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Aug 11, 2011 1:28 am
Aug 11, 2011 1:28 am
Subject: Re: G9 gearbox
Hi Bill
Glad you got the gearbox back together. The problem with the front propshaft are those almost rigid canvas/rubber couplings which are so stiff that they require quite precise alignment. Similar problem to my boat which has its propshaft connected to the engine by two rigid flange half couplings with no flexible coupling and alignment is critical. When lining up my propshaft I use a magmount stand and dial indicator (scriber to start with until it gets near) mounted onto one half coupling and then rotate it round the o/d of the other. This measurement then allows the adjustment of the engine up/down and side/side. The angular alignment is then checked with feeler gauges between the coupling faces but adjusting the angular alignment then requires further up/down and/or the side/side adjustment so the two measurements have to be adjusted together. The problem with the Lagonda in using this method is that the drive flanges are triangular not round and the engine/gearbox are 6"apart . If you had a lathe you could turn up two flanges and drill three holes in each to mount onto the clutch shaft flange and gearbox input flange. You could mount onto the clutchshaft and turn the o/d after drilling the holes to make sure they're true. The clutchshaft would have to be located in some way to stop it moving in and out. Mount a magmount and dial gauge on the gearbox flange and locate the dial gauge pointer on the clutchshaft flange outer diameter and rotate round and hey presto the up/down and side/side misalignments should be determined and the gearbox mounts adjusted to get closer. You could then use an internal micrometer, vernier calipers or a short bar with feeler gauges and measure tthe distance between the top/bottom and side/side which will show angular misalignment which would then require further gearbox mounting adjustments. Each adjustment will get it closer. On the boat with a rigid coupling they ecommend about 0.003" max outrun but with the car having flexible couplings I think that's a bit fine. Have a look at 'Boat propshaft alignment' on Google and it might give a few more tips. It could of course be that the alignment might be OK but the fibre discs or propshaft may be out of balance and a change round to a different position might improve things. My M45 special has an Alvis gearbox and I was missing the front driveshaft so I had a short propshaft made up using two Hardy Splicer joints with a rigid tube. I had to make two converter flanges for the triangular to round and these allowed me to line the engine/gearbox alignment up as above. I relied on the cluch shaft splines for any longituninal movement, as indeed does the fibre couplings. Having a bit more movement in the Hardy Splicers than the fibre discs I am sure puts less load on the clutchshaft bush and gearbox bearings when misalignment is present and chassis twisting take place. It works great and has been raced, hillclimbed and had road use with no vibration or problem.
A bit of a chore to get it right but how much smooother when it's right
Hope you get the problem sorted
Regards
Peter.
Hi Bill
Glad you got the gearbox back together. The problem with the front propshaft are those almost rigid canvas/rubber couplings which are so stiff that they require quite precise alignment. Similar problem to my boat which has its propshaft connected to the engine by two rigid flange half couplings with no flexible coupling and alignment is critical. When lining up my propshaft I use a magmount stand and dial indicator (scriber to start with until it gets near) mounted onto one half coupling and then rotate it round the o/d of the other. This measurement then allows the adjustment of the engine up/down and side/side. The angular alignment is then checked with feeler gauges between the coupling faces but adjusting the angular alignment then requires further up/down and/or the side/side adjustment so the two measurements have to be adjusted together. The problem with the Lagonda in using this method is that the drive flanges are triangular not round and the engine/gearbox are 6"apart . If you had a lathe you could turn up two flanges and drill three holes in each to mount onto the clutch shaft flange and gearbox input flange. You could mount onto the clutchshaft and turn the o/d after drilling the holes to make sure they're true. The clutchshaft would have to be located in some way to stop it moving in and out. Mount a magmount and dial gauge on the gearbox flange and locate the dial gauge pointer on the clutchshaft flange outer diameter and rotate round and hey presto the up/down and side/side misalignments should be determined and the gearbox mounts adjusted to get closer. You could then use an internal micrometer, vernier calipers or a short bar with feeler gauges and measure tthe distance between the top/bottom and side/side which will show angular misalignment which would then require further gearbox mounting adjustments. Each adjustment will get it closer. On the boat with a rigid coupling they ecommend about 0.003" max outrun but with the car having flexible couplings I think that's a bit fine. Have a look at 'Boat propshaft alignment' on Google and it might give a few more tips. It could of course be that the alignment might be OK but the fibre discs or propshaft may be out of balance and a change round to a different position might improve things. My M45 special has an Alvis gearbox and I was missing the front driveshaft so I had a short propshaft made up using two Hardy Splicer joints with a rigid tube. I had to make two converter flanges for the triangular to round and these allowed me to line the engine/gearbox alignment up as above. I relied on the cluch shaft splines for any longituninal movement, as indeed does the fibre couplings. Having a bit more movement in the Hardy Splicers than the fibre discs I am sure puts less load on the clutchshaft bush and gearbox bearings when misalignment is present and chassis twisting take place. It works great and has been raced, hillclimbed and had road use with no vibration or problem.
A bit of a chore to get it right but how much smooother when it's right
Hope you get the problem sorted
Regards
Peter.