REAR-MOUNTED CRANE

[kthompson]

Aussiebushman, may I ask why you have your tires on backwards with a rear blade turn to pull you may be rotating it to push, but with a large dozier blade on it is reason I am asking.

As to your jib, worked in many aspects of a company who made cranes and many did have jibs on them. One of biggest benefits of them was they allowed some offset for handling lighter lower past say a wall the boom itself would not give the reach needed. But far from an expert on some things mentioned here: have two questions, one myself would be concerned about the load you could end up on the third arm mount if hooked there and the other is could you use a 12 volt winch to life the load? Now I know a winch is not rated for lifting so take that into safety consideration. Then the jib will not be approved by any government agency either, well would not in the USA.

 

[Spanner]

Aussiebushman, may I ask why you have your tires on backwards with a rear blade turn to pull you may be rotating it to push, but with a large dozier blade on it is reason I am asking.

That's so he could justify buying the chains (to the wife).

...
could you use a 12 volt winch to life the load? Now I know a winch is not rated for lifting so take that into safety consideration. Then the jib will not be approved by any government agency either, well would not in the USA.

A small winch can lift a larger load using a multi-sheave block-&-tackle set-up. That may help you. I take it your need to lift is not for height but for positioning?

You might consider scaffold pipe rather than box-section for your arms.

Also, bear in mind, the top link is in the centre of the lower arms and will need a spreader to make a connection to the boom.

As said earlier. Triangles. Triangulate everything in all directions.

You may find an Army Surplus boom at Corrowa (sp?) this week. Or look for an old Holmes-type wrecker crane.

Oi, Oi, Oi !

 

[davedj1]

I meant more like this one:
http://www.tractorbynet.com/forums/...ting/246973d1326844404-boom-pole-ck27-001-jpg

 

[Aussiebushman]

Thank you Dave.

Hope I did not sound dismissive about your suggestion and that my return message explained my thinking. It is always good to get alternative views/suggestions because even if not adopted they often lead to other solutions not previously considered

 

[Aussiebushman]

Just noticed more responses:

may I ask why you have your tires on backward

s

Happily my ex-wife is not involved (she took my 30' catamaran instead). The reason for the tyre direction was to create more clearance between the wheels and the tractor body so chains would clear the sides. Chains are essential due to the excess tyre wear causing them to slip on muddy ground. It was not worth the trouble to change the tires on the rims and in any case, I found info on this site that reversing the treads actually gives better grip.

One of biggest benefits of them was they allowed some offset for handling lighter lower past say a wall the boom itself would not give the reach needed

Also

I take it your need to lift is not for height but for positioning?

Precisely! A 12V winch cannot really be justified because this rig will be used only infrequently and adjustment by moving shackles on chains is simple and free. The tractor is used only on the property - never on public roads so approval is not an issue. Re load, the rig should easily lift a ton or more (the chain block is rated at 1.5 tons). Can't see 3 mm wall RHS bending but if it does, it will be easy to replace. Sure scaffold pipe will do, but I already have the steel RHS - bought for another job but not used

No one commented on my idea of mounting the arms onto the rear blade instead of onto the pins. The problem with the latter is having to make/buy much longer pins to go through the arms of the rear blade as well as the lifting frame OR remove the blade completely it to put on the lifting rig - a PITA The blade is massively constructed so I can't see any issue with support or safety

 

[Dave M7040]

Just noticed more responses:

s


No one commented on my idea of mounting the arms onto the rear blade instead of onto the pins. The problem with the latter is having to make/buy much longer pins to go through the arms of the rear blade as well as the lifting frame OR remove the blade completely it to put on the lifting rig - a PITA The blade is massively constructed so I can't see any issue with support or safety

My thoughts re a rear blade mount.

The 3 pt hitch has no ability to hold the blade down and in some situations this may prove to be very critical. In engineering we are always trying to avoid putting hinges in a structural element. However, I am a mechanical engineer not a structural one so others may have a different opinion. The blade would in effect be a hinge since it is not restrained fully like a bulldozer blade.

Next, having the forces on your tractor applied where it is the strongest is a good idea in my mind. I would remove the lift arms and attach your crane to their mounting pins.

The top link mounting is the one area I am a bit cautious about. The supports for the crane shown in your first posts seem quite close to the crane arm itself and this is not a way to get a lot of support without a lot of stress on the tractor.

Why not a leg which you could swing out from the crane arm and it would sit on the ground with a big foot. Now to do anything to your tractor would have to lift the rear end which is not going to happen.

Having a way to transport your crane to where you want to use it could involve the top link.

When you are done perhaps it is time for a patent

Dave M7040

 

[texasranger556]

The reason for the tyre direction was to create more clearance between the wheels and the tractor body so chains would clear the sides. Chains are essential due to the excess tyre wear causing them to slip on muddy ground. It was not worth the trouble to change the tires on the rims and in any case, I found info on this site that reversing the treads actually gives better grip.

If you swap tires with rims left to right you can keep clearance without running them backwards. The design of the chevrons is to push loose material to the outer edge of the contact patch if the tire starts spinning...exposing more compact earth below.

I remember a show years ago talking about 2 wheel drive monster trucks that run the front chevron tires backwards because they are used only for steering and braking...which makes sense when you think about the forces involved.

I suppose running tractor tires backwards may help with flotation in super soft/muddy areas with no "bottom" to speak of, but then adding thick chains likely cancels out the direction of the tire tread in practical application.

What ever happened with the boat recovery project?

 

[Aussiebushman]

Thanks again guys

Re mounting points

The blade would in effect be a hinge since it is not restrained fully like a bulldozer blade. Next, having the forces on your tractor applied where it is the strongest is a good idea in my mind. I would remove the lift arms and attach your crane to their mounting pins.

I agree with your logic and I'll see how difficult it is to remove the arms. The alternative that I think I prefer is to use the pins on the linkage because if I do that, I can leave the rear blade in place. It is secured with Cat 2 pins that are UNDER the Cat 1 pins. By welding steel sections at about 30 degrees to the bottom end of each frame they will engage without fouling. I concede this is not as strong as you recommend but no worse than using my existing jib

Good point about the angles

The supports for the crane shown in your first posts seem quite close to the crane arm itself and this is not a way to get a lot of support without a lot of stress on the tractor.

A previous suggestion of adding a strut would help overcome that - see new sketch. The black dotted lines represent adjustable chains coupled to the top link housing that fortunately is extremely solid. By placing TWO hang points on the frame, the chain block can be moved - shown at the extreme end in the new sketch

Thanks for asking about the boat recovery. I did mention that all my potential helpers were incapacitated in one way or another so I have been on my own. My brother is coming here in a couple of weeks so he will be pressed into service - everything is ready to go

 

[Renze]

I see a number of large cranes with jibs which have this general design which gives a good angle to support the outer end of the jib.

Dave M7040

Biggest bend moment will be closest to the base, i.e. at the toplink attachment point. Extend the pull rod to the 3pt attachment point, perhaps attach the toplink to the bridge, so the hoist leans back, and adjust the angle in the boom pole accordingly.

You can adjust the ratio between lift force and height, by choosing the top link hole higher or lower.