Daily Archives: March 22, 2021

Weather related slowdowns at mi Casa

And it’s not the kind of weather you might think. I woke up feeling like I just went 12 rounds with Mike Tyson because of the change in the weather since yesterday, which has included massive changes in the pressure and a frontal passage. This in turn has messed with my sinuses which in turn causes me to experience headaches that range from “mildly uncomfortable” to “somebody please shoot me”. It was so bad I couldn’t even get out of bed until after 1600 because it hurt to open my eyes, not the usual “my eyelids are glued shut” I experience later in the spring, but “the exertion of opening my eyes is more than I can handle” situation. Or in terms that fit the modern vernacular, I didn’t have the spoons to open my eyes. Using the muscles to open my eyelids was just too much pain.

So I can’t open my eyes or get out of bed for a while, what do I do when I’m not sleeping? Same thing we do every night Pinky, try to take over the world build things in my mind. And of course what I build in my mind is also what I build in real life as I have the energy and funds for it, the Sprint-T. I had a bit of a dalliance with an air-cushion vehicle for a while, but that was merely a palate cleanser to keep my mental gears churning at full thinking power. Along those lines, the best shape for an ACV that doesn’t go at high speed over the surface is a circle because it has the highest ratio of enclosed area to support the weight of the vehicle to perimeter where the air can leak out and has to be replaced by the source of air used to create the cushion. Also it has the greatest stability for shifting loads like people getting on or off before settling down for the trip or moving around in the passenger compartment. One thing I also noticed was that when the speed forward exceeded a certain threshold the ram air pressure exceeded the pressure of the cushion needed to stay up the pump or fan could be shut down to save energy and reduce the costs for operation while the air is replaced by air coming in from the front. Obviously the speed of this transition was variable based on the size of the front of the air cushion and the size of the cushion. And I have already spent too much time relating my cogitation about the ACV and not enough about building the Sprint-T, IMHO.

One of the things I have been thinking about was getting the longest torque arm I can stuff in front of the rear axle, because longer arms have less-violent reactions to engine torque in both directions. This is also why I went to brake floaters to decouple brake forces from the torque arm and prevent wheel hop under braking. Well, if the torque arm is too short wheel hop can happen just from the engine resistance of compression which makes slowing down from speed dicey. So, I’m trying to figure out as long a torque arm as possible which is constrained by the front U-joint of the driveshaft and the end of the transmission tailshaft, which are determined by how far the engine is set back from the front axle. And this dimension is the major determinant of how much static load is on the rear axle, which is one of the things that sets the traction limits for the rear tires. See, changing one thing has a carry-on effect that changes dozens if not hundreds of other things. Or as Roseanne Roseannadanna’s father used to say “It’s always something.” And if you got that long-dead comedienne’s catch phrase you are officially old. But, yeah, a too-short torque arm can lift the back tires off the ground just from a too-rapid shutting of the throttle plate changing the torque from positive to negative, which can result in back tires that want to see what’s out in front as the wheels try to drive the engine instead of vice-versa. Now with the brake floaters a touch of brakes when slowing down generates forces that push the axle down against the torque reaction trying to lift the axle up, but I prefer to build a car that doesn’t always require pushing on one pedal or the other to keep the back end in the back. Which brings us back to fitting the longest torque arm that will fit in the car, or using a link between the torque arm and the chassis that doesn’t transfer forces when the driver is not pushing on either the go or stop pedals. The simple way to do this is with a chain instead of a solid link, and the most convenient place to anchor that chain is to the transmission mount crossmember.

Another thing is the mounting point for the forward end of the torque arm can’t be too far forward or back or the slip joint will either bottom out against the transmission or pull out of the transmission as the rear axle winds up or down against the torque arm. This is mainly due to the length of the torque arm as the axle’s fore and aft position is controlled by the swing arms that connect the axle to the springs and also the rest of the chassis.

And I had to take a break from the computer because a front literally came through as I was typing and my eyes started hurting so bad I had to quit and close the laptop and lie down on the recliner with Mrs. the Poet while she watched TeeVee. And while I was not writing I had a forced BIOS update take over the laptop. I’m hoping this does something useful to the computer like fix the microphone issue with the headphone jack. And we are continuing to get wave after wave of thunderstorms passing through that alternatively reduce and aggravate my headache, as the ambient pressure goes up and down. Right now the storms are past, but a few minutes ago the storm was raging on top of us and my face felt like cold crap. Seriously bad pain there. But now I’m much better with almost no discomfort, not even approaching the level of “pain” yet.

And this seems like a decent place to stop, there was a lot of information in the post, and a lot of words to convey that meaning..