Why the TS stopped running

[carcrank]

On the third day of the rally my TS failed to proceed about half way to Horsham. I just pulled the motor apart and it seems that the bigend nut came undone and the piston hit the top of the head
pictures attached.

In the second picture you can see the bigend bolt with a bit broken off, I think this was the problem as the nut had no "locking" mechanism.

Also thanks to Neville and the guys for a great rally, well worth going to even though I now have some work to do!

Regards

Mark

[Ian]

Mark, it was good to see you there - no other damage to the motor ?

[carcrank]

That seems to be all, so not too bad really.

[Chris]

Hi Mark
    Sorry to hear of your breakage. Unfortunately this kind of event is not uncommon. I have heard of several similar incidents over the recent past. The bigend bolts are threaded into the conrod and should be quite tight. The nut then goes on the top and should also be tight. If the original design of bolt is used then these are split at the top and the split can be opened up to prevent the nut becoming loose. In spite of this it is not unknown for the nut to become loose and the bolt also to become loose. Sometimes the resultant clatter can be picked up before the bolt breaks. If one bolt or the other does give way the result is usually a bent or broken conrod, and a damaged piston. Sometimes the cylinder barrel is also broken and even the crankcase can be wrecked and the crankshaft bent. It sounds as though your damage, although bad enough, is not as bad as it could be. It is also known for the bolts to give way without having become loose also conrods to break without warning and pistons to break up similarly. It is difficult to suggest any precautions to take against these events except to ensure that the engine internals remain effectively lubricated and to be aware that these machines although having a quite lively performance are in fact in the main over 85 years old and probably subject to metal fatigue and wear. Over exuberant use of the throttle lever is inviting disaster when you have conrods not much more than 1/8" thick and are running with original worn cast iron pistons. Good luck with your repairs. Chris.