Tag Archives: Sprint-T

Yesterday was Fair Day

I did a food tour of the State Fair Of Texas yesterday, until I ran out of coupons. I took some pictures but not of everything. Anyway, this was lunch.
Corn fritters and jalapeño creamed corn

$1 root beer 12 oz

I also had a $4 lemonade that I think was 16 oz, and a $1 bottle of water. I forgot to take pictures of them.

This I wanted to stuff into my bag and take home for the Sprint-T, but it didn’t fit through the top of the bag. This is about as far as they could push the rules that required injection at the throttle body, and you can just barely see the coil pack on the front of the engine if you follow the plug wires back to the front. The ECU is mounted to the back of the engine stand but would be on the top of the dashboard under the windshield in the car. The throttle body is a standard Holley part that NASCAR requires, that Holly uses for their EFI conversion kits, because it worked and was cheaper that way.
TRD Cup series engine with manifold runner injection and individual coils for each plug mounted to the front of the engine
And in this picture the coil pack is clearly visible along with the tiny alternator and the Holly EFI throttle body.
Good view of the front of the TRD engine

Something I noticed at the back of the engine was the bellhousing pattern appeared to be the same as the SBC and LS engines. I guess this was to make it easier to use available parts to connect the engine to the rest of the drivetrain.

Something else I saw at the Ford display was they had various sizes of SUVs, pickup rucks, and some Mustangs, and that was it, no actual passenger cars other than the Mustang. Their brochure listed another car, the Fusion, as available in 2020, but I saw nary a one in the display. Now there were some car-sized SUVs on display, basically full-size station wagons that didn’t have a sedan counterpart, some smaller and some bigger than the 1971 LTD wagon the family bought when we got back from when we were stationed in Africa.

And I have been transferring pictures from my phone to my computer to my blog media file for hours, and I’m ready to quit now.

Advertisements

I have been having bad brain days for a while

This is normal right after my death day, and it doesn’t matter if there’s a big shindig, or I’m all by myself like this year. The difference is when there’s a big shindig it doesn’t last very long, and when I only have the cats to be with I get down for much longer. This year the cats didn’t show up either but they did come back in the morning, but I still got way down. This was a bad year for this particular problem. The only social group I interact with any more is the RPG Group. And nobody responded to my Twitter invite or my FB save the date. I never saw the FB thing go live so that might have been a mistake on my part setting that up.

But anyway, the end result was a lack of desire to write anything more complex than a grocery list, or work on the Mini Sprint-T, or the Sprint-T. I knew I was starting to come out of it when I started thinking about building a car for SCCA Solo racing A-MOD using a V-twin engine from a cruiser motorcycle and a setup that was basically a scaled-up shifter Kart with the suspension and brakes needed to be a legal A-MOD car. I planned on using Midget or Micro-sprint spindles (pretty much the same thing) with pavement brackets for big brakes on both sides (dirt spindles have a smaller brake on the left side only), hung on an axle made from wrapping carbon fiber around a foam core and steel inserts for the kingpins to ride in. The idea was to use a beam axle to keep the tires pointed in the right direction for camber and then make that sucker as light as possible for the lowest unsprung weight. I was going to use a rear axle from the mini- or micro-sprint to connect to the chain drive from the motorcycle engine with a jackshaft for initial gear reduction and moving the final drive to the center like on the Grind Hard Plumbing Princess Jeep only with much less articulation because pavement racer instead of dirt crawler/buggy like the Princess Jeep. But what they did prove was that using a small sprocket on the axle prevented chain bind or jumping when the axle was twisted through a range much further than an A-MOD Solo racer would ever see outside of a wreck. So Imma steal that idea for my car.

Also the reason I’m stealing the jackshaft idea is I’m mounting the engine way off center to balance the driver weight and to keep the polar moment as low as possible by keeping as much mass in the center of the car as possible. Driver to one side, engine to the other with both as close together as physically possible given the need to balance left-to-right and the need for the final drive chain to ride in the center of the axle. I’m leveraging my skinny butt to get as close to the centerline as the chainguard will allow, because I’m only 13″ wide at the hips. This reduces my moment arm from 11.25″ in the Sprint-T to 7″ leaving clearance for the chain and chainguard because I don’t have to leave room for another person, just the engine. I have really wide shoulders and a really skinny butt, like my Dad, and that’s the main reason why the driver moment is so large in the Sprint-T because I have to leave room for a passenger by the rules for Goodguys.

I also knew I was getting better when I started looking through the Hoosier tire catalog looking for the right tire to use when racing the Sprint-T in SCCA Solo events. Basically I was looking for short, wide and sticky that would fit a 15″ X 8″ or X 10″ wheel because there are light, strong, and cheap wheels in those sizes available in several different offsets that fit one or the other of the bolt circles on my hubs. I also used more than just the road racing tires and went into the pavement oval listings to see if there were any tires that came close, and I found a couple in the section for Modified class, and pavement sprint and Supermodified classes which despite being vastly different in layout use pretty much the same tires. Those tires were larger in diameter than my ideal of <23", but were considerably wider than most of the road race offerings with tread widths of 11-13" compared to the 8-9.5" of the road race catalog. The suitable tires for the pavement oval racers were 24-25.5" in diameter compared to the road race tires in the 22.5-23.5" diameter but much narrower as the diameter decreased. Also the oval racing tires are bias-ply while the road race tires came in a mix of bias and radial depending on the size, which tosses another variable into the mix. Radial tires have higher peak grip given the same size and compound, but bias tires are much more controlable at the limit and come in wider tread widths with stickier compounds, so ultimate grip becomes a wash. Also, the reason why there are so many size and compound choices in the oval tire section of the catalog is oval cars run different size and compound tires at each corner in the sprint and Supermodified classes to balance the handling or to use different diameter tires to force the car to turn left when running a locked rear or a solid rear axle (same thing, just built differently) so the right tire drives the car to the left.

It has been a bit difficult to type this in as Clint has decided to lay on my lap on his back demanding tummy rubs which means I have to type with one hand while holding the cat with the other to keep him from sliding off my lap and grabbing me with his claws to keep from sliding. That usually results in long deep scratches. And now he lost interest and has left the room.

Which makes for a good time to end this and hit "Post"

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.

Still thinking about the Sprint-T

Thinking about the possibilities with the turbochargers linked in the last post has kept me awake at night (maybe a little more than if I hadn’t been thinking about it). OK, seriously, this has been the kind of conundrum my mind refuses to let go of.

Let’s start with the knowns and unknowns in this scenario:
1. The turbos are too small for the engine at max RPM and are flow limited so theoretically the boost curve will peak at some point before redline and decline from there.
2. The wastegates are probably too small to prevent overboost at speeds below torque peak because there is likely more exhaust flow than they can dump (the turbo is designed for a 1.8l engine and each bank is 2.65l). The corollary of this is at some point boost creep will become a problem if the engine can’t handle all the boost the turbos make and has to use the waste gate to dump some of the boost.
3. At this point how much boost the turbos will make is unknown, the only thing I do know is it won’t be as high at power peak as it will at a lower engine speed. Also unknown is how drastic the dropoff in boost will be from peak to redline. The listing claims each turbo will flow 250+ HP so I’m going to get pessimistic and say maybe 400-450HP flywheel HP which would be about 7 or 8 pounds of boost on a 5.3l engine at peak.
4. There is a possibility the engine/turbo combination can be run without connecting the wastegates to manifold pressure and without excessive boost in the low RPM range. This is the Best Case Scenario, that literally the only other thing needed is charge coolers, or running a fuel or water or water/methanol spray into the turbo inlet to cool the charge under boost, or some magics that otherwise don’t require adding more hardware to the engine. And also with this combination the possibility that the engine hits peak power at peak turbo airflow and just sustains almost 450 HP all the way to redline. That would be Seriously Best Case Scenario, peak power in a usable RPM range and no dropoff until time to shift to a higher gear because the engine safely won’t go any faster. I will still need to have some method of bypassing the turbos for running 87 octane between races unless somehow the engine will not self-destruct under boost with unleaded regular, but the probability of that is less than my surviving getting hit with a truck doing 60 MPH. It might happen once, it might even happen twice, but to bet it will happen on a regular basis is playing Russian Roulette with only one empty chamber instead of only one bullet.

Now some of this can be seen in this Engine Masters episode as their single turbo has more airflow than the two turbos I’m contemplating but still it’s a stock 5.3l LS architecture engine identical to what I’m trying to find with boost, just more airflow above torque peak than the two tiny turbos I’m thinking about, but notice how much they get out of the boost they get. Also notice they have an intercooler that will cool far more airflow than what the two tiny turbos will generate and get charge temperature down to a safe level for 93 octane and moderate boost. Also their single turbo probably doesn’t make near the boost the small twin turbos make at lower than NA peak torque RPM, so the Tiny Twins will probably make more torque below peak.

Anyway there are many things I could do, and what I really want to do is leave as much junk off as I can and not put the engine survival in jeopardy.

I haven’t felt this bad since The Wreck

Slight exaggeration, I’m sure I have felt worse than this since the wreck, but I managed to wipe the memory from my mind. Something is growing that “doesn’t like” me and it feels like I was punched in the face and my eye area is swollen and I don’t see so good right now. Of all my allergy attacks this year this one feels the worst. I’m tired all the time even when I’m not taking the generic diphenhydramine that is also on my list of approved sleep aids, and taking even the reduced dose puts me right out for hours. I spent a lot of time lying down because my leg is treating this like the histamine reaction is because of muscle strains or something and it gets uncomfortable like it’s swelling or something so I have to elevate the leg. Also I still haven’t managed to get my sleep cycle back to sleeping at night and active by day so Mrs. the Poet is annoyed I’m making noise at night and in the bed all day.

On the Sprint-T front, I’m thinking about other directions for making power where I need it for racing while still having a car that is capable of running 87 octane on the street and Interstate without destroying the engine with detonation. One thing that I saw was an article on the Hot Rod magazine web site on running close to the same engine as I’m planning on using a cheap small turbocharger that was too small to even cause the waste gate to open at peak RPM because it lacked airflow capacity, but generated good boost and throttle response in the RPM range I will use for racing. This would require running E85 racing, and somehow only getting enough exhaust to not restrict the intake when running 87 octane (the local unleaded regular blend), or stuff it and don’t worry about it just driving around and bypass all the exhaust around the turbo(s) using exhaust cutouts on the pipes leading to the turbo(s) and just use the stock exhaust manifolds and running the stock camshaft so the engine budget is only the cost of the turbo(s) and the plumbing that connects the exhaust to the turbo(s) and back to the intake, and maybe a Charge Cooler of some kind on the intake side.

I’m looking at a pair of $99 Amazon turbochargers for a 1.8 liter turbo diesel economy car instead of the $163 single turbo in the article because quicker initial spool, desired HP range (the tires I can get plus the light weight mean hooking more than about 400 HP to the ground is a lost cause). The tricky part will be running oil lines from the 5.3l that was never meant to run a turbo to the turbo that was intended for a dedicated OEM turbo installation on a 4 cylinder engine. Not an insurmountable obstacle, just a bit tricky unless the kit includes diagrams for the oil system. And the other tricky part is running the exhaust and compressed air from the passenger side turbo, because everything is directed to the wrong side of the engine for that side, unless the turbo is oriented with the inlet facing forward and the exhaust inlet facing down and the compressor housing is rotated 180° on the driver’s side turbo. It looks like this is possible from looking at the pictures on the listing. Also from looking at the pictures the gas speed going into the turbine is going to be quite high as the inlet is only 1.5″ while the exhaust flange on the 5.3l exhaust manifold is about 2.5″. That means quick spool, but it also means the turbo will be an exhaust restriction at high RPM.

Now before I buy anything I need to price the difference between the turbochargers and traditional performance parts, as in a cam swap kit with valve springs and free-flowing exhaust manifolds. Either way I need to run 2 maps because the 87 octane is going to be optimized for scooting around town and good gas mileage on the highway while the E85 tune is for racing. But the map, and MAP sensor (Manifold Absolute Pressure) is going to be very different between the turbo and NA (Naturally Aspirated) versions. More fun when tuning.

And now that the sun has set my face feels much better so whatever is beating my face up is a day blooming plant. I’ll be back later.

Can’t stop thinking about the Mini and Sprint-T

First thing I was thinking about was making an oil pan for both that clears the bottom part of the front hoop, as that has to go right where the rear sump for the oil pan goes on both the SBC in the Mini Sprint-T and the LS engine in the Sprint-T. That’s not so hard for the SBC model in the model version of the Sprint-T, just cut the bottom off the oil pan and stick another one on that clears the frame parts. But for the LS engine in the real thing it’s a little more difficult. A completely new pan would need to be fabricated from scratch which is pushing my skills to the limit. I can do some stuff, I know how to do more stuff than I have the eye-hand skills to do.

In other news on the Sprint-T and its smaller cousin, major changes to the forward part of the frame for increased crash resistance and torsional rigidity. The crash resistance would come from bending the bottom frame rail to make it a single piece from the rear hoop to the front suspension mounts and making the full size version from 0.120″ wall instead of the previous version 0.060″ wall. Since the diagonal leading from the top of the front hoop to the front suspension crossmember would still be 0.060″ wall it would buckle first causing the engine to go under the passenger compartment in a frontal collision, with the lower rail failing at the bend to allow this. The other thing was a bolt-in set of diagonals that would triangulate the upper part of the front frame in race mode but be left off in street mode for better forward vision and to allow the upper diagonal from the front hoop to fail in a known way and direct the engine under the car in a frontal collision. The small amount of additional flex in street mode would be offset by the greater safety in frontal collisions, because while the bottom part is completely braced by the welded-on belly pan (with an access hatch for changing the oil) and the sides are triangulated by the upper and lower diagonal braces from the front hoop to the front suspension crossmember the top part is completely unbraced and would allow some deflection in torsion without the bolt-in brace. What I’m envisioning is a double triangle brace that would bolt in at both ends of the top member coming off the front hoop at both the front hoop and the front suspension crossmember and also the center of both the hoop and the front suspension crossmember. It would form overlapping triangles that run from the top of the front hoop to the center of the suspension crossmember, and a second triangle from the ends of the suspension crossmember to the center of the front hoop, and a piece that runs from one side of where the two triangles intersect to the other, making even the braces triangulated. I’m thinking this set of braces would be made from lighter wall tubing and also in a smaller diameter since it wouldn’t be highly stressed and also is mounted fairly high in the frame so someplace added weight is bad for center of gravity issues.

Also on the triangulation issues are the engine and steering box mounts. The steering box mounts need to be braced side-to-side so it doesn’t deflect under cornering loads and cause inconsistent steering reaction depending on speed (faster causes greater side loads on the steering requiring more input as speeds increase not related to slip angles from the tires, which reduces the feedback to the driver as to how much traction remains at the front tires), and the engine mounts need to be braced so they don’t become a point load on the lower rail of the frame and introduce a new buckle point in a frontal collision while at the same time it needs to provide a consistent buckle point for the upper diagonal to direct the engine under the car in that frontal collision. There are a lot of things to think about when you build a car from scratch, like where I brace the engine mounts.

Another thing I have been thinking about was the pushrod and rocker arm linkages for the front suspension. I have been thinking about this because it 1) allows for easy wheel rate and ride height adjustments going from street to race mode, and b) makes changing corner weights super easy. When changing the wheel rate the effective rate changes as the square of the ratio between the leg of the rocker arm attached to the axle and the arm attached to the spring and shock absorber so making the arm attached to the axle longer makes the rate go down while making the arm attached to the spring longer makes the rate go up, and adjusting both can give me the perfect rate for street and race without having to buy two (or more) sets of springs and shock absorbers, meaning I just need to carry extra pushrods that cost roughly $20 each instead of multiple sets of springs and shocks at anywhere from $100 to >$500 each. The ones I’m looking at now are $250 the pair or roughly $125 each. The other thing I have been looking at is how the rocker connects to the moving bits in the suspension, because the pushrod has to be over the axle, while the coilover has to be to one side or the other of the axle so it has room to travel. I guess this implies I need some method to make sure the rocker arm only rotates through the axis it is supposed to pivot on as a lever system and not on the axis between the pushrod and spring attachments because there is a moment arm between the two created by the need to have one on one side of the rocker arm and the other on the other side of the arm and not just on opposite ends of the rocker arm. Hypothetically with the rocker arm suspension one could adjust corner weights without needing to roll the car off the scales and drive around to get the shocks to settle because you never move the shock when adjusting the weight, only the pushrod.

And this is the wordiest I have been in quite a while, which just goes to show what my true passion is these days.

Stuff arrived!

This is another unboxing blog post of stuff I got for the Sprint-T. I sold an article, which is something we writers do to make money. Don’t bother looking for it, I sold it without a byline because I made more money that way (no exposure), and I used part of the money to get parts for the Sprint-T, specifically front brakes. It was an article about computer history told from a first-person perspective, because dangit I’m that old that I can tell history in first person. I did have a computer with Windows 3.1 and before that a TI99/4A, and before that a Burroughs that weighed in just shy of 500 Kg. I also built a C/PM computer that I never got to use because I couldn’t afford the 8″ floppy drive… And those wirewrap sockets also cost out the yingyang.

But anyway, The Stuff! I got the biggest disc brakes I could buy for the spindles I bought way back before I evicted Chris Christie from my neck.
The box that was sitting on the porch.
As you can see I got excited and forgot my phone when I started to open the box.

This was the bottom layer of an incredibly Tetrised packing system.The box that holds the actual discs inside the box everything came in.

And there was stuff inside that box.That is a 12.19 inch diameter vented disc made from a proprietary iron alloy

By this time I had remembered to go get my phone and was taking pictures as stuff emerged from the boxes inside the delivery box. This is the hub.This was the least-blingy option for the biggest brake that would fit the spindles.

The front of the hub free from the plastic bag, isn’t it pretty?You can see the machining marks if you look closely that lets you know this was the as-machined front of the hub.

The level of bling with this part number was very high, but there were options that made this look plain. This was the as-machined back of the hub.Plain anodized and not even polished, I went for function but still, look at that machining.

This is what connects the disc to that gorgeous hub.I'm not sure how they made the adaptor that connects the disc to the hub, but the standard of machining was not as high as those gorgeous hubs.

This is what squeezed the pads together on those gigantic discs.Top view of the calipers in the safety of the storage bag. Gotta keep those sanitary if I want to make consistent stops.

Those pads are going to get really squished by that thing.Bottom view, with bubblewrap occupying the space where the pads go to prevent damage or contamination to the pistons.

Speaking of pads.This is a set of Street/autocross compound pads, near race level performance but with the durability needed for streets and highways

And the box those come in.I don't know if you can read that compound label from this angle, but that's a box

The unsung heroes of any build, the hardware that holds it together.Nuts and bolts without which this build won't get built.
Yeah that picture was taken in kinda low light and brightening it up enough to make it look the same as the others caused a loss of quality in my picture program.

And the bracket that holds the calipers to the spindle.This is a high-precision part that keeps things from rubbing together until it's time for things to rub together.

And those are all the pictures, but not all the post.

Besides being the biggest brake kit that would fit the spindles, this is also the biggest kit that would fit inside a 15″ wheel, meaning that’s the smallest wheel I can run. But if I’m serious about running Goodguys I can’t run anything smaller than 15″ anyway because that’s about the smallest wheel they still build high-performance street tires for. So, there are a few 200 treadwear rated tires in 15″ but the widest is 245mm section width and about 23.5″ diameter. Good diameter, but a bit skinny for hooking up 300+ HP coming out of a turn, that’s good for making smoke but not so much for going fast. My next choice is 17″ diameter wheels that have tires available up to 315mm section width but unfortunately 25.5″ in diameter. This is bad because extra diameter means more inertia to speed up or slow down because the inertia varies linearly with weight but as the square of diameter and did I mention the tires get heavier as the diameter increases? And I have been picking over the data from the LS Miata swap forums because same engine same power level and similar tire sizes, but I will have a much lighter car than a LS swapped Miata.

So, I need to get up before noon tomorrow but I’m having a heck of a pollen problem. and so is Mrs. the Poet, and she snores when her allergies kick up which makes catching Zs in the same room a bit of a challenge. I think I’ll hit the diphenhydramine and try to sleep on the other room with the alarm set to get me up, and put the post and me to bed.

Happy Star Wars Day

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.

I forgot the pictures and other stuff

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.The special Heim joints bolted to the axle brackets

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. 🙁

Take cover, I’ve been thinking again

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.