Straightening a 9 inch Diameter Rudder Post.

jackie schmidt

jackie schmidt

New member
I have mentioned that one of the services we offer is straightenning things that get bent under Boats. This could be either the Prop Shaft or a Rudder.

One of our customers docked a 3000 HP Push Boat yesterday that had a bent Rudder. The Shipyard cut the blade off, and sent the Rudder Stock over for us to straighten. Here are some pictures of the Stock, and the Straightenning Rig we use.

As you can see, all of ththe tonnage is maintained in the Straightenning Rig and the Stock. The arms are adjustable so we can put "precision tonnage" at any point on the piece. No force is exerted on the Lathe what so ever.

We designed and built this rig. This one is 500 tons. We have a 150 ton, a 300 ton, and a 750 ton. You can see it in it's storage stand behind the big Lathe.

The whole operation took 2 men around 3 hours.

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sdean said:
Hey Jackie. How far back do you stand while you are putting pressure on the stock?
Click to expand...

We stand back behind the big Lathes headstock, keeping eye on the pump's pressure gauge. When dealing with this degree of tonnage, you don't Want to be standing by the piece.

We warm the Rudder Stock just enough to take the chill off.
 
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Straightening Stuff

I gotta give ya credit on that set-up..... ingenious... and crafty..... after pressing you re machine...???
bill
 
Jackie your amount of God given common sense is truly a blessing. When I was young and I mean real young and around twelve I was continualy taught if there is a will there is a way. I was also given the ability living on a farm / dairy to put it use. Sometimes with success and at other times not and what a positive life learning experiance. The feed wagon at that time would constantly have the nuts on the live floor coming loose and would always end up in a big train wreck. This was pre lock tight days and my uncle who I lived with at time got into my aunts sewing kit. Wrapping the bolts with sewing thread before screwing on the nuts finaly curred that issue and I always reflect back on it as just being God given common sense and the will to find a solution to the problem.

Yours Sincerely
John Louis
 
bill larson said:
I gotta give ya credit on that set-up..... ingenious... and crafty..... after pressing you re machine...???
bill
Click to expand...

It depends. If we can get the journal area straight enough, and it's not too deformed, they can stick it right back in. The worst case is we reweld the Stainless Steel on the journal and re-machine it.

This one, as bad as it was bent, did straighten up close enough in the journal area. Since the boat had to go, they welded the blade back on and used it like that.

This type of work requires quite a bit of skill, and judgement. It borderlines on an artform, knowing just where the bend originates, and how to finesse the straightening rig to apply just the right tonnage.
 
dmort said:
Wouldn't bending it that much weaken the shaft?
Click to expand...

We can judge how much tonnage it takes to straighten the Stock as we work it out. If suddenly it starts moving with considerable less tonnage, then we can make the judgement call as to whether to use it.

We have a gauge on the pump graduated in 50psi increments up to 10,000 psi. This allows us to put a very exact amount of tonnage where needed.

Of course, if any fractures appear, we have the option of cutting it down and submerge arc welding it back. If they are too deep, it's dead.

As I stated in another post, this type of work requires considerable skill, and judgement on the part of the person doing the straightenning. Over the years, we have mastered the process.
 
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Amazing. What was the runout when you were done? Was any final machining done in this case?

Thanks for sharing - I really love seeing this kind of work.

GsT
 
GeneT said:
Amazing. What was the runout when you were done? Was any final machining done in this case?

Thanks for sharing - I really love seeing this kind of work.

GsT
Click to expand...

Often, we can get it back to where all of the criticle machined surfaces are within thousandths of an inch. But sometimes, the piece just will not cooperate, and that means re-welding and re-machining any surfaces that are runnng out too much.

We do straightennng on a daily basis. It is a part of the rebuild of just about any shaft.
 
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