Articulated Arm Holder

[sanddan]

Great project, just found it and looking forward to further updates.

The sticking could be due to the aluminum housing. Both aluminum and SS are "grippy" materials, the ease that they gall in threaded joints is a common example. Maybe try making the housing out of reg steel as a test.

I made a set of arms using the plate method with a locking bolt at each joint. It works ok but I used steel for the plates and hard ball bearings for the pivots and the joints don't lock as easy as I would like. I think for that design aluminum for the plates works better as the aluminum grips the ball bearings better.

 

[rwm]

Sandan- I did see the arms you made. Part of my inspiration in doing this! I tried the ball bearing idea and it failed. No improvement. I think you are correct that the main friction issue is between the Stainless wedges and the aluminum housing. Before re-making the housings I will try polishing up and lubricating these components.
Robert

 

[TOOLMASTER]

spring between wedges

 

[dlane]

Looks good , just wondering if that mag base holds the arms up when extended?.
I made one that is a little smaller for holding small parts while welding and wish the mag was stronger.

 

[rwm]

Spring between the wedges is an excellent idea and one I considered. The problem is there is very little room to put one. I could machine pockets into the wedges.
The good new is, after polishing and lubricating the joint surfaces the wedges release just fine! It's a success!
In answer to the strength of the base:



The joint at the base will slip before the base breaks free.

Here are some test shots:







I call this myth plausible.
It will not hold a lot of weight but it was not intended to. If I stay close to the base the weight capacity is dramatically increased as you would expect. This will be very useful. I plan to leave it attached to the work area for immediate use when I need a helping hand.

Robert

 

[brav65]

Great project, do you plan on any drawings? It would be nice to know the specifics of the rationale s you used to size the various components.

 

[sanddan]

Great project, do you plan on any drawings? It would be nice to know the specifics of the rationale s you used to size the various components.

I second this.

I really like how this turned out. It would be a great project to do.

 

[Firestopper]

Nicely done Robert. That "third arm" will come in handy.

 

[rwm]

I don't have a good program for making prints. I could certainly provide dimensions or some hand drawings.
I might consider some small changes: You could do 12" arm segments. 14" may be more than necessary for most jobs. I would enlarge the elbow diameter to 2-1/4" so you could use a 1-1/4" wedge. Then you could cut a 35 deg angle which would release nicely.
R

 

[rwm]

3 lb gear test:



R