Broken Oregon 511A Spring

[Wood Doctor]

The lift spring broke today and sounded like a 22 rifle when it did. After it snapped, the grinding wheel fell dead down on the saw chain and caught me by surprise. Quite a shock.

I ordered a new spring from Tecomec and it should arrive in a week or so. Meanwhile, I thought maybe I could make a temporary repair so that I could keep going. I've got a dozen dull chains backed up. So, I thought perhaps I could use a door spring or big rubber bands to pull it back up and let it down. For several reasons, that failed.

Then I remembered that gravity might help. I added an 18" long hardwood board, about 1" square to the back of the bench mount platform that I use to hold the grinder, using a 1/4" bolt so that I could easily position it. Then I attached a rope pulley to the end of the board with a screw eye. Finally, I tied a 5-lb weight to the lower end (an old splitting wedge) using 1/4" twine and tied the other end to the sharpener's handle. Here are three Pics that show it all. The left Pic shows the sharpener all the way up and the center one shows it in the sharpening position:

In the sharpening position, the 5-lb weight is about a foot off the floor. This works so well that I almost wish I could cancel my order for the new spring. The reason is because the force supplied by the weight is constant as the grinding wheel drops down. This is really comfortable as you work. The spring, on the other hand, increases the lifting force as the grinding wheel and motor drop down. Also, I doubt that this mechanism I made will ever break. The $10 spring already did.

WDYT?

 

[eric_ssi]

Interesting... I may steal that idea. Those springs are junk and I tend to keep spares around. When I have to wait for a replacement to arrive, I use a black bungee-cord and a bit of starter rope to suspend the grinder arm from an eye-bolt in the ceiling. Almost the same effort as the spring, but I like your idea better.

 

[Wood Doctor]

Interesting... I may steal that idea. Those springs are junk and I tend to keep spares around. When I have to wait for a replacement to arrive, I use a black bungee-cord and a bit of starter rope to suspend the grinder arm from an eye-bolt in the ceiling. Almost the same effort as the spring, but I like your idea better.

I tried a similar version of your bungee cord idea before I came up with this design. Once you get used to the constant force, it's almost addictive. Plus, you can easily control the amount of the force holding back the wheel. Just add or subtract weight from the cord.

I suppose it's a matter of taste or personal preference, but those darned springs keep snapping and when they do, you can lose a sharpening wheel rather easily when it bangs down on the chain.