Any body built a knuckleboom loader

[muddstopper]

I have thought about that, but I just aint sure. The bearings are located in each end of the hub (inner/outer). The wheel flange is in the middle of the hub. The springs that the housing bolts to is toward the center of the housing, outside the range of the bearings. I am thinking the housing spindle would feel the same effect of side load whether it is on a truck or on the boom. I dont know any other way to figure it, and I certainly dont know if I'm figuring it correctly. I wish someone with experience with this sort of thing could add their :2cents:

Just to add, I havent measured the bearing spacing, but the distance between the inner and outer bearing on a large truck axle is pretty large, guessing 12inches or more. I can overbuild this by adding a solid shaft thru the middle of the spindle and adding another bearing at the bottom of the shaft if necessary, but that shaft would still depend on the outer bearing of the hub for top support. I dont think I would gain anything by doing so.

 

[mikehaugen]

I have thought about that, but I just aint sure. The bearings are located in each end of the hub (inner/outer). The wheel flange is in the middle of the hub. The springs that the housing bolts to is toward the center of the housing, outside the range of the bearings. I am thinking the housing spindle would feel the same effect of side load whether it is on a truck or on the boom. I dont know any other way to figure it, and I certainly dont know if I'm figuring it correctly. I wish someone with experience with this sort of thing could add their :2cents:

Just to add, I havent measured the bearing spacing, but the distance between the inner and outer bearing on a large truck axle is pretty large, guessing 12inches or more. I can overbuild this by adding a solid shaft thru the middle of the spindle and adding another bearing at the bottom of the shaft if necessary, but that shaft would still depend on the outer bearing of the hub for top support. I dont think I would gain anything by doing so.

I'm no engineer, but the way I figure it, a 40,000lb hub mean each bearing 20,000. If you stick a big arm hanging out, the force(torque) will be applied to both bearings, each bearing individually will see that load instead of both sharing the load.

I imagine a tee bolted to a wall- if the bolts are 6" above and below the part sticking out and you have a 5' arm hanging out with 100lbs at the end, the top bolt will have 500lbs of force pulling out, and the bottom will have 500lbs pushing into the wall. If you hung it from the ceiling instead, they would share whatever load was on it.

I would figure half of the 40,000lbs as a capacity(20,000 for each bearing). So if you have say a 20' boom, and the bearings are 12" apart that is a 20:1 leverage ratio. I would say it could hold 1000 lbs. Now obviously we know they can hold more than their rating, and they may be adequate... I just don't know.

 

[mikehaugen]

If you built a tower and put the entire axle (shortened of course) next to the tower and put a plate on both top and bottom hubs with your pivoting mast next to axle it would utilize both hubs and be of a push/pull force on the hubs and would at least double the capacity. You could probably get at least 270 degrees of swing out of it.

Sorry it probably isn't clear, if I was at my computer I would draw a picture.

 

[muddstopper]

A pic would clear it up, but I think I understand.

My 40,000 lb rearend is rated at 20,000lbs per side. I plan on using just one side. The bearings should be able to hold 20,000lbs, 10.000lbs per bearing, but the spindle at the axle tube needs to hold 20,000lbs also. The bearing should transfer the load to the spindle. Its the spindle i am concerned with breaking off. The way I am looking at it is the wheels on the hub should transfer all weight to the spindle and the spindle transfers the load to the springs, which are located away from the hub and bearing. I will get a measurement to see just how far. If the axle tube is secured at the same point as where the spring was bolted, then it should hold up 20,000lbs. Now I dont know if this is correct, but I am thinking that the top bearing should support 10,000lbs of side force of the boom pulling, The bottom bearing should support 10,000lbs of the boom pushing and the total is still 20,000lbs and that weight is what is transfered to the spindle. Probably doesnt work that way, but that is what I am thinking.

The only way I can think to stiffen it up would be to use the axle shaft bolted to the hub as it normally is, and add a bearing to the other end of the shaft, but I dont really think that will help and only add extra weight. The alterative would be to install a bushing inside the top of the spindle tube to fit a large shaft and then add another bushing or bearing at the opposite end of the axle tube to support the shaft. That would certainly stiffen the spindle and take some load off the bearings. I havent went an got the axle housing yet, so I cant do any kind of measurement to see just how big the id of the spindle tube is. A big truck axle hub is about 8 1/2in OD and pretty thick, 3/4 wall?? maybe more. Spindle tube probably around 6in??? just guesses.

 

[mikehaugen]

My 40,000 lb rearend is rated at 20,000lbs per side.

Yes, I was thinking incorrectly. For some reason I was thinking 40k per side. All I can say is to try it. Trying to come up with exact numbers, to me it will come up short. But as I said it may be just fine because of the de-rating. Also they are designed to hold the load at 70 mph and see a lot of shock loads.

 

[CDN Farm Boy]

As I read along with this, something just isn't sitting right to me...that something is missing in the calculations. I figured out what it is this morning.

You say you are looking to pick up 3000 lbs at the end of the 16' boom. My math tells me that will equate to 48,000 lbs of leverage at the pivot. Never mind the specific design of the pivot, I don't think you'll have enough counter weight in your 7000 lbs trailer to do it. Yes, outriggers will shorten the lever length but have you checked on this part of the math?

 

[bigdeano]

If I were building this, I would look into the idea in post #43. Stand the whole rear axle up on end and use both wheel flanges to mount your crane to. Probably a 1 or 2 ton axle would be strong enough to carry the torque imposed on it. Then you could use the 4:1 gear reduction with a hyd motor to pivot the crane. You wouldn't need a big expensive sprocket.

 

[bcp]

Some ideas:

Home Made Trailer and Crane

Build your own professional Forestry-Trailer!

Bruce

 

[jimmysisson]

Here's an example of a unit for sale near me: 2008 Metavic Forwarding Trailer (might have to copy-paste)
The post does not look as rugged as you're talking about re the truck axle. Might be going back to pipe-in-pipe plus a thrust bearing could be simpler?
Jim

 

[mikehaugen]

A pic would clear it up, but I think I understand.

I spent hours on this computer simulation so I hope it helps. The Yellow would be some sort of post, the black is the truck axle, and the red would be the pivoting mast. Like I said, it won't get you 360 degrees, but hopefully close to 270 or so.