Slipping boom brake on P&H TC440

[joer00]

I bought an old P&H TC 440. I fixed up everything and it basically run incl operating the boom up and down.

A few days ago when lowering the boom it started to run down and before I could do anything the emergency pawl system abruptly stopped it.

There was no load on the boom and just one extension attached (i.e. 20 foot base, 30 foot extension and 20 foot tip).

I was reading in another post (https://www.heavyequipmentforums.com/showthread.php?50349-Manitowoc-2900T) that on some cranes this might happen in wet conditions. That is exactly what mine was, it was after heavy rain and I saw that on the brake drum it was wet and greasy. Also I check the spring AFTER the incident, and stupid me, yes it as at 13.2 cm not the factory length of 11.8 which I adjusted now.

Boom and cables look fine and I can put the boom up BUT The wormshaft got damaged and is slightly wobbling now. After adjusting the spring to factory settings I VERY CAREFULLY tried to lower the boom which worked for a short time but than stopped. Reason is that with the wobbling the teeth hang on the emergency break pawl.

So well I have to replace the wormshaft. Now how to best do this ? I assume I would at first remove the emergency brake pawl and carefully lower the boom. Can the wormshaft be removed without taking apart the whole upper crane part ?

Did anybody do this yet and does anybody have an idea where to get a new (or used) wormshaft ?

Anything else I should obey/do after such an incident ?

 

[joer00]

I am looking at http://constructioncranes.tpub.com/TM-5-3810-288-12/TM-5-3810-288-120171.htm and I might be wrong that the brake was the issue ? The drawing looks to me like the pawls SHOULD IMMEDIATELY lock when lowering and this would activate the planetary to rotate the run the oposite way so the boom gets lowered with the motor power ?

So what made the boom start to go down fast and what made the emergency stop ?

 

[Buckethead]

I am looking at http://constructioncranes.tpub.com/TM-5-3810-288-12/TM-5-3810-288-120171.htm and I might be wrong that the brake was the issue ? The drawing looks to me like the pawls SHOULD IMMEDIATELY lock when lowering and this would activate the planetary to rotate the run the oposite way so the boom gets lowered with the motor power ?

So what made the boom start to go down fast and what made the emergency stop ?

Other than cleaning the greasy boom brake drum, I would not do anything until you get a P&H TC440 manual for your serial number range. (That manual you posted says it's for an M320t, that might not be the same.) The only thing I remember about P&Hs is that that they had a hydraulic control system similar to the brakes of a car. And that system was prone to all kinds of leaks and sometimes the operator would have to pump a pedal or lever to get it to work. Again, I would not touch it without a manual.

 

[joer00]

Never posted and update. The simple reason was that the fiction shoes axles where not lubricated. SO friction was enough on perfect dry conditions but not in rain. Once the boom started falling with the higher drum speed the pawls finally kicked in.

 

[Tugger2]

That boom will run if the hydraulic pressures are not right when you push the boom hoist lever. You need to feel the pressure on the lever ,this may take a couple of quick half strokes if theres air in the system or bad seals. When you engage the boom hoist ,its one control you dont feather,its either in or out. This applies to to most friction cranes . air or or hyd. ,pressures need to be there to either engage the a planetary or sprague clutch in that split second the boom hoist brake is released. Even if the systems are in good shape a boom can run by partial engagement of the control lever.

 

[joer00]

That boom will run if the hydraulic pressures are not right when you push the boom hoist lever. You need to feel the pressure on the lever ,this may take a couple of quick half strokes if theres air in the system or bad seals. When you engage the boom hoist ,its one control you dont feather,its either in or out. This applies to to most friction cranes . air or or hyd. ,pressures need to be there to either engage the a planetary or sprague clutch in that split second the boom hoist brake is released. Even if the systems are in good shape a boom can run by partial engagement of the control lever.

Thanks for the reply, but this is not the case for the P&H crane. Once the break is released and the pawls kick in, the boom can't run. You can even unmount the break and the boom won't run IF the pawls work correctly. As I mentioned in my last post, it is super critical to have those pawl axles lubed and make sure the friction shoes are shimmed correctly so they are fully pushing against the drum.

If anybody has real life experience, I still have issues with the boom. If I tie the boom break spring to what the manual says, I hardly can lift the boom. I f I set it manually until the boom lifts easy, it will slip under heavy load. I still don't fully understand how the break is released when the boom goes up. Must be some directional "thing", i.e. it locks when turning right but releases when turning up. The manual does not specify the "gap" distance of the brake parts on the opposite side of the brake cylinder, maybe this is set wrong on my machine ? I did put new break liners on and re mounted them.

 

[mitch504]

If you are looking for real life experience with cable cranes, read this thread:

https://www.heavyequipmentforums.com/threads/old-conventionals-at-work.71071/

 

[joer00]

If you are looking for real life experience with cable cranes, read this thread:

https://www.heavyequipmentforums.com/threads/old-conventionals-at-work.71071/

Cool, have to add pics of mine there. Thanks for the thread !