The Hoisting Cart, part 3: The Jib Housing

 For those unfamiliar with this term I keep using, a "jib crane" is one equipped with a (typically) flat boom, one end of which is fixed to another support such as a wall or mast.  There are a half dozen or more sub-types...

 In the case of a mast, a portion of the boom Usually projects rearward past the supporting mast, with this rear end being secured, through a housing or simple tension members, to a bearing on the mast.

 In those designs, the useful part of the boom is always longer than the rear part, so the rear parts always see some multiple of the load.  This combination essentially tries to bend the top portion of the mast when the boom / hoist is loaded.  The mast must be strong enough to withstand the load overall, and the local material thickness must also withstand the concentrated load of the jib bearing.

 By way of illustration, to the right is a mockup of how mine is arranged.  My boom is just a two by four... I just, it is a 1.5in x 3in steel rectangular tube, 36in long.   The rear part extends 12in back from the center of the bearing, thus it creates a 3:1 lever.  More on the boom in Part 4.

 My jib housing encloses the mast, but does not use solid sides to restrain the boom.  Instead, I fabricated two straps, 0.75in x .125 CRS material, with heavy eyelets at each end (to prevent bolt holes from distorting over time under 600 lbs of force; 400load x 3boom ÷ 2straps)

 The eyelets were cut from .25in plate and welded to the ends of the straps.

 All fasteners used in the boom and jib housing, bearing plates, etc. are 3/8in x 16 gr.8.

 The straps had to be cut and welded carefully to length, with the boom supported at a 90º angle to the jib housing, to also ensure the thrust bearing surface meet perfectly flat, and stay that way.

 The jib housing by itself is not complex: it is 4in x .125 CRS tube, cut to 12in long.  It needs fastenings at its bottom end to hold the diagonal straps securely, it needed some way to retain the bottom jib bearing(s), and it needed fastenings to hold the top bearing assembly in place.

To restrain the top bearing assembly, four bolts were wanted, and a place to put them in the jib housing.  Ordinary nuts would hardly suffice, so four threaded bosses were made...

These are plain CRS, no heat-treat.  The bosses are welded exactly flush with the end of the tube, so that when the bolts are tightened, the bearing plate is not distorted.

I made the threaded boss for the diagonal straps as a single piece for strength.

No, I am not worried about the bolts being in shear because I looked up the shear strength and it's insane.  No worries. 

The complete housing, post primer.  All parts once completed were degreased with acetone, and abrasive blasted before paint.  All paint steps were baked on (either in the sun on hot summer days or with heat lamps in winter.)

The upper bearing assembly consists of a .313 (5/16in) plate with a steel tube (the housing for the pilot bearing) heat-shrunk into a hole.  The housing had a small shoulder turned, and the plate was turned around the hole, to ensure the housing went in square.  The plate was then turned on the lathe with the pilot housing in a chuck, so that the thrust bearing surface is ansolutely square to the axis of rotation of the pilot bearing housing.  Thus, the pilot housing won't change angles when the boom is turned.

The corner holes were marked by clamping the plate to the jib housing using soft-jaw clamps, with both sitting on the bench.  A transfer punch was placed through the welded-on long nuts, and a long brass punch was used to reach the transfer punch.

Two retaining flanges for the boom were then welded to the top of the plate.  Because the boom fits over the pilot bearing and is very unlikely to bounce off it, these were perhaps unnecesary, but they make me feel better.

Welding them was fiddly; I wanted good penetration, so the flanges had to be spaced away from the bearing plate a bit.  I used two pieces of MIG wire for this.  Then, allowance had to be for the thickness of the paint it was going to get after welding.  I guessed on that; after poking around the net for "how thick is a coat of rattlecan spray paint" I figured about .020 (.005 per coat) so I used three note cards (.007 ea) to space the brackets away from the boom.

I lingered too long at the end of one bead, the heat soaked into the plate too far, and zorched the bearing liner which I had already - optimistically, short-sightedly - pressed into the housing.  I made another, pressed out the old, pressed in the new.  All the actual bearing pieces are serviceable or replaceable.

The damage and the thrust bearing surface are visible.  Only the plastic bearing liner was harmed, the thrust bearing surface was easily cleaned with a bit of green scotchbrite pad.

All corners or edges get "broken" or chamfered, every hole gets chamfered.  This is necessary to obtain satisfaction and to prevent laceration.

<-- Once complete, it looked like this (a primer coat getting baked under heat lamps).  It takes about four to six hours to bake a coat, there are one to two coats of primer (depending on my skill level that day) and two top coats, so each part spends about twenty hours being baked.  This dramatically hardens/toughens the paint, assuming it is quality name brand oil-based enamel.

This brings us to the bottom jib bearing, the one which transfer the boom load (via the diagonal straps) to the mast.  Given what it is doing, we want this to have a large bearing surface to reduce friction and maximize bearing life.  I looked at actual ball and roller bearings for about five seconds before I remembered I am not James Pierpont Morganand decided to DIY something.

Next, some form of journal bearing came to mind.  I wanted all the bearings to be lubrication free so that neglect wouldn't make it fail quickly.  Brass and bronzes on steel make for nice slippery bearing surfaces, and my original concept for the jib housing was to be an open frame made from angle iron, so I thought this was the way to go:

I had several bits of "yellow brass" left over from an old project, so I created a proof of concept using a fly cutter again to cut the curve at exactly the same curve as the tube.

In the end, I decided I did not like this, because the open frame design would allow shop grit to get into the bottom bearing.

Once I decided to use square tubing instead, it occurred to me that I could just cut a three inch hole into a 4in sq. piece of slippery plastic and move on with my life.

This we then do... after waiting months to find a 1in thick (0.75 would have been sufficient) plate of real nice graphite-impregnated acetyl onb eBay, it was a matter of a couple hours to knock out the bottom bearing.

I had to mill a slot in the side to clear the factory weld seam on the inside of the square jib tube.  Each corner has a hole for a SHCS to secure it in the housing.

Making the matching holes in the corners of the already-finished-and-painted jib housing was fun okay not really.

Good thing I own a mill.

Now the bottom bearing is recessed a little from the bottom opening of the tube, and since the top is closed off, gravity will tend to keep crud out of there.

The bearing turned out to be perfectly snug, the two foot lever of the boom making it very easy to turn, with only the slightest hint of "stick-slip" which will likely go away with use.


I think this is everything for the jib housing.  If I find more photos, I might come back and add something.

In Part 4 I'll describe the boom.  I am very nearly done with the hoist cart documentation series, except for proof-reading and adding some photos and descriptions of parts I may have missed, such as the counterweights in Part 1.  I might write up the counterweights in a Part 5 instead of wedging them into Part 1 and making it even longer.  Dealing with the way this blogging platform handles images, videos, and text wrap is a PITA, it's easier to start a new article than MUNG up one I've already worked to format.  Bloody Blogger won't even let me put more than one image in a horizontal row. 

Fookin' hale, mon.

The Hoisting Cart project, part 2: The Mast

 The mast is a fairly critical part, in that it must support the weight of the load, but because there is a two foot boom between the mast and the hoist, it must also support a significant bending moment, which is applied sideways onto the mast by the jib housing.  For this reason, I decided to use a brand new piece of stock tubing whistled up from McMaster-Carr.  The tube is mild carbon steel, 3in. OD, .125 wall, and about 7ft long, cut down from an 8ft piece.  I literally had to save for a couple of years to afford it, but was determined not to worry about rust-introduced pits and weak points.

<-- The height of the existing light fixtures in the shop determined the height of the mast.

 The mast connections to the cart have already been described.  Where the holes for the retaining bolt (in the bottom bracket) were made, the mast was reinforced with a tube, like so:

This spreads any loads on the bolt over a much larger area than the thin walls of the tube, ensuring the holes in the tube do not deform over time.








 The load on the boom is supported by two bearings on the top of the mast; a thrust bearing to take the vertical load, and a pilot bearing to prevent the boom from simply sliding off of the thrust bearing.
 

Half of each bearing is connected to the top of the mast (the inner part in the drawing), the other halves are part of the jib housing (the outer part in the drawing).

I changed the design from what is shown in this sketch, instead using an inch thick piece of steel to hold the pin (part of the pilot bearing) and to form the bottom of the thrust bearing, instead of having the bearing surface thin and braced with triangular webs, which was going to be hard to make.












That process looked like this...

Chose some plate and a piece of hard shaft from the scrap bin. 

Little was needed to make the pin besides cutting to length, making a bevel on the end to aid assembly, and polishing it to a fare-thee-well, because it bears against a dry bearing liner of Nylatron GSM.  (no maintenance)

Did the usual things to make a square plate round.  Bored a very precise hole in the center, a few thousandths too small to admit the pin.

Heated up the plate until the pin dropped in and let it cool.  Never to be removed again, they are one piece now.  Could that pin be pressed out with a hydraulic press?  Maybe.  I don't want this part to come apart.

Machined the OD of the bottom bearing assembly to the ID of the mast.
The lip on the chuck side plus the close fit lets this sit in the top of the mast without fasteners or welds, meaning it's easy to service some day should the need ever arise.

This shows the general arrangement of the lower bearing assembly inserted into a scrap of mast tube, with a scrap of the square jib housing tube around it.  A large acetyle washer sits on the big flat part to make the lube-free bearing surface of the thust bearing. A cylindrical bearing lined with Nylatron GSM rides on the pin.  Both of those are part of the upper bearing assembly, which is bolted to the top of the jib housing, so that will be covered in Part 3: The Jib Housing.

The Hoist Cart project, part 1: The Cart

I already made a few posts here about the hoisting cart, but they were rather sparse and incoherent.  The next few posts are intended to describe each of the major parts of the project.

This post is incomplete, I will come back in some
hours or days and add photos and a description
of the two counterweights, which haven't been
described here yet.

 The basic cart came to me as an alley gift, found with a bunch of other trash for the Large Item Pickup Day, one block from my shop, and less than a month after I realized I needed to make the hoist mobile.

(rather than fastened to the rafters over one end of the mill table, where it could only be used on one machine)

The cart turned out to be the bottom of a hotel bell-cart with a rated capacity of over 1,000lbs.
The deck is made of 3/4in hardwood ply, there are two steel hat sections running the length of the underside which create tremendous strength, and four casters are mounted to the hat sections. 
The casters are rated for 800 lbs each.

Finishing the cart proper involved adding an upper deck of 3/4 ply, both to give the thing a reasonable work surface and more importantly, something to hold the mast upright.

Uprights between the two were fabricated from black pipe and flanges.  Diagonal bracing made of 0.75in strap and welded to the tops and bottoms of the uprights transfer forces acting on the mast back down to the bottom deck.  Counterweights are mounted beneath the decks at the end opposite the mast to keep it from tipping the cart when a load is on the boom.  Outriggers at the mast end, prevent it from tipping the cart when a load on the boom is swung around.

 The cart is mostly completely now, save for filling the lower counterweight with lead shot, and fabricating and installing the outriggers.  That will happen when finances permit, but that could be a while because someone in Washington nuked the low-income healthcare program I was dependent on, so I am more broke than ever before.



The rest of this post contains details about the custom hardware which was fabricated to hold the mast to the two decks.

Because the mast needed to be as tall as possible to be useful in my shop, and because the door opening is much shorter, the mast needed to fold down, complicating the mounting of it.

For the top deck a hinged mount was created and welded to the mast.  The hinges are two large bare-steel "weldable" (no holes) hinges from the hardware store.  To disassemble the mast from the cart, the hinged bracket can be unbolted from the deck surface.

Because all of the weight and bending moment on the mast is concentrated where the mast connects (at right angles, even!) to the two decks, the brackets were made very wide and deep, in order to engage a large area of the plywood.  Both brackets fit tightly on the plywood, and are clamped tightly in place with many bolts once installed.  This ensures the plywood does not see concentrated forces which could bend or break the wood fibers, leading to eventual failure.

Since I wanted a very close fit of the mast to the bracket, a hole saw cutting out the notch would not do.  I set up a fly cutter for that diameter, and used the mill to make the notch, ala the short video...

The lower bracket is designed to guide the bottom of the mast into place when it's being erected.  It has some holes and a bolt to make sure it stays put, and because the bracket creates a lever which tries to break off the edge of the deck when the mast is loaded, I added a brace under the deck to transfer the downward weight of the load to a wider area of plywood.  It also prevents the bracket from trying to twist at the edge.

That's really about it.  Once fit and function were verified, the parts were degreased, abrasive blasted, primered, and painted safety yellow in a vain attempt to save my shins in the future.

The outriggers are not installed yet, but when they are, they will look something like this...

I really wanted them to swing out or slide out, but I couldn't make it work in the space available.  So there will be a pair of sockets mounted to the bottom deck, into which the outriggers will slide and be retained with a pin.  When not in use, I'll provide some sort of broom clip affair to stow them out of the way of work and ankles.

interim project: making a boring bar longer

 My lathe came with a small amount of tooling, most of it in poor shape.  Some of it - the Dorian QC tool holders - is quite good tho.  It was a mixed bag and I've been slowly making improvements for maybe twenty years.

 One of these tools was a rather nice 0.75 x 6in boring bar, which someone had turned down so the end would fit in a 0.5in Jacobs chuck.  So when it is mounted in a proper 0.75in Dorian boring bar holder, there's only about 3in available now.  I could also gripe that it requires triangular HSS stock which isn't exactly common, but it was free.  Sharpening that cutter tho - bleh.  Clearly I need a Quorn grinder for my life to be complete.

 I have a need to reach at least six inches into my lathe's spindle, so I've been thinking about how to stick some more boring bar onto the end of the one I've got, to make it 10 or 12in OAL.  I have a piece of 0.75in rod which was formerly a rail for linear ball bearings.  It has a few transverse threaded holes in it, but that shouldn't matter too much. 
(he said, optimistically)

It appears to be mildly heat treated, which is desirable because it makes my rod stiffer.  What?

The question then is how to stick the two bars together.  Since one has been turned down, the most obvious answer is to make a hole in the end of the new rod to leverage that.  Since I'm only interested in joining them securely and permanently, I won't explore set screws.  That leaves:

• making a sliding fit hole in the new extension and brazing the two together
or
• making an interference-fit hole and heat-shrinking the two rods together

Both are fiddly and require some planning.  Brazing is only semi-permanent; if I really wanted to, I could separate the two pieces again by heating.  If I shrink-fit the parts, they become one piece forever and ever amen.

 I am leaning heavily toward the shrink-fit option mainly because I don't have any brazing flux on hand (I'd like to try something new) and because a foot-long bar can always be pulled back in the mount to stick out however much one wants.

 I have had limited success with heat-shrinks.  It's easy to wing it, and hard to get good results that way.  The best results are obtained using the shrink-fit allowances found in Machinery's Handbook, and a bit of simple math.

This would not be do-able at all, if I had not recently bought a small boring bar that takes inserts.  So I can just barely get away with making a hole with a drill bit (which hole will just barely admit my little boring bar) to then bore a more precise hole for the "male part" on the part with the business end.  I haven't run the formula yet, nor looked things up in the allowance table, but my guess is the hole needs  to be between two thou and three thou smaller than the "pin".  Tolerances typically go to four decimal places, but I do not own a micrometer, only a pair of calipers.

On an aside: if the pin and socket locations were reversed, ie; if I needed to make the hole into the existing boring bar, I would use that opportunity to put a dampener inside it.  This consists of a small cylindrical mass of a higher-density material like lead or tungsten, either cemented rigidly into the hole with a filled epoxy, or suspended in the hole within silicone rubber.  Factory bars with this feature cost at least 4X the price of a non-damped bar, but it's a lot harder to get them to chatter!

More on this story as it happens...

Built-Up Edge: what it is, why it's making your metal-working life difficult, and what you can do about it

Built-Up Edge
Q: Why is my surface finish mediocre?
Q: Why is my tool wear excessive?
Q: Why do my carbide inserts keep chipping/cracking/breaking?

A: Built-Up Edge

-

Q: What is Built-Up-Edge?

A: If you have ever drilled aluminum and noticed aluminum building up on the
cutting edges or tips of your drill bit, that is a Built-Up Edge.
BUE happen when removed work material builds up on the rake face of a cutting
tool.


-

Q: Why should I care, what harm does BUE cause?

A: BUE impairs surface finish and leads to high cutter wear and early cutter failure.

-

Q: What causes BUE?

A: Any or all of:
1. incorrect cutting speed
2. lack of coolant/lubrication
3. incorrect rake angle or other tool geometry problem (most often rake angle)
4. a dull cutter
5. rough (unpolished) top deck of cutter - AKA the rake surface, where chips or
BUE form
This is an excellent electron micrograph “slo-mo” (a series of stills sequenced
together) of BUE formation:
https://www.youtube.com/watch?v=mRuSYQ5Npek
-
Q: How do I prevent BUE?

A: Not too surprisingly:
1. Use the correct speed & feed for your material and cutter (HSS or carbide).

2. Use a cutting fluid that offers both lubrication and cooling - small amounts are
needed, you donʼt need a system.

3. Use cutters with the correct geometry - generally speaking, the one geometry
that matters most for avoiding BUE is rake angle.

Generally speaking, you will use more positive rake angles (cutting face is tilted
toward workpiece) for softer materials such as
aluminum, brass, copper, low carbon steel, while negative rake (cutting face
tilted away from workpiece) is used for harder
materials (tool steel, cast iron), interrupted cuts, or high force applications. I
personally prefer HSS for interrupted cuts.

Positive rake angles create a sharper edge, reducing cutting forces.

Negative rake angles increase cutting edge strength and resistance, make the
edge more durable.

4. Sharpen HSS cutters, rotate or replace carbide inserts, good luck with brazed
carbide - got a diamond tool grinder?  Me neither, thatʼs why I use inserts.

5. Polish the top surface of your cutting tool. Be careful, this can dull the edge
and require re-sharpening afterward. WORTH IT.

Coatings (on carbide inserts) can also make a world of difference, but each
coating is specific to one material or family of materials.

So if youʼve got the ubiquitous cheap Chinese inserts with the yellow TiN coating,
youʼll want to know that TiN is an outstanding “non-stick coating” for aluminum
only. It wonʼt help you with ferrous metals, or with cupricmetals, etc. If you get a coating that does great with one of those, it wonʼt do so well with the other materials.

If you can find the inserts cheap, this is not grossly expensive to deal with, but when youʼre talking about say, end mills, keeping a set around for three or four families of metals gets real expensive real fast.

Me not having a money tree, I mostly use high-cobalt HSS cutters with no coatings at all, and I discourage BUE formation with brushed-on Tap Magic.  I sound like a get kickbacks
from the company but I donʼt, I just like the product best out of the several mostwidely-
available fluids I have tried over the years.

suddenly, a wild hoist cart appears! (as I resume blogging)

This is the story if a shop material handling cart with a crane attached to one end.  It exists because I tried to lift my 125lb rotary table by myself and threw out my back for 18 months.

 Now, if I hadn't broken this blog - for years - with an obscure setting which much later caused Google's new media policy to break... you might have seen all the many, many efforts that lead up to this point.

 The project is not quite complete even now, as it needs outriggers and one counterweight needs to be... filled. The ouriggers are  waiting for money for the steel to make them.  We're broke, so anything I do goes very slowly.

Now that I finally found and fixed the picture posting problem with Blogger™, I'll be making a long series of posts about this project starting Real Soon Now.

EDIT, LATER: I am writing up the entire build process of the cart and its parts in a multi-part series.

In a 'Git 'Er Done' style, I'm getting the parts written and posted as quickly as I can, but I reserve the right to go back and add/replace photos or edit entries for readability, completeness, appearance, etc.

IYGIYGI

 test number ninety-

Well I'll be a son of a bitch, images work again!

We now resume our irregularly-scheduled programming, which is hardly in progress.

old men and their backs

Confusedious say...
"Give a man a shop full of material handling gear including an overhead hoist
and he will find a way to hurt himself pulling weeds in the garden."

 So yeah, I may have done that today. The city hath given me until 7-10-2024 to clear up my weeds but my back now has a serious soft-tissue injury, pinched nerves, the whole bit.  I'll say it doesn't hurt as much as passing a kidney stone - it's about comparable to busted ribs.

 In other news, we may have found the not-quite-dream-home in the mountains we've been dying to compromise on, and we're checking out the issues pretty hard. (one being a lack of a well)

This raises the issue of how to move:
    • a 300 lb compressor
    • a 400 lb workbench
    • a 500 lb toolchest
    • a 300 lb welding table
    • a 1,200 lb lathe
    • a 2,000 lb mill
from Denver to Somewhere West of Ft. Collins. 

 If I take the lathe off its (heavy, but low) stands, I can move it the same way I moved it here; in a pickup truck or a moving truck. The latter requires pallets and a banding kit or the like, but would allow moving
more parts at a time safely.

 Some items like the workbench require either four strong backs or the completion of my hoisting cart -- which is only useful on smooth floors.

Some items like the mill come apart into three or so large pieces which go on pallets using a hoist - a finished hoist cart would be awful handy at the destination for re-assembly.

Nothing to be done for the compressor or welding table; they're heavy, too bad. :/

 The good news is the property we're looking at doesn't have an especially steep driveway and does have a large garage.  But we are far from closing, with too many questions.

 More as it happens...

changes

 Contemplating the very real posssibility that I will need to move several tons of machinery, a ton or so of tools, a half a ton of work surfaces and maybe a quarter-ton of materials from central Denver to Damnearwyoming, Colorado.  I am not sanguine about this.  I am also not sanguine about being nickeled-&-dimed to death making a long move from urban center to the boonies, so hiring riggers for such a long trip seems unlikely to be in the cards. *sigh*

working in the shop again

 I'm getting some of my old mojo back, so I've started putting the (messy, neglected) shop back in order.

 Cleaned, lubed, and adjusted the mill, and swapped the rotary table for the vise (thank the gods for cheap hoists, that damned rotary weighs 130 lbs) so it is now ready to do some precisely located holes in a new, small project.  Unfortunately, I can't show or reveal that project.

 I also serviced the lathe, and in so doing, realized there was an oil reservoir on the saddle (for the cross feed mechanism) which I had never noticed, and therefore never added oil to.  Oops.  Filled that up until the sight glass showed it. D'oh!  Since it is a clapped-out 1970s SEIG (factory in Shanghai, manufactures Grizzly, Jet, and others) that was not well-cared-for before I got it, it's not the end of the world if I shorten one gearbox's life a little.

 There is a lot of other work that needs doing, including fixing a water supply valve in the bathroom, cleaning the shop vac which is full of stinky black yuck from last year... that kind of thing.

 At least I have an air conditioner, although it is on the small side for the space. The "white rubber roof coating" I put on the roof years ago disintegrated and blew away so the roof is black again (hot), and not insulated underneath because I'm lazy and hate working with insulation.  All the wiring I needed to put in the ceiling joists is done, it really ought to get insulated and rocked in... with my copious amounts of spare change... OTOH, the small A/C unit could easily handle 90º days if the roof and ceiling were righteous.

 After this it will soon be time to revisit the 3D printer.  More as it happens.