Hello everyone. I need some help with joinery. I made a typical rookie mistake; "that's easy, all ya gotta do is..." and now I find things aren't as simple as I had thought.

I'm an old guy who likes to build things. I know age is relative 'cause I've got lots of old relatives. My Doctor called last week to tell me my birth certificate had expired. I didn't even know it had entered it's grace period. I was a little upset at first but then I remembered I have the extended life warrenty. Good until 2058.

So a while back I was daydreaming along and stumbled upon the idea of building a Hay Derrick, sometimes called a Mormon Derrick. A Derrick is a balance beam hoist on skids, that was used to stack loose hay. It was powered by a team of horses and no Tim I don't know what breed of horse. Derricks were generally limited to areas that would allow hay to be stacked outside, uncovered, without fear of it composting from to much moisture. Livestock and hay were comon on farms in Idaho and Utah so prior to the 1930's/1940's nearly every farm had a Derrick. Tractors and hydraulic's put and end to that. There just wasn't any other use for one besides stacking hay. Examples around here were proably built in the early 1900's. These machines lived outside without protection so most are sad condition.

My carpentery skill level is... well, ah, lets just say calling me a wood butcher would be a promotion. I work slow and make lots of mistakes. But my mistakes are very accurate, and well thought out mistakes. I think accuracy is important even when doing it wrong. I never know when I might accidently be doing something right.

I know that this request has very little to do with the type of timber frame most here are interested in and even though my joinery experience is thin, I'm still trainable and willing to learn. The more I study the Derrick the more I see that I really need advice from experienced people if I want the thing to stand safely on its own 2 skids. Is anyone interested in reading more?

Thanks Ida-ho

Is that the only picture you have?
Do you have any dimensions?

And, yes, of course, welcome....

Hello Jim, Derick. Yes I have lots of drawings. I haven't kept any pictures because most derricks around here are in pretty bad condition.

I'll start with form and function so everyone can see how it worked. After that nomanclature, 'cause I'm not to sure about what to call each piece.

These machines were not designed to move long distances over rough ground. I think mostly they were left in a stack yard and just pulled around as necessary to complete the hay stacks.
You see in the top right of the first drawing, the Boom Hoist cable. That's where the team of horses is hooked. At the top center; the Boom Anchor Cable is a static line from the boom butt to the skid log on the frame. Its function is to index the boom to the same start position under no load conditions.


This second drawing shows the hoist cable route. The machine should always be tip heavy. That is the CG of the boom is forward of the mast/boom-hinge/swivel. The condition drawn shows the load at full height and max rotation. Under a no load conditon the boom would index to level horizontaly because the boom butt anchor cable is approx the same length as the mast height. Now glance back to the first drawing, if the boom was in a no load position the boom butt cable would be straight up and the boom would be pointing toward the words 'stack continues'.

These two photos are of a scale model. The first shows the machine in a no load conditon and the second shows max lift and rotaion. These pic's demonstrate the relationship between mast height, base dimensions, max elevation and max rotation. Note the triangle formed between the hoist cable , the boom butt anchor cable and the skid log that both are hooked to. A small base/tall mast means less height and rotatoion because the two vertical elements of the triangle are longer than the base, but you can get the mast/boom close to the stack. A large base/short mast means more rotation/elevation but you can't get the mast/boom as close to the stack.



Hay was hauled by wagon or bucked to the stack and positioned in front of the stack. The Derrick used an over-center dump basket (jackson fork) to lift the hay up over the stack where it was dumped and moved around by hand (men on top of the stack) as necessary to keep the stack square. When a load is hooked up and the hoist cable pulled, most of the force goes into lifting the load and just a little into rotaion. When the cable stop hits the tip pully that freezes the cable in all pullys except the boom butt pully and the boom rotates and elevates to get the load over and above the stack. When a section of the stack was completed the Derrick was moved forward and the stack continued.

That's a very brief outline of the machines basic operation. Any questions? Next is nominclature.

Thanks Idaho

Hi Ida,

The structure that you have drawn is very similar (read almost identical) to a post mill trestle. The terminolgy therefore might be Main post (obvious), Quarter Bars (braces), Cross Trees (x base), Crown Tree or Jib (arm) and I am unsure what the perimeter beams would be called.

The positioning of the wire ropes is very important since the workings of this type of structure is quite complicated and dependant on the design of the joints and the restraints imposed on the degrees of movement applied / allowed at each joint.

The design of this type of structure is really beyond the scope of the amateur carpenter since it is in essance a lifting device and as such carries all the attendant risks and liabilities associated with same.

Regards

Ken Hume P.Eng.

Thanks for reading these posts Ken. I appreciate your concern. This is either a fools quest or a difficult challenge. It depends on how much water is in the glass. I'm committed to this project,about two years worth. I've finished the Mast/Jib truss, all the pulleys, the hinge/swivel, mounted the spindle and cut a 6 inch tenon on the base of the Mast/Main Post. I have on location the Skid logs and all the rest of the braces.

I also have zero credibility here. Do you think this is the wrong place to ask advice about the joinery necessary to safley build a Derrick?

Thanks SWIdaho

Hi Ida,

I don't think that this is the wrong place to ask for advice but how will you judge how good that advice might be ?

I have spent a long time thinking and analysing the performance of post mill structures and came to the conclusion that they are inherently dangerous, historically having claimed many lives.

For example the rear stay wire appears to be anchored to the foot of the rear quarter bar. Imagine what happens when you put a load on the front of the jib. This wire will try and pull apart the joint at the foot of the rear quarter bar. If it suceeds then a disproportionate collapse will follow.

Enough said.

Regards

Ken Hume P.Eng.

SWIdaho, do you have photos of what you have done so far. looks like you have started the project already beyond the model stage. I am guessing you know about the Small Farmers Journal and Lynn Miller. I am sure they would enjoy hearing about this. Now I have to ask, are you a teamster? Or is this for the enjoyment, is the derrick going to be used? What advice do you need on joinery?

In "A Days Work" there is a picture of a derrick being used to lift stone for a building foundation. Very stout. It was a simple gin pole with a boom. I think the boom could be positioned at different points on the pole via block and tackle.

As for breed most likely the larger work horses from the war horses of Europe. Cattle were to slow for the time period, the farms were into production with multiple hitches and even mules. Tim

Hello Ken, Tim. Ken you are correct and I don't have any rebuttal. Just feeble excuses like 'it will never be used as a hoist', and 'it's only art and not intended as a working machine' even though it does function, and of course 'the public won't be allowed access'. I just really want to finish this. There is no extra load on the jib anchor wire until you pull on the hoist cable. Then the load is spread between the anchor wires' anchor point and the hoist cable anchor point. Both points are on the skid log, as I have it drawn. That would try to twist the skid log off the side of the machine. please keep your eye on things here, OK?

Hi Tim. Sorry about the horse crack. I really enjoyed that thread with all the pictures and talk about bents and why was one bay higher than the other. I'm not familer with the Small Farmers Journal. I'll do a search. As above this is a pleasure-learning project. The picture shows most of whats been done. The wooden box is a Kestral nest fitted between the king post legs. The hinge swivel join hanging under the Boom/Jib fits onto the spindle on the mast/main post. There is a metal frame under the bird house. I'll show joinery questions in my next post.

Thanks SWIdhao

Welcome Ida;

Maybe you have already seen this but look at page 19 of this barn book for a photo of a "'see-saw' type of Mormon derrick".

http://www.bearriverheritage.com/content/WYSIWYG/SE%20Idaho%20barn%20book%20low%20resolution.pdf

Jim

Hello Housewright, thanks for the link. Nice tour.

There are a few different ways to configure the cross trees and quarter bars. I'll show the layout I've choosen. If anyone has more accurate nomenclature, please tell me.

The first drawing is what I'm calling the subframe. It consists of skid logs with strechers (???) and tension cables to put the jionts in compression and to hold the box square.

The second drawing shows the double cross trees and quarter bars. These could be rotated 90 degrees but that would put the double cross trees on the strecher. The strecher is about 10 inches in dia. and the skid log is about 14 in.

The third drawing shows the 4 braces. (braces, lean poles, tormentor poles, flying buttresses) What's the correct name? I feel the braces need to go on the corners so the jib can swing in front of and over the hay stack. Remember, there is a pully at the base of the main post so the hoist cable has to operate between the two off-side braces.

Question 1. What joinery at the strecher/skid log connection?

Question 2. What joinery at the double cross tree/skid log connection?

Question 3. What joinery at the quarter bar/strecher log connection?

Question 4. What joinery at the brace/strecher/skid log connection?

Question 5. What joinery at the main post/brace connection?

Thanks SWIdaho