Monocopter Launch Rack

[JAL3]

I was not very happy with any of the strap hinges I found for this project but I finally settled on a 4" job from Lowes as being the only one I could find that would fit. It was also cheap enough to do for a proof of concept test. I drew out the pattern in a CAD program and printed up lots of drilling templates. I started with the arms and taped a template on one end of each one.

 

[JAL3]

Having had problems with wandering drill bits, I drilled a small pilot hole for each bolt location.

 

[JAL3]

The full size holes for the #8 bolts were then drilled.

 

[JAL3]

The hinge was then bolted to the arm with some nylon keeper nuts to keep things in place.

 

[JAL3]

On the box end, a template was applied to the bottom right corner and taped into place. It was then drilled in two stages with pilot holes and then full size holes.

 

[JAL3]

One of my concerns was the transmission of the moment from the deployed arms to the relative thin material of the box through a fairly small group of three bolts. To help spread out the force, I applied a template and also drilled what I called the plate washers.

 

[JAL3]

The first of the arms was then mounted into place.

 

[JAL3]

When the first arm was in place and seemed to work conceptually, I did the same thing with another arm on the left side of the box, mounting it just a bit higher so that the arms would clear each other when closed.

 

[JAL3]

I then repeated the process with the other two arms on the back side of the box.

 

[JAL3]

Having the arms in place was exerting a significant amount of torque on the box and, depending on what position the arms were in, led to a degree of twisting in the box. To address this immediately, I decided to install the saddle before tackling the vertical support of the arms. The midpoints of the box and the saddle were marked and then the saddle was put into place and held there with a clamp.

 

[JAL3]

I then proceeded to drill the box and the saddle for the bolts to hold it in place, 2 on each side. Unfortunately, I eyeballed this part and, while serviceable, the bolt pattern on the front is not sightly. Having the saddle bolted into place, though, did significantly stiffen the box.

 

[JAL3]

I had planned on using turnbuckles to provide some vertical support to the extended arms. All the ones I found locally that were right in terms of diameter had throws that were too short so I bought some extra long eyebolts and replaced one of the ones in each of the turnbuckles.

 

[JAL3]

On the leg of the base, I drilled a pair of holes to receive a wire rope clamp.

 

[JAL3]

My plan was to use the clamp to grip one end of the turnbuckle and I thought the wire trough would make things a bit stiffer.

 

[JAL3]

To make the connection on the arm itself, I drilled a hole to receive the pin from a shackle. I wanted to be able to take it down quickly and the pin seemed the best alternative at the time.

 

[JAL3]

The shackle was then coupled to the turnbuckle and the pin installed. It did indeed give me the vertical support I sought but the wire clamp had been a mistake. When it was tightened down enough to be usable, the support could only work at right angles to the box.

 

[JAL3]

While I pondered the general cussedness of the mechanical linkages, I turned my attention back to the saddle. It was to be the basis of the 5th launch station and I wanted it to be able to handle 1/4", 3/8" or 1/2" rods. I started with the 1/2" and drilled a hole for it in the center.

 

[JAL3]

I then tapped it to receive a 1/2" bolt and got a lesson is how tough it can be to turn a tap wrench by hand. Before this, the only thing I had ever tapped was a piece of brass for a #2 screw.

 

[JAL3]

To make the rod, I started with a grade 8 half inch bolt.

 

[JAL3]

I then used a metal cutoff wheel on a Dremel tool to cut off the head. It took a while.

 

[JAL3]

The rod was then test fitted in the saddle and found to work.

 

[JAL3]

I wanted the central launch station based on the saddle to be versatile and able to handle more than just the 1/2" rod. It was to handle 3/8" and 1/4" as well. As such, I went through the same procedure with the 3/8 as I had done with the bigger rod and located it halfway between the 1/2" hole and the edge of the box. Unfortunately, I relied on eyeball measurements and the bit drifted a bit.

 

[JAL3]

The process was then repeated on the opposite side of the hole for 1/4".

 

[JAL3]

As mentioned before, the wire rope clamps held the turnbuckles in place a little too tightly. I decided to try things out using just and ordinary U bolt and placing a nut on both sides of the support leg.

 

[JAL3]

That did indeed give the turnbuckle more ability to adjust to different angles.

 

[JAL3]

A new hole was drilled and the vertical support was reassembled.

 

[Chrisn]

I then tapped it to receive a 1/2" bolt and got a lesson is how tough it can be to turn a tap wrench by hand. Before this, the only thing I had ever tapped was a piece of brass for a #2 screw.

Did you start with a taper tap? (if you have one) it would have made it easier. Remember to use some cutting fluid to extend the life of the tap and to turn the tap counter clockwise every few turns to break the chips. Also worth checking you drilled the correct size hole to begin with. Luckily it is only thin/soft? material you are tapping but anything thicker you might have ended up with a broken tap.

 

[JAL3]

Did you start with a taper tap? (if you have one) it would have made it easier. Remember to use some cutting fluid to extend the life of the tap and to turn the tap counter clockwise every few turns to break the chips. Also worth checking you drilled the correct size hole to begin with. Luckily it is only thin/soft? material you are tapping but anything thicker you might have ended up with a broken tap.

I believe that the tap I was sold was called a taper tap. It was the one sold to me by the bolt company when I explained to them what I was trying to do.

I did not use any oil or any other cutting fluid. Nobody told me I should but I guess I should have figured that out. I did back off every few turns.

As to the broken tap, that will probably be covered in the next installment.:eyepop:...:y:...:dark:

 

[JAL3]

With the vertical supports in place I decided to go ahead and drill and tap for the primary rods for stations 1 through 4. These are the stations at the end of the arms. The ultimate goal is to make these accommodate 1/8" and 3/16" in addition to the "standard" 1/4" but I started off with the quarter and centered it in the middle of the 3" section that has the square profile at the tip. I followed the same procedure I had used with the saddle: drill, tap, test fit.

 

[JAL3]

This worked well on the first 3 arms but on the fourth, I broke the tap off in the hole. I don't have much experience with this stuff and I tried drilling it out; the steel of the tap was much harder than the steel of my bits. I finally decided to go ahead and put the final paint on this arm and then turned it over to a friend, Ken Kryszak, who has experience as a machinist and said he would get the thing cleared out