Bus Engine Rebuild – Part 2

This weekend I started putting the engine back together, and I’ve decided to replace a number of parts:

  • Camshaft – A few of the lobes were worn down, limiting valve lift. Replaced with a very mildly modified cam that will provide more power to go along with the new higher transmission ratios.
  • Lifters – Lifters had worn slightly concave rather than the correct slightly convex.
  • Connecting Rods – All rods weighed the same but were not balanced end-to-end and there was not enough material left to grind off and correct the problem.
  • Bearings – The bearings were OK but it’s easy enough to replace these while the case is open.
  • Pushrod Tubes – These could have been reused but were a little beat up and now is an easy time to replace, ensuring no leaks.
  • Oil Cooler – The old cooler was made in 1971, no telling how much build-up there was inside preventing heat transfer. Replaced with a larger cooler from a later engine style.

It’s mostly reassembled now, including shimming the crank/flywheel for proper end play and verifying with a dial indicator to 0.001″ (end play is critical on aircooled VW’s). I also modified the fan shroud to accept the bigger oil cooler and also re-built the thermostat. The thermostat is a sealed copper accordion that expands when heated. For some reason mine had expanded permanently; these are no longer made and becoming increasingly rare, so I had to fix it. Luckily I was able to find information about others who have had the same problem and I was able to fix it in the same way; the fix consisted of unsoldering the end plate, compressing the accordion, dropping in a bit of rubbing alcohol, and resoldering the plate before it had a chance to evaporate. The thermostat is now completely contracted at room temp and begins to expand around 80°C, allowing it to push on a linkage that opens cooling flaps in the fan shroud.

The new bearings are “structurally guaranted[sic]”, hopefully that’s just a typo and not a clever way to dodge claims – “they weren’t guaranteed, they were guaranted

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Bus Engine Rebuild

A slight change of direction with the transmission rebuild. I was looking forward to going through the transmission and readjusting everything to make it work again, but to get more speed I would have needed to swap out the ring/pinion gear as well as 4th gear. The cost for these gears separately was not too much different from the cost of a rebuilt transmission that included these gears. Because of this, there’s a rebuilt transmission on the way that already has the ‘correct’ gearing. Since this is a hobby I normally don’t think about time too much, but this also buys me a lot of time that gives me a chance to instead go through the engine while I’m waiting for the transmission to arrive.

I started going though the engine this weekend. There wasn’t anything necessarily ‘wrong’ with it, but it was put together somewhat hurriedly prior to having the bus at the wedding; I’ve since had a chance to second-guess a few things I did, especially with balance. I stripped it down to the case and this time gave it thin coat of black paint; heat has been an ongoing issue and changing the color to flat black will actually improve heat dissipation slightly. Overall everything looked good, bearing wear looked normal.

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VW Bus Transmission – The Sequel

This weekend I finally pulled the engine and transmission from the bus – each time I’ve done this I’m amazed at how few connections there are and how relatively quickly it goes. The goals for this effort are to figure out what happened that caused the breakdown last year as well as fix the problems that had been occurring since the original ‘rebuild’ (more of a clean and reseal). These problems included:

  • Immediate pop out of 1st gear and inability to hold in gear. This effectively meant no 1st gear, requiring always starting in 2nd gear.
  • 4th gear popped out under load, but could be held in place by a bungee cord. This worked, but is a really inconvenient way to drive and would eventually cause excess wear on the shift forks and slide gears.
  • Gear oil leaking from center. This should be an easy fix, I didn’t originally realize the paper gaskets used for  the reseal were not treated; using gasket sealer this time should solve this problem.
  • Too slow. Currently the bus red-lines in 4th gear somewhere in the low-to-mid 60MPH range, which mostly rules out interstate travel. More flexibility to do longer trips and even to more easily run errands locally would be nice to have. The engine is a little bigger than stock and should be able to handle the higher load, but gearing changes will be needed to get the RPM’s down.

I started disassembly and found that the internals seem to be in incredibly good shape, the teeth show little or no wear even looking under a microscope. All the gear ratios match what would be expected for a ’67 bus except 4th – for some reason it has a 0.88 ratio rather than the 0.82 ratio that would be expected. The 0.88 4th gear would be consistent with a beetle transmission, so I think this information combined with the amazing internal condition tells me that the transmission was replaced with a new or re-manufactured beetle transmission (while keeping the bus axles and reduction boxes) at some point very late in the bus’s history. The top speed would have dropped dramatically after this change and perhaps this contributed to it being parked semi-permanently in the early 80’s.

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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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Atlas/Craftsman Metal Lathe

This winter I’ve done some much needed cleaning and painting of the garage; it’s survived the bus restoration and countless other small projects. This has put the jet engine project and bus transmission on hold, but I’m in no particular hurry with either.

Also, recently I picked up an old Atlas (Craftsman) lathe I found on Craigslist with lots of tooling. This style of late was made by Atlas from the late 1930’s through the late 1950’s; based on the numbers engraved in this one’s bearings it seems to have been made around 1956. The manual that came with it was published in 1967; but I later found a receipt for the manual, proving that it was a replacement and explaining why the lathe in the manual looks like the late 1950’s through mid 1970’s version – both machines have all the same features and function the same though. For the most part it was in good shape and only needed some heavy cleaning, repainting, and a new motor capacitor; there are a few mechanical areas for repair/improvement that I will tackle, but nothing that prevents it from operating now. The original motor used a flat capacitor that’s no longer made in it’s motor base, so I had to get a little creative with mounting the replacement on the side of the motor.

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No particular project in mind for this, but no doubt it will come in handy with other projects especially since it has the milling attachment allowing it to serve as a small mill as well.

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Jet Engine Update

The jet engine combustor is now mostly complete, all that’s left for it is to #1 drill/tap for the spark plug and fuel injector(s) and #2 add an intake duct for compressor air. I’ve also mostly completed the 3D model – there aren’t many straight lines or surfaces on it, remembering all the 3D modeling tricks to make this was a lot of fun. I even went a bit overkill with the model – I may not actually build a bell mouth intake, screen, and/or jet tube.

1 Capture3 Capture Capture2

The biggest looming challenge is deciding on a hole pattern for the flame tube. It’s critical that the flame tube holes are in the right places to correctly ‘hold’ the flame through various engine speeds, particularly while starting. If there are too many holes the air will mix too readily and the flame will be blown out, not enough holes and the engine will starve for air and not achieve self-sustaining operation. This is the biggest area for experimentation on the system and it’s why I made the flame tube easily removable from the combustor, modifications may need to be made.

Beyond that, everything else is just basic design, fabrication, plumbing, and wiring:

  • Finish 3D module including stand w/ various support systems
  • Oil system (Oil tank, oil pump, electric motor)
  • Fuel system (This will be propane at first for simplicity and safety, but provisions may be made for future use on Diesel/Kero/JetA)
  • Starting system (Air jet strategically aimed at compressor wheel)
  • Ignition system (old ignition coil excited by a power transistor pulsed by the control system)
  • Electrical design, construction, and programming for instrumentation & control system (tachometer, temperature sensors, etc)
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Broken Bus

Today as I was backing the bus into a parking place, the clutch pedal suddenly became unusually light. It did not stall as I slowed down, so the clutch wasn’t stuck engaged – however once pulled out of gear it would not go back in while running, meaning the clutch was at least partially engaged.

I’ve always thought of the engine/transmission that are in the bus as temporary – I didn’t do much to these other than disassemble, clean, and reassemble. As such, there have been one or two roadside repairs needed, but I’ve always been able to MacGyver it well enough to avoid a tow. That wasn’t the case this time and I had to have it towed a few miles back home.

It’s not a problem with anything I can see on the outside (pedal/cable/fork), so instead something has occurred somewhere inside the transmission. I didn’t hear any pops or bangs, so likely it’s something along the lines of a bent clutch fork. I’ll pull the engine/trans over winter to both find out the problem and also rebuild for more speed, less noise, etc.

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Gas Turbine!

Before anyone gets excited, this is in reference to BUILDING a gas turbine (jet) engine rather than flying one, but it should be almost as much fun…

I’ve had a gas turbine (jet) engine on my ‘some day’ projects list for a long time. While cleaning the shop the other day I realized that I now have basically everything needed to complete this: a spare turbocharger, old oil pump, numerous microcontroller demo boards, various switches & sensors, scrap metal, and an assortment of plumbing fittings. All that’s needed to make it happen is to design and build it – a fun ‘free’ project.

I started on the combustor tonight. Fabrication should be generally easy compared to the CNC machine build, however without a lathe or mill there are some parts that I will have to fabricate creatively. I have jumped the gun a bit in not designing digitally first. In general the design will consist of wild guesses based on other similar projects online; so I haven’t lost out on anything by not having a digital model first, but I will create one as I go to make future changes easier to understand.

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