Crank Pulley problem

[Doherto]

This is going to blow your minds as it has mine. I removed my crank pulley to have an additional pulley added to it as I am trying to fit Air Conditioning to a Daimler V8 250. I pulled the pulley off initially without too much of a problem and then replaced it many times, without tightening, as I measured everything to try to align a compressor to it. Now the pulley has been away and had a PK4 pulley fitted to it, I tried to re fit it to the crank. IT WILL NOT FIT BACK ON. I have measured the crank at 35.03mm and the hole in the pulley at 34.8mm No way it's going to fit but WHY, HOW. I don't expect many replies to this but I have no idea how and why this is happening and cannot think of any mechanical reason or solution. The easy solution is not possible as I cannot have the pulley reamed out as it's a taper shaft. Yes it's the original pulley before someone suggests it was swapped when away.

[Dave Eynon]

Have you contacted the company who modified it as their method may shed more light onto how it has happened?
Dave

[Doherto]

Dave, sorry I should have clarified that. Yes, I spoke to the engineering company and they confirmed that the pulley was clamped on the outside and the centre bore not touched. I'm back in the garage this afternoon pondering the problem again but not hopeful of finding the reason or the solution. Tony D

[Dave Eynon]

Has the "clamping" process been so extreme that it has reduced the original bore? Industry often use heat to expand pulleys on to shafts, or conversely freezing to contract. That way making an interference fit easy to assemble. It looks like you will need the services of an engineering shop to re-machine the pulley centre.
Dave

[Doherto]

OK spend another few hours scratching my head again. I have measured my crank at 34.91mm and the hole in the pully 34.8mm ( measured each many many times) How I have this situation I have no idea but at least I have now stopped trying to rationalise it and started to look for solutions. I have spoken to Jonathan at J and E Engineering in Crawshawbooth ( specialist Daimler Engine engineers) and at least have found out that the pulley IS NOT tapered and so can be reamed. Jonathan is not too happy to do it but cannot believe the situation as well. I will take my pulley to him on Monday and try to fit it to other cranks he has in his workshop and then find the best solution. Next update on Monday evening. Tony D

[JimMann]

Hi Tony, before visiting the engineering shop, I would follow up on the suggestion from David E regarding the heating / cooling solution. Take your original pulley and immerse it in a bath of boiling water for 5 minutes. Lift it out - using tongs / pliers and then wearing gloves, attempt a fit to your crank. Be prepared to put it on in the correct location / orientation, as it may not slip off again so easily without further heating in-situ, using a torch of some description.

The size differential is in the 0.2mm range, so it does not have to expand / contract much to achieve the correct fit, without extreme measures.

Jim Mann

[Doherto]

Jim thank you for your reply although I have tried heating the pulley as I have a blow torch but could not freeze the crank as I did not have the product to do that. I think I prefer the reaming though as, you never know when I may need to remove it. I have experience of snapping a pulley in the past and have heard of many others having the same experience. Tony D

[piman]

Hello Doherto,

a crank pulley should not need to be heated to fit it, that only makes it more difficult to remove at a future date.
Perhaps you will have a better idea if you have now been to the engineers?

Alec

[Doherto]

Problem solved. Went to J and E Engineering to speak to Jonathan. Rather that look into the bore for a problem first, as I did, he looked on the outside. Although we could not feel any burs or clamping marks he, and then I, could clearly identify where the boss was clamped for machining. I thought that a metal bore with the walls about 8mm thick would not compress but Jonathan confirmed that as it was just cast metal, it could be easily done if over tightened in the clamps. He reamed the first 10mm of the bore so that it fitted onto a spare crank he had and yes when I returned home it has fitted nicely on mine. The picture somehow clearly shows the marks but they are not as visible in real life. The Air Con project continues. Tony D