Jet Engine Oil System – Test Run

Tonight I tested the oil pump – it worked so well that the pressure blew off one of the plastic tubes I was using for testing and sneezed oil over everything. After I cleaned up the mess I connected it into the system and did another test run. The extra resistance of the oil passing through the turbo bearings caused the pump to stall out on the first attempt. The pump was originally designed to move air, so it’s not surprising that oil was too much of a load. To remedy this I made a new crankshaft for the pump on the lathe with as short of a ‘throw’ for the piston as possible. With the shorter throw, the pump is moving less oil per rev which reduces the load and prevented the motor stall. After this change it successfully ran continuously and held an average pressure in the system of about 75PSI, right about where it needs to be. To keep things simple I don’t have a bypass or pressure regulator in the system; because of this the pressure gauge flutters with each pump stroke but this doesn’t hurt functionality.

The motor draws about 5A, at 12V this is ‘only’ 60Watts and is about the same or even a bit less than when it was an inflator pump. Since it will now be running for longer time periods though I need to keep an eye on the motor temperature. I also need to protect the plastic gear from the (eventual) heat of the combustor above. To address both of these problems I’ll likely make a heat shield for this area as well as add a cooling fan.

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Jet Engine Oil System

This weekend I resumed work on the jet engine project. When I last left off I had just completed the frame and mounted the turbocharger/combustor. I had also fabricated an oil tank out of an old propane tank and mounted it under the turbo, but had hit a bit of a wall with what to do for an oil pump. There are electric oil pumps available, but basically all of them would be overkill for this application. Also, since this is a hobby I’d much rather put in the time to make something custom vs paying for parts. Turbocharger jet engines have been done by many others, my approach with this is to see how compact and well packaged I can make one – that doesn’t happen by bolting together a bunch of off-the-shelf parts.

I had considered using the bus’s old oil pump, but this created more problems than it solved (connection of inlet/output pipes would be a challenge as would driving it and selecting a motor). Today after a taking a fresh look at it I realized that an old 12V tire inflator pump that I had could be adapted to work. The plastic casing had broken, but the ‘guts’ were all metal and should hold up to oil pump duty. The only problem was that the cylinder head of the pump had no way of connecting an inlet pipe – being designed for air, it just drew in air from a small hole. To fix this, I made a new cylinder head on the lathe with one large hole in the center. A tee fitting screws into the head and I’ll put a check valve on each side. This larger single-hole head should also help compensate for the increased load of pumping oil, much thicker than air. Once I start running oil through it I may have to make some tweaks to avoid overload (lower voltage, thin oil, etc) but this at least gives a path forward for experimentation.

I also shortened the oil tank to make more room underneath for other support systems and made a threaded port on the lathe to weld into the tank to connect the oil pump. The welds aren’t the greatest looking, but are leak-free and that’s what matters – they should clean up OK after some grinding. For now the whole project is in fabrication mode, but once everything is in place and working I’ll go back and do body/paint work on all the parts to make it look nice too.

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VW Bus Adjustable Front Beam

During the original bus rebuild I had ‘flipped’ the front spindles to lower it some. Stock height on buses was alarmingly high, lowering allowed for better handling and gave the possibility of the bus fitting in the garage with a roof rack. The spindle flip, however, lowers by a fixed 4-5″; just low enough that the front wheels would rub the wheel wells during bumps or heavy braking/cornering. Cornering was particularly exciting since the outside wheel would rub, slowing down that wheel with the tendency to make the turn tighter – or “positive feedback” for those of us that are into control systems (not a good thing).

To remedy this, a way was needed to raise the front back up an inch or two. Old VW’s use a very unique front suspension design with two sets of torsion leaf springs inside of a beam with two tubes. The leaf spring packs are held fixed in the center of each tube and are capped at both ends with the four trailing arms. Minor raising and lowering can be accomplished by changing the angle the springs are held at the fixed center point. The center spring holder is held by divots crimped into the tube which engage with holes in the spring holder; these divots were drilled out which freed the holder. Toothed sections were then welded to the tubes; when the center is bolted in place a nut is tightened against a toothed plate that engages the teeth, holding the torsion spring pack at the new angle.

Lots of things had to be disconnected and then reconnected to get the beam in/out. This made it a greasy, awkward, and tedious job but overall it went well. The only hiccup was that after the beam was re-installed the shift linkage interfered with the adjuster bolts, though I had read this could happen. To solve this problem I welded a chunk of plate steel to the bottom of the linkage to hold the geometry and then ground out a strategic section of the linkage tube. The plate is as strong or stronger than the tube, and it’s in just the right spot to clear everything above/below it. After everything was back together the bus is level and no longer rubs the front wheels!

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Atlas/Craftsman Lathe Reversing Switch – Finished

Tonight I finished up the lathe reversing switch linkage by stamping and painting the cover plate and making a knurled knob that roughly matches the others on the lathe. The lathe allowed the inside diameter of the knob to be bored precisely enough to get a good interference fit on the shaft – no need for any fasteners.

Lathe Reversing Switch Handle Lathe Reversing Switch Handle Lathe Reversing Switch Handle Lathe Reversing Switch Handle

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Atlas/Craftsman Lathe Reversing Switch

Originally the Atlas/Craftsman lathes spun in only one direction; because of this they came with only an On/Off switch integrated into the lathe’s headstock. At some point in my lathe’s past the On/Off switch was removed and a reversing ‘drum switch’ added. The drum switch gives the flexibility to spin either directions for special uses (cutting metric threads, power tapping, etc) however it’s it’s too big to fit in the lathe’s headstock.

The previous owner had the switch mounted on a wooden arm extending up from the lathe’s workbench; re-using this idea would work but since I’ve moved the lathe to the shop countertop the arm would need to be rebuilt and I also don’t like the aesthetics or the need to reach over the spinning work to turn it on/off. Another option would have been to mount the switch under the lathe base, however for the carriage to clear the switch would require raising the lathe – it was already at a good working height and raising would effect stability/rigidity as well as being susceptible to dripping oil. Lastly, it could have been mounted just anywhere on the ‘outside’ of the lathe (on a guard door, past the tailstock, etc) – none of these locations seemed great and overall this just seemed like giving up.

So what I ended up doing over the past few nights was locating the switch in the only volume of space just big enough for it, under the motor. This location has the added benefit of making the wiring short and simple. As-is, this is of course very inconvenient, but I chose it with creating a linkage in mind. The addition of the linkage allows the original On/Off switch hole to be utilized (previously this was just an open hole), puts the control in a convenient place, and makes it look like it was designed this way. The linkage was a challenge and took a few iterations to get right. It consists of a 1/2″ OD steel tube that runs through the headstock, supported by two metal plates I fabricated. At the end of the tube I welded on a nut to accept a bolt that bolts on another arm I fabricated. The arm has a bolt welded through it that engages with a slotted lever welded to the drum switch’s lever. The resulting contraption actually works very smoothly: pushing IN runs the spindle forward, pulling OUT runs it reverse, and returning to center is Off. All that’s left to do is create a matching knob and mark/paint the switch plate.

Reverse Forward Off

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Atlas/Craftsman Lathe Carriage Hand Wheel Fix

The hand wheel for the carriage (longitudinal/Z axis) of the lathe had a bit more up/down slop than I liked. To remedy this I used the lathe to fix itself. First the ‘apron’ (front plate) was removed from the carriage and mounted in the milling attachment, the smallest boring bar that came with the lathe was used to widen and true to the hand wheel hole. Similarly, I skimmed the surface of the hand wheel shaft to ensure it was perfectly round. With the larger apron hole and slightly smaller shaft I was able to create and fit a brass bushing to take up the space between. The outside diameter is a press fit into the apron and the ID has about 0.002″ of clearance to allow it to turn but without the slop previously seen. I only took pictures of the first step, I’ll take more for future lathe projects.

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Custom Storm Window Hardware

A few years ago we glassed in the screen porch. Installing “real” windows would have completely changed the porch and been fairly pricy. So instead I made my own custom wood frames to match the size of each of the screened sections and had regular sheet glass cut to fit in each of the frames. I then installed the frames with hinges at the top to allow the windows to either be propped open or latched closed. This keeps the porch generally the same, but with the windows closed allows just enough heat to be retained to over-winter some plants. Since this is completely custom though, I couldn’t find any good options for hardware. For the last few years I’ve “temporarily” had the windows either held down with screws or propped open with paint stirrers.

This weekend I finally got around to designing, fabricating, and installing the custom permanent hardware. The hardware consists of a regular butt hinge that I pressed the pin out of. I then welded a sheet metal section to one side that I had bent to 90° and drilled holes in. The modified side is mounted to the house and the smaller side is mounted to the frame. In the closed position the hinge holes line up and a securing pin, made from 1/8″ wire, is inserted. In the open position a prop rod, again made from 1/8″ wire, connects the two hinge holes and holds the windows partly open for somewhat of a “bahama shutter” look.

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Golf Reverse Camera

The rear VW emblem on the golf serves a number of purposes:

#1 – It’s an emblem.

#2 – It’s the latch and handle for opening the rear hatch. Pushing in at the top of the emblem causes the hatch to unlatch and the bottom of the emblem swings out to use as a handle for lifting.

#3 – (what this is all about) It’s a back-up camera. When in reverse, a small camera is pushed through a trap door behind the emblem causing the emblem to swivel up. The golf’s controller knows not to unlatch the hatch if it see the emblem swivel while in reverse (because it’s the camera that has swiveled the emblem, not a person).

Having a backup camera on a car that I can practically lean back and touch the rear windshield from the driver’s seat doesn’t make a lot of sense, most of the time. I have gotten used to it though – it’s great for towing and I have lines on the garage floor that allow for precision parking every time, maximizing usable garage space. A few weeks ago the camera stopped working; I investigated further and found that one of the arms of the extension mechanism had broken off. At that time I grafted a sheet metal strap onto the plastic mechanism and melted parts of it back together. This lasted a about a week, so this weekend I re-produced the entire plastic part completely with steel.

During the many cycles of assembly and dis-assembly of the camera mechanism I encountered a problem where any time it was put into reverse the hatch would open! This is kind of a funny outcome since it’s still fulfilling the purpose of more visibility when in reverse, just in a different way. This would be inconvenient, to say the least, so I tracked the problem down to some frayed wire connections. The shorted connections caused the hatch switch signal not to be ignored when the camera was deployed; re-terminating the wires fixed the problem completely.

 

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Cupholder

Today I fabricated a cup holder basket. It’s made entirely out of the frame from one of those annoying corrugated plastic signs someone had planted in my yard, so it was basically free. There was an original accessory cupholder of a similar design that I got the idea from. The original was more in tune with 1960’s european beverage size sensibilities; I’ve created mine to work with 2010’s US sized cups.

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