opinions on tab washers and props ??

[LeonF]

When I upgraded my prop some eighteen months ago, I thought the washer was bent when I removed the old one, and threw it away. Now realise that this was intentional. However the yard put on the new one, with no washer..it is a tapered shaft with a keyway, and a domed nut with no split pin. Removing the prop this year was quite a job, had to use a hydraulic puller in the end. My question is whether a washer is neccessary..I get different opinions. Some say that with a tapered shaft it is not essential, some that they wouldn't go without as if the keyway broke and the prop spinned I could unwind the nut and lose the prop. Also, which way should the tab washer be bent...backwards towards the prop, forwards towards the nut, or one bit forwards and the other back ?? Ta

 

[Topcat47]

The tab washer should go between the nut and the prop. One side bent around the nut to stop it spinning, the other around the prop boss. An alternative is to use a shakeproof washer but I'd rather put my faith in a split cotter pin through the nut and shaft myself.

The tapered shaft and key is to locate the prop radially (stop the shaft running inside the prop boss), the washer to stop the nut comming undone.

It's not uncommon for tapered shafts to cling to the bore of the prop such that a hydraulic tool, heat or even both is needed to remove it.

 

[philip_stevens]

If the tab washer is anything like the one on my prop - and I have just made a new one from brass sheet - then there should be two tabs, and a short inside tab.

The short inside tab is bent at right angles to the washer, and this locates in the keyway. One of the other two tabs should be used to go over a flat on the nut to stop it undoing. The reason for two tabs, is so that you can use one of the other, as they are 90degrees from each-other, and the nut has 6 sides (hex).

If you make a new washer, the outside diameter should be the same as the o.d. of the nut, and the inside diameter should be the shaft thread o.d. The inside tab need only be 2 or 3 mm long to locate in the prop keyway. The tabs can be 8 to 10 mm.

The i.d of the washer I have made is 19mm, the o.d. was the nut o.d. across the peaks of the nut - the nut size was 33mm across the flats.

 

[LeonF]

Thanks guys. What is a shake proof washer ?? I am pretty certain that the previous one didn't have an inner tab...seem to remember that it was just a circle with the edge bent over which was what made me think that it had been damaged by something catching around the prop. A friend has made me two very oversized washers with the correct i.d. so I can try and shape it to serve it's purpose. What is the easiest way to cut brass plate ?? A hack saw, jigsaw or a set of metal pincers ??

 

[philip_stevens]

I cut the o.d. with a hacksaw to give a rough shape, then used a fairly course flat file to round it off, and a smaller file to make the tabs. For the i.d. I used a cone cutter with stepped diameters to get it to 19mm. For the inside tab, I cut down with a junior hacksaw blade put through the hold and put back onto the frame.

To bend over the inside keyway tab, I put the washer into a vice with about 3mm of the tab cut showing, and gently tapped it 90degrees with a small hammer and a brass drift. This inside tab should be the same width as the keyway in the prop.

Ideally, cut the i.d to about 1 or 2mm short of the size, cut the inside tab and bend it over, then open out the i.d. to the size you want. This will allow you to get a bit longer inside tab.

A shakeproof washer can be either a stared washer, or a cut washer which is in a very slight spiral - will not lay flat. If you use a nyloc nut, these should only be used once.

 

[LeonF]

The friend who made me two washers never queried the size and in error I asked for an OD of 17cm...really meant 7!! However this meant that I could cut two nice tabs, and it is all fitted and done. Just need to keep an eye on it I have been told, as the washer is brass and the prop and nut are presumably bronze. Next time I will try and get the washer made in bronze. Thanks again guys.