Tag Archives: technical stuff about building cars

Glutes still hurt

That’s pretty much standard these days, but that doesn’t keep it from getting really annoying. If I had the funds I would be getting a massage every week, just my neck and my glutes, and a full body massage once a month to catch everything else.

I entered a contest for a 427 cu. in. small block Ford engine that puts out a smooth 450 plus crank HP. The only problem I have is the transmission to bolt to it for the Sprint-T. Ford overdrive automatics have a bad reputation for puking internal parts when they are bolted to high power engines like the one I entered to win, and I still don’t have enough space to put three pedals between the left side of the transmission tunnel and the inside of the body for a manual transmission. But there are people who say they can bolt any transmission to any engine given enough time and money. Time I sorta got, money, not so much. But if I win this engine it’s a huge step forward for the Sprint-T, and has the “advantage” of putting a Ford in a Ford. Some people think that’s important or something. For me in this car, an engine is an engine, power and weight are more important than brand. The frame has room for just about anything smaller than a Roll-Royce Merlin.

We are still waiting to know when the money from the trust is deposited to my account, and for my first Social Security check to hit the account. We are all on tenterhooks because of previous economic disasters that have befallen Casa de El Poeta, and kinda crossing our fingers that nothing else strikes before then. Between this influx of cash and Social Security we should be semi-permanently above water, assuming Trump doesn’t destroy everything on the way out the door. I know that’s a huge assumption, but we have to keep hopes up.

Currently listening to “The Pretender” by Infected Mushroom.

Is it over yet?

Everyone I know is cautiously peeking through the figurative bunker door hoping against hope that the election is over and that Trump is going to accept the results. Mrs. the Poet is celebrating a little early, I think. I’m still not taking full breaths yet.

What I have been doing is going over the Sprint-T front bulkhead over and over, looking for places to reduce weight/increase rigidity. I haven’t come up with much, as I have gone through this process hundreds of times already. Basically I’m going through and seeing if there is a way to beat the “choose two out of three” dilemma from the “cheap, strong, light” triad by changing size of the structural members. And I’ve got it down to “it depends on where the volume discount starts”, on the price difference between the sizes of the raw stock. Because of the SCCA rules I have to make some parts out of 1.5″ diameter 0.120″ wall DOM round stock, but the rest of the car I can make from 0.060″ wall, which will be more than enough if I use corrosion prevention to maintain wall thickness. But I can save weight even more by using smaller diameter stock for bracing, up to a point. 

Some of the bracing will be easier and cheaper to make as an extension of the main frame members using the 1.5″ diameter 0.060″ wall stock, but some will be lighter/strong enough if I use 1″ diameter 0.060″ wall tubing. It’s basically a case of which is cheaper when I buy the stock, meaning I need to get both choices fully designed down to the BOM. 

And I’m starting to fade, and have problems seeing, after a very exciting championship race for the NASCAR Cup, with congratulations going out to Chase Elliot. Chase wasn’t who I was rooting for, but with the way he won his way into the Four, and the way he dominated the race after getting moved to the back after failing his first two trips through tech, I concede his worthiness, especially when my choice finished 4th out of the four. Denny Hamlin is still the best active driver to never win a championship, a distinction I hope he loses soon next year.

I haven’t been well lately

My sleep schedule is still borked, and I’m still getting muscle “not feel goods” and a bunch of other things. I mean nothing really hurts, just a whole bunch of things that don’t work anywhere close to “right”, and it really annoys me. I’m supposed to be able to do almost anything to my body and still have it work right, and this recent bout of “not working within design tolerances” is just really pissing me off.

On things that are not my body, I think I might have the mount for the steering box nailed down so it won’t flex under load and cause steering to be imprecise. I mean it’s probably overkill by several magnitudes, but I’m pretty sure I have enough bracing so that it won’t move when I make rapid changes in direction. Moving the box in front of the axle made a big difference, because now I have structure above the mount I can tie into and prevent side to side flex in the mount. There’s not even a possibility of other movement, because first of all there are no forces in those directions to speak of, and second because for all the other forces there are already massive trusses in place just because that was the easiest way to build the mount.

On the steering arm, still waiting to purchase cutting tools large enough to handle the 1/4″ thick stock needed for the forces involved, because basically I’m looking at buying everything I already have all over again, but bigger/heavier. I’ll need a new drill press, new saws, bigger drills, the whole shooting match. This means about a thousand dollars in tools, maybe a little less if I buy used. But looking at Harbor Freight, getting a drill press big enough to handle drilling the holes for the 5/8″ heim joints is the big $$ item. The cheapest press is this one. And it barely fills the bill.

I think maybe I can use my angle grinder and metal cutting wheel for rough cuts and the grinding wheel for the fine shaping, but it will be slow work and there will be many chances at messing up the part because of how thick the stock is. For cutting thicker stock they have a bandsaw that will do the work, faster than a cutoff wheel but still pretty slow. I’m going to have to think about the bandsaw, but the drill press is probably a must just because my other drills are not up to handling the size of the drill bits needed for the job. The biggest bit my hand drills will handle is 3/8″ and the drill for the 5/8″ threaded hole is 9/16″ while the non-threaded hole is the full 5/8″. I don’t know what the chuck capacity is of my current drill press, but the piece is pretty much worn out from building bicycles. If I try to drill too fast through even just thick wood the chuck falls out of the press. It worked fine for a long time, but it’s just worn out now.

And I guess I have run out of things to write about, other than because of the weather change it is now in the 60’s F inside my office. My thermometer/clock says it’s 67°F in here and my fingers are not as nimble on the keyboard as they are during the summer when even with the AC on it stays 76° in the house and my hands and fingers all work perfectly without hesitation🤣. That’s a joke, nothing on me works perfectly or without hesitation. Everything is out of whack to some degree, but most of me works best between 75 and 78°F. Above that and I start sweating, too much below that and things start getting stiff, and then they get painful. And we are at the upper boundary of stiff and painful today.

Well I’m going to call this the end of the post, you should go have a nice day or something.😉

 

Well, that was quite a race!

It didn’t turn out quite the way I wanted it to, but wow! what a race on the Roval at Charlotte. It was raining at the start, then stopped, then eventually got sunny leading to a track that was tricky to drive every lap. And tricky to drive leads to exciting racing.

I’m not going to lie, my guys didn’t win, and they were in a “points below the cutoff line in a cutoff race” situation. Those were Clint Bowyer, who is retiring at the end of the season, and Kyle Busch the reigning champ. Clint I just wanted to see have a shot at the championship in his last season, because he’s always been a good driver and also a good person from what I can tell. Kyle just didn’t get a fair chance this year because of the rules changes caused by the Stupid Virus. Kyle’s style is to make the car perfect in practice, and there was no practice this season after the Stupid Virus. My problem was they can’t both win, and the only way for both to go to the next round was for the 88 car to blow the engine on the pace lap or similar and Clint and Kyle to finish 1-2 in that order. Did I mention I don’t particularly like the driver of the 88?

In other news, I’m still evolving the mount for the steering box and changing the front bulkhead in the process. I decided the car would be faster if I made the bellypan all the way across the car to the outside edge of the fender, which meant I needed to do something to support the leading edge around the front tires. Since the front tires would get pretty close to going parallel to the front axle, I subtracted the diameter of the street tires from the axle width to come up with 31″ clearance at full lock, which just happens to be the same width as the radiator. Which means the extension of the front frame rail really needs to be on both sides of the car, making the bottom of the front bulkhead way wider than the original design of a point at the bottom intersecting the main frame rails also coming to a point.

The new bulkhead is radically different. Where there was a straight tube across the top from one shock mount to the other with a tube from each shock mount to the center V-point and some internal bracing to prevent flex, the new design has a straight bottom tube that runs across the intersection of the main frame rails to the rail extensions spaced 31″ across outside to outside, and a tube from that intersection to the shock mounts and another horizontal tube across to support the downforce-generating nosepiece from underneath so it doesn’t need to be cut and fitted around the bulkhead, and is way easier to install and remove for maintaining the steering, and has the secondary effect of making as much downforce as the nosepiece can make. This upper tube will be 31″ wide and the vertical from the extension to the upper tube will also act as the mount for the steering box. And then there will be another tube from that intersection to the shock mount, triangulating the mount, and a tube from the intersection of the upper bar and the vertical from the extension to the point where the main frame rails intersect with each other and the front bulkhead to triangulate the steering box mount and the place where the load from the shock mounts feeds into.

I really need to draw this out and show what I’m writing about, because while there are a lot of words, there are not a lot of tubes involved, only 10 total in the front bulkhead, and just 6 more that intersect it. Which sounds super complicated, but not so much when I visualize it. I just wish my hands worked better and I had the tools and the paper to draw it like I see it. But if wishes were horses we would all ride everywhere. And that is a saying that predates bicycles it’s so old.

And I didn’t finish my statement about supporting the front of the bellypan. Well I need to establish the swept curve of the tires moving to lock between straight ahead and the tire parallel to the axle, which is a fancy way to say I need to trace out the curve of the outer corner of the tire tread, all the way until the tire is at right angles to straight ahead, and then copy that curve on a tube roller (which I still have from building bicycles) on a chunk of light 1.5″ tube. That will be the leading edge of the bellypan from behind the tire to the frame.

I will have other tubes on the outside edge to support the bellypan all the way to the edge so I can use it as a step to get in the car, and so that any downforce it generates goes all the way to the suspension like good ground effects. I already know that there will only be a tiny amount of downforce even on the freeway, but I want every ounce I can get.

I was also thinking about the A-Mod car because I had an allergy attack that made me sleepy so I went to bed, but then wouldn’t let me sleep. So I stared at the shadows on the ceiling and planned the Next-To-No-Car-There-Car. Basically just enough frame and body to hold a body to the right of center with outriggers to mount coilovers and the bits to hold the left side of the suspension in place, and a big empty space to be filled with a motorcycle engine that gets moved from side to side to balance the body in the part of the car designed to carry the body. That’s about as far as I can get without drawing tools and paper.

So, that’s what happens when I have too much time to think, and there’s a really good race on the next morning.

OK getting down to brass tacks on this steering business

First, an etymology of the phrase “Getting down to Brass Tacks” because I know it and I think it will add to the conversation about the steering. The origin of the phrase relates to custom saddles for horses and cowboys, and literally refers to the size and number of the brass tacks used to secure the final seating surface to the frame of the saddle. This was important because too few or too small of tacks would cause the saddle to fall apart, and because the polished brass tacks were a decorative touch and too many was considered to be low-class, or <i>nouveau-riche</i>. And that should be in italics but I have to switch back and forth between editors so fvque it.

Anyway, this part of the design is very detail-oriented, in that the same parts from different suppliers will require different fitting because while they might be the same internally (spline count and/or shaft diameters) outside they are very different. Like about a quarter-inch different in outside diameter between basically the same U-joints from different manufacturers means some will clear the inside of the bellypan without relief dimples and some will require about an eighth of an inch or so relief dimple to not foul the U-joints when the steering wheel is turned. So I have to do a lot of catalog and website browsing to find the outside diameter of the various U-joints, so I can pick the ones that won’t require extra work on the bellypan.

Actually there is only one place where the outside size of the U-joints is at all important, the place where the steering shaft goes under the radiator, between the frame rails, and above the inside of the bellypan. The current plan is running a 3/4″ shaft under the radiator in the 1 1/2″ gap caused by the radiator having to sit on top if the bottom frame rails, and tucking that shaft up as close to the radiator as possible. I can get bearings that can be mounted so the shaft just barely clears the bottom of the radiator mount, meaning the U-joints have 1.125″ radius clearance without having to dimple the bellypan. Most of the U-joints I’m looking at will clear that with no problem, but there are some that don’t and I have to make sure I don’t get those. So I have to mark the ones that I know will fit and then cross them against other considerations, like how strong they are, and how much flex they have. Price is also a consideration, but there isn’t much leeway there. They pretty much cost what they cost, and there isn’t much difference between suppliers.

Anywho I have also figured out what to do with some of the leftover heavy angle stock: the panhard rod (or track bar, the two are interchangeable) needs a sturdy mount on both ends, and the quarter-inch thick stock will be perfect for that, being practically inflexible for the size needed for that bracket, no deflection at all as short as they are. And because right angles and flat surfaces, it’s practically self-jigging.

And I don’t know if I mentioned it explicitly before but because of the thickness required to prevent flex in the steering arm, the part is thick enough to be threaded for secure connection to the rest of the car. No extra nuts required, but I will use a safety nut on the bolt through the heim joint at the end of the drag link, because that bolt will be hanging down and could fall out of it wasn’t safetied somehow, which could cause a total loss of steering control. I don’t think saying that would be bad is any overstatement. The safety nut in this application would be equal to a double nut safety, as the threaded steering arm would function as the first nut.

And I’m getting a notification from my computer that my OS wants a shutdown to update, I’m starting to glaze over and try to faceplant into my keyboard because trying to think about something on-topic to write about. So this looks like a good time and place to stop writing this and publish and reboot.

This post is going to be heavy on the technical stuff

I hope this works, again, but here goes nothing.

I’m writing this to the beat of Frankie Goes To Hollywood “Two Tribes (Carnage Mix)” on my YTM player while I sort out how to commit acts of authorship, on the very technical subject of how to make threaded holes in the steering arm, so that the various things that need to be attached to the steering arm and vice-versa can be attached via threaded fasteners. To do this I consulted the Oracle Google who directed me to the Wizard Wikipedia

who has knowledge in all things arcane. And that last little bit was either appended to the link text, or placed in a separate paragraph below. Apparently the bugs are not properly exorcised from the editor.

Anywho, the plan is to tap threaded holes in the steering arm to accept the bolts that hold the caliper bracket to the other side of the spindle, and the bolt that goes through the heim joint on the drag link that acts as a tie rod end and put a nut on the bolt to lock the assembly together and prevent accidental disassembly while in use. That means drilling three holes of odd size, with the two holes for the bolts to the spindle being the same size and the hole for the heim joint being much larger. Since the caliper bracket uses 1/2″fine thread bolts I use the appropriate drill to make the final hole after drilling pilot holes because my drill press slips if I take too big a bite from quarter-inch thick stock. I have no idea how I’m going to drill the hole for the heim joint, because the biggest drill I can chuck in the drill press is several sizes smaller than the drill I need to use for a 5/8″ fine thread bolt. And before anyone can make a comment, the drill press was a gift, I was building bicycles at the time, and the press was sized for the materials and thicknesses I was working with at the time it was given to me many years ago. Also I think I wore that sucker plumb out back when I was building bicycles.

But, yeah, that’s the gist of it. I need to make 3 holes of certain sizes, perfectly perpendicular to the piece, and then thread them (also perfectly perpendicular to the piece), and the holes are on different planes of the piece.

Still thinking about improvements

Yep, mind still churning about the Sprint-T. This time I’m thinking about how to mount the steering box.

There are two orientations the box can take and still turn the front tires in the correct direction as commanded by the steering wheel: the kit orientation was pitman arm pointed forward controlling a steering arm pointed back, or the OE orientation of the pitman arm pointed back controlling steering arms pointed forward. The problem I’m trying to solve is making room for the engine and radiator and also sneaking the steering shaft from the steering wheel to the box around the radiator without hanging out in the breeze.

Aero is not critical but it is important for freeway fuel economy. I mean there is going to be a lot of junk hanging in the breeze simply because T-Bucket, but that’s still not an impediment to decent but not fantastic aero. For examples of decent aero and exposed wheels see https://www.google.com/search?rlz=1C1CHBF_enUS809US809&sxsrf=ALeKk02olFWp4zhsrQs1tNKIuVFdAMTU0A:1602022917053&source=univ&tbm=isch&q=images+lakester+racers&sa=X&ved=2ahUKEwiP3JG3gKHsAhUEKawKHdSNBDoQjJkEegQIChAB&biw=1517&bih=694 “lakester racers” that are required to have exposed wheels. The old belly tank racers are a good example of that.

Anyway, I have been thinking about it and there is a 1½” gap under the radiator because it sits on top of the frame that would be good to sneak the steering shaft through without hanging out in the breeze. The closest to a problem would be clearance for the U-joints to turn that close to the bellypan. And something to block the air from going under the radiator, but that would be a great place to mount the bearing that guides the steering shaft under the radiator. I really need to find out how big are those U-joints that connect to the steering shaft. I may need to make a relief bump in the pan for the U-joints to swing, but if I need one it wouldn’t be very big.

The other problem is properly bracing the top of the box to prevent it from rotating in reaction to the forces from the pitman arm hanging off the bottom of the box. Side to side is easy, just weld the mount to the top of the frame rail. Boom, you’re done! The other is a bit more tricky, because there has to be something to brace against to do the top part of the mount. On the kit the mount welds to the side of the frame rail, so the twisting moment from the force through the pitman arm is close to zero and is resisted easily by the sheer mass of the frame rail and the extremely short arm the force has to act through. It’s basically all sideways against the rail for the kit mount. Now there is another frame rail to run a brace from on the same side of the frame, plus its mirror on the other side of the frame for slightly better angle on the force. Which brings us to the actual point of the post, the reason why I mentioned the OE orientation of the steering box: I’m thinking of attaching the steering box mount to the front bulkhead with the drag link under the steering shaft and ahead of the axle.

If I move the box in front of the axle, then I could brace the top of the box against the front bulkhead at whatever place is convenient to mount the brace. The bottom of the mounting bracket still mounts to the frame extension that also acts as the mount for the panhard rod. As a point of fact, that was the original reason for the frame extension in the first place, someplace to mount the frame end of the panhard rod so the panhard rod could be the same length and parallel to the drag link for no bump steer. And now it looks like I only need to make a slight adjustment to the front of this extension to mount the steering box, because there are braces from the bulkhead in two directions to locate the front and triangulate it in two dimensions, and the vertical one can be used as the actual place to weld the mount.

So these are the pros and cons of moving the steering box in front of the axle:
Pros: simplifies the top mount of the box, lighter, gets the drag link completely away from interfering with any suspension links.
Cons: puts weight in front of the axle, increases to moment resisting changes in direction, susceptible to damage when hitting curbs while parking.

And that last one is only mentioned because it is a slight possibility, not because it’s likely to happen, and a curved skid plate in front of the box will prevent even the slight possibility from coming true. Or it might not even be a possibility because of how high the box has to be mounted for the drag link to be level, especially if I don’t drop the drag link at the steering arm on the spindle. I think mounting the drag link to the top of the pitman arm and the bottom of the steering arm will give enough offset to prevent binding. This will raise the bottom of the box to about 9-9½:” above ground with the street tires. Considering the frame is about 6″ above ground with the street tires that would be a very tall and vertical curb to hit the steering box. It would have to be a really tall and narrow parking bumper that didn’t block either front tire, a freak of parking bumpers.

And I still haven’t gotten this editor down pat, because I have no idea how to insert text to a link and not leave the URL all over the page, so I’m going to quit fighting it and publish the post.

I need to think out loud some more

And you get to read it, lucky you! This is one of the ways I solve problems, but I usually don’t keep the process after I’m done, but I’m thinking since this isn’t how to make a man-portable nuke, or how to shut down the stock market, or any other destructive thing that could cause chaos and destruction if I let it out in the wild, this one I will let people see the process.

The problem needing solution tonight is the question of will using a Powerglide transmission and a quick-change rear axle be better for the autocross and still usable for just driving? From known data the QC has about 10 pounds less mass than the 9″ Ford rear end or is way cheaper than an equal weight fabricated aluminum housing 9″ Ford, going back to the Eternal Triangle: Light, Cheap, Strong, pick any two.

The other thing is you can’t street drive with the PG without changing the final drive ratio from the race setup, the ratio is Too Low for any highway driving. The final drive for the autocross setup is top of the RPM band in first gear at 40 MPH. For an LS engine that would be 6500 RPM. Now because the PG comes in two low gear ratios, 1.78 and 1.82 you can see the problem. Even going from the 23″ tall race tires to the 27″ tall street tires that would make the freeway RPM an unbearable 3110 or 3042 depending on which ratio transmission I get. Either one would result in horrible mileage, horrible engine noise and added wear and tear on the engine. What I’m looking for is a highway cruise of 1900 RPM or less, so you can see what the problem is.

Now the reason I want to run the PG is weight, both absolute and rotating mass. My other options are the 4l60 and variants, or the 4l80, the first weighing in at almost 200 pounds with fluids, the second is 240± with fluids. A fully race prepped PG is [drum roll] 96 pounds with fluids so 100 to 140 pounds less weight on a car that would weigh 1800± pounds with the 4l80. And do I really need to show how much 140 pounds off an 1800 pound car is as a percentage? Plus I don’t have the actual rotating mass for all 3 transmissions but I know the 4l80 is the highest and the PG is way lower and the 4l60 is somewhere in the middle but closer to the 4l80. And going back to Commonly Held Beliefs About Rotating Mass For Hot Rodders every pound of mass rotating at engine speed is equivalent to 5 HP, so going from the 4l80 to a PG not only takes 140 pounds off the static mass and sprung weight, but it takes a Large Amount off the rotating weight. As an added bonus the PG is one of the strongest automatic transmissions you can buy for normal car engines. Of my two choices the 4l80 has the best power handling but slightly worse ratios which is why I was looking so hard at the 4l60 based transmission. But neither of them can hold a candle to the PG in torque capacity. The PG is pretty much the standard transmission for a Monster Truck with 1800-2000 HP alcohol-fueled big-block engines, so strong, and light, and low rotating mass.

But to use it with the Sprint-T I need a way to easily change the final drive, or invest in a truck and a trailer to haul it between races and pretty much resign myself to only driving to my local grocery which is close enough to not drive me crazy with the RPM and noise from the engine. That’s where the QC axle comes in, it takes about 15 minutes and about $70 for a different set of spur gears to set the highway cruise to 1900 RPM. Now the QC cost is about $1k over the Ford 9″ unless you try to get the Ford as light as the QC and carry two center sections to have the race and highway ratios because part most of the higher cost of the QC over the 9″ is magnesium and aluminum EVERYTHING. Also changing the final drive on the 9″ requires hours of work setting the lash and engagement depth on the gears, or carrying around a spare centersection to swap from one to the other, and also about an hour of laying on my back at the race track going from one to the other. The QC requires an extra set of spur gears at $70/set and about 15 minutes unbolting the rear cover, swapping the spur gears, and bolting the cover back on and putting the gear oil back in the housing. That last bit is very important if I want to keep driving more than a few miles from the track.

Now I have been thinking about it and I can live with a PG and highway gears without much problem beyond the one they made fun of back when the PG was a production transmission installed on common road cars, driving 70-80 MPH still in 1st gear, as there are only two plus reverse. Actually if I have my sums right the shift from 1st to high under full throttle would be at 131.5 MPH. Which is even funnier than the vaunted 70 MPH shift from 1st to high ridiculed in the magazines of the times. The engine would remain below 3500 RPM all the time and would rely on low RPM torque and the torque converter to run without stalling. Which is almost the same as the speed the engine would be forced to spin at 60 MPH with the race gear all the time, so from one extreme to another in engine speed. Engine speed in 1st gear at 40 MPH with the highway gear would be 1976. That is a swap I can live with. Especially with the benefit of 100 pounds less empty weight and a similar but lower reduction in rotating weight for racing the autocross. But if I decided I needed a higher engine speed for around town but not making long trips on a freeway, all it takes is consulting a chart, picking a gear set, plonking down another $70, and spending another 15 minutes under the back of the car changing the spur gears. Or maybe just swapping the gears top for bottom on the race gears, because that would be a thing that was possible because the spur gears for the race gear would be a reduction set to get the RPM that high for that slow is WOW! The race gear needs to be 6.11:1, and the highway gear needs to be 2.54:1 and there is no way to get from one to the other without using different spur gears. If I get the low-inertia (rotating mass) 4.12 ring and pinion I can get close at 6.08 and 2.79 with only one set, giving me 2083 RPM at 60 MPH, but if I get the more common and slightly cheaper 4.86 the 6.12 spur gears give me 3.85 swapped top for bottom, which would be a decent setup for around town but loud and drony 2875 RPM for highway use. The bad thing about the 4.86 is the tallest final drive I can get is 2.58 which is Really Close resulting in 1926 RPM at 60 instead of 1900.

I shall have to let this one percolate through the grey matter for a while, comparing the costs of the 4l60 variant that will support the engine I get with a 9″ rear housing to fit the Sprint-T, and the costs of a PG and QC to fit the Sprint-T including 2 sets of spur gears, or a 9″ to fit and another center section. And looking at the assembled and ready to go 9″ center sections the cheap ones with a spool are $620 plus tax, for a race-only application. The ones with the highway gearing higher than 3.00:1 are scarce and expensive because most vehicles are equipped with overdrive transmissions to bypass the need for such tall gears. They used to be very common in the ’70s before overdrive transmissions were common, but I’m only finding used gears above 3.0 and even those are way expensive, so I might have to run the QC if I choose to run a PG. Or it just might not be economical to run a PG because of how expensive the support equipment required to run it on the street especially when a 4l60 can get 6500 RPM at 40 MPH with a 3.62 rear end ratio on the 23″ race tires, and get 1900 RPM at 60 MPH with the same rear end ratio and the 27″ tall street tires. Now that’s not a standard ratio but the common 3.50 is super cheap (for a 9″ rear end ring and pinion) and gets the race ratio close (41 MPH) and is just a tiny bit tall for the highway ratio resulting in 1830 RPM instead of 1900. Even closer is the Ford 8.8″ rear axle which (some of them) came with a 3.55 and a limited slip. Much more thinking is required, and as you can see there was already much thinking and consulting of texts and web pages done to get this far.

Still thinking, but more specifically

Relax, I’m thinking about the steering on the Sprint-T, not doomsday devices. Besides doomsday devices are a one and done thing, and unlike most mad scientists (we actually prefer the term aggravated engineers, thank’ewverra’much) I actually thought ahead and know if I blow up the world I lose my place to sleep at night, lacking a means of space travel. Besides have you checked the price of plutonium lately? No, thanks, I’m out of the doomsday device business.

So, back to the main topic, I’m pricing the specialty metal to make the steering arm that makes the steering quicker, and it’s super expensive for what I need. I mean in absolute terms it’s not much, it’s just I have to buy 4 linear feet of stock to make a part that will be just over 6″ long finished. And that 4 feet of stock costs $33, so most of the stock is wasted unless I find something else that needs to be that strong.

Cutting the stock to the length I need for the steering arm, henceforth to be named “the part” in this doc, I need to cut about 8″ to make the part. The part needs to have an arm that is 33/16” from the spindle axis to center of the hole for the drag link, but there is the attachment hole to the spindle on the other side of the axis from the drag link hole to also account for, plus the gussets needed to prevent flex in the part because the load will be off-axis no matter how I bolt up the drag link to the part. And dropping the drag link down to clear the suspension links will make the leverage off-axis greater causing more flex in the system. Therefore the part needs to be made from heavy stock, and gusseted, to keep the flex as low as possible.

I don’t think there will be any detectable flex in normal driving, but autocross and SCCA Solo Racing are not “normal” and put the steering under about as high a stress as you can get without going off-pavement or banging curbs. And now that I think of it there is a slight possibility of banging an actual concrete vertical-faced curb doing that, so I guess that means another gusset. The plan is now to have a gusset on either side of the bolts holding the part to the spindle, because curbs. Anyway, this stock is right at the limits of my welding equipment and cutting tools, so if I need to use heavier stock to make this part I will have to farm the part out to a professional with better equipment.

Just a passing note, I made the suggestion on Twitter that if @realDonaldTrump refuses to vacate the White House as he claims he will, then he should be treated like he says protestors against police brutality should be treated, but obviously in fewer characters because: Twitter. I’m now locked out of reading Twitter until I apologize by taking the tweet down, which obviously I will do as soon as Agent Orange apologizes for saying the same thing about protestors or when pigs fly. I don’t care, either one is equally likely. I don’t really need Twitter, it was just something to kill time with.

And with that act of defiance I’ma put this thing to bed.

More thinking about the Sprint-T

Just because I’m not working any more doesn’t mean I can’t stay awake at night and think about things on the Sprint-T. On the contrary, now that I don’t have to think about working, I can think even more about the Sprint-T. And because I don’t have any budget to build things I can think about how to do things as cheaply as possible.

I was thinking about how many turns lock-to-lock the steering will have with the shorter steering arm on the spindle compare that to other methods of changing the ratio. OK with just changing the steering arm on the spindle the turns lock-to-lock won’t actually change unless something in the steering hits something before the steering box hits its internal stops, but the front wheels will turn twice as far for each turn of the steering wheel. But since the front tires can’t turn anywhere near as far as the box can try to turn them, assume a stop in the system limits the travel, so how many turns lock-to-lock can we get from the system instead of the box?

The 20:1 box has 5 turns lock-to-lock by itself, moving the pitman arm 90° of arc. That’s 45° left and right of center, which is pretty decent angle but not great. But 5 turns lock-to-lock is terrible. So the problem then becomes how much angle to allow vs. steering wheel turn. Doing the steering arm half as long as the pitman arm gets 180° of movement which has already been categorized as “too much”, but the total ratio is “not quick enough”. Seriously this will be a huge improvement, but still not quick enough for the autocross racing the car is intended for. But at the double throw, the overall ratio is 10:1 at the tires, with 2½ turns to get the stock 45° of steering movement. Now if I restrict the angle at the front wheel to 120° of lock which is way more than what I get with the steering arms from Speedway (which are designed for freeway driving and cruising around a fairground car show, not racing autocross so nothing bad about that) I still get 31/3 turns lock-to-lock, which gives the equivalence of a 131/3:1 box with everything set to “out of the box” in the steering linkage. The really annoying thing about making this post is I have one word “wheel” that refers to two completely different things, and trying to disambiguate the difference between the steering wheel and the wheels the car drives on. I had to go back and change a few words back and forth.

Anywho, I can rapidly change the overall ratio at the front wheels by making a new arm with the distance from the steering axis of the spindle to the pivot point of the arm closer or further away. I should probably make at least one arm with several pivot points to see how the turn-in of the car changes, then build one arm to not have a bunch of holes in it and be neater for appearance. And I should also be looking at what’s available in angle iron to see what I will be working with to build the final arm. But this seems a good place to put this to bed, and maybe myself as well.