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Oct 25, 2015 9:12 am
Oct 25, 2015 9:12 am
Subject: Re: LG45 Engine Mountings: Assessment and Replacement
Mark,
I had been assuming your plan was to remove just the engine mounts with the rubber bushes. I don't think removing the brackets to the chassis makes it any easier. The slotted nuts for the front chassis brackets are on the outside of the chassis so not too hard to get off, however the brackets are trapped there as you cannot get them out without raising the engine.
With the rear brackets, as you point out, they hold the big wing mounting boxes on the outside of the chassis. You may have noticed there are thick aluminium spacers between the wing box and the chassis. Unfortunately these are not fixed with regular bolts. There is a slotted nut on both ends. What you can't see is that they are double ended bolts (ie like a stud with a hex head in the middle). The hex bit is recessed in the aluminium spacer. You either have to remove the whole wing box to get a spanner on it (And that means the wing too as the bolt is trapped there unless you can pull the wing box outwards and you can't do that with the wing in place.) or try to undo the inner slotted nuts and hope the bolt doesn't rotate. You could put a spanner on the other slotted nut inside the wing box but you will not get the bolt right out without removing the wing box. There is also a risk that the nut on the wrong end will undo, then you're stuck (there isn't enough bolt to get a lock nut on to hold it).
If you do manage to get them out and replace the rubber mounting bit you can't tighten the bolts as you need the adjustment provided by the slotted holes to get the engine lined up. So you're still faced with getting split pins in with the engine in place - with the added problem of getting the split pin holes lined up.
I would suggest removing the engine completely and then make up a jig that has the main bolts attached that is referenced to the chassis. Remove the jig. Replace the necessary parts. Then replace the jig and tighten the nuts plus put in the split pins. When you put the engine back in the main bolts should, hopefully, line up and push back in. Then align gearbox.
David
Mark,
I had been assuming your plan was to remove just the engine mounts with the rubber bushes. I don't think removing the brackets to the chassis makes it any easier. The slotted nuts for the front chassis brackets are on the outside of the chassis so not too hard to get off, however the brackets are trapped there as you cannot get them out without raising the engine.
With the rear brackets, as you point out, they hold the big wing mounting boxes on the outside of the chassis. You may have noticed there are thick aluminium spacers between the wing box and the chassis. Unfortunately these are not fixed with regular bolts. There is a slotted nut on both ends. What you can't see is that they are double ended bolts (ie like a stud with a hex head in the middle). The hex bit is recessed in the aluminium spacer. You either have to remove the whole wing box to get a spanner on it (And that means the wing too as the bolt is trapped there unless you can pull the wing box outwards and you can't do that with the wing in place.) or try to undo the inner slotted nuts and hope the bolt doesn't rotate. You could put a spanner on the other slotted nut inside the wing box but you will not get the bolt right out without removing the wing box. There is also a risk that the nut on the wrong end will undo, then you're stuck (there isn't enough bolt to get a lock nut on to hold it).
If you do manage to get them out and replace the rubber mounting bit you can't tighten the bolts as you need the adjustment provided by the slotted holes to get the engine lined up. So you're still faced with getting split pins in with the engine in place - with the added problem of getting the split pin holes lined up.
I would suggest removing the engine completely and then make up a jig that has the main bolts attached that is referenced to the chassis. Remove the jig. Replace the necessary parts. Then replace the jig and tighten the nuts plus put in the split pins. When you put the engine back in the main bolts should, hopefully, line up and push back in. Then align gearbox.
David