Gear box fell off

[Robin2]

In case anyone is interested ...

 

A few weeks ago as I was mooring just before Blackburn I lost all drive from the engine. Luckily the boat was close to the towpath. When I lifted the engine cover lo and behold the PRM 120 gearbox had parted company from my Isuzu engine. Obviously the last burst of reverse was the straw that broke the camel's back.

 

The six bolts that hold the gearbox to the engine had worked loose for some reason. Someone suggested the propshaft had been misaligned but at that stage I had no means to check it.

 

Most of the threaded holes in the gearbox housing (where the missing bolts should have been) were damaged and it looked like a replacement gearbox would be necessary. However after thinking for a while about the potential damage to my savings I remembered that, in my trusty toolbox, I had some J B Weld epoxy that I had bought a few years ago "just in case". This is a high temperature epoxy intended for fixing engines etc.

 

I cleaned out the damaged threads (with my Lidl tap and die set) and epoxied studs into the gearbox. When it had hardened I fixed the gearbox back in place using nuts, spring washers and threadlock.

 

And I made sure that the propshaft is properly aligned - and checked it again two days go.

 

So far so good .......

 

 

A very helpful engineer called Gary Walker called to look at the gearbox on the evening of the problem and could have fitted a gearbox the next day but later I concluded that a DIY repair was possible. If anyone would like Gary's phone number send me a PM.

[Justme]

If they cause problems or you want to do a long term repair check out helicoil inserts.

 

Easy to fit & keeps the same bolt size.

[paulcatchpole]

If they cause problems or you want to do a long term repair check out helicoil inserts.

 

Easy to fit & keeps the same bolt size.

 

I was going to suggest the same, but then wondered if there'd be enough space if the holes are at the perimeter of the casing - any idea on what the drill diameter is for something like an M8 or M10 helicoil? If there were threads remaining, as seems the case, I'd probably have used bearing lock to lock the studs in place. Good point though!

 

PC

[BEngo]

I was going to suggest the same, but then wondered if there'd be enough space if the holes are at the perimeter of the casing - any idea on what the drill diameter is for something like an M8 or M10 helicoil? If there were threads remaining, as seems the case, I'd probably have used bearing lock to lock the studs in place. Good point though!

 

PC

 

Near enough the same as the nominal diameter- the diameter of a thread is the OD of the male thread. What a helicoil does is clean out the old thread and then put a diamond shaped coil of wire into the hole with half the diamond in the part and the other half sticking out as the new thread.

 

N

[Robin2]

The problem was that some of the bolt holes had been partly broken away and I am happier with my solution in so far as the studs are no longer required to screw into the aluminium casting. Putting nuts on the studs just involves steel on steel rather than steel on aluminium.

 

I was surprised that the original fitting seemed to have neither spring washers nor threadlock.

Edited July 5, 2010 by Robin2

[lazyboy]

The problem was that some of the bolt holes had been partly broken away and I am happier with my solution in so far as the studs are no longer required to screw into the aluminium casting. Putting nuts on the studs just involves steel on steel rather than steel on aluminium.

 

I was surprised that the original fitting seemed to have neither spring washers nor threadlock.

 

The original factory fitting should of included loctite thread retainer and a flat plain washer on each bolt. How old is the engine/gearbox.

[Robin2]

The original factory fitting should of included loctite thread retainer and a flat plain washer on each bolt. How old is the engine/gearbox.

 

The boat was new in 2004 so I presume that is also the age of the engine and gearbox.

 

The bolts that originally held the gearbox on included a washer as part of the bolt head and the underside of the washer had grips on it. However I'm not sure how much grip they would have got on cast iron.

[Ian B]

2005 narrowboat ,1300 hours on the clock ,Had the same problem,started about 3 months ago (vetus 1500 & Technodrive)

 

parted company in lock at Wigan,the bolt hole threads were damaged and had to be helicoiled, month later parted

 

again !!, now bolts have been head drilled and wired, fingers crossed OK now