McVities choccy digestive tube! - and glued it in place where the side of the slip ring had been. Polythene is an extremely good insulator and a piece only just thick enough to hold itself up will insulate from an HT spark of higher intensity than a fifty year old magneto is ever going to produce! Usually, I use hard set Araldite, but as I had the Plastic Metal to hand and read the instructions to find that it was a VERY good insulator, I used that. It works just as well and sets hard in ten minutes.

A wipe off during re-assembly revealed that the mag appears to have seen little service as the slip ring isn't grooved, the points cam only slightly marked from the running heel and there is clean grease in the bearings.

Regards,

Kim Siddorn

You probably know this but the slip ring is an early thermoplastic. It can be easily and safely removed with the aid of a hot-air gun. ttfn Roland

That's right Roland, but I am mean, mean, mean and didn't want to replace the slip ring (currently £25 & upwards, I believe) when I could fix it in the warmth and comfort of me own 'ome whilst watching "Without a Trace" - and for the cost of a little resin! ;o))

Anyway, I do love to fix things, so satisfying. I have, in the past, fixed a cracked and guttered slip ring, filling the crack with Araldite and filing the running face smooth with a square file. It did some tens of thousands of miles thereafter & was on the Velocette when I sold it.

Regards,

Kim

"Roland Craven" wrote

Indeed I did Tom! ;o))

Regards,

Kim Siddorn

Perhaps you meant brush holders?

Tom