AMP-1 Rocket Engine

A fixture was made to machine the two plates properly by cutting a stock of aluminum so that pin would be a snug fit in the hole bored on the plate. This pin was then threaded for 1/4-20 so a nut could secure the plate to the fixture and prevent rotation of the part on the fixture. This process allows the diameter and chamfer to be cut without having any chuck jaws interfere. 

In preparation to machine the diameter of the end plates, the center holes needed to be re-drilled so they would be as perpendicular to the face as possible. To accomplish this, the end plates were set up on 1-2-3 blocks in the mill/drill and clamped down. Using a 3/8" end mill, the center hole was re-drilled. By using an end mill, the bit would end up being reluctant to follow the previous hole as a normal HSS drill bit would have a tendency to flex and walk. It was also OK to use a normal end mill because the hole already existed. Otherwise, a proper center cutting end mill would need to be used if there was no hole but at that point, a normal drill bit would be better.  

The two high torque servos for the main propellant valves arrived today. Immediately, one of them was opened up and connected to the Arduino UNO for testing. Using a 12v power supply and some quick testing code borrowed from Arduino's site the servo was commanded to rotate 180 and cycle back. This was then adjusted to 90 degrees for operating the 1/4 turn high pressure ball valves that will be on the test stand. It was soon found out though the 12v was probably not going to give it enough power to overcome the friction of the valve. A rough estimate of the torque at 12v is 90 in-lb, seemingly enough to move the valve but it did not want to move. A proper apparatus still needs to be made to properly test the servos with the ball valves.

As a quick nighttime project, the two 12" stays were machined to length and chamfered on the ends for welding. Here's a series of pictures depicting the process. After the two stays were complete, initial setup work was done in the lathe to prepare to make a fixture for turning the O.D. of the end plates down to fit into the barrel. 

First off, the second end plate was drilled today with some minor complications similar to the first. The major one being overloading the spindle on the mill/drill. I had not realized how much load was actually being put on the motor during the drilling operation until noticing the motor was too hot to even touch. To see how bad it actually was, I took a heat gun to it. Well you live and you learn. Fortunately nothing ended up being fried but it is definitely not good for the mill/drill.  After drilling the plate, work was done on machining both diameters and chamfers on the barrel. This was done on the lathe with a boring bar in the quick change tool post. The raw barrel was not very concentric to start with so it was difficult to get it as centered as possible to make the cut. In the end it will work out but it was not where it should be in relation to the drawings. However, the two cut diameters and chamfers are concentric to each other as the first one was used and ...

Today, some work was done on the first of two plates that will eventually be welded onto the fuel tank barrel. As mentioned before, the end plates would be cut with a 6" diameter hole saw bit in the mill/drill. This work ended up being quite tedious and time consuming as the mill/drill is far under powered for this operation. The hole saw had a tendency to grab and stall the spindle of the mill/drill and cause the machines breaker/fuse to trip constantly. While this is not necessarily good for the machine, this was the easiest method to cut out the blank end plates. After about a hour of cutting, success was finally reached with the first cut out.

To construct the fuel tank, two circular plates need to be machined to a precise diameter to fit inside the diameter of the tank barrel called out in the fuel tank assembly drawings. The only problem with this is actually cutting out the blanks to be machined. The raw material to form the end plates is coming from a 18x18" 3/8" thick 6061 aluminum plate. Unfortunately, the shop does not have sufficient equipment to cut these out with a saw. The only capable piece of tooling would be a 6" hole saw that was found and a mill/drill. The intention is to clamp the large plate onto the table of the mill and cut a massive hole out with the hole saw bit. Obviously using an ample amount of coolant and lubrication to decrease tool wear. After cutting the plate, the hole drilled in the center from the hole saw center drill will act as a mounting point for a fixture that will be chucked up in the lathe until the entire process is done for both plates. However, that will be done after...

While plotting out the construction of fuel tank, a slight issue arose regarding the load the flat end plates would see during tests. Having overlooked this initially, some quick calculations were done to find out exactly how much force would be put on those plates during normal operation and during hydrostatic testing. To find the force on a specific area, specifically the circular face of the end plates, an area calculation would need to done. For this tank, the internal exposed diameter is exactly 5". So The area formula  would be: A=pi(r)^2 . Plugging in for r (radius) gets pi(2.5)^2 which is equal to 19.635in^2. Now with the total exposed area, the force over that area can be found by plugging in maximum pressure the tank will see. For the hydrostatic test, a pressure of 1.5x the working pressure is used to insure safe operation of the tank. For this tank, the maximum operational pressure will be 400 PSI, therefore, the hydrostatic testing pressure will be 600 PSI. 19.635in...

This is the start of the blog for the AMP-1 Rocket Engine project, a bi-propellant liquid/gas fueled uncooled rocket engine. This blog has been created after many hours of work already completed so it will jump right into the project. I'll work on adding some pre-blog work I've done at a later time. For now it will start today, 11/20/18, with some of the work that has been done recently. Fittings and Stainless Steel Tubing Today, a shipment of fittings and stainless-steel tubing arrived for plumbing of the test stand. To ease construction time and increase quality of the finished product, Swagelok equivalent fittings were bought. This brand of fittings called Yor-Lok are made of 316 Stainless and will suit this application well as they have high corrosion resistance. Some inline check valves for the fuel lines and hex nipples were also bought to connect all the brass tees to form a manifold going to the fuel tank. Overall, most of the fittings have been purchased in prepa...