cutting a column and saving strength?

[oldgoaly]

If I wanted cut out oval access points in the column so I could get wrenches on the nuts to remove the arms. Would encircling access hole with bar stock and some reinforcement bars be able to keep the columns strength? Trying to make the lower arm have 2 positions. Also just don't want rely on threads in the column. even add some Vinnywheel arms for a super ewheel in the future??? pic might help explain????

[dmc1]

Rather than putting in access holes, I would consider drilling and tapping the appropriate size thread in the ends of round bars. Drill holes through the opposite wall, insert the bars, and weld in place. That would give you captive nuts, and also transfer some of the load to the other side for additional stiffness of the connection.

As an alternative to drilling and tapping a bar, you could weld nuts to the end of pipe or heavy tubing.

Dave Cameron

[oldgoaly]

Dave,
In the middle to the bottom of the column is problem I see after welding column to base. Just don't have confidence in hand drilling holes and tapping them, hand drilling can enlarge a hole vs in a bridgeport. Think I just don't want to strip a thread when everything is attached. Pics of a yoder show how they made access points, that is where I got the idea from. tt

[steamingd]

Options if you have a large enough drill (a mag base drill is your best friend at times):

1) Make up spools with the correct size holes either through drilled, or as an assembly of three pieces welded together, with the center piece a section of schedule 80 pipe, or by using DOM tubing with the correct inside diameter. The spools need to be perhaps a half inch longer than the dimension of the outside to outside of the column. Drill holes large enough to accomodate the spools in both the front side and the back side of the column. Weld the spools in the column with the front side nearly full penetration, and grind the surface flush. The back side welds can be fillets, using the face of the spools as the nut surface. Attach the arms with through bolts or grade 8 all thread.

2) Drill and tap pieces that will be welded flush with the mounting surface for the arms. (could use heavy section nuts also). Drill holes in the column large enough for the threaded pieces to be welded into. Use a nearly full penetration weld, and grind the surface flush after welding. This method does not provide for an easy fix if the threaded holes become damaged.

3) Drill or torch a large enough hole in the rear of the column to get a socket in to hold the nuts. These holes could be reinforced with a scab plate.

To answer your question though, I do think that a round hole not over 25% of the column width with reinforcement at the center line of the column would not sacrifice any significant strength. After the arms are attached, stop blocks or better yet, jack screws could be installed top and bottom to prevent movement.


What is the section size and wall thickness of the column? It looks like the column is rectagular in section, and you are planning to attach the arms to the wide side of the column.

Later,
Dale M

[captainkirk]

What about a clamping plate on the back side and increase the width of the mount for the lower arm so that bolts would go on the outside of the column. Use heavy grade 8 bolts and a braced plate so as to keep it from bowing in the middle, large thick wall channel would work really well.

You could then use a large diameter piece of all thread as an adjuster, just loosen the bolts and adjust the screw for height and tighten the bolts back down.

Just a thought

[TheRodDoc]

Cut a hole in center of tube big enough to get your arm through. try to place it so as to reach as many bolts as you can from that one hole. And not directly behind any bolts if possable. And not in the section between the arms. Round or square.

If arms are weldable add braceing as in drawing to move all bolts to outer part of tube. holes in tube as close to sides as the nut with wrench on it will clear on the inside of tube. This will be the solidest point to bolt to you can get on the tube.

If you want you can weld a renforcment plate around the hole but I don't think it is really needed.

boltonarm.jpg

[Rick Mullin]

I cut 1/2 plate squares and drilled them on the mill for accuracy, Rough cut holes in the column. Laid the column on it's back and built the arms, column, reinforcing plates, bolts and nuts all on the floor. That way I could handle the weight and get everything perfectly aligned. I reached up inside and MIG welded the nuts to the inside of the column. I then welded the plates to the outside of the column. I have had the machine apart several times and it always falls into alignment. While it was lying down, I welded some X braces inside to eliminate torsional issues that I had encountered in my previous machine. The one at the top is great for picking the unit up with a lift to move it. Your son is tall and slim. He should be able to stretch in there. Have a little butter available in case he gets stuck.

I might also suggest that you duplicate the bolt set-up on the opposite side of the column. That way you have the ability to make a double head later on or adapt some other piece of equipment. I have found it to be very handy. I bolted such things as a beader pedestal and am considering a louver press. The side outrigger mounts should also be large enough and drilled to allow for a second set of arms. The footprint of the machine is large so you might strongly consider ultimate multiple usages.

I would avoid cutting access holes. You never know what future purpose the column might hold. Keep in mind that the originals were cast and those holes may have been an important part of the manufacturing process and structural integrity for that choice of material. Kirk can shed some light on the dynamics of casting vrs. plate steel.
Rick

[anders nørgaard]

Originally Posted by oldgoaly

... Trying to make the lower arm have 2 positions...

Terry,
If you have two positions on the lower arm, wouldn't that call for the upper arm to be adjustable as well. I would guess that different distance between upper and lower would influence the hitting force quite a bit

If you need the arm to be adjustable for persons tall or short, I think I would make the adjustability on the column, below the lower arm... just a thought

[bobadame]

You could drill and tap a couple of plates maybe 3/4 or 1" thick and then weld them to the column.

[Rick (madera)]

my thoughts on drilling and taping holes, I would not do it. My feeling is I would want ALL of the shoulder of the bolt to support the weight and take the hammering and none of threads.