Category Archives: Bus
The last few months have been very busy so I haven’t done much with the bus. We did get the photos back from the wedding a while ago, they came out great!
Wet-Sanding & Polishing
Today I worked on wet-sanding and polishing; starting with the blue areas. The paint straight from the gun leaves a finish that is shiny, but has the texture of an orange peel. The goal of wet sanding is to level off all the peaks of this orange peel texture so that the paint is flat. First 500grit is used, then 800grit, then 1500grit; the panels are kept wet and rinsed frequently to avoid dust build-up that could scratch the paint. It’s critical that the surface is not sanded below the lowest low spot of the orange peel texture, otherwise primer could be exposed and repainting would be required. Luckily the low spots, being untouched by the sanding block, are visible fairly readily as slightly darker spots. After the sanding is completed the paint is flat, but dull looking from the very fine sand scratches. Polishing with rubbing compound and a rotary buffer brings the shine back. The passenger side of the bus is mostly complete; I’ll likely get the driver side complete by the bus’s first long trip, but I’m unsure about the front/back/white areas.
Passenger Front Seat
The only seat component missing in the whole bus prior to today was the seat bottom of the passenger side front seat. Since the bus has the “walk through” option instead of the standard front bench seat, the seat bottom is hard to find. So tonight I built a seat bottom out of foam until an original seat bottom can be found. I used carpet padding since it’s fairly cheap and locally available; the technical foam industry name for this stuff is “rebond” since it’s made from foam scraps glued together. Rebond is also used in modern car seats, so although a seat made from carpet padding sounds weird, it’s actually correct/ideal. I glued the layers together with contact cement and then shaped the whole stack with an electric carving knife. The result is very comfortable and compresses much less than I was afraid it might.
Interior Panels Complete
I finished up the last two big interior panels tonight; all that’s left to do on the interior is:
– Two tiny hardboard/vinyl panels for behind the sun visors
– Rubber/trim around the bottom of the front seat pedestals
– Plywood/vinyl panel under the rear seat
– Make/install vinyl seat covers
– Passenger front seat bottom
Rear Floor Mat
Today I put in the rear floor mat and completed a few more interior panels. The floor mats are reproduced, but for something that will get abused they’re expensive (expensive shipping too), and the reproductions are known to wear out quickly. So to get around all of these problems I instead used a big (4’x’8) generic rubber mat that I already had; I think it’s sold as a horse stall mat, so it should be very durable. The mat is also very heavy, so it should help the inside of the bus sound less like a big metal trashcan, despite being built like one.
Today I borrowed Christina’s sewing machine to start on the 3-part panels. Construction is fairly simple; it’s just a matter of making two parallel seams that are the correct distance apart. After this step, the resulting piece gets attached the same way as the single-color panels. The stainless trim attaches by drilling through the panel, installing the clips, then bending the clips over on the back of the panel. I finished 3 panels today, only 5 more to go…
Vinyl arrived today, the colors very closely match the original “Aero Papyrus” color scheme. The layout will be the same as original also, the only difference will be the texture of the white vinyl; it was originally a ribbed pattern that is no longer made. I was able to get all of the single-color panels wrapped tonight; tomorrow I’ll work on the more complex 3-part panels.
I spent most of tonight installing seals and adjusting the latch on the passenger front door.There’s an adjustment window of about 3 angstroms between the door closing well and it only staying closed when slammed. The latches have 2-stage catches and I have the 1st (outer) catch working well; the inner catch may not work until the new seals have time to break-in/compress. I’ll try for some improvement tomorrow night and then move on to the driver side.
This weekend I fixed the timing problem and it’s 100% better than it was. In search of lower temperatures at high speed I also changed to 5W20 oil; unlike watercooled engines that regulate their temperature directly with a thermostat, the VW aircooled engines primarily regulate their temperature indirectly via oil pressure. When the oil is cold it’s slightly thicker, causing the oil to compress a spring loaded valve and bypass the oil cooler; once it heats up it becomes thinner, allowing it to flow through the oil cooler in the fan shroud. In this way, the oil temperature is kept under control. However, if the oil pressure is too high even when hot, the oil will still bypass the cooler. In my case the oil pressure is high due to tight bearing clearances from the new bearings, and high RPM. It may get better as the engine breaks in, but for now I’ll just keep it at 55MPH or less except short bursts; the real solution here is getting the RPMs down with different transmission ratios. I also made good progress toward wetsanding and polishing, and got vinyl on order for all interior panels and seats.
“Timing is Everything”
Since the rebuild I’ve had trouble getting the bus to do 65 for more than about 5 miles without getting into the danger zone of overheating. I’ve looked at various things in the process of debugging this but tonight I think I finally found the problem; and it’s related to the way that the ignition timing works…
(Begin technical rant, or just skip to the picture at the end) To adequately explain the problem I first have to explain that in an internal combustion engine the spark is timed so that the explosion in the cylinder is peaking just as the piston is beginning to move down; the explosion pushes the piston down, which ultimately moves the bus. However, the explosion is a chemical reaction, and it takes roughly the same amount of time to occur regardless of how fast the piston is moving; so when the piston starts to move faster (higher RPM) you have to start the explosion sooner to keep the explosion peak at the same place in the cycle. This moving of the spark event is called ‘advance’ and it’s accomplished with a very clever spring and counterweight mechanism inside the distributor, as the engine goes faster the counterweights fling outwards, moving the spark trigger (points) and advancing the timing. Additionally, because higher quantities of fuel take longer to burn, the timing also has to be advanced in proportion to load. This is accomplished by a vacuum canister on the distributor that’s connected to the carburetor, the more air/fuel that rush through the carburetor, the more vacuum is drawn on this canister, moving a push-rod that further advances the timing. I found that the canister on the bus’s distributor had ruptured, causing not only the advance to be too low, but also a vacuum leak (which is also bad for other reasons I won’t get into).
So what it boils down it is that at high RPM under load there is not enough advance due to the ruptured canister, the explosions are happening too late, which means that they’re not as effective, which means that all the explosions have to therefor be more powerful to achieve the same level of power, which means more fuel, which means more heat; and thus the overheating problem. I have a replacement vacuum canister on order which should not only solve the overheating problem but increase MPGs substantially. If you made it through all of that, here’s a picture of the bus from tonight while I was figuring all this out…