Removing a gib key, especially those really old stubborn ones, has been a topic of discussion on the Stationary Engine List many times and there are numerous ways of approaching the problem. They all involve two things: loosening the key (which is probably seized tight) by heat, penetrating oils or solvents, etc.; and removing the key with either a wedge and hammer, a puller of sorts or a percussion/impact/slide hammer to shock it loose. Of course, if all else fails, you can drill it out.
My little Ruston & Hornsby PT was leaking oil from the timing gear cover and the two bolts (1/4-inch countersunk machine screws) that needed to be tightened were directly behind the flywheel rim with no way of reaching them. The flywheel was going to have to come off.
I restored this engine two years ago so I knew the gib key would not be too tight or rusted and would be a simple matter to remove. But I was loathe to use a wedge or any method that involved pressure against the flywheel, as this could have damaged the paintwork.
The design for a gib key puller I came up with is very simple and can be made by anyone with very basic tools (welder, files, drill press and hacksaw - a lathe is a great help but not essential). The materials all came from my scrap box.
I have not put sizes to my drawing for obvious reasons. This one was made for my Ruston, but will also work on my Wolseley engines or any engine with a crankshaft diameter of 32 to 38 millimeters (about 1-1/4 to 1-1/2 inches). Just remember the inner diameter of the ring (Ring A) must be big enough to fit over the crankshaft plus the height of the key (not the key's head, the slot fits over that). The two adjusting bolts align everything for a grip on the gib head and a straight pull. Remember also that the big bolt that exerts pressure will work best with a fine thread. And don't forget to oil it before use. The tool is robust enough to take a hammer blow to shock the key loose, but also strong enough to exert steady pressure for a more gentle release. (Of course this depends on the materials you use as well as your welding skills).
Since making and using this one, I've had ideas for improvements. One is to make a universal one-size-fits-all puller. This would be easily made by not welding the front ring in place. Instead, just cut a slot through the pipe to allow insertion of a piece of bar stock and a means of holding it in place to grip the gib key head. Any ideas for improvement will be graciously accepted.
I'm not trying to re-invent the wheel; remember, my initial idea was just to make a puller that would not damage the paintwork on an already restored engine, but this puller does seem to have great possibilities.
I do realize this puller is not the answer to every gib key problem. There has to be enough space between the head of the key and the flywheel to insert the tool. Also, if the gib head has broken off there are other problems, but this tool would be able to grip a welding bead on the end of the key.
At the end of the day, this puller will do a great job in most cases, but you will still have to loosen a stuck key with penetrants or heat. I think this tool - if strong enough - will also break the head off a gib key that is really stuck, so just use your head and be careful. It will certainly work better than a wedge and will do less damage to the surrounding old iron.
Jerry Evans is a Stationary Engine List member from South Africa. Contact him at: firstname.lastname@example.org; www.oldengine.org/members/evans/index.htm