Tag Archives: finding technical information

Nothing much new

I’ve been doing some figuring on the intake manifold and cam combination, but TBH this one is not well covered in the public literature and simulations. Except for the Holdener videos this is pretty much terra incognita for published data. And not to be tooting my own horn, one of the things I was really good at was drawing correct conclusions from insufficient data. And right now I’m dealing with way too little data, essentially only 5 data points between the Holdener videos and two other TPI videos, and those two went with the commonly accepted practice of short duration cams with the long runner intakes. Like 240° advertised duration or less short. My theory hypothesis is 270°@0.050″ lift at a minimum and 290°@0.050 preferred, those are considered radical durations that would have terrible idle and low RPM manners if not for the stupid long runners, but even so would not work without the large cross-sectional area of those long runners giving good airflow for the upper RPM ranges.

On other things I’m putting out an ad for someone to make my car work as DLC for GT5 so I can drive it on the gokart tracks I built with the track editor in the game. Translating that to English I’m asking for someone to code the Sprint-T as Down Loadable Content for Gran Turismo 5, so I could make it usable in the game. I could use the free classifieds in Grassroots Motorsports to request submissions. The thing is I have zero idea of what information would be needed for the game version of the Sprint-T. I know the tuning choices give 3 selections each from 3 categories of tire, and some cars have the option for tuning the power output from the engine, to that means a variable with a range for power and also variables for grip and hydroplane resistance in the tires. Now how sophisticated the tire modelling is??? it could be as simple as a simple ratio for grip that is dependent on tire choice or a multi-variable algorithm that takes temperature and depth of standing water along with a bunch of other things into consideration. And there’s nothing I can find on the internet about it. I can find some of what has to be simulated in this formula “Pacejka Magic Formula” Physics Doctorial thesis on the web and simplified formulas for designers and in video format Brian Beckman: The Physics in Games- Real Time Simulation Explained. The biggest thing is the physical limitations of the CPU and GPU as the formulas get to various limits that end up dividing by very small numbers and the answers get larger than the registers in the CPU or GPU. Which has nothing to do with how GT5 stores its car models, just a taste of what’s involved in building that model. And after all that I still don’t know how to get from the piles of parts distributed around the house to driving pixels on my TV screen, which is why I’m thinking about paying someone to do it for me.

And I just face-planted in the keyboard because I’m glazing over at the programming details that don’t apply to this situation, so this is a good place to put this to bed and me shortly after.

OK Finished the Archive Crawl of QC

I finished the archive crawl of Questionable Content last night early early this morning and saw patterns in his creative processes, but I really didn’t help my problem. I did see an ongoing art evolution that gradually became more of a character evolution, but aside from taking my mind off the subject enough that I am able to post this about my observations I didn’t find anything that would break my creative block, at least as far as writing is concerned. Now for the Sprint-T and the Mini Sprint-T I have found a few things to move that design along, but only in details. So far the major parts of the build are pretty much set in stone, but there are a ton of details that have to be resolved before the design can move forward as the tiny details cascade backwards into major changes in other parts of the build.

One of those tiny details is the steering arm location and orientation on the spindle. There are two locations and two orientations that result in 4 different locations for the drag link connecting the pitman arm on the steering box to the steering arm on the spindle. This cascades into different locations for the steering box because the drag link needs to be pretty level, or close to it if other things get in the way, which basically means there are 3 different places I need to put the steering box depending on how I mount the steering arm on the spindles. That’s because there are 2 combinations of mounting position and orientation that put the drag link in pretty much the same place.

Actually there’s no real technical reason for making the drag link level. The drag link and the panhard rod or lateral link (same device, different names) need to be parallel to prevent bump steer, and ideally the lateral link should be roughly level with the ground to prevent excessive side-to-side motion which would change the way the car turned depending on ride height. In the end it just makes things slightly easier to finagle to have the lateral link level at design ride height, and as stated earlier having the drag link parallel to the lateral link prevents bump steer and other steering maladies.

Another tiny detail is mounting the alternator, and I think I have that one nailed down. The only belt-driven device on the engine will be the alternator as the power steering will be electric, so no power steering pump, no AC so no AC compressor, and the water pump will be electric to reduce total drag on the engine and also improve cooling efficiency by driving the pump at the speed for best cooling regardless of the engine speed. That only leaves the alternator that needs to be driven by the engine directly. As I pointed out a while back there are 3 bosses on the passenger side of the block that are designed to have a bracket for an engine driven device bolted to them, the bracket for the AC compressor specifically, but there is no reason why that device can’t be the alternator instead. What I was thinking is a plate that bolted to the side of the block and another plate that gets welded to that plate that the alternator bolted to with one bolt hole being the arced slot that the bolt that adjusts the tension of the belt slides through. That front plate can be just bent from the side plate to avoid a welded joint, but that’s more of a “what can I do with the materials and tools I have?” than the other kind of design question. Obviously both bolts that go to the alternator would have to be on the same plane or pretty close (talking washer thickness differences more or less) which means I need to do a little bit of measuring when I go to the parts store to pick out an alternator, but for the Mini Sprint-T I just pull one from the parts box and bend a bracket from sheet plastic to glue to the block and alternator to hold it. I just have to line up the crank pulley and the alternator pulley until the glue dries, then run a simulated belt around the pulleys.

And there is a valid reason the alternator goes to the passenger side of the engine that goes back to mounting the steering box on the driver’s side of the frame and leaving room for the box and the steering shaft. If you thought Tetris was fun wait until you have to package the front end of a hot rod. At least when I have to shave material off the model to make things fit a hundredth of an inch on the model is a quarter of an inch on the full size car, or what’s basically molding flash on the model is major structure on the real car. And the engine and transmission is going to be offset to the right to counterbalance my weight to the left, another design decision made a long time ago. I have to find good weights for the engine and transmission.

I have a weight from a GM technical publication of 255 pounds full of fluids for the transmission, and a weight from a GM parts catalog of 614 pounds for the fully-dressed version of the motor I will probably get from the junkyard but nothing accurate for the junk I will be pulling off. Anyway I can assume about ~50 pounds for AC and power steering and assorted junk brackets so 565 for the engine and 255 for the transmission and 30 for the full of fluids torque converter adds up to 850 (!) pounds for everything on the right side of the car, balanced by my 210 way further from the center on the left. Doing the math my moment is 210 pounds times my arm of 11.25″ or 2362.5 Pound inches of moment and dividing that moment by the 850 pound engine gives a 2.78″ moment to balance or 2.8″ to take the driveshaft into account. That works out to 0.112″ on the Mini Sprint-T which is enough to be noticed on the model. The inside to inside on the Sprint-T cowl is 26″ and the bellhousing on the back of the engine or front of the transmission is 19″ outside to outside and moving the engine 2.8″ to the right gives me 0.7″ clearance on the right side of the engine if I use a mini starter instead of the honking huge OEM starter that actually sticks out from the side of the engine, getting back to the subject of Tetrissing the engine compartment. And I know I did this calculation for an SBC a while back, but I didn’t feel like going through the archive to find it because I just finished diving the QC archive in the way early hours of this morning and diving a comic archive is much quicker than looking for specific words in a blog archive.

And it’s getting late because I have been watching YouTube videos between paragraphs and I have almost 1200 words according to the editing program that comes with WordPress. So this seems like a good place to wrap this and post.