Tag Archives: technical stuff about building cars

The bandaids are off

Well the full extent of the damages are now visible as I am between bandages. I think the thumb will be OK going without another bandage, but the index finger needs antibiotic and another bandage. The index finger got really close to losing the chunk off the tip, but I think it will heal without the big ugly scar.

The index finger in all its gory glory.
Very close to losing the tip of my finger.

The thumb injury can barely be seen a day later, but it bled like I severed a major artery when I did it.
'Tis but a scratch.

Construction on the Sprint-T will have to wait until the index finger heals over so I don’t get bad stuff into my bloodstream through the break in the skin, but I have been thinking about order of construction for the frame.

First thing I need to make are the roll hoops because they dictate where everything else in the frame has to go. And I have been thinking about how to make two perfect hoops. The raw stock is a thermoplastic, meaning it can be formed easily when warmed to something under its melting point but above room temperature, a candle or similar is a good heat source for bending styrene plastic. I just need to use a round thing to bend around that has the same radius as the anvil of the tube bender, in scale, and a flat surface to make the second bend against to get all three legs in the same plane, easy-peasy. So, put the anvil of the mini bender on a board or something and put marks on the board for a 90° bend and where to put the leg of the first bend to get the distance between legs on the hoop the right distance apart. Put the top of the hoop on the mark for the beginning of the 90° bend with the leg from the first bend on the mark for how far apart the legs should be and make the second bend and cut the legs to length after bending.

The next thing would be to cut two pieces of raw stock to a scale 52″ for the main rails between the hoops, so the bracing inside the hoops will just clear the body when everything is together. And since this build is going to be fitted with a bellypan, the bellypan would be a useful place to use as a jig for getting all the bits and pieces for that level of the frame together. So cutting the bellypan to size, gluing the lower frame rails to it and the roll hoops to both seems to be the next logical order of operations. After that the crossmembers that run between the legs of the roll hoops seems to be next. Measuring the height of the top of the bellhousing for the horizontal brace across the front hoop and cutting stock the same width as the crossmembers would be the next step as would placing that member at the right height. Doing the same thing for the harness bar on the rear hoop would be next.

At some point I would need to bend the top rails for the frame and put them in, this would probably be a good time. Also for the diagonal from the top of the rear hoop to the bottom of the front hoop. The other diagonal is going to be more tricky because of the pickup point for the front of the swingarm coming from the rear axle. I need to see where the front of the swingarm is in relation to the diagonal to see if I have to make a jungle gym just for getting that point solidly located in space, or if I can just kink the diagonal a bit to catch it, then run another diagonal from the pickup point to the bottom of the front hoop to triangulate it and to the top of the rear hoop to preserve the triangulation of the front to rear diagonal.

And I have no idea where the top mount for the front coilover needs to be to clear the front tire at full lock and full bump, like when I hit a curb on a tight corner with the inside front tire. That would be an ungood thing to happen in a run, but to have the tire hit the frame would make bad plusungood, if not doubleplusungood. And yes, that was Orwellian New Speak used to describe an engineering scenario. I respect the classics. I mention this because I lack the tools to determine on my computer where the diagonal from the bottom of the front hoop has to be to clear the tire at full bump and full lock, without making the bracket on the axle any higher than it has to be for the coilover to clear the steering. Sure working from the side view I could just make the diagonal just tangent to the tire at full bump and call it “good enough”, but that would make the axle just a tiny bit heavier than it has to be, which is all unsprung weight. And my views on unsprung weight are only slightly less negative than my views on drunk drivers.

I can calculate the tangent based on diameter at the tangent point at full lock where the inner edge of the tire crosses the plane of the diagonal between the bottom corner of the front hoop and the top of the coilover, without needing to use 3D modeling but there are still width effects I need to account for and dynamic effects like axle flex and frame flex. Now frame flex is going to be measured in hundredths of an inch on the full-scale car, but I can’t get an accurate estimate of the load to determine axle flex beyond the load needed to get the spring compressed to full travel. At that load the axle flex is going to be in the same range as the frame flex, 0.01″ or less but the shock load against the bump stop could get another 0.02″ on top of that and times the moment arm that could get the tire as much as 0.08″ higher and closer to the diagonal, which would mean moving the top mount of the coilover even higher to clear the tire at full bump and full lock. Or I could just make the diagonal clear the straight ahead tangent at full bump and let the difference in height at full lock provide the dynamic clearance.

And if a picture is worth a thousand words I just posted more than 3000 words counting the pictures.

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I really don’t have much to write about

I walked 2.29 miles (3.68 km) going to get my toes done, buy breakfast sausage for cheap$1.67/lb, drop by the ATM for Mrs. the Poet, and get a Whataburger and fries. Then I took a nap. Whoo! living the life.😑

Still thinking about the TGS2 because what else would I think about if I wanted to stay sane? Since the part I didn’t have totally nailed down before I was still thinking about getting that upper coilover mount figuratively nailed down in every plane and triangulated against flex. Basically the plan is to run tubes from the upper and lower frame rails to the upper mount from two verticals between the rails, one vertical right in front of the firewall, and one just in front of the axle. The bottom of the upper rail will be 1.5″ (3.81 cm) plus the thickness of the bump stop, that I haven’t sourced yet, above the tube of the axle. The bottom rail will be 7.5″ below the center of the axle at intended ride height, or 6″ (15.24 cm) measured to the top of the rail, with a bracket coming from the rail to support a droop stop 1.5″ from the bottom of the axle at normal ride height. Yep, that comes to 3″ (7.62 cm) axle travel at the frame, which is normal for a T-bucket front suspension. What’s not normal is to control the axle with both bump and droop stops, normal is to use the shock absorbers for this function. But it really tears up a shock to use it as a droop stop and even worse to use a shock as a bump stop without an external stop fitted over the shaft. Basically without an external stop the shock piston slams into the foot valve and after a couple to a few times of that happening you no longer have any dampening control over the axle travel. So belt and suspenders there will be a bump stop on the coilover, and another on the frame.

Now where the frame leaves the front of the body the top of the top tube is 17″ (43.2 cm) from the bottom of the bottom tube, leaving 7″ from the top of the axle to the bottom of the top tube, lots of space to mount a bracket and bump stop and still leave 1.5″ for travel up. In fact good design principles require less than 1.5″ clearance between the bottom of the bump stop and the top of the axle so that there is enough travel to cushion the axle before reaching the limit of the shock and slamming into that foot valve. It might touch the valve but if I do my job as an engineer there shouldn’t be enough force to damage anything.

Now one of the problems I’m having is getting springs light enough for the front end because there is so little weight on the front end with the mid-engine configuration, without installing ridiculously long shocks. The shortest shocks I can find that will hold the springs are nearly 20″ long extended and 13″ compressed. The issue is the free length of the springs, and there has to be enough extended length to get the spring in place without compressing it so the adjustable seat can be spun on by hand so it doesn’t get cross-threaded. The problem is the shock has to mount as close to the kingpin as possible to control the single-wheel motion, and I need to limit wheel travel to keep the TGS2 from turning into and off-road buggy and to control camber, body roll, and prevent the frame from crashing into the ground. And the weight situation is we are talking about a car with a race weight around 1300-1400 pounds with more than 60% of the weight on the back and about 240 pounds per wheel on the ground and less than 25 pounds on the spring. It doesn’t take much spring to control that little weight, but a lot of shock dampening to control the unsprung mass. The sprung/unsprung ratio is almost off the chart for this car. It’s not bad in back, but there is just too much previously bought parts weight up front that isn’t resting on the springs. And seriously, all that weight just in the front axle and suspension does a serious negative to polar moment.

Looking at the numbers makes me seriously question my tire choices for the street setup because each tire weighs 31 pounds, without the 24 pound wheel. Fifty-five pounds is a ridiculous amount of unsprung weight per corner for a 1300 pound car with more than 60% rear weight distribution. Seriously the wheels and tires together weigh more than the rest of the front end minus suspension.🤯 Also I need to move more stuff forward of the center of the wheelbase, to keep the weight more forward and also keep the polar moment low. Also, seriously, this will probably raise the car weight more than a little. The race tires are a little better at 23 pounds each and the aluminum wheels are about 20 pounds going by shipping weight. So that’s a huge chunk off the unsprung weight.

And I have been thinking about the TGS2 in street rod parameters rather than mid-engine sports car parameters because Goodguys is a street rod and muscle car sanctioning body. Thinking in the proper terms gets the tire weight down to 20 pounds and the wheels are a smidge lighter at about 18 pounds. Still more than the sprung weight for each corner… I seriously need to redo my weight estimate because of how heavy the front axle, brackets, and spindles are. I’ll ponder my calculator and weight charts more now that I have weighed the parts I have on hand and use known weights whenever possible and get back to you later.

I’m not ignoring the recent events involving guns

I’m just trying to not think about them. Because there’s nothing I can do that will change our gun laws one iota, nothing I can do about liars occupying the White House who do nothing except tweet and play golf and drink Diet Coke and eat McDonald’s all day. I write about building a car now, because when I wrote about bike wrecks I made myself crazy and super depressed, and I don’t like being crazy or any level of depressed.

Seriously this is like the 300th mass shooting in the US this year and if the other 299 or so haven’t gotten the ball rolling another one won’t either, even if it’s a hate crime. A hate crime that we enabled by allowing people to buy what are essentially low-performance weapons of war without proof of need or even proof of sanity. It’s just ridiculous how easy it is to buy devices capable of killing so many people in so little time. I mean, sure I said similar things about cars, and I mean them, but at least you have to show some degree of competence to own a car (license), show some financial responsibility (insurance), and register the damn thing with the government (tags). I’m convinced the only reason why we aren’t up to out necks in bodies is it takes a fair degree of skill and a smidgen of depravity to use a gun like that, plus bullets are expensive. It takes a lot of practice to get skilled, and since ammunition is so expensive that degree of practice is also expensive. That’s one reason so many mass shooters are either well-off, or ex-military so they get the ammo to get the practice to get the bullets on target. The last time I shot a long arm was when I was in the Army, and it has been more than 20 years since I shot a pistol, all because I can’t afford to shoot the guns I (used to) own. I let the last one go when my dad died and we sold his guns off, I put mine in with his and Mom’s.

But, I haven’t written about the shootings until now because I have nothing useful to add.

Something else I can’t do anything about is the depravity of men. The reason the synagogue shooter gave for targeting the sanctuary is he “wanted to kill Jews”. There is nothing I can do about him wanting to kill Jews except prevent him from acquiring the capability of carrying out the desire, and as already demonstrated there’s Fuck All I can do about crazy people getting access to that capability. Unless you are convicted of a violent crime there is absolutely nothing preventing you from getting your hands on as many guns and as much ammunition as you can buy or physically carry, whichever limit you hit first. And even a conviction for a violent crime might not prevent you from legally owning a gun, if the conviction was not properly recorded, or if the crime is not sufficiently criminal to warrant preventing you from buying firearms, like many misdemeanor assaults or cruelty to animals.

So to keep from stewing about all the things going on that should make me insane I have been building cars in my head, making sketches on paper and designs in my head about what to do to solve the myriad of problems that come from building a car from Bits You Bought At Random (Not Really At Random It Just Seems That Way). Basically every time I buy something I freeze that part of the design, and everything else has to work with or around the parts I already bought unless it becomes cheaper to abandon the sunk cost. And that phrase means that replacing or bypassing the parts I already bought is significantly cheaper than using them.

For example, I have a straight front axle that I bought so the hubs up front would have the same spacing as the hubs on the front of the minivan used in the rear as a mid-engine, which I bought when I had some more money than I have now and less expenses, and before I discovered I wasn’t going to get the minivan because Mrs. the Poet told the people not to give it to me 😦 She told them something about not wanting a derelict vehicle in the driveway because Codes would tow it, after we had already solved that issue. But anyway, now I have to build with that front axle and spindles unless it would cost less to do something else in the front suspension than to complete what I already have. And as I only need to buy shocks and springs, 4 straight links, hubs and disks, and calipers and fabricate a few brackets to finish tying all those bits together there is little possibility I could make anything cheaper unless someone gives me a small RWD car with a complete front suspension to swap out, and given what happened to the engine and transmission that was supposed to come from the minivan… I’m putting that possibility on the same level with meeting a Sasquatch or Santa Claus in person. Not saying that’s not going to happen, just getting the car and the required bits removed before Mrs. the Poet finds out the car is in the driveway and at no cost to me is a low probability event. It might happen but I would need Mrs. the Poet to not be at home for an extended period and also for it to be cool enough to remove the bits in the driveway and not get consumed alive by insects. Those conditions almost never line up because she goes to see her family in July and August, and it doesn’t get cool around here until, well now, and it’s still kinda warm this time of year. So free car when Mrs. the Poet is gone, and cool enough to not die working outside. It could happen, someday.

Or I might win the lottery and have enough money to buy what I need and also a place to work away from the house. Which do you think will happen first, free car or win the lottery? Leave a comment.

We have such small dreams

Mrs. the Poet and I were discussing what it would feel like to be rich while talking about the take home from the Lotto Texas drawing tonight. And as we did it dawned on me just how small we dreamed. And how little it would take for us to feel “rich”.

The big thing we kept coming back to was inspired by end-of-the-month grocery shopping, and having to eliminate items from the cart as we got closer to the budget limit, exchanging branded items for store-brand items, and just not buying stuff we could survive without. And a big part of our definition for “rich” became “don’t have to take stuff out of the grocery cart because we can’t afford it”, and the corollary “buy what you really want”.

Later we expanded on that to “have all the bills paid at the end of the month and still have money left over” and “get everything fixed and not have anything in the house that wasn’t fully functional”. Basically get back to where we were when I was working 7 days a week at TI back in the 90s, bringing home 20 hours of extra pay a week. We made a total of $57K that year or $100K in today’s dollars. We had a nice townhouse, savings, and I was taking flying lessons once a week. I had a “hot hatch” for autocross, my 87 Hyundai, and was building a Pt. 103 legal ultralight, so I was living my dream life at the time. So that’s what we are looking for with the lottery, living like I was working 60 hours a week at a good paying job, minus the working 60 hours a week.

And since I can’t stop thinking about the Sprint-T after considering the dynamics of the right side torque arm 22″ off center I changed my mind again and moved the torque arm over to the center section of the rear axle. Seriously the right side torque arm has the potential to steer the car left under power. And turning the swing arm into a two-piece radius rod would bind the axle as the car rolled into and out of corners. Not severely, but a bind at any rate. So the swing arms are back to free movement on both sides, and a new low profile torque arm is added to the right side of the center section.

Also the frame design was changed to the side rails extended to the far end of the car and a X braced crossmember placed vertically across the end to support the gas tanks and battery and the tonneau cover for the pickup bed. The bed is going to be similar to the original bed in that it won’t be attached to the bucket, but much deeper than the original Model T pickup bed, with the tonneau more or less level with the back of the body and the floor at the same level as the bottom of the bucket more or less, and the vertical crossmember will be supported by two diagonals running down from the top of the rear roll hoop, one to the bottom and the other to the top. There will also be two bolt-in braces at the rear of the frame to allow mechanical access to bits in the back and also allow the body to be bolted to the frame after the frame is completed. One brace will triangulate the rear hoop to prevent deflections during a rollover wreck and also provide a place to mount the shoulder harnesses, the other will be a brace across the top pair of diagonals from the rear hoop to the rear crossmember to stiffen the frame in torsion.

And yes I’m obsessive about frame rigidity especially in torsion. Torsional rigidity is essential in tuning for handling balance with springs and anti-roll bars, with a frame that is not torsionally rigid the only way to tune front-to-rear balance is by adjusting the roll center heights. While this works for fine adjustments it takes way too much movement of the roll centers to have that as the only way to adjust balance. That’s why the design for the Sprint-T has an adjustable mount for the Watt’s link, so that the rear roll center can be precisely tuned to balance the handling front to rear. The TGS2 has adjustable anti-roll bars to the same end for quickly adjusting the balance of the car for street or autocross or Solo racing, street driving requires a touch of understeer, but not too much while autocross requires a fair amount of oversteer, with Solo in the middle but biased more to the oversteer side because it’s basically the same as autocross, but faster. Goodguys course rules require top speeds “around” 30 MPH, where Solo rules allow speeds up to about 70 MPH. The descriptive term is “highway speed” for Solo, which was 55 MPH when the rule was first written and now could mean as fast as 80 MPH. Either way, Solo racing can get much faster than a Goodguys’ autocross or it can be about the same, so requires more tuning flexibility. But toss street driving into the mix, and you really need a simple and quick way to adjust the balance of the car from front to rear and back again.

And I mention the TGS2 because I haven’t given up on the mid-engine bucket if someone gives me a FWD car to use as a donor vehicle for an engine and transmission. I’m open to free 😈 I mean seriously open to free, as long as it is done legally, like asking to haul off a car from your land, or something like that. And seriously if you have a vehicle you need hauled off leave a comment 🙂 I will find a way. And if it’s a FWD minivan with an automatic transmission, well I’ll just suffer the ignominy of driving a slush box. Seriously, as light as the TGS2 is going to be it won’t take much to make it a rocket for SCCA Solo, even if the mid-engine makes it ineligible for Goodguys. And there is a chance I could still run Goodguys with a minivan engine and transmission stuck in the back of the car.

I’m not filthy rich

My ticket did not have the winning Mega Millions numbers. To be precise my ticket had nothing in common with the winning numbers. The closest my ticket came to winning was the jackpot total printed at the bottom. And at the end of the news was the announcement that if nobody won today Friday’s draw would be for $2 billion. That’s roughly $44,000,000 for the first year after taxes. To put that in perspective the jackpot for tomorrow’s Lotto Texas drawing is $13,500,000 over 30 years, or less than a third of the post tax first year take home. And because I’m not super greedy, just regular greedy, I bought a ticket for the Lotto Texas drawing.

Lotto Fever has not been the only thing running through my mind, I have also been thinking about making the Subaru powered variant of the Sprint-T lighter. If my math is right, I can save 7 pounds by fabricating an aluminum housing for an aluminum 9-inch center section, but I won’t save any money and I won’t be able to find the right final drive ratio to match the Subaru 5 speed transmission for racing or cruising the Interstates between races. The available ratios are kinda thin taller than 4.11, and especially between 3.50 and 3.00 as in there was literally nothing in the current catalog between 3.50 and 3.00. OK looking in the wrong page of the catalog, there are actually 3.50, 3.40, 3.25, and 3.00 in the other side of the catalog. The street side of the catalog doesn’t get as low (high numerical) as the race side, but it has much more choice taller than 4.11. Anywho, just thinking out loud again, looking for better options and not finding any.

And I was watching some racing videos last night and saw a ISMA supermodified racer that was running an interesting setup with a ball joint upright on a twin tube truss beam axle. I could only see the back of the right end of the axle because the camera was on the right side pointed forward from the driver’s seat area, but it looked like an inverted Pratt truss because they wanted as much of the load carried in compression as possible to avoid welded joints under tension and still wanted triangulation. Or it could have been a modified Warren truss with one vertical member to provide a place for the 4-link to tie in. Either way it gives a way to run different spindles and hubs if I didn’t already have an axle and spindles. But I’m keeping options open for a replacement that is lighter than the boat anchor I have at the moment. Not that it’s an actual boat anchor, just like 10 times stronger than needed for a 1300 pound street car, and correspondingly 10 times heavier and it’s all unsprung weight. Unsprung weight is bad because it’s basically uncontrolled dynamic weight. Sprung weight, as the name suggests, is weight controlled by springs and dampers (shock absorbers).

One of the options I have been looking at was making an axle from a foam core and carbon fiber for light weight and super stiffness. I could build for the same breaking load as my steel axle, or go for the same yield load, but since carbon fiber has the same breaking load as the yield load but there is a huge difference between yield and breaking loads for steel I’m thinking there is a larger safety margin matching the breaking load. I was also thinking that doing a final, non-structural, layer of Kevlar I could protect the assembly from abrasion and contain the sharp bits of carbon fiber when it does break using the different moduli of the two materials. Simply put the Kevlar has about the same strength as carbon fiber, but it has to be stretched a lot farther before it breaks so what breaks the CF won’t rupture the Kevlar layer which then contains the broken bits unless the load or impact also tears the Kevlar. I could use the same spindles I have now or I could adapt aluminum upright/titanium spindle sprint car spindles, or I could whittle aluminum uprights to use lightweight GN hubs and spindles with the same kingpins and bushings as my early Ford spindles. The sprint car spindles and uprights are tempting but questionably legal for road use. Anywho, carbon fiber over foam is about 1/5 the weight of steel for the same breaking strength, partially because the foam acts to prevent the CF from deflecting but adds little weight, and makes manufacturing the part easier because it provides the shape for the part, just lay up and use wicking peel plies inside a vacuum bag to remove excess resin. So end result is stronger, lighter, and almost as easy to make as welding it from steel except for the cost of materials.

Going to miss the Fair this Year

Due to a combination of bad weather and finances we are going to miss the State Fair of Texas this year. It has been cold and rainy the past two days, to the point I’m actually wearing a shirt in the house, and all the AC units still working are now shut down. I even slept under a blanket for the first time in ages, April or May at least. The office temp has warmed up to about 64°F.

One of the reasons I go to the Fair is to look at the cars, both for ideas for the T-bucket, TGS2, or Sprint-T, and because we are also looking to change our car-free status some day. Mrs. the Poet is having more and more trouble getting around, so at some point we are either going to have to buy a car, or get a subscription to Lyft or Uber or something. The other reason we go to the Fair is to try the food. You know, some of that deep-fried badness that tastes so good and is so bad for your arteries. But Mrs. the Poet can’t walk so good and especially with the weather turning colder her mobility is even more restricted. So with the forecast calling for an 80% chance of rain, and temps in the low 60s or high 50s F it’s pretty much a no-go this year because getting to the food takes lots of walking. There is discount food on Senior Day, but to actually get a meal you have to go to several vendors, because the cheap drink is one place, the cheap dessert in another, and the award-winning main dish is all the way over on the other end of the food area that’s about a quarter-mile away, leading to miles of walking between the car show and the food chase. So, no Fair this year. And because of the rain we have been having there has been a lost of flooding, both from rising streams as well as flash floods because the soil is completely saturated and there’s no place for the water to go except into the streets and storm drains that are already backing up because of rising streams and rivers.

On other fronts, I’m doing beans and rice again tomorrow because I need to help the food budget and that’s about the cheapest big meal I can make. The ingredients cost about $3 including spices, and because I’m using a slow cooker I’m not using much electricity either. And I really like the end result after the 8-9 hour process. And I had better like it because the recipe I’m using now makes enough food for 2½ dinners, or 2 dinners and a side or light lunch. So if I don’t like what I fix I’m seriously out of luck. When Mrs. the Poet is out of town that goes double because that means 5 meals in total from that one batch of cookery. Now if I chose cheaper ingredients it would be even cheaper, because brown rice is expensive compared to white, and there are less expensive varieties of beans I could use, but it wouldn’t taste as good and as many meals as I get from one batch of beans I need it to taste as good as I can make it.

Getting back to the Sprint-T for a few words, the deal with the transmission on the EJ20 Subaru engine might be a few pounds heavier than other possible combinations, but the cost of the combination is less than the cost of a rebuilt T5 transmission alone for the RWD conversion of the Subaru, not to mention tons less work because I don’t have to make a new bellhousing that connects the Subaru engine to a Borg-Warner (now made by Tremec) transmission. The transmission is one of the few things on the Sprint-T that weight is less of a concern than cost or ease of installation, because it sits in the middle of the car front-to-rear and just has a negative effect on the power-to-weight ratio and doesn’t affect things like polar moment or balance.

We have actual cool

The office temperature was 74°F (23.3°C) this morning! It was cooler than that when I went shopping for a solution to the drain plug problem we are having in the kitchen sink and redeemed a coupon for a free Avocado Bacon Burger at the local Whataburger. Then it was about the same as it is right now outside: 66°F.

Mrs. the Poet is not sure she likes the solution I found for her constantly failing drain plugs: what Lowe’s calls a “suction stopper” which is basically a round sheet of rubber that covers the drain, and a stainless mesh filter that fits inside the drain and removes for cleaning. Total cost $7 and the only failure points are eventually the rubber will age into uselessness (almost typo that would also have worked: “uselessmess”) and the mesh can be torn if a fork gets caught in it. Unlike the one we bought last year for $3 at the local grocery that has a built-in failure that is pretty much guaranteed because that’s exactly how all 3 of the last ones we bought failed, there is a barbed insert that fits through a hole in the rubber stopper, and after some use the water pressure in the full sink will overcome the tenacity of the barbed insert and the stopper gets left behind when the rest of the assembly is removed to allow drainage. This is another design defect in that the strainer has to be removed to drain the water so it doesn’t actually strain the debris from going down the drain. The new plug and strainer doesn’t have this failing.

I’m still thinking (Danger Will Robinson!) about the Sprint-T design, this time about the lateral location device for the rear axle. With the various types and sizes of tires I will be using some adjustability in the rear suspension to change the balance of grip front to rear. Looking at the many ways to get this adjustability the simplest way is adjusting the rear roll center height by moving the vertical attachment of the rear lateral location device. Well, I did the bending stress on a 1.125″ fine thread bolt and for the LS and lighter engines this will be just big enough to not fail in long term use. There might be some flex while racing, and it is a definite failure point if I bang a curb with the right rear tire on the street, but the flex will not be noticeable to the driver and I’m not supposed to be banging curbs anyway. Construction will be super easy: After I cut the pivoting piece for the Watt’s link I cut a 1.125″ hole in the center for the pivot bolt then weld a fine thread nut with a grease fitting over the hole and machine out a bit of the arm to clear the bolt in use. I don’t know how much adjustment I will actually need and I could probably rebuild the mount for the pivot arm with only as much bolt as I need left unsupported from flex after I finish testing. Then I could just machine away the rest of the bolt past the support structure and save that little bit of weight.

Speaking of saving weight, I’m having some issues with how to attach the bracket for the Watt’s link to the rear axle housing, mostly because I still haven’t settled on which rear axle to use, the nine-inch Ford with an aluminum center section and a fabricated aluminum housing and axle tubes or the Winters V8 quick change with a magnesium center section and aluminum side bells with aluminum axle tubes. The generic Nine Inch would be a touch cheaper and has more clearance at droop, while the V8 is slightly lighter and has a better selection of final drive ratios. That availability of final drive ratios might be the thing that swings the decision. Anyway, the Nine Inch housing will have to have a mount welded on the back, while the V8 can have the bracket bolted with longer studs on the side bell, making modification a simple matter of unbolting the test bracket and bolting on the permanent bracket, another point in favor of the V8 QC axle.

And this once again points out that designing a car from scratch is a good thing to do for us old people with ADD because there are so many sub-systems that have to be hashed out so progress can still be maintained when interest fades on whatever I’m working on at the moment.

I’m all pink

I got some sun out at the Hot Wheels Legacy event this morning. The fun started at 0600 when my alarm went off so I could catch the bus. Then I did the usual morning routine and was out the door about 0635, caffeinated and hydrated and pop-tarted. When I to to the bus stop I checked the itinerary and discovered the schedule I looked up was for Friday, not Saturday, after I had already activated my day pass and couldn’t get a refund. So I was committed to doing something or just throwing away $3. I knew that the closest approach during the weekend was the corner of Garland and Beltline, which was a bit of a slog, but doable if I stayed hydrated. So I set out on a 2 hour journey with a 1.8 mile walk to the event.

AAnnnd the battery on my new laptop needs to be recharged, so this will be continued later.

The heat is taking a break and Mrs. the Poet returns

The forecast high for today is was “only” 103 104°F getting down to 75° in the AM. And to welcome Mrs. the Poet back Tuesday the forecast high is just 99°. Mrs. the Poet is strongly considering staying in Upstate NY, except that her ticket is only transferable if her flight is cancelled. I know the cats will be glad to see her, they wander the house calling for her like they expect her to appear from the air or something. And I’m missing her, too.

On the Sprint-t project I have simplified the body mount somewhat. Instead of welding a box structure with a complex flange and dozens of holes in the top that would allow water intrusion, I moved the face between the floor and the filler over to the other side of the mounting nuts with a simple bend to carry the flange up close to the nuts through the cowl pinch which won’t affect the mount stiffness since there won’t be any bolts except next to the firewall. This would have almost the same effective stiffness as the more complex mount with all the fiddly out-of-position welds I would need to do standing on my head. Most of the welds I could do outside the car on a bench, but there would still be some yoga welding in the car, only about a third as much as the other design. This design leaves the nuts and bolts inside the body and exposed for maintenance. And there would literally be a line of bedliner caulking the bottom of the body outside in the joint between the body and the frame.

Like I posted earlier the design is getting to the fiddly bits like body mounts and making sure the floor doesn’t oilcan when I get in and out of the car, without disturbing the smoothness of the belly pan that is the other side of the floor. This excludes running beads on the floor because that also is either a bump or a depression on the belly pan. This leaves welding light angle sections or just vertical flanges on top of the floor like for the body mount. And I forgot to reiterate the floor/belly pan is a structural part of the center bay to prevent distortion of the roll cage in a wreck and also act as a transmission mount. I decided the trans/driveshaft tunnel will be removable from the inside of the car for installation and maintenance of the drivetrain. This solves a ton of issues with keeping water out of the interior and also keeping the belly pan smooth, and makes the floor a better structural component for the frame. Otherwise I would have to figure out how to route the shear loads around the hole in the floor to get the transmission in and out, and make a removable cover for the hole. This would be a weak point in the frame that would be a bear to fix without adding a bunch of extra weight.

And I have to get the clean sheets out of the dryer and put them on the bed. I had some bug bites that bled a little on the sheets, plus there was the matter of sweating making the bottom sheet dingy looking, so I got some bleach at the store and tried to whiten them. And it doesn’t matter if I succeeded or not, they go on the bed tonight so Mrs. the Poet has a clean place to sleep tomorrow night.