Uncle Ben's BMW - Paint
Where we left this project months ago was I had managed to get the engine back together after discovering shot rod bearings. Next was to put it back in the frame and get this project to a roller. I really want some of my shop space back! That necessitated painting the frame and other bits.
Let me preface this - I hate painting. It's not my thing. In the end I'm kinda aiming for a decent "5 foot" finish. (You know, looks good from 5 feet away or more?)
I've always wanted to try automotive paints and thought I would give a try on the BMW. I decided to use Eastwood paints - they target the DIY market and their stuff is a good compromise between cost, east of use, quality and variety. I chose the DTM Epoxy Primer and a Single Stage Black Urethane. But first I had to build a spray booth, sand down or media blast the parts, figure out a way to mount the frame so I could get at it, and acquire some safety gear (fresh air respirator, hood, suit, etc).
There's tons of info on the net about building you're own small booth. I went with the painters plastic over a PVC frame, cheap box fans with furnace filters, and fluorescent lights style.
What this is really for is two fold - 1) to contain the overspray and fumes, 2) keep contaminates out of your new paint finish while it cures. This style of booth is probably just OK at both, but better than nothing. I did notice there definitely was a positive pressure as there was overspray blown out all around at the bottom of the frame and floor joint creating yet another thing to try to clean up.
Here are some various bits masked off. I think this was the most enjoyable part of the whole thing. It's clean, easy and kinda looks cool when you're done.
Ready for paint. Turns out kinda. Well lets just say I learned a lot. The overarching problem was the fact I had too much going on in here. The parts were too close together, they were too high to paint comfortably, I had a lot of trouble getting all the sides (I had to hold and manipulate with one hand while painting with the other. I got lots of runs. I got lots of overspray. I missed some places.
It was horrible.
Primer on. Another mistake, don't get black primer if you're going to shoot black as a color coat. You can't see where you need to paint. I should have used a grey primer.
I ended up sanding the primer out on the frame sections (where there were runs and stuff) and respraying. (The other pieces ended up being good enough). This would have gone great had my stupid painting hood (which inflated due to the fresh air system and pressurizing and popping up the top a good 6 inches) not collided with my fresh 2nd coat. I'll have to sand that down and touch it up tomorrow. Sheesh!
Did I say I hate paint? The prep work. The set up. The space it takes. The mess. The clean up. The chemicals. The safety issues. The ease with which you can totally screw it up.
I think I've proven to myself, once and for all, that if I need to go beyond rattle cans - I'll send it out.
Shop Air Update
Here's the basic layout of the shop. The circle with an "x" in it represents a ball valve.
Below is a pic of the chart in ThingSpeak. The slopes of the different curve segments are calculated below:
So it appears the best the system can do is around 2 psi/hr. That's with as little of the system as possible in the mix, i.e. best case. That said ,there's still the compressor check valve, a water separator/filter, air line quick disconnect fitting, and 3 ball valves in the mix. It's possible the air line quick disconnect fitting could be the bulk of it, however the filter also has an auto drain feature which could be leaking too.
UPDATE: I've been opening up each end point separately and it looks like the Bridgeport is kinda a problem. I'm pretty sure it's the Kurt Power Drawbar IN/OUT switch - I knew it was leaking, but it's leaking more than I wanted. I think the rest of leaks are probably a collection of minor things I'll have to find by soapy water, etc.
A couple of years of ago I finally added hard lines to my air compressor throughout the shop. What a nice upgrade! No more hoses all over the floor. However, it seems my copper sweating skills are maybe not what they should be as it seems to leak a fair amount of air. After I switch off the compressor it takes something like 4 hours for the system to depressurize.
I felt I could do better.
But how to isolate the problem? And how to make it a complex project?
Well, that's easy. Just build a wireless network connected microcontroller with a pressure sensor, an SD card for logging, and a graphical display. Have all your data get collected in two ways - 1) local to the SD Card and 2) upload to ThingSpeak.com.
My thinking is to attach the logger to different segments of the air line. As I move away from the compressor - therefore adding more pipe joints, valves, equipment - I should be able to deduce from the pressure decay rates what the relative leak rates are per section. That should give me an idea of what to work on. Additionally, I can verify my repairs in quantitative terms.
So after a few days of cobbling things together
Here you can see it's attached to my air lines - running about 115psi.
Close up of the mess. The screen is an older Arduino TFT (now discontinued) with an SD card socket. The smaller chip above that is an ESP8266 WiFi chip. For $5 you can't beat it!
The ESP8266 is a 3.3v part which needs some juice when transmitting. I happen to have had lying around an old XBee shield that I had previously added a 2 channel level shifter to. It took care of both issues as it also has a robust 3.3v power supply.
Here's a link to the ThingSpeak page where I'm uploading the data : https://thingspeak.com/channels/6008
I'll have to update this as start logging the system and try to figure it out.
After getting the 4th axis up and functional, I thought I might as well try a project utilizing it. My concept was to create a dining table using the rotary as well as some old barn wood we had left over from building our house. Here's the CAD version of the idea. The original concept had this with two legs. After calculating how much aluminum that would take and how long it would take to machine, I scaled it back to a single leg.
I had wanted to use the rotary as a true 4th axis (simultaneous movement in all axis), but ran into trouble creating the gcode. My skills in NX 7.5 just weren't up to the task. So I back-pedaled and went with more of an indexer mode - basically turn 90 degrees between each operation. Although it's not what I started out wanting - it still allowed me to machine all four sides without removing it from the fixture.
Which brings me to the fixture. I've never really put much time into setups as I usually just want to get the part done. This time, I realized the number of parts I wanted to make plus using the 4th axis required one. I'd also never used dowel pins for location devices, so thought that would be fun too! Although it's a bit cumbersome to mount and dismount the part, it worked as designed. When I originally made the fixture, I was a bit careless about maintaining parallelism between the top and bottom. I realized this at about the 3rd part when I was having trouble with things matching up when the rotary went all the way around. Once I fixed that - it turned out to work very well.
Once I got that sorted, the first operation was to cut a chunk off the raw 5"x2.5" stock.
Next up was to add a set of holes - 3 threaded and 2 reamed (for the dowel pins to locate) on both sides to use for mounting in the fixture.
Then I sawed this at a 30 degree angle to make 2 blanks. Here it is mounted up on the fixture in the rotary about to do the first position.
I had never used dowel pins to align a jig and got to use over/under reamers to make it work. It was actually pretty easy and it really made things very predictable and repeatable.
To complete 1 part took around 55 minutes of machine time. Most of this was trying to get a very fine finish on the contoured areas which took a lot of passes.
I was originally planning to do enough for 2 legs, which would have required 48 sections. At an hour each, that really added up.
Once I had the buttress pieces done, I moved on to the leg. I mounted the lumber in my lathe and turned the ends. What a mess! Turning wood in a metal lathe gets sawdust everywhere!
After turning that down, I slipped on some aluminum collars to each end and put together what I had for a bit of a mockup.
Now that I had the leg mostly there - I started in on the top. I had wanted to make it up out of a bunch of strips and glue/screw them together. I really ran into issues with warped and twisted strips. I ended up wrestling it around to something I considered acceptable, but it was a lot harder than I thought it would be. It ended up being 48x36".
One feature I attempted was to use 5 threaded rods to hold the top together. Although I got it done, it was probably the worst part of this whole job. I really underestimated how much trouble it would be to drill straight holes though 3 feet of 3/4" strips of wood of varying species! I thought it would be fun to make a set of custom nuts to hold it together. I wanted to recess them into the side of the top. I based the design off the 12 lobed base.
You may be wondering how I got those nuts tightened up. Well you make a tool of course!
I wanted to have a plate mounted on the underside of the top to use to attach the leg and also to help stabilize the wood. I found a galvanized round cover of sort make out of diamond plate. I was going to expose the diamond plate, but ended up liking the other side more.
Next was the base. I found a 20" diameter metal plate that was apparently used as a pipe cap. It probably weighs about 80 lbs and was a bear getting into the mill by myself! I milled a pocket in the top for the leg and on the underside I added pockets for 6 feet, plus thread milled the outer holes to accept an adapter I needed for the feet.
I realized I needed a way to securely mount the aluminum collar on the ends of the leg so they wouldn't spin. I decided to glue it on, but then added a wedge - just to make sure!
And here's the final result!
Some additional notes:
I think the overall design was OK, but in looking at the finished product I think it didn't come together as well as it could have. Not bad for my first attempt at furniture, but there's room for improvement. My brother pointed out there should be some metal form from the base/leg coming up through the top. I think he's right as that aspect is sort of the point of the whole thing. My wife thinks there are too many materials involved and it doesn't really come together - she's right too. Additionally I think proportions of the top to the base are off, I probably should have gone with a circular top. Although I largely managed to solve it, there is tendency for the top to be able to spin on the base as the compression collars just don't provide enough force to resist that.
VH-65 Seal Repair
After rebuilding the VH-65 and mounting it, I kept my eye on the oil level. After a few weeks it fell below the sight glass and I knew I had a leak. I had really fought with the large seal in front and immediately came to the conclusion I had messed it up. Careful observation seemed to show that it was leaking as there was evidence on the front of the rotary.
It's kinda hard to see, but there is some faint staining right below the seal area as shown here.
First up - remove the old seal. Easy - just drill a small hole in the seal and use a slide puller!
My problem the first time was I had no way to evenly pull in the seal. I had tried to gently hammer it in, but I knew at the time I had deformed it. I needed a tool.
When I was scrounging around my local surplus yard, I found a scrap ring of 6.5" ID aluminum. Perfect. For $10 it was mine. All it needed was to a bit of machining to open up the ID a bit and face it. I used the T slots in the face and a couple of scrap plates to rig up a way to pull it down. I carefully tightened each nut so as to install the seal square and even. It went in pretty easy.
I topped it up with oil and I'll keep any eye on it for the next few weeks a see what happens.
When I had purchased the rotary, the Fadal logo plate was missing. One happened to come up on eBay, so I decided - what the hell.