I first tried welding up the very worn slot, turned it down in the lathe and then tried milling out the slot. But the metal was too hard so I turned the shaft and milled out a new slot.
This was OCRed (Using Adobe Acrobat 9 Extended) from this month's Flat Four amazingly without any correction. I have left one (%= 1/2) error in so you can see what might occur.
WORKSHOP OBSERVATIONS
Vic Morrison
WATERPUMPS RE-VISiTED
There has been a few cases of premature failure of waterpumps after about a year since being fitted with new seals and bearings etc. so a closer look was needed. I had reconditioned the waterpump from Tony Hawkins' Javelin about a year before so was horrified to receive a call from Tony telling me there was water pouring from the back of the pump. Just a fortnight earlier Garry Corner had to do his pump again having found the seal had split so expected to see the same when I pulled Tony's apart but in this case the two halves of the seal rubber had completely separated which leads to the question as to why.
New seals were sent down overnight from our Jowett Parts (excellent service as usual) so could study these which look very good and compare with an original one that Bryan Spragg had given me. If you sit them on the bench side by side the new ones being supplied now are about 2 to 3 mm taller than the original. Also the coil spring in the new seals is much stronger and a heavier gauge than before so they don't compress as easily.
Now as has been documented before (but sometimes forgotten -I had -) these new seals should not be compressed more than 2 to 2 % mm but unless some machining is done, when the waterpump is bolted together the seals are fully compressed and the spring coil bound as a result, so the new seals are very much overstressed leading to a very short life. So how do we solve this problem?
In the case of the front seal it is easy to see when the face of the impeller contacts the seal. Place a tube of some sort, the same length as the boss of the front pulley and by winding the nut on, take note how far the shaft comes through the front bearing race before stopping against the shoulder on the shaft. If it is more than 2 % mm then the difference has to be machined from the impeller, or the housing bored out by the same amount. I chose to machine the impeller (much easier) on Tony's pump by 2 % mm. This then gave the required nip or crush of 2 % mm of the seal. Because you cannot see the rear seal more care is required. Clean the front hOUSing where it enters the main pump body so that it fits together easily. Fit the rear seal and then push the front housing (the shaft must be tightened up to the shoulder) with the gasket in place of course and you should feel when the impeller touches the seal. Now measure the distance from the flange of the front housing to the face of the main housing where it bolts up to. Note this measurement and take 2 % mm from it. This is the amount that has to be machined from the back of the impe!ler. In Tony's case it needed another 2 Y, mm from the back of the impeller which meant that I had reduced the original distance from the front and rear face of the impeller by Smmfln other words, if I hadn't done this the seals would've been crushed by 5mm, twice that of what is recommended.
For the fina! assembly seat the seals in their housings with sealant and a smear of vaseline on the face of each seal, then bolt the pump together. When turning the pulley there should some resistance but not excessive.
I gave the pump back to Tony to fit while I crossed my fingers and waited for the phone call. It came in the affirmative which was a relief. It made the National Rally OK so now time will tell as to how successful we have been.
