I just got finished watching a good race, Denny Hamlin won, Kyle Busch won 2 of the three races this weekend but not today, and I have to go do things tomorrow. I need to pay for my phone, I need to shop for a new mattress for the bed in the big bedroom, and I need to get a massage.
Also I need to figure out where the links for the front axle are going to fit on the frame so I can make the links to length in scale for the Mini Sprint-T. It’s basic trig and geometry, the axle is x distance from the front hoop, the lower rail is y inside to inside and y+3 outside to outside and the links have to be l distance apart to clear the tires at full lock. This has been determined previously to be 31″ outside to outside, and the links are 1″ diameter so the links have to be 30″ center to center. The only dimension that is unknown at this point is the altitude of the triangle formed by the front hoop and the lower frame rails, because I still haven’t set how far in front of the axle the forward crossmember is, because I still haven’t decided if I want big or small body shocks. The big body shocks use 3″ OD springs, the small body use 2″ OD springs and there is 0.5″ difference in how far forward the front crossmember sits which means there is maybe 0.125″ difference in where the lower rails are 30″ apart center to center measured from the front hoop.
And it has occurred to me that some of you don’t know where the transverse structural parts go and what they are called on the Sprint-T and because it is the same but in scale, the Mini Sprint-T. From the front, there is the front crossmember that holds the front coilovers over the axle and the radiator gets mounted to the front of it and the mount for the track bar that locates the axle from side to side, then the front hoop that is 1.5″ X 0.120″ for most of the structure and 0.060″ for the rest of it because it’s part of the roll cage that has to be 0.120″ wall thickness except for the part that isn’t roll cage but frame, then the rear hoop that is the same as the front hoop, then the rear crossmember that basically doesn’t do anything except hold the rear of the frame apart and protect the fuel tanks in a rear end crash, and provide additional torsional rigidity by increasing d4. The point of interest in today’s post is the front crossmember because the lower rails meet at the center and the upper rails are right over the coilover mounts and also pick up half of the mount to put the upper mount in double shear. The triangle formed by the lower rails determines how far the rear mount of the links that mount the front axle are from the front hoop because the mount has to be 30″ center to center. The links have to be parallel to work best with no bump steer from moving the ends of the axle when the car rolls in a turn. So the center of the rear mounts on the frame have to be the same distance apart as the mounts on the axle to keep the links parallel.
Anyway finding the location for the rear mount is a simple ratio. The problem is I don’t know the terms for the ratio beyond the first term. That term is 30/46.5 or 0.645161290323. That’s the ratio of the center separation of the links to the center separation of the frame rails at the front hoop, the term I’m missing is the distance from the front crossmember to the front hoop to multiply that by. I know about how far that is but not exactly how far that is. But if I think about it some more I can make it so there won’t be a difference because I’ll use the distance for the larger spring and just enjoy the extra clearance if I decide to use the smaller spring instead, so doing some quick calculations, the rear axle is 5″ behind the rear of the body, the body is 52″ long and the rear axle is 100″ behind the front axle and the front hoop is right in front of the firewall and where the frame rails meet the front hoop is 58.5″ in front of the rear axle or 41.5″ behind the front axle and the front crossmember is 1.5″ in front of the front axle, so the distance from the front hoop to the front crossmember is 43″ so the rear mounts for the links are 43-(0.645161290323*43) or 15.258064516111 from the front of the front hoop. Rounding makes that 15.26″ from the front hoop and links that are 23.25″ center to center after using the distance from the center of the rear axle to the center of the holes for the Heim joints on the 4-link brackets and the size of the vertical member supporting the rear mount which will probably be 1.5″ X 0.060″ to make it stiff enough in bending with the load triangulated at both ends, which I just decided. The diagonals will run from the top of the front hoop and the bottom of the front hoop so there will be no possibility of hitting the frame with the front tire at full steering lock. And as previously stated there is another diagonal that runs from the top of the front hoop to the top center of the front crossmember so there is a parallel frame member to capture the top of the rear mount for the links and make that area fully triangulated.
And this has turned into one of the longest non-wreck report posts I have done. So since I don’t want to overload people doing an archive dive, this seems like a good place to take a break and put this post to bed.
The parts I bought this January finally arrived today. The backgrounds are the business cards for the company I bought the parts from, to give you an idea of scale for these parts, and I’m using “scale” in two forms for this. The parts are for the Mini Sprint-T in 1/25 scale.
Again, the backgrounds in the picture, the dark part, is the business card of the company that I bought these from. They literally get lost on a standard size business card. And there was a note inside the delivery envelope saying the guy that runs the whole show for this company just got out of the hospital after 2 months. And those thin pins coming off the top row of rod ends fit snugly in the stainless steel tubes I bought to make the links for the 4-link, and the plan is to add a tiny drop of solder to the end of the tube to hold the rod end and jam nut in place. The jam nuts are those hex-shaped things above the rod ends.
And I need to get to bed, so the blog post needs to, too.
That used to have “and the Feed” back in the day when I was still covering bike wrecks every day, but since I stopped doing that my mental health has improved considerably. That’s a little on the scary side that this state is “improved” over where I was just a few years ago.
Anyway, the race was in Las Vegas and was 400 miles long, and Joey Logano won. The new package has slowed the cars way down on the track but they still have the same pit road speed limit they did at last year’s Las Vegas Spring race which means the pit crews are still facing Certain Death if they get in the way of cars moving at or near highway speed, but the cars are now going slow enough on the track that there is very little possibility of one leaving the track and going into the stands and killing a bunch of people. The last time they had a car going too fast for the retainment system they got really lucky and there were only minor injuries to the spectators hit by debris. The new rules can be summarized by “Big spoilers, tiny spacers” as the Big Tracks (basically anything over a mile long) have tapered spacers between the throttle body and intake manifold that reduce engine power to about 550HP or a bit less, partially because that was the cheapest way to do it and partially because the cars were Too Fast everywhere except short tracks and road courses. So now they have most tracks limited to 550, Daytona and ‘Dega are going to be about 400HP if I’m remembering that right, and short tracks and road courses are going to get full effective use of the intake system to make the 750 HP those engines are capable of. To make sure everybody stays inside the track fence and out of the crowds they bumped the rear spoiler from less than 3″ to
almost 8″ tall and added a bunch of front downforce to keep the cars aero balanced with about the same downforce on each end. Teams are still trying to figure out the suspension settings that work with the new package because this was a major change from last year even though they kept trying to say it was only a “minimal change.”
One thing that is changing on the Mini Sprint-T and Sprint-T is how the rollover structure integrates with the frame structure. Simple terms the upper frame rail is getting moved back out to the furthest edges of the frame again by squaring off the corners of the roll hoops but also leaving the hoops inside exactly like the SCCA wants it. The hoops will be bent from a single length of tubing as specified in the rules, but there will be short stubs of frame-size tubing welded to the outside of the bends to pick up the upper frame rail. The diagonals will still be rollover structure wall thickness and also have the bends to catch the top of the rear hoop, a bent gusset to catch the vertical leg of the hoop, and a frame thickness stub to catch the intersection of the tangent stubs from the vertical and horizontal legs of the hoops and tie everything together in a lightweight super triangulated space frame, and also what I hope is a rule-complaint roll cage. I’ll have to wait until tech inspection to find out, though.
I have a visit to the Lab Rat Keeper the day before Valentine’s day for a quick blood draw and BP check, and maybe a hamberder or something at one of the several fast food joints in the area. The covfefe house is closed, but despite having a large chunk of the building burned away the Mexican chicken place almost across the street from the office is still serving food. I’ve never been there, it might be a good time to try it out.
On the Sprint-T and Mini Sprint-T front, there has been a minor change in the design around the main cage. Basically the upper frame rail is now running in segments inside the hoops instead of over the corner after I did another stress analysis that showed too much bending stress on the hoop with the rails running outside the bends and the diagonal braces welded to the top and sides through bends and/or bent gussets. What I had before was the rails welded to plate brackets on both sides of the hoops in line with the horizontal and vertical legs of the hoop. What I have now is the rail welded to the top of the hoops right at the end of the bend and also where the diagonal welds to the hoop, kinda sorta. Actually the diagonals have the same size bends as the hoops so the bends line up, and using the same bend to make the connection to the vertical leg as a gusset to carry those loads directly into both legs of the hoop without imposing bending loads that have to be carried through the bend in the hoop. That’s because the bend is the weakest part of the hoop, but by using gussets and routing loads away from the bend it can be made to not fail in a wreck.
On the down side dividing the upper rail into segments and welding it to the top hoop next to the bend slightly reduces the d4 effect for torsional rigidity, because this change moves the top rails about 9″ closer together side-to-side. Instead of being 48″ apart they will be 39″ apart across the top of the cage. That’s a 56% reduction in stiffness in that plane, but that plane only contributes 25% of the overall torsional resistance of the frame. Basically this keeps both of the side planes that resist forces up and down of the total twist vector at the same stiffness, and has no effect on the bottom plane at all so even though that one plane is reduced 56% the total stiffness is only reduced by about 13% total in torsion. Noticeable but not critical. Second downside is the reduction in the access hole in the top of the cage by 4.5″ when it was already barely wide enough to get in and out without twisting sideways. So guess what I get to do getting in and out of the car?
In things that have nothing to do with me or the Sprint-T personally, the squirrel apparently made its escape prior to the arrival of the people we paid almost $400 to remove it. Also Mrs. the Poet has fallen and bruised her backside, enough that she makes involuntary noises about every other step, sometimes very loud noises accompanied by rude words. I’m not so bothered by the rude words as I am the volume used and the frequency. If her butt hurts she needs to lie down and let me take care of her instead of running around complaining I’m not doing anything for her.
Two days ago it was 80°F for the high, this morning it was 24°F for the morning low. The cats can’t figure out what they want to do, one stays out all night and as much time on my lap as he can during the day, the other spends all night inside and most of the day outside. Both of them are crazy by human standards, and at least one by cat standards.
I need to find where the woodcutting saw went other than “in the garage somewhere” so I can finish making the bending jig for the Mini Sprint-T. And I have determined the Mini will have Tri-Y headers on one side and Sprint style Four-into-one headers on the other because it will be an engineering model and both options need to be shown for “reasons”.
Also I want to build another chassis with an extra rear hoop for a cover over the pickup bed to provide covered storage on the road, someplace to put my luggage than inside the cockpit or in the tire trailer with the gas storage tank. I don’t want my clean clothes and driving suit for racing to reek of E85 or 87 octane. Yes I’m still planning on running two tanks on the car and offloading the cheap transit gas and switching to a separate tank with the “good” gas at the track since I learned that E85 can give a power boost to the midrange and bottom end even if the engine runs fine on 87 octane. If the engine is set up to barely tolerate 87 as long as the gas pedal isn’t pressed too firmly then E85 can give a boost through the entire RPM range. Also I kinda need to figure out how to cover the pickup bed without creating a huge flat surface to catch the air driving down the road. I’m thinking making the roof contiguous from the top of the windshield to the rear of the cover would do it, but that would make getting in through the top of the roll cage tricky to impossible.
Something else I have been contemplating is quickly removable fenders for streamlining and spray control during transit, given how bad huge exposed tires are for both of those. Again the issue is enough coverage of the exposed frame to work as intended without keeping me from getting in and out of the car at gas stops. The plan is still climb through the roof using the diagonals on the sides of the cockpit as a ladder to get to and from the top of the cage, so those diagonals need to be usable as a ladder while also out of the airstream for the highway. I’m thinking lots of hook-and-loop fasteners for the roof and the parts of the body that need to be movable for getting in and out. But that’s for after I get the car running enough to see if I even need to use a body and fenders beyond the fiberglass bucket.
I found a You Tube video that makes me seriously reconsider using the FIRST TPI efi manifold. One of the things I had been led to believe was this manifold had an extended RPM range and kept on making power at high RPM. Well, I guess compared to the original TPI from the ’80s and ’90s that would be true, but this test showed a power peak well below the calculation crossover at 5252 RPM (HP= Torque in Ft-lbs*RPM/5252, the point where Torque = HP is 5252 RPM) and the BluePrint crate 383 makes more power and continues to breathe through a Chinese dual plane manifold and 750 CFM carburetor. Now granted the FIRST manifold made 44 more Ft-Lbs of torque, the type of head used for the FIRST manifold test was not listed, and the cam was not mentioned, but the BluePrint engine made the same torque (440 Ft-Lbs) with both a flat-tappet and a roller cam and that Chinese dual plane manifold and Holley 750 CFM carburetor. Something else not mentioned was the headers used in the FIRST test, where the BluePrint tests with 13/4” long-tube headers. Now for an engine packing 383 cubes that is a low-end torque header. Note edited 2019/26/1 to correct header tube diameter from 15/8” to the current size after getting better information.
Well, I plan on making a trip to Lowe’s today to get a couple of 5/16” bolts for the roll cage bender, a 5/8” bolt for the exhaust turnout bender, and a can of butane to make the bender work. So I should probably get to bed now.
Mrs. the Poet said I should just put the checks for the taxes in the mail this week and not worry about it. We kinda played some for the Shadowrun game on Sunday, but mostly with the weather doing the yo-yo thing I have been doing my “bear in winter” impression. Seriously this weather is seriously sapping my desire to even get out of bed at whatever time I stop sleeping. I have been huddled under the covers being borderline depressed, as in episode depressed, and not managing to work up a care to even check what has been wrought against the country by People Enabled By Russians. I mean I saw the kid from the Catholic school bothering the Native American Elder after marching against women controlling their own bodies. Because that is a thing that Catholic School Boys do, protest women controlling their own bodies and bother Native elders.
Other than that I have to pretty much force myself to eat anything after breakfast because I’m just not hungry after I get morning coffee, even if “morning” is 1300-1600 or so, like I wrote earlier getting out from under the warm blankets is very hard because warm, and because there is a cold draft blowing under the desk where I do my computer stuff now. Out away from the desk is fine, but under the desk is freezing (well colder than the rest of the room) and I really don’t want to get out from under the blankets to go work on the computer, which I have to do because otherwise I can’t post to this blog. Seriously, I can’t type worth a damn on my phone so if there is going to be a blog post I have to stick my legs under this drafty desk. I keep a blanket to cover my legs when I’m using the computer because otherwise I’m overdressed for the temperature if I’m warm enough under the desk. And with the current weather it’s even worse than normal because the wind forces the cold air through the leaks in the window.
Anyway, to kill time I have been looking some more at the FIRST TPI intake and fuel injection manifold, and it seems to be an intermediate step for the SBC between the LS engines and a carburetted engine, with low RPM torque like a dual plane intake and small 4BBL and high RPM like a single plane intake with a huge Dominator-style 4BBL. Or in other words very much like an LS engine with the plastic manifold but still only coughing up SBC change instead of LS engine co$t$. I think I mentioned this build is more about powerband than peak HP, because there is at least one turn that will see near idle speed in first gear on the majority of Goodguys courses and almost no place to use a high peak power. That is exactly what this manifold is made for.
And making another right-angle turn at full speed in the narrative, the stainless steel raw stock for the Mini Sprint-T suspension came in today in another ridiculously overpackaged container. The shipping container was worth more than the raw stock inside it. Anyway what came today was 1mm OD stainless tubing that will fit the simulated heim joints perfectly from Dirt Modeler and is something else that requires the use of the butane torch I bought at Harbor Freight to join together with intended parts. I still have the pure solder (no flux) left over from making the hot water heater for the camp shower a few years back, there was a minimum required quantity that was about 3 times as much as I needed to make the heater, so I have enough for several thousand simulated heim joints that require only a tiny drop of molten solder to affix them permanently.
I know, pics or it didn’t happen, but I forgot to take pictures. I still haven’t gotten any butane for the bender, but I’m working on making diagonals to fit smoothly to look like both crossing diagonals are one continuous piece. It’s tricky, and kind of a cut and try thing to get both halves to match up. Many mistakes were made and discarded.
I have been so busy with this I forgot to take pictures, forgot to watch the Formula E race I recorded, and would have forgotten to eat if Mrs. the Poet hadn’t made dinner and yelled at me to come eat after I checked to see if the meat was done enough. I have been seriously spaced about this.
And now I need to check e-mails and get caught up on the day.
And I used one to make copes in the rod I’m using to represent the tubes of the frame. I need more practice, but I got one that fit well and looks almost like the 1:1 Sprint-T will look when completed. Now the 1:1 car will use tubes of different wall thickness for areas of the frame that are loaded more or less with the wall thickness adjusted accordingly, but since they are all the same OD but different ID I use just the one size rod for everything on the frame. That is the same stuff I’m using for practice because I have tons of it, and I need to get those joints as close to perfect as possible.
Not much to say except I used the back side of a triangular file to form the cope and the melting effect of solvent plastic cement finishes the actual cope when I force the joint together. Once I got it down it worked surprisingly well. The second try worked perfectly and also auto-aligns the joint to the center of the vertical member, or whatever orientation the coped rod is forced against.
In other news Mrs. the Poet’s new vacuum cleaner sucks, and that’s a good thing because that’s why we got rid of the old one that stopped sucking, sucking up the dirt. She made a test run and then did the entire house while I was doing my first search for the hand files. She is much happier to have a vacuum that sucks again.😁