May the Fourth be with you 😄! Yes I know I have used the same corny joke for years, think of it as a tradition. After all traditions are just stupid stuff we do over and over.
I’m still working on the details for the Sprint-T. Right now I have a detail that’s kinda important, but not easy to find out: How far below the input shaft does the oil pan of a 4l80E hang? This determines if I have to redesign the front hoop or the engine oil pan, and how high the engine will sit in the frame. Because I’m pretty sure they don’t make a low profile extra capacity pan for this transmission, and the distance from the input shaft to the bottom of the pan determines how low the engine can go in the frame, which sets a bunch of other things. The most important thing is will the bottom part of the front hoop clear the front of the flex plate that goes between the transmission and the engine. Because this is kinda esoteric I’ll explain that the flex plate attaches to the crankshaft on one side, and to the torque converter on the other and the torque converter sends the power to the transmission and also drives the pump on the transmission that powers the bits that allow the transmission to shift and drive the car.
Now the 1/25 engine I have has a manual transmission cast into it, but as explained earlier I only have room for 2 pedals in the footbox, and a manual requires 3, a clutch pedal in addition to the gas and brake. This means I need to alter the bang box to have the same height as the slush box so the engine fits the frame as in the full-size version. Also the intake manifold on the model engine is the LS7 version and the one on the real car has a 99%+ probability of being the taller truck version because that’s the likely source for the engine, and that manifold has better performance in the RPM range I’m going to be racing in. That means I’m going to be modifying the Corvette engine cover to resemble a “shaved” truck manifold to get the height right. Basically I’m just going to remove the script from the cover and narrow it a bit to get the width of the truck manifold, and fill in under the sides to get the look like a shaved truck manifold. Since I’m using this ECU I’ll have to use the older drive-by-cable gas pedal and throttle body which is NBD for the model but a major consideration for the real car. Also, another reason for the truck manifold is better gas mileage for freeway driving than the car-type manifold. And the real reason for the model is to have a 3D reference for building the full-size car since solving these problems in plastic is way cheaper than solving with multiple mistakes in steel or fiberglass and carbon fiber.
And Mrs. the Poet wants me to get to bed “early” because we may need to do the grocery shopping early today, so it’s time to put the post and the author both to bed.
Whatever engine I get will most likely need an ECU of some type, and I have been studying the installation and operating manuals for the Microsquirt, which costs about the same as the OBDII dongle needed to reprogram OEM ECUs. I will have to build a harness for the engine not matter which ECU I use, even if it’s the one from the donor vehicle the engine came with, because the engines I can afford are on the older end of the spectrum and the harness is likely to be dry rotted. Unless someone gives me a totalled-out vehicle with an engine and transmission I can use of recent-manufacture that still have decent wiring, which is a low possibility scenario. Given my luck I’m not going to say it’s impossible, because there have been a lot of “impossible” things happening to and around me, but realistically, yeah that’s not gonna happen.
Now the funds I have dictate $800 max for the engine with all the electronic bits and bobbles stripped off, $330 for the Microsquirt, and $40 for the bare harness plus finding and buying the various plugs and terminals, plus either an old-school non-electronic transmission or a standalone controller for the computer-controlled transmission, or if a 4l80e bolts up some kind of logic cam that attaches to the shifter and turns switches on and off to match the physical position of the mechanical shift control inside the transmission so that I can change the gears. Now this would be lots cheaper if I could roll around in the dirt at a junkyard and get these parts myself, but that is another thing on the list of things I can’t do anymore as a subset of “things that require being able to get up off the ground unassisted”. So I have to pay for someone to roll around under cars in a junkyard for me which eats into my budget.
But getting back to the premise of this post, I have been working on stuff I can’t show you because it consists mostly of reading .pdf files uploaded to my computer and taking notes in another file on my computer and apparently Notepad is no longer a thing in Windows but Word is? And WTF is Sticky Notes, is that like Notepad? And yes it has been ages since I did anything offline with Windows. Anyway I know Word, sort of, and that is what I have been using to take notes on using the Microsquirt. The files aren’t as compact as with Notepad, but I have almost 400 GB free space on the hard drive and another 90 GB free on the USB drive, I got all the space I need for anything short of video editing. So word files that use too much space compared to the amount of text are not going to be a major concern.
And this afternoon I’m going to get the tickets for the trip to see my friend for the last time before he moves to be with his wife in DC and won’t have room to put us up when we visit any more, and maybe pick up another one of those portable light switches that stick to the wall. The desk lamp in the room isn’t connected to the wall switch and the lights that are need fixing, so I’m going to slap one of those $3.00 lights on the wall so I don’t trip over anything trying to get to the desk lamp. So it’s nighty-night time for this poet/engineer. Speaking of poet/engineers I have a bone to pick with Howard Taylor about engineers and poetry. Prior to getting killed I was an in-demand spoken word poet and a decent shade-tree engineer.😛
That’s basically all I have to say right now. I have been looking at an engine controller that costs less with the tuning software than the OBDII Dongle to control the factory controller for the LS Family of engines. But I still don’t have an engine to use it on, so …
I just got finished watching a good race, Denny Hamlin won, Kyle Busch won 2 of the three races this weekend but not today, and I have to go do things tomorrow. I need to pay for my phone, I need to shop for a new mattress for the bed in the big bedroom, and I need to get a massage.
Also I need to figure out where the links for the front axle are going to fit on the frame so I can make the links to length in scale for the Mini Sprint-T. It’s basic trig and geometry, the axle is x distance from the front hoop, the lower rail is y inside to inside and y+3 outside to outside and the links have to be l distance apart to clear the tires at full lock. This has been determined previously to be 31″ outside to outside, and the links are 1″ diameter so the links have to be 30″ center to center. The only dimension that is unknown at this point is the altitude of the triangle formed by the front hoop and the lower frame rails, because I still haven’t set how far in front of the axle the forward crossmember is, because I still haven’t decided if I want big or small body shocks. The big body shocks use 3″ OD springs, the small body use 2″ OD springs and there is 0.5″ difference in how far forward the front crossmember sits which means there is maybe 0.125″ difference in where the lower rails are 30″ apart center to center measured from the front hoop.
And it has occurred to me that some of you don’t know where the transverse structural parts go and what they are called on the Sprint-T and because it is the same but in scale, the Mini Sprint-T. From the front, there is the front crossmember that holds the front coilovers over the axle and the radiator gets mounted to the front of it and the mount for the track bar that locates the axle from side to side, then the front hoop that is 1.5″ X 0.120″ for most of the structure and 0.060″ for the rest of it because it’s part of the roll cage that has to be 0.120″ wall thickness except for the part that isn’t roll cage but frame, then the rear hoop that is the same as the front hoop, then the rear crossmember that basically doesn’t do anything except hold the rear of the frame apart and protect the fuel tanks in a rear end crash, and provide additional torsional rigidity by increasing d4. The point of interest in today’s post is the front crossmember because the lower rails meet at the center and the upper rails are right over the coilover mounts and also pick up half of the mount to put the upper mount in double shear. The triangle formed by the lower rails determines how far the rear mount of the links that mount the front axle are from the front hoop because the mount has to be 30″ center to center. The links have to be parallel to work best with no bump steer from moving the ends of the axle when the car rolls in a turn. So the center of the rear mounts on the frame have to be the same distance apart as the mounts on the axle to keep the links parallel.
Anyway finding the location for the rear mount is a simple ratio. The problem is I don’t know the terms for the ratio beyond the first term. That term is 30/46.5 or 0.645161290323. That’s the ratio of the center separation of the links to the center separation of the frame rails at the front hoop, the term I’m missing is the distance from the front crossmember to the front hoop to multiply that by. I know about how far that is but not exactly how far that is. But if I think about it some more I can make it so there won’t be a difference because I’ll use the distance for the larger spring and just enjoy the extra clearance if I decide to use the smaller spring instead, so doing some quick calculations, the rear axle is 5″ behind the rear of the body, the body is 52″ long and the rear axle is 100″ behind the front axle and the front hoop is right in front of the firewall and where the frame rails meet the front hoop is 58.5″ in front of the rear axle or 41.5″ behind the front axle and the front crossmember is 1.5″ in front of the front axle, so the distance from the front hoop to the front crossmember is 43″ so the rear mounts for the links are 43-(0.645161290323*43) or 15.258064516111 from the front of the front hoop. Rounding makes that 15.26″ from the front hoop and links that are 23.25″ center to center after using the distance from the center of the rear axle to the center of the holes for the Heim joints on the 4-link brackets and the size of the vertical member supporting the rear mount which will probably be 1.5″ X 0.060″ to make it stiff enough in bending with the load triangulated at both ends, which I just decided. The diagonals will run from the top of the front hoop and the bottom of the front hoop so there will be no possibility of hitting the frame with the front tire at full steering lock. And as previously stated there is another diagonal that runs from the top of the front hoop to the top center of the front crossmember so there is a parallel frame member to capture the top of the rear mount for the links and make that area fully triangulated.
And this has turned into one of the longest non-wreck report posts I have done. So since I don’t want to overload people doing an archive dive, this seems like a good place to take a break and put this post to bed.
The parts I bought this January finally arrived today. The backgrounds are the business cards for the company I bought the parts from, to give you an idea of scale for these parts, and I’m using “scale” in two forms for this. The parts are for the Mini Sprint-T in 1/25 scale.
Again, the backgrounds in the picture, the dark part, is the business card of the company that I bought these from. They literally get lost on a standard size business card. And there was a note inside the delivery envelope saying the guy that runs the whole show for this company just got out of the hospital after 2 months. And those thin pins coming off the top row of rod ends fit snugly in the stainless steel tubes I bought to make the links for the 4-link, and the plan is to add a tiny drop of solder to the end of the tube to hold the rod end and jam nut in place. The jam nuts are those hex-shaped things above the rod ends.
And I need to get to bed, so the blog post needs to, too.
I forgot the picture of the stuff I got for the Sprint-T, and I forgot to tell you what I weighed after fasting at the Lab Rat Keeper. And other things as well.
First things first, this is a picture of the stuff I got combined with stuff I already had so you can see how it goes together.
These Heim Joints have 3/8” holes and 5/8” shanks to fit the brackets and the links available. The brackets obviously have the holes and can’t be drilled larger without weakening them to the point that a minor wreck would tear the holes, requiring major repairs to the axle. So what I have planned is making the weak link where the links meet the frame. The plan is to use cheap, fragile aluminum body Heim joints that break at impact loads but still strong and rigid enough to not flex in regular use. And the next weak link is the links themselves, internally threaded aluminum tubes, that bend under impact loads but like the frame mount Heim joints don’t flex during normal operation. The intent is to absorb impacts by bending or breaking cheap parts that are easy to replace without damaging expensive parts that are difficult to replace, or have a long lead time to replace like the 4 week lead time for the front axle.
Now, my weight at Wednesday’s visit to the Lab Rat Keeper showed just how much I have for breakfast, particularly how much coffee. I weighed 211 pounds (95.7 kg) the previous visit, but only 208 (94.3 kg) this visit. My normal breakfast before a visit is a package of PopTarts and a “my cup” (750 ml) of coffee, and I usually have a light meal right before bed at about 0300. I have measured the capacity of this “cup” several times and the only way it reaches the manufacturer’s 1 quart rating is to leave the lid off and fill it to the brim, but measuring to the inside top of the lid gets 750 ml. But anyway no 0300 meal and no breakfast has me at 208 pounds.
Also there were races today, but if you were interested in that you would either have watched them yourself, or accessed a sports site to find out who won. I will say that the semi-local IndyCar race Will Power broke while leading. 🙁
I saw a video on YouTube about choosing the best LS family engine for your car, and boiled down it was “The best engine is the one you can afford with all the bits still attached”. So I have been prowling the FB Marketplace ads for truck and SUV engines from the right eras and there are a bunch that are more-or-less in my price range, but the big problem is I need a truck to get one home. That means unless I can convince a truck-owning friend or family member to help me pick it up, I’m not getting that engine. Impasse. I can afford to buy it but I can’t afford to get it, which negates my ability to buy it. And if I can’t bring it home it doesn’t matter if I can afford to buy it.
And once again I’m facing frustration because I don’t have the resources needed to complete a project. This has become a familiar situation, but unlike previous times instead of dropping it and moving to something else, I’m persisting and moving as the opportunities present themselves. There will be other engines, I will have access to vehicles that can transport one and I will have the funds when the opportunity presents itself to avail myself of the situation. In simpler terms, eventually things will fall my way. I just have to keep working to make sure that when things fall my way I’m in the right place to catch them. Prepare for the worst, expect the best, and just be ready no matter what happens.
One way to be ready is information, know what you can use so you can use it when you have access to it, which is why I have been snapping up LS family swap and performance books every time Amazon puts them up for loss-leaders at the Kindle store. Information is one of those things you don’t know you need until you need it, and it’s better to have and not need than need and not have. And on that note I’m putting this one to bed.
I have been thinking about the Sprint-T again. Specifically thinking about that super muffler that will require I drill hundreds if not thousands of holes for exhaust pulses to pass through so the gas flow is not impeded by shock waves, like the walls of a supersonic wind tunnel. And doing some research on those tells me that if this muffler is long enough I don’t need to use any absorption material between the core and the shell, just a bit of empty space to let the sound pulses bounce around and dissipate. Now exactly how much empty space is “enough” may require some experimentation.
The thought of running experiments for not enough, just right, and too much empty space has me slightly excited. After all, this is the Holy Grail for street performance, and more than a few race tracks. A muffler that is both quiet and doesn’t choke the engine down at higher RPM is seriously sought after, especially if it lasts at least as long as the straight pipe it would be replacing. Now the down side of this would be the problems in mass producing the core. Obviously doing it the way I’m going to, drilling holes in a tube by hand, just ain’t going to fly. Other ways could be a CNC machine that drilled holes in a tube, welding perforated sheet as a tube, forming perf sheet into a flanged half tube and then welding or using screws to make the half tubes into whole tubes, or some other method I haven’t thought about yet. And a quick Google search showed there are companies making perforated tubing to order in whatever diameter or wall thickness I can imagine. But anyway the experiment for me requires making the core then attaching the outer housing some way that centers the core and makes sure it stays centered, and making the same core fit different sized housings to see which one makes the engine quiet without packing material. That one I already have figured out, make toruses with the inner diameter the same as the OD of the core, and the OD the same as the ID of the housing. Most of the rings would be tack or skip welded to the core to keep them in place as the core is inserted into the housing but the ends would get fully welded to prevent noisy leaks…
And after building one would get installed as a control on one side of the engine, while the rest are installed on the other side for comparison, with both getting measured so if the sound level changes I can be sure it isn’t because of changing conditions, and if conditions change use the control muffler to normalize the test results. Now if I had unlimited test resources I would test things like if the space between the centering rings changed the results, how much changing the diameter of the housing compared to the core changed the sound, and if there was an optimum length for the housing beyond which the noise level didn’t go down, that kind of interesting stuff that can only be determined by cut and try or by using a supercomputer to model the gas flow. And three guesses what I don’t have access to here at Casa de El Poeta, first two don’t count because there are only two choices. With what I have now my experiments are limited to outer housing diameter and length, after I get an engine to test them on…
And it looks like I have typed enough tonight, this should hold your imaginations for a while, while I think some more.
That used to have “and the Feed” back in the day when I was still covering bike wrecks every day, but since I stopped doing that my mental health has improved considerably. That’s a little on the scary side that this state is “improved” over where I was just a few years ago.
Anyway, the race was in Las Vegas and was 400 miles long, and Joey Logano won. The new package has slowed the cars way down on the track but they still have the same pit road speed limit they did at last year’s Las Vegas Spring race which means the pit crews are still facing Certain Death if they get in the way of cars moving at or near highway speed, but the cars are now going slow enough on the track that there is very little possibility of one leaving the track and going into the stands and killing a bunch of people. The last time they had a car going too fast for the retainment system they got really lucky and there were only minor injuries to the spectators hit by debris. The new rules can be summarized by “Big spoilers, tiny spacers” as the Big Tracks (basically anything over a mile long) have tapered spacers between the throttle body and intake manifold that reduce engine power to about 550HP or a bit less, partially because that was the cheapest way to do it and partially because the cars were Too Fast everywhere except short tracks and road courses. So now they have most tracks limited to 550, Daytona and ‘Dega are going to be about 400HP if I’m remembering that right, and short tracks and road courses are going to get full effective use of the intake system to make the 750 HP those engines are capable of. To make sure everybody stays inside the track fence and out of the crowds they bumped the rear spoiler from less than 3″ to
almost 8″ tall and added a bunch of front downforce to keep the cars aero balanced with about the same downforce on each end. Teams are still trying to figure out the suspension settings that work with the new package because this was a major change from last year even though they kept trying to say it was only a “minimal change.”
One thing that is changing on the Mini Sprint-T and Sprint-T is how the rollover structure integrates with the frame structure. Simple terms the upper frame rail is getting moved back out to the furthest edges of the frame again by squaring off the corners of the roll hoops but also leaving the hoops inside exactly like the SCCA wants it. The hoops will be bent from a single length of tubing as specified in the rules, but there will be short stubs of frame-size tubing welded to the outside of the bends to pick up the upper frame rail. The diagonals will still be rollover structure wall thickness and also have the bends to catch the top of the rear hoop, a bent gusset to catch the vertical leg of the hoop, and a frame thickness stub to catch the intersection of the tangent stubs from the vertical and horizontal legs of the hoops and tie everything together in a lightweight super triangulated space frame, and also what I hope is a rule-complaint roll cage. I’ll have to wait until tech inspection to find out, though.
I should be on my way back from visiting the Lab Rat Keeper instead of composing a post. But the tubes they need for this study still haven’t arrived from the people doing the study. I’m starting to wonder what they are trying to study in my blood.
On another note I’m almost done reading a book about the Mercedes pushrod engine that won Indy in 1994 when USAC changed the rules to make the pushrod engine more durable. They could have done that by allowing larger V8 engines at the same boost as the DOHC engines, but they didn’t and only the Penske team had the super pushrod engine because they were the only ones to build to the rule change. Now they have what is essentially a spec series that no longer allows innovation but back then they had multiple engine manufacturers and some sold more than one type of engine, and everybody had to build or buy their own chassis and body. So there were lots of different solutions to the problem of winning the 500 mile race on Memorial Day. The name of the book is Beast: The Top Secret Illmor-Penske Race Car That Shocked the World at the 1994 Indy 500. I mean seriously a SBC destroked to 5 liters wasn’t even that hard a build, it could be done with factory parts (and was during the Trans-Am racing heyday with the 302 Z28) and would live all day at the same 700 HP the DOHC engines were making, and there was also the slightly smaller Ford 302 that was sold in the Mustang every day…
I’m reading the book because it was a $0.99 special for Kindle while I was on Prime, and I take inspiration for the T-Bucket build from many sources. Also it is a good book, well-written, and perfect to read a few chapters from before I go to bed. Also I can relate, while not as awesome as building an engine from a blank piece of paper I am building a car from basically scratch here. Problems arise that must be solved, in both scenarios.
Moving back to the Mini Sprint-T build, I’m having parts supplier problems with the stuff I bought from Dirt Modeler. I paid for the order 2019-01-23 and here it is 2019-02-27 and no parts. Now I can build this model without the stuff from Dirt Modeler, but it would look much better with them. Especially the seat , which is basically the same seat I have with a few lightening holes to reduce weight and increase manufacturing costs at full scale. In scale it doesn’t cost any more to put the holes in than leave them out because the whole part is made by photoetching, a process I used to work with when I made computer chips at TI. Basically the part is laid out in CAD, an image is generated and projected on to a sheet of metal covered in a photosensitive acid resistant coating that hardens when exposed to light (or gets soluble when exposed to light, there are many different kinds of resists) and the part that is not the pattern gets washed away (called “developing”) and then they wash the sheet with acids or other corrosives until they have a 2D unfolded version of a seat, or a computer chip, or thousands of other applications that use this process. The site is only showing 5 seats remaining so they removed the seat I bought from stock, but as of today’s mail it still hasn’t made an appearance at Casa de El Poeta.