Oil line failure - it could be you
Posted by: Mark Drake
Date: July 29, 2013 07:59AM
That’s steam cars for you…
After nearly 3000 wonderful and reliable miles with my 740 Roadster, on return from a brilliant one-week tour of the Cotswolds (huge thanks to Les and Pat for setting this up), unfortunately the car suffered an oil line fracture near the inlet to the engine. As I was driving in very hilly territory, the damage came quickly and irreversibly.
I spent Sunday removing the engine and trying to assess how the failure occurred un-noticed until too late. On the 740, the oil delivery is indicated on a pressure gauge helpfully calibrated with ‘Off’ and ‘On’ sections, no actual pressures; there is no winker (although this would not have helped either). The pressure gauge pulses with each shot of oil and is a fair indicator that the lubricator is working well.
The oil is fed via a chassis mounted, spring-loaded check valve into a flexible, coiled section which then connects to the steam inlet elbow. I tested the check yesterday and it opens at about 140 psi. Most of the time in the steady cruise the steam chest pressure is around 120-130 psi, which means that the oil pressure gauge still indicated a good healthy pulse because the lubricator was still having to overcome the spring loaded check. I’m going to put in a much weaker spring in the check to lift at around 10 psi, in the hope that a sudden fall in oil pressure will indicate a problem. I’m also going to take a closer look at what can be done to ensure a more reliable flexible pipe to the steam elbow to avoid another fatigue fracture.
I’m telling you all about my woes in the hope that I may save someone else from a similar fate. Please regularly check your oil lines for integrity, preferably a pressure test. If you have a pressure gauge as oil indicator then make sure that the check valve spring is only just strong enough to close the check in the thick oil; any stronger and it could mask a problem.
Sadly the cylinder block is unrecoverable - during the restoration I had machined the last of the ‘meat’ from the port faces, with no further opportunity for another go; I know that I could probably add new port faces, but I’m not sure that I can face (ha ha) the effort!
So, if anyone has a 20hp cylinder block in usable condition and surplus to requirements and preferably with valves, then I’m very interested! Please let me know right away, private message would be best, the Club tour at Frensham is only 3 weeks away – so there’s a challenge…
Happy steaming everyone,