Monday, 19 November 2012

Christmas Present

V1 Machined Bracket
This year's Christmas present to me is a shiny new lightweight alternator. Not very exciting in itself, but it does give the opportunity for a little engineering - which is a good thing. The new alternator is about 1/2 the size of the venerable Lucas ACR unit that's been on the car since I built it, but all you get is the alternator - no brackets or adjuster & even the pulley's wrong, being the old style single Vee. So I started drawing up a machined bracket, but the cost of having one made, or alternatively the time to make one in Neil's man cave were both prohibitive, although it would've been a pretty thing.
V2 Two Piece Extruded Bracket
 So, back to the drawing board terminal, I did a little Ebay engineering & found some alloy extrusion, with  little thought I came up with a cunning plan to use 1 1/2" x 1 1/2" channel to make a beam, with a shorter piece of 2" x 2" extrusion turned through 90 deg to make the lugs that would mount the alternator. It's not as nice to look at as v1, but at less than a 1/4 of the price, it has it's merits. With the design more or less finalised, I looked at pulleys. The alternator is unusual in having a 15mm shaft, most are 17mm, so that limited my options, then there was the size. The alternator has a "red line" at 18,000 RPM, so I did some sums & with the Zetec having a red line at 7,000 RPM, I needed a pulley no larger than 60mm dia. A company called Brise had a selection, but with prices around £70 they were a non-starter, Burton were offering a steel "Cosworth" pulley at £30, but someone on the SKCC forum suggested a Co. called "Woods" who's catalogue boasted hundreds of pulleys, but only 3 in the right size range. An e-mail to them got prices in the £8 - £10 range - much better.

Then I looked at Ebay again & found a small engineering company selling a 53mm pulley with a titanium nut for £19 - SOLD. 53mm gives an alternator RPM at the engine red line of just over 17,000 RPM, so just within limits. I've ordered the extrusion as well, so some parcels should be coming my way - we LIKE parcels

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