Tag Archives: technical stuff about building cars

Now I have time and I have something to write about

OK I was thinking last night and I figured out how I can do the thing by myself without having to spend $40 for the other thing to use to make the thing. I just need to buy a chunk of extra heavy angle iron and drill 3 holes after cutting to length.

Seriously I can get some thick angle iron from Lowe’s or the Metal Supermarket (yes that is a real place near downtown in Dallas), a step drill bit from Harbor Freight, and drill 3 pilot holes and use the step bit to get the desired size holes and I would have the thing I desired for less than half the cost of modifying the other thing because I would still have to get the step drill to drill the hole in the steering arm from Speedway at the right distance. I already have the cutting tools for the cutting to length and to clear the kingpin boss on the spindle from when I was building bicycles (what, you forgot about when I used to build bicycles?), and I still have many things that can be used to drill precision holes in (other) things if I have the right drill bits. And as I was just saying, I need to get a step bit anyway.

Anywho, it’s really simple. I know what the distance between the ½” holes on the vertical part of the steering arm need to be, and when I get the steering kit from Speedway I’ll know what the distance of the pitman arm is, and by simple ratios I’ll know what the distance to the 5/8” hole for the drag link end needs to be. There will be no need for anything like Ackerman or the like because this is strictly to transfer the motion of the pitman arm to the spindle and the Ackerman is already taken care of through the other steering arms and the tie rod. If I wanted to get fancy I might weld part of the vertical web that I need to remove to clear the kingpin boss on the spindle to the vertical and horizontal part of the arm between the spindle and the hole for the drag link to reduce deflection of the horizontal part under hard cornering. It likely won’t do any good if I buy thick enough angle iron but, you know there’s no such thing as “too safe”. And there is also the possibility that I can’t find angle stock in that thickness. And adding the support from the vertical to the horizontal flanges of the piece will stiffen it up considerably. And if I can’t get the thick stuff I will have to weld the connection from the vertical to the horizontal.

That’s it, I’m starting to get a sore butt from sitting in front of the computer.

Still thinking part infinity gauntlet

Basically I’m a non-stop thinking machine, grinding on the problem that is the Sprint-T. The problem I’m grinding on this time is quicker steering and more angle at minimum cost. I keep wanting to change the input on the steering box, but last night as I was staring at the ceiling it came to me that it would be much cheaper to change the steering arm on the spindle than to put a steering quickener on the input shaft.

Basically I buy this flat plate steering arm and drill 1 hole to change the ratio at the spindle instead of this steering quickener box which is more than twice as much and weighs more than twice as much and has no adjustability. The change in steering ratio is fixed by the gears inside the quickener, but I can change how much I speed up the steering by drilling another hole in the arm closer to the kingpin than the original 1:1 arm. I can make the steering as quick as I want, not just twice as quick, and unlike the steering quickener box, I get more angle to go with the faster steering. And the small hunk of steel is seriously lighter than the steering quickener box, a few ounces compared to just under two pounds. I can’t emphasize that part enough. The downside is that is unsprung weight at the spindle compared to sprung weight at the box.

Something else I can’t stop thinking about is the limit to angle is the tierod hitting something on the axle, which means I get the most angle by putting the tierod in front because of nothing to hit except the axle itself which is almost 180° of angle. I can’t actually get that because the drag link then becomes the limit as it hits the brackets holding the axle to the frame, but placing the tierod in front means one less thing to get in the way. And thinking about that makes me think that if I route the drag link under the brackets that hold the axle so that it can’t hit anything I have no limit except how far the pitman arm moves before hitting something or the limit stops in the steering box. If I drill the hole to make the steering arm effective length 3/4 the length of the pitman arm I get 120° total steering angle which TBH is way more than enough, but only 1.5 times as quick. Drilling that hole half the length of the pitman arm quickens the ratio by 2 times and requires less throw on the pitman arm.

So to summarize, by changing one part there’s no limits to how quick I can make the steering, and no limits to how far I can turn the front wheels to the side. That’s a win on multiple fronts.

Ooopsie! The box won’t fit there

Doing the figures again, and the steering box won’t fit behind the radiator. The problem is how high the drag link has to be and the fact that the pitman arm has to go under the radiator if I put the steering box behind the radiator. The box fits fine, it’s everything else that doesn’t fit. So the box can’t go there.

So, putting the box in front of the radiator the problem is getting the steering shaft around the radiator. Now a brainstorm I just had before I sat down to compose this post would be to split my steering quickener in half and put half in front of the radiator and half behind the radiator and extend the shaft between the two to fit around the radiator. Since I have to put in the quickener anyway, I might as well use it to sneak the steering around the radiator. There is a minor problem with one side having to be pretty large to get the reduction right, so there will be that hanging out in the wind, but in the grand scheme of things that is pretty minor. And I can make that better by having most of the reduction behind the radiator behind the fan shroud where it doesn’t block airflow so the part hanging in the breeze can be smaller. In case you didn’t figure it out, my homemade quickener uses two stages of reduction to keep the size of the slow side sprockets down to something reasonable. The company I’m sourcing the parts from has parts I could do a single stage reduction with, but the one sprocket would be about 8.6″ across not counting the chain on it which is a lot to hide behind the radiator fan shroud. And then there is still the other side that has to stick out the side of the car.

But, anywho, putting the steering box in front of the radiator and getting the steering shaft around the radiator with the steering quickener lets me put the radiator lower in the car because I don’t have to put anything under it except the lower radiator mount. I have been measuring the nose to see how far the front has to be in front of the axle to get the radiator underneath the bodywork or if I have to finagle the steering quickener to get everything under the nose. Easy way to figure that out is use the vertical part of the radiator mockup and see how far forward in the nose it will fit and still have room for the frame and lower radiator mount. And since that is a bit of a job that will have to wait until later, after I finish this post.

Speaking of finishing the post, I have something to do in meatspace for the lady we used to rent a room to. So I’ll proof and post this now.

Thinking about what I need to make an autocross-specific engine

I have been watching Richard Holdener videos on YouTube, for data on making the “best” engine for my Sprint-T. The TPI intake from the late 1980s had extremely long intake runners that made huge torque at low RPM, way more than what a “normal” engine of this size could produce.

TPI MEGA TEST-WHAT WORKS BEST? As you can see, Richard ran a “too big” cam for the stock TPI, and basically lost nothing at low RPM while the big cam prevented the engine from falling on its face as the RPM went past peak torque.

TURBO TPI-BOOSTED TUNE PORT Boost just made things more awesome

TPI TECH PLUS BOOST-FASTER THAN FORD? More boost makes more better.

Taking the results and projecting to the LS, what I need is a super long runner manifold with as large intake ports as will bolt up to the heads, and as much displacement as I can get controlled by a 300° duration cam with big lift, about 0.600″. Basically what I’m looking for would be something like this intake with spacers to extend the runners or maybe 3d printed plenums with extended runners built in, plus a super rowdy cam and let the intake runners “fix” the low RPM problems caused by the too-large cam while the cam “fixes” the lack of power at high RPM problems caused by the intake manifold to make an engine that makes power everywhere on the RPM range. That is what I would do if I had an unlimited budget.

But because my budget is very much limited, I’m going to have to take what I can get and like it…

Still thinking about… things

Not to sound ominous or anything, just that I have been letting my ADD do its thing and letting my mind wander around a bit.

One thing I have been thinking about is I used a wrong number in the sitting beside the engine SCCA A/Mod car. The engine extends 9″ to the left of center on the left, not the 8″ I used to figure my offset, so y=x-16 rather than 15, and the 7″ comes from the fact that I have room left over in my 14″ wide racing seat. And before anyone else can say anything yes I have a narrow butt. Anywho, I was also thinking that I could use 3 pedals if I sit next to the engine because I basically have as much room as I want to the left, and 14″ is plenty of room for a 3 pedal footbox. With the linked pedal set the brakes and clutch pedal could be mounted in the 7″ to the left leaving lots of room for the linkage to the gas pedal to the right.

Odd as it might seem the car that has the driver to the left of the engine has more room for the pedals than the Sprint-T because of the body limitations being 34″ wide at the floor in the middle of the car and the firewall only being 26″ wide. This limits the engine offset to 13-(engine width to the right) inches, or about 3″ for the LS engines, leaving just 16-9 or just 7 inches of space for heels with no room for the right foot to lean to the right. Sure feet will fit there but there isn’t much room to shift from side to side to keep your legs from cramping on long trips like the trips to the races planned for the Sprint-T. It will work, I have tested it by sitting with my foot in one spot while working on the computer for a few hours, but it is uncomfortable as all get-out. The seating position is really better for autocross racing or SCCA Solo racing than it is for long highway trips. For racing the seating position holds the driver in position directly on the controls, but for long trips that is a liability because the driver can’t move without moving the gas or brake pedals, which means that long trips will require frequent stops for driver comfort.

Something else I have been thinking about is building myself a trike I can get in and out of so I can start riding again. The easiest thing to make would be a tadpole trike, or reverse trike as some call them, 2 wheels in front, and a regular bicycle rear triangle in the back for the rear wheel. One thing I have been thinking about for this vehicle is how to make the pedal reach adjustable for different riders without having to alter the chain to fit each rider, because I know that I’m not going to be the only person to ride this trike. Something like this will invite other people of limited mobility to want to ride, for the same reason I want to build it, wanting to ride still or again but can’t get on or off a regular bike any more. So what I came up with is having a regular bike driveline mounted to a boom that has a pivot concentric to the rear cluster so that the pedals can be moved fore and aft in an arc while the tension on the chain to the rear wheels stays the same. All the fiddly bits are in a small space that is easy to get to on the front of the trike, and it can be removed for extensive maintenance or repair. The chain to the rear wheel can be fully enclosed to only need annual or biannual maintenance and also not transfer grease to the rider’s legs if inadvertently touched.

And I have been thinking about all this stuff in a vain attempt to not think about other stuff like BLM and COVID-19. I can’t for the life of me figure out why any of this is controversial. Police shouldn’t predate on unarmed black men, and when there is a virus that is spread by breathing covering your mouth and nose to keep virus-laden particles from getting out or in. You prevent yourself from getting sick, but more importantly if you are pre-symptomatic or asymptomatic you don’t get other people sick. So stay home when you can, and wear a mask when you can’t stay home. The life you save may be mine!

Christmas came early

I wasn’t expecting this until tomorrow or Monday, but having it now is still good. “This” is my stuff I bought with my part of the stimulus check. And this is a picture of “This”.
big boxes, what could be in them?

Boxes usually have things in them, and while the one box was mostly empty space there was something interesting in there making the space “mostly” and not “entirely” empty.
The yellow on the screen is much brighter than the yellow in person, think School Bus rather than raincoat

There was also a T-shirt in the smaller box with the roll of fender material. And yes those are actual catalog numbers in that graphic.
the graphic is an homage to the model car kits we used to build as kids too young to work on real cars

There is also a roll of HDPE sheet in yellow but that was visually uninteresting so no picture. You’ll see it when I show the stages of building the fenders.

Speaking of the fenders, I have finalized the design for the rear fenders, but building them will have to wait until I get the frame built. That’s because I don’t know how much rear overhang I have yet until I get the rear axle and the fuel cell or tank I’m using. I’m pretty sure I’m using this fuel cell or this same capacity fuel cell . Those are just for driving around between races but this cell is for racing with. The big tank gets pump gas, the little tank gets E85 and a more aggressive tune on the controller to make full use of the octane and charge cooling effect of the fuel.

I’m about to mock up the radiator and use that to mock up the nose to the right width. That means I’m going to cut some two by fours and nail them up in a rectangle the size of the radiator and use that to figure out how much to cut from either side of the center part of the nose. I’m going to do woodwork, pray for my survival. 😂

Today I spent my share of our stimulus on parts for the Sprint-T

Basically I bought a modern-day track nose and a roll of fender material and a T-bucket T-shirt .

I was thinking about the rear fenders and how the rear parts of the front fenders would not work for the rear fenders because they have to be a minimum of 30″ behind the rear of the rear tire in order to minimize wake and skin drag and that was Just Too Long for a Bucket. Buckets are supposed to be fenderless or cycle fenders at most, but I’m just using the Bucket as a leaping-off point.
See? No fenders.
But anyway, the rear fenders will probably share the front design with the fronts, except no headlights or mounts. In fact I think that up to the rear of the tire the front and rear fenders are pretty much the same. behind the rear of the rear tire things are different. I really need a flat surface to mount the tail lights . Having a flat surface on the back of the rear fender does that and makes for a visually cleaner and more modern rear presentation. I was going to go for mounting the lights on the the back of the bed, but really the fenders will work better. Mounting lights to the tailgate just exaggerates the fact the bed has no cargo capacity, I mean above and beyond the visible lack of a floor. But you have to either be close enough to look down and see there’s no floor or get underneath to see there’s no floor, but with lights flush mounted to the tailgate it makes it kind of obvious. Also the slight amount of side area on the back of the rear fenders provides a space to mount some kind of side marker light. Thinking out loud again…

And something that was in this morning’s paper a study I was part of as a test subject showed an extremely strong correlation to a blood marker and having many forms of cancer. In other words it looks like there may now be a simple blood test for cancer. No more biopsies, invasive exploratory surgery, or radiometric body scans needed, go straight from finding a lump to getting a simple blood draw to removing the cancer, or just getting the blood test once a year and then getting scanned to find the cancer.

Still thinking about building the Sprint-T

And also its scale replica, but that’s pretty much a given. I think all the time, either building things in my mind or writing stories about things and people not in this world. It’s a good thing I’m not a billionaire, because if I had the money to build some of the things I think about… Well let’s just say the world would be very different. I like to think it would be better, but only from some points of view, for other people it would be Hell, so yeah, good thing I’m not a billionaire.

So, anyway, thinking about things, like how long the legs on the hoops for the cage should be, how to build the fenders, how if I made the front fenders from HDPE I could make them a bit shorter than if I used something like carbon fiber or any of the metals because I wouldn’t need to have any clearance to the top of the tire from the inside of the fender at full bump because HDPE flexes instead of breaking or cutting the tire. I was thinking that the structure needed for the headlights would basically work for the front part of the fender, because the headlights needed a rigid and vibration-free mount so the light only goes where it’s supposed to and I was already putting the light at the top front of the fender for aerodynamics and because it was out of the way, oh and because making one thing do the job of three or four without having to be any heavier is my jam (air guitar sounds). The kit version of a T-Bucket from Speedway uses the front shock mount as a headlight mount, so it’s not like my idea is unprecedented. It’s a little different but not completely out of left field.

And my YT Music app is playing “The Song That Must Be Played At Full Volume” aka “Won’t Be Fooled Again” by The Who. So excuse me while I Rock Out a bit here. (Full Throated Scream) Yeaaaaahhhhh!!!!!!

(8:31 later)Yeah, rear fenders, important bits, still trying to figure out what shape they need to be. There are many problems to be solved here: 1) keeping stuff from getting thrown on my car and other cars when it rains, 2) streamlining the rear tires, 3) fitting into the look of the rest of the car, 4) cooling the rear brakes. Of those parameters only 3) is optional-ish because if I get 2) and 4) right I basically cover 3). One option I’m considering is making the rear fenders a copy of the fronts minus the headlights, because that would be easy since all that requires is making 2 more fenders exactly like the fronts except without lights in the front. I guess I could use a repro ’59 Caddy tail light to finish the back of the fender. The downside of making the basic shape of the rear fenders identical to the front is while it ties the car together there is a bit of visual monotony in having what amounts to boxes over the tires with streamlined front and back bits on both ends of the car. But that’s what the Mini Sprint-T is for, trying out ideas to see what works and what doesn’t.

And my neck is sending scatalogical telegrams right now because I have been sitting at the computer for too long, so this is a good place to end today’s missive.

All those words and I forgot to say what I came to say

Since this is a follow-on post I won’t use much space this time. What I originally came to say was that while I was trying to figure out how to build the Mini Sprint-T I figured out how to build a better frame for the 1:1 Sprint-T. Anyway, what I had decided for the Mini was front and rear hoops that went all the way down to the belly pan and had the frame rails glued to the front and back of the verticals of the hoops, instead of continuous frame rails and the hoops on top of the rails. What evolved from that was a lower rail with 0.120″ wall inside the roll cage area and 0.060″ wall in front and back of the cage so that in front or rear collisions the lower rails would collapse first and send large objects attached to the frame under the driver compartment and not into the driver or passenger.

So, when I build the frame I bend up the hoops and leave the legs 1.5″ longer (scale) than I would with the legs on top of the frame, and glue the lower rail between the legs. On the real 1:1 car that part would be the 0.120″ wall. Also the top rail would be one continuous piece from the front bulkhead to the rear bulkhead, which means I will need to figure out how far to bend it where it comes past the front and rear hoops. On the 1:1 car it will be 0.120″ wall and the biggest length of tubing on the car and run the full length of the frame and require careful gusseting where it passes the front and rear hoops. That’s also true on the Mini Sprint-T, but the mechanics are completely different because of the scale.

And since this is just what I should have posted yesterday instead of rambling, this is a good place to end.

Can’t stop thinking

And one of my favorite subjects is how to make the Sprint-T lighter and safer, which was not caused by seeing Ryan Newman’s Daytona crash. Actually it was brought on by wanting to make the frame fail in such a way that the engine didn’t try to join me in the driver’s compartment in a frontal collision. Second consideration was using as much 0.060″ wall tubing as possible. I say “as possible” because while some of the 0.120″ wall tubing is required by safety rules, some of it is required because of the stress risers created by the 0.120″ wall tubing.

And once again I wish I could show you what I see in my mind, when I’m thinking about the Sprint-T. The rest of the time I don’t want you to see what’s in my mind, that’s like being on the wrong side of the eyewall of a hurricane full of garbage. But seriously, I wish I could show and not tell about the frame for the Sprint-T.

OK basically The Rules require the hoops and diagonals and upper parts of the roll cage to be 0.120″ wall, but to balance things out so the cage holds together that means the bottom frame rail has to be 0.120″ as well at least between the rear and the front hoops. The fun(?) part is deciding how far back the 0.120″ wall has to go, at least to the rear hoop but behind that do I want 0.120″ all the way to the rear bulkhead/bumper, or do I want that to be a crumple zone up to the rear hoop? Going back to The Rules at least one of the diagonals must be a single length of 0.120″ wall tubing the same diameter as the hoops (1.5″), but do I want/need more than one diagonal, and if I want/need to have two diagonals do both of them need to be 0.120″ or can the lower stressed one be 0.060″? Add into the mix that I can also have a rear hoop and a left and right hoop, and run a diagonal from the front crossbar to the rear corners of the left and right hoops and get a much stiffer but slightly heavier frame.

But we were approaching the point of diminishing returns for frame stiffness given the suspension design of “stick” axles front and rear. I mean the main point of torsionally stiff frames is to keep the front and rear wheels at the best camber angles and also to balance the roll rates so the weight transfer between the front and rear outside tires can be tuned for desired handling behaviour. Well stick axles don’t change camber angles unless the inside tire is lifted out of the plane parallel to the ground which likewise limits the weight transfer ratio between the outside tires. And that one didn’t come out completely right, as the inside wheels can also go over a bump and remain in contact with the ground and not be lifted by trying to transfer more weight than exists on the inside tire by either excessive roll angles or by roll centers that are too high and transferring weight without compressing or extending the springs. This is the mechanism that allows changing the handling by raising and lowering the roll center on one end. The closer the roll center is to a line running through the center of gravity of the car the less control the springs and anti-roll bar exert over the weight transfer and also the less the car will roll over on the suspension in a turn. Get the roll center higher than the center of gravity and the car will try to roll opposite the cornering force and pick up the inside tire. This is why standard kit T-buckets are no good for autocross and Solo Racing because they have such high rear roll centers to compensate for the “normal” size difference between the front and rear tires on the street.

Anyway, back to the frame. Running left, right, and rear hoops will give me four uprights on the rear so lots of crush resistance where the majority of the driver sits, which is good. But also less tie-in at the top of the rear hoop which is ungood (not actually bad becauuuse there are other ways to tie-in and brace the top of the rear hoop). And running left, rear, and right hoops means an extra hoop of 0.120″ wall plus the crossover bar over the front of the cockpit and the verticals under the crossover and the diagonals from the verticals to the rear hoop have to be 0.120″ where front and rear is just the two hoops plus the crossover bars between the two hoops and whatever gussets they get attached with and the diagonals that are a single piece of tubing between the hoops. Like I said, compromises and where weight can be saved.

Also, while I’m trying to do this for the 1:1 car I’m also trying to figure out how to build the 1:25 Mini Sprint-T, which is where this mess got started because of the upper rail running from the front bulkhead spring mount to the front hoop.