Tag Archives: mid bucket

A minor breakthrough

Still thinking about making the TGS2 lighter and simpler to build and I had a minor revelation. If I lower the 3″ tube until it is on the axle centerline that will reduce the bending moment enough to not need any bracing other than what is provided by the double-shear spring mounts (that’s a plate on either side of the coilover heim with the mounting bolt going through both plates) welded to the top. That unloads the top radius rod on the 4 link allowing for higher loads from restraining the brake rotation etc.

Someone asked me IRL how I know there is going to be so much weight in the back of the car. That one is simple: The engine and trans combined weigh 620 pounds with the CG about 10″ in front of the rear axle centerline on a car with a 100″ wheelbase that will weigh about 1600 pounds. I’ll let you do the math yourself, after I set the equation up for you. The arm for the drivetrain is 90″ and the weight is 620. The arm for the rest of the car is going to be 40″ if we are incredibly lucky, probably real close to 50″ split the difference and call it 45″ and the weight is 980. Moment is weight times arm. Add the moments together and divide by weight. That is the total arm of the car, between 63 and 65.5 and since we used the front axle as zero datum and we have a 100″ wheelbase that makes the rear percentage equal to the momentarm, I.E. between 63 and 65.5 percent. I learned this one when I was taught weights and balances for flying. Yes, I used to be a pilot before the wreck. Sioux this one was for you 😀 Math IRL for your students. Oh and the reason I don’t know the exact arm for the rest of the car is there are a bunch of parts I don’t know the exact weight for nor where they will go on the car when it’s finished. So I had to use a SWAG for the arm of the car without engine.

Excuse me I zoned out for a moment listening to an old piece from the ’70s on YTM; Mike Oldfield’s “Tubular Bells (Pt.I)”. They had just gotten to a part of the piece I call “The Procession of the Instruments” that starts about 17:00 into the piece, and continues to the end of Side One of the LP. This was one of my first experiences listening to polyrhythmic music, which my mind finds very relaxing. Anyway, Mike says the name of the instrument and they bring it up in the right channel then mix it over to the center front then over to the left and back but still up enough to hear if you focus on the sound. I didn’t know this at the time but polyrhythmic music has a calming effect on people with ADHD and PTSD. At the time there wasn’t any such thing as PTSD by that name, it was “Shell Shock” and didn’t happen to kids (that they knew), but I had been diagnosed with “something” tied to my high IQ, that we now know as ADHD. Anywho, when I listen to polyrhythmic music I zone a bit and get real calm.

Back to the car, I’m really feeling torn between totally enclosing the roof and windows and saving weight. Putting a roof and windows on it will make the car look more complete, but will need A/C in the summer. Or I could figure out some other way to keep dew and rain off the instruments and save about 50 pounds, most of it off the back of the car, by leaving the A/C in the donor vehicle and cooling the car by leaving the windows off. That would save even more weight but lower the gas mileage on the Interstate a bit. Basically all I really need is something to cover the cluster and seat when I’m not driving. I could make a snap-on cover like old hot rods and sports cars used in the ’40s and ’50s, called a tonneau. These days a tonneau is basically the thing that goes over the pickup bed when it’s empty, but back then it kept the interior clean and dry when the roof was down or if there wasn’t any roof at all. I bet I could make something with the HDPE sheet and some Velcro™ and get the same effect and roll it up inside the car when I was driving.

And I think I have meandered across the screen enough for today.

Finally a positive message about self-worth

Something Positive “Someone” in my case is Mrs. the Poet and my credit union account. Yes, my credit union account is listed as the beneficiary of my credit union life insurance policy when Mrs. the Poet dies. That way I don’t have to update the paperwork as relatives die off, whoever gets control of my finances after I die gets the money. Whoo hoo! big money. I think I’m up to $10K now. After the cremation that leaves about $7K for the beer bash.

I got the locks sheared and am now sporting a fresh flat top haircut with the little bits of hair still going everywhere. I think I will need to take a quick rinse under the shower before bed tonight to get a good sleep. I was upset to find out the stylist who has been cutting my hair the last couple of years is quitting the end of this week. Now I have to find another stylist/barber that knows how to do a flat top. I tried the #1 all over and it makes me look like I’m on my last week on death row with the shape of my skull. Or that someone is getting ready to break the rack (cueball). I think between the flat top and my winter beard I do a pretty good job of disguising the shape of my head most of the time.

I was thinking about the front axle, that if I have the ability to make it I could have saved a bunch of weight. I ran the numbers and the 2″ X 0.25″ wall tube is massive overkill for my application. Emphasis on “massive”. The whole unit less brackets weighs 28 pounds, the bare tube just over 23 of that. With the coilovers mounting as close to the ends as I plan I could build a 6000 pound front end and it still wouldn’t overstress the axle. That’s about 4 of my whole car sitting on the front end and no damage. If I had the tooling to make an axle I could make mine from the same tubing as my roll bar and still not bend it. That would weigh right at half of the one I bought, but nobody else could use it if it didn’t get put in a Mid-Bucket. There would be plenty of safety margin for a car with only 500 pounds on the front end, considerably less for a front-engine bucket, and none at all for a fat-fender rod. Now if I really wanted to go light I would swap the 2″ steel tube for a same size one in a weldable aluminum alloy and get an 11 pound axle instead of 28 pounds. But it wouldn’t last long with the forged steel spindles because of dissimilar metals corrosion.

It has been a long day today, I’ll write more later.

Still thinking

One of the things that has been gnawing on me a little is I missed another Ride of Silence this year. For those new to my blog since I dropped the bike wrecks click on the tag RoS or Ride of Silence to see previous posts about it. I started missing the RoS when the tumor on my neck got so big that I couldn’t ride any bikes. But after Chris Christie was removed from my neck I got to the point I could ride bikes with a very upright riding position or recumbents, but not very far. Well now I can’t ride anything except a bus or car because Arthur Dent is causing troubles. I have a pain that starts in the middle of the dent and radiates to the end of the trapezius in one direction and up the back of my neck in the other, and makes my deltoid and rotator cuff tingle like they are trying to go to sleep. It’s very annoying but not much of an impediment except to bike riding at the moment, but it feels like it is trying to get worse.

I’m stalled on the Mid-Bucket (aka the Thunderbolt Grease Slapper 2) ATM because I lack cash for parts or raw stock. I still haven’t replaced my ID since the last time I lost my wallet, because I needed my ATM card to get the cash to pay for it. ATM card should finally get here this week and I will renew my ID early so I can go to Nashville and see the eclipse this August. When I get stalled on one project my mind starts on a new project immediately, in this case a lighter weight version of the Sprint-T with the Pentastar V6. Basically it is just the same as the V8 version with lighter components because of less weight and lower power. Remember the vicious circle of too heavy so other parts have to be stronger and heavier making the car heavier so other things need to be stronger…? Well this is the benign circle of less weight allowing for less heavy supporting and connecting parts. And the weight came to under 1400 pounds with the balance almost 50-50 I can use all the same size wheels and tires on each corner. If I could have gotten one of those free things would have been a lot easier.

Pole Day for the Indy 500 is on the idiot box so this is time to wrap this up. Congrats to Kyle Busch on winning the All-Star race last night in a masterful performance. Condolences to Sebastien Bourdais on that wreck at Indy yesterday and wishes for a quick recovery.

Opus the Unkillable

My biggest impediment is my sense of esthetics

My main guide to engineering is the math, but after that is my sense of engineering esthetics. And sometimes that gets in the way of finishing a design. Seriously, the single 3″ tube would have worked fine for the de Dion suspension, but a truss would weigh less and be stiffer, by a small amount on both counts. And the new truss is much simpler both to build and to mount than the previous truss of 0.5″ thinwall tubing with a plethora of tiny triangles in two planes as it is just 7, 1.5″ X 0.120 wall round tubes in a single plane. The tube diameter and wall thickness are enough to hold the toe and camber alignment while the truss is strong enough to take all the vertical and horizontal forces with a huge safety margin. The truss weighs 20 pounds with brackets, not including the filler wire from the welds. This compares to the 3″ tube which comes to exactly the same weight but not as stiff vertically. Or as pretty to look at, which as I wrote earlier is an equal criteria after weight.

I mean face it, the 3″ tube would work just fine and probably less than 3 people out of 100 would be able to feel the difference in stiffness compared to the truss. Even fewer than that would care about the looks of the truss compared to the single tube. TBH even I am just the slightest bit ambivalent about the difference in appearance between the truss and the single tube. There is the simplicity of the single tube across the back of the car, but on the other hand there is the zen-ness of the collection of triangles running across the back of the car, even if it is hidden by the bodywork for aerodynamic reasons. There is also the fact that I can lower the roll center by almost 2″ in the rear to reduce oversteer slightly with the truss. And finally there is the cost issue, a single 58″ 3″ X 0.120 wall tube is less than half the price of the 132″ of 1″ X 0.120 I would need for the truss.

And even while I’m thinking about the rear suspension I’m still thinking about the cockpit and a possible roof and side windows. Mrs. the Poet is still saying there is no way I’m going to be able to get in and out going through the top of the roll cage after climbing the side of the frame. I have zero doubts about getting in and out of my own car, if for no other reason than I will have lots of time to use the frame as exercise gear to get my upper body strength up. Or I could screw together some black pipe for a dipping rig and chinup bar and continuously build my upper body every day. 😀

And I think I need to go to bed now, and so become the Nighty Knight.

It happened again!

I was thinking while walking again, and I wondered if a single 3″ OD 0.120 wall tube weighed more or less than the complex truss of half-inch tubing I designed for the de Dion suspension that still needed more work to actually support putting a spring on it. So when I got home I looked up my truss calculations and found I was putting just shy of 15 pounds of tubes in the version that just kept the rear wheels pointed in the right direction.

Then I ran a quick bending load calculation on the 3″ tube and it won’t need any extra support aside from the gusseting action of the spring mount (I mount coilovers in double shear mounts and tie them with bulkheads). Then I looked up how much it would weigh…18 pounds for just the bare tube, 20 with the brackets to make the upright adjustable.

Five pounds, I spent hours with a calculator, and paper and pencil for a design that saved 5 pounds and still needed more work to get right. Five freaking pounds, at minimum wage those pounds cost me about $20 each, maybe more. Probably more. A classic case of over-design. Now granted it would take a huge shunt to make a rear wheel point in the wrong direction and there is a good chance the tire would get knocked off the rim or the rim bend or break first, but the fact remains I couldn’t mount a spring anywhere except the upright or trailing arm without redesigning the truss, and adding weight, when I discovered that there was no way to balance the handling without moving the rear springs inboard. Now the fun part is moving the spring mounts on the frame inboard to prevent frame flex.

There are a couple of ways I can move those mounts in to get the springs off the ends of the axle. One is just change the mounting point to the crossmember and make that a truss to handle the bending load. Or I could continue to mount the springs to the heavily triangulated intersection of the upper frame rail, lower frame rail, center top hoop of the roll cage to upper frame rail brace, crossmember, lower crossmember to watt’s link center mount brace and taillight mount (that’s the intersection of 5 tubes in 3 different planes triangulating the mount to kingdom come) and move that complex intersection inboard a few inches as needed. Right now that intersection exists only on paper, not in steel, so moving it is just a matter of changing a drawing. This would also have an effect on the engine mounts as the tubes they mount on get moved inboard an as yet to be determined amount.

Now I’m going to open up a beer and eventually go to bed.

Opus the Unkillable

Late Night thoughts

I’m awake at 0424 and thinking again, about enclosing the cockpit to protect the instrument cluster &tc. I was also thinking I could use the HDPE to make a fake rag top. Using the white HDPE to make the roof hatch look like a “regular” Bucket top until I use it to get in the car, with the side windows to make it look like a “normal” car.

I’m also trying to figure out how and where to mount the mirrors for street driving, and I’m leaning to a pair just inside the windshield posts for my side view mirrors and another pair on either side of the seat for directly behind me.

I’m going to go to bed now and let this ferment a while, then come back and complete it.

OK I’m back it’s right at 1800 and the ideas about the top and windows have been rolling around since I got up and started sipping coffee. Part of the problem is ventilation. Gluing the side windows in would be easier and better looking, but leaving the windows shut in the summer while waiting to make a race run would make for a very uncomfortable car. Somehow I have to keep air moving through the car even when it is not running. Maybe a solar powered fan of some kind? And definitely hook up the AC for summer driving. Fixed windows and top with no AC would be looking for heat illness issues especially here in TX during the day. And with the Goodguys event just down the road in Ft. Worth I will definitely be driving during the heat of a TX spring and summer.

Mirrors are another issue, but I think 4 small ones should do the job. Put 1 each at the lower corners of the windshield for side views and blind spots and 2 more on either side of the seat at the top of the windshield for direct behind views and I think we’re covered for that. Just make sure the field of view is not obstructed and I can adjust the mirrors to work as long as they are not obstructed.

Now how to construct this top, well I’m still figuring that part out. The back part was easy to figure out. Most of the back will be a flat window except the part that wraps around the corners of the body, which will be molded to the radius of the corner all the way up to the top surface just like it was a rag top, and the side part will be on a diagonal like a traditional rag top.
Notice the way the side of the top goes up and to the back?

And this in white.
Famous T-Bucket from the '60s

The top on mine will more closely follow the top picture in that the top will be level front to back, but much lower because I won’t be sitting as high in the body as the seats in that car.

And now I want to go for a walk, so Bye!

Still thinking (know where your local fallout shelter is located just in case)

One thing I have been thinking about is the rear suspension. Well two things actually. The first thing was it saves less than $40 for me to use the steel swingarm/spring mount in the Mid-Bucket suspension, and it seriously complicates the rear frame. The second thing was that putting the rear spring that far out on the suspension complicates the roll stiffness bias. Putting enough spring to give the right rate for a 2 wheel bump over the end of the axle just makes the roll rate too high for the light front end even with the front springs almost on the kingpins. Seriously I’m going to mount a spindle with the steering arm on the axle and put the side of a pencil against the steering arm with the point against the axle and turn the spindle back and forth and watch the mark on the axle. The point that is furthest away from the kingpin boss is the closest point of the lower spring mount on the axle. That will give me the most front roll stiffness I can get with just the springs. It still won’t be enough to balance the car with the springs mounted on the trailing arm or to the rear upright. So I either have to use a front anti-roll bar, or I have to mount the rear springs closer to the centerline.

Mounting the rear springs closer to the centerline means making the de Dion truss strong enough to handle vertical forces. I have been thinking about that, and if my sums are right putting a truss of 1″ square tubing with 0.5″ round verticals and diagonals on top of the 0.5″ round tube truss would support the rear of the car with adequate safety margin. “Adequate” in this context means no damage if I hit a few pot holes or slide off the track during a time attack run, it doesn’t mean taking the car off-roading in the desert.

The other thing I have been thinking about is how light I could get a front-engine bucket like the Sprint-T. By adapting an A-904 Torqueflight to a Pentastar V6 with a steel 9″ Ford rear axle I could get 1450 pounds without even trying hard. Start swapping out an all-steel 9″ for an aluminum and magnesium quick change in the rear axle and carbon fiber in the driveshaft and we are looking at a 1400 pound bucket with 305 HP on 87 octane regular without changing anything in the engine or calibration. Get serious about making the frame lighter with aluminum instead of steel and a space frame instead of a ladder and maybe 1375 pounds. About 4.5 pounds per HP. That’s like a 750 HP Corvette or Viper running on Regular gas. As in car*√-1, imaginary. Even with the frame from the Speedway kit we are talking a hot rod that could give anything short of a Hellcat or Z06 a run for its money 0-60 MPH, on 87 octane regular gas. There are 2 ways to make a fast car, 1) lots of power and 2) no weight. 1) is fast in a straight line, 2) is fast everywhere. I think I like 2) better.

Incidentally, did I ever say how I figured out that I needed to use different size tires and how different they had to be? The book Chassis Engineering has a graph of grip over load for a typical race or passenger car tire. The problem here is it’s a graph for just one size of tire, and has to be scaled for a different size of tire. The way I did it was to leave the shape of the graph pretty much alone for the big tire and then scale the grip by dividing the load and grip by the ratio of the squares of the widths between the tires. F’rinstance the street and street tire autocross will use 195/50 fronts and 245/40 rear tires so the graph was scaled down by a factor of 1.58. This is not perfect, but it is close enough that I can come close to getting the balance right with just the springs and a light anti-roll bar to make up the difference of not having the perfect spring rate. For street and highway driving I will need slight understeer for stability, but for the autocross I need a slight oversteer for better turn-in and rotation through the middle of the corner. I’ll be able to do this with just a swap of shocks and springs which I have to do anyway because I need a lower ride height for autocross than for the street. Theoretically I could do that without changing springs and shocks but that would require carrying around a slew of scales and platforms and adjusting before and after the competition, or I could just do that once and pull those shocks off and put them in a case with labels as to which one goes on which spot on the car. Instead of spending time adjusting and re-adjusting the spring seats to lower or raise the ride height and move the weight around to balance the car in turns, I do it once at a test track and then just swap the coilover shock/spring units at the race from street to race and back to street in just a few minutes instead of the hour or so (if I get lucky) each way adjusting the spring perches.

And I have wandered around the verbal landscape long enough, time to wrap it up and do something else.

Opus the Unkillable

Design is getting down to brass tacks

That is a very archaic turn of phrase in the headline, it means discussing the ornamentation on a custom saddle and dates from at least as far back as the 17th century. Today it means getting to the fine details of a deal or design. As of this point the front end is approaching brass tack territory.

I went back to earlier drawings of the front end and found a couple that placed the crossmember above the front axle, but not as high as the one I discussed yesterday. So I went back to that and moved it higher, and also added the radiator mounts and body supports in front and hung the rack off the backside. I dropped the MD3 nose from the design in favor of making less drag and downforce with a nose made from the same HDPE panels the rest of the body is going to be made from. The right side of the rack might protrude from the body at full left lock but I don’t care at this point. That is a minor aesthetic point that is overridden by making the damned thing work right. There is nothing for it to interfere with on that side.

At this point I have started thinking about the cockpit design, specifically protecting the instrument cluster from the environment while parked outside, and making the cockpit tolerable at highway speed. Putting a roof on took care of most of protecting the instruments from condensation, rain, and bird poop. Further enclosing the environment with some kind of side windows will do a better job of preventing condensation and blown rain from getting to the instruments. I don’t know if that would be enough to allow driving in the rain, but it will probably do a lot for making the interior livable at highway speeds by reducing cockpit wind and turbulence. The original cockpit had no windshield or side windows with the driver wearing a helmet with a face shield all the time, even on the street. That was back when the car had a V8 in the front and the driver sitting on the left side of the cockpit. Now I’m even thinking about heat and AC 😇. There are races in FL during the winter that might be fun to run in, which means driving in winter, which means a heater. Driving in the rain means a fogged windshield which means a defogger which means AC of some kind.

I even looked up what sender to use on the gas tank so the gas gauge works right (10-90 ohm). Really this started when I discovered the entire instrument cluster came out as a unit. And that the engine and transmission controllers expected to find the instrument cluster before they would let the car run. Since I need a tach and speedometer and the computers know how to use the ones in the cluster and everything will need to be “unconfused” L8r, why not use the OE cluster? It saves having to buy those instruments later and figuring out how to make everything work together which is even a bigger hassle than telling the computer it isn’t in a minivan any more.

And now it is about time for my walk, so more thinking about random things.

Opus the Unkillable

About that post Sunday

What more can I say except that alcohol, diphenhydramine, and exhaustion are a bad mix every time? I took the allergy pill about 3 hours before I started typing, went for a 2.6 mile walk, then had a beer when I got home. Then I sat down to post what profound thoughts had come to me on my walk when the world started tilting and the keys on the keyboard started moving around. I think the straw that broke the camel’s back was piling the beer on top of the mild dehydration I had following the walk. That made me more susceptible to synergy from the allergy pill, the alcohol, and maybe my antidepressant.

Anyway, what I wanted to talk about Sunday was thoughts about getting the rest of the car skinned out as cheaply as possible. I can form this material about as easily as I can sheet metal and have it hold that shape after forming. The trick is to heat it before forming then holding it where you want it until it cools. I don’t even have to paint it because it comes in colors that are all the way through the material. I can use heat from a heat gun to weld it to make parts that are bigger than the 22″ wide rolls it comes in. I can use that same heat gun at a lower setting to form the material around a buck to make body panels. In fact that is the intended use as sold for this product, body panels for race cars. Add in the fact that this stuff is about half the weight of aluminum and that all of the body panels on my car are non-structural and I think I have found the perfect material for my hot rod.

There is a downside to this, the material shows scuffs and scratches and is easy to scuff and scratch. That means I will have to replace the plastic panels more frequently than if they were painted metal. But even that downside has an up side. I don’t have to replace the damaged panels with exact duplicates, I can change them to change the styling of the car. Or just the color if that’s what floats my boat. And I can also change the rear aerodynamics at a whim.

That last sentence is also one of the things I have been thinking about to reduce the inherent oversteer of this car. Understeer to neutral is what is desired for highway driving, and planting the rear end with aerodynamics is a good way of getting that. I have also been thinking about a “billboard” rear spoiler to create downforce and pull hot air out of the engine compartment. The way that would work is the rear fenders would sweep up from the running boards to a 45° angle that will be continued in a full-width rear spoiler across the engine compartment with screening keeping debris out of the engine and transmission as the low pressure area behind the spoiler sucks air from in front of the fenders through the engine compartment and out the back. I’m still working on that one so the rear fenders are subject to change.

Something else that the plastic could be used for is making a roof hatch to keep the rain off. Run the windshield to the same height as the roll cage and leave a strip across the top that I can pop-rivet the plastic to. Run the plastic over the cage and use Velcro or similar to hold the back of the roof down against the roll cage. Voila! Sun and rain protection. And it would keep the bird poop out of the interior. 😀

And things are getting late around here and I have things I would like to do on the computer that don’t involve using the keyboard.

Opus the Unkillable

It’s ‘Dega baby!

Just finished watching the Xfinity race from Talladega. There were lots of wrecks but not while I was watching. I kept coming back to the aftermaths instead of the actual wrecks. I don’t like wrecks, I hate seeing good race cars torn up, I’m also not very happy about seeing crappy race cars torn up. I mean sure I am less unhappy about crappy cars getting torn up, but at the Xfinity and Monster Energy Cup levels there really are no “crappy” cars, just “less perfect” cars that could run just as fast with a few adjustments. Part of that is rules, part is the teams are just that good.

Watching the Xfinity and Cup Series is part of my inspiration for both the Sprint-T and the Mid-Bucket. Also I watch YouTube videos of Goodguys Autocrosses from recent years and SCCA Solo events that have Modified category cars for when I run slicks. Speaking of slicks, I just can’t find 16 X 12 wheels in my bolt circle at a reasonable price, so that means the 6″ Formula Vee rears on the front on the 4″ wide wheels, and the 12″ wide tires on 10″ wheels on the back.

And now the ARCA cars are about to run (on the tube at least, I don’t know if this is live or tape-delayed) and in about an hour is the IMSA race from COTA outside Austin. So then I start flipping back and forth. And I won’t have the split attention that will let me write and watch 2 races at the same time so I’ll go ahead and end this post.