Tag Archives: Mini Sprint-T

Still nothing interesting to report

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.


What’s with this weather?

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 something that made me rethink what I had planned for the Sprint-T

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.

Nothing much to talk about

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.

Progress, but without pictures

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.

I found the files

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.

This is the leg that had the cope that was better then the cope on the other side. The joint in question is the one on front and to the right of the picture.

Now the joint is in front and to the far left. You can see the fit of this side is not as tight as the other.

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.😁

Finally getting some work done on something

It wasn’t much, but it took a while to do and then more time to photograph. I did some experiments with the nippers and building junctions where tubes intersect on the real frame to see how close I could come to IRL appearances with the tools and materials I have.

The one to look at here is the one with the vertical sticking up on the far right

The one we are looking at here is the one I did first with the non-flush side of the nippers, where I failed utterly in getting a smooth junction. That is the one that is on the right side of the picture, the gaps are huge.

Again on the right, with the junction made from the flush side cut

Again the junction in question is on the right side of the picture, this time the smooth side of the cut from the flush cutting side of the nippers. This is a much smoother junction than the other cut but still has undesirably large gaps. This is a very simple to construct junction compared to the first junction. Just do the flush side towards the work piece when making the cut and stick it in there facing the junction.

This was two 45° angle cuts facing each other and the vertical member on top and on the right side of the image again

This time I cut the flush side towards the work piece at a 45° angle and put those together like a mitered joint and glued the vertical on top. This was the smoothest junction yet, but there are still some large gaps showing. I have one more junction to do before moving to other cutting methods, the 45° like the mitered joint but against the vertical instead of under it. I’m cutting and gluing that joint between sentences of composing this post. And I’ll post the picture in this post tonight if I can.

Looks pretty good from the outside

Focus problems but you can still see the large gap on the back side.

This is almost as clean on the mitered joint on the outside but there is still a huge gap on the inside because the geometry just doesn’t work to join round stock with straight cuts. The mitered joint with the vertical member on top was the best so far as gaps and other fitment issues are concerned, but still not even close to what can be seen in the real 1:1 world. Basically I need to use rounded cutting tools like files or sanding sticks to make the joint fit like it does in the 1:1 version.

So the next step is to use the miniature files I bought a few years ago for this project to cut some “copes” in the stock to get better looking joints. Or just call it an engineering model instead of a display model, and don’t worry about the appearance. The lengths of the members would be outside to outside, or inside to inside depending on the orientation of the joint and would be made with the flush cut side of the nippers against the work.

What do you think?

Stock and tools are on the premises, building to commence soon?

The tools and the last of the stock arrived yesterday, and for the most part I’m happy. The stock that replicates the bars in the 4 link and the swingarms is like wet pasta flexible, but I’m hoping for something with a bit more rigidity when it gets cut to length. Part of it is the long column problem, and part is styrene is just not as rigid as other plastics in part because it is heat-formable. So it’s a worse case scenario of unfavorable physics and materials coming together to make something nobody wants to deal with. Except I have to because reasons.

Technically I don’t have to deal with it, I could buy some 1mm O.D. brass or stainless steel tubing and have a much more rigid stock, but that is not compatible with the rest of the materials I’m using, it doesn’t glue the same and putting the fittings on it would be a bit of a logistics problem not to mention the color-matching issues between painted brass or stainless steel, and styrene. Paint just doesn’t come out the same on the metals as it does on plastic.

Also I played around a bit with the tools and while I can do more than I could with the big knife and the single-edge razor blades I was working with I’m still not happy with the control I have making cuts in thick materials like the 0.040 sheet I got this week. What I really need is something like the big knife, but as sharp as the razor blades, so I have the control I have with the big knife. I think I saw something in the Harbor Freight catalog that will do the trick, but I’ll know more when I get to the store when I go to get the butane torch.

And I need to get to bed now, so this is the end for tonight.

Still thinking, this is not a drillllllllll

As the saying goes, fair warning. I am thinking about the Mini Sprint-T again. I realize this does not carry the same imminent danger to life and limb as its larger counterpart, unless you are the guy with the scalpel-sharp knife cutting plastic to bring the thoughts to fruition. Then fingers might be at renewed risk, but only mine. I did almost lose the end off one about 50 years ago while building a plastic model. But that is a tale for and from a different time.

One of the things I need to think about is stuff connecting the front and rear axle to the frame. In most kits this is usually molded as a single piece that gets glued to the frame and axle(s), but I have to build mine from raw stock and sometimes from hardware from a 3rd party like Ted’s Modeling Marketplace or Dirt Modeler . But mostly it is a matter of putting the axle in place and then figuring out where is a good place on the frame to tie in the locating links. And possibly adding more uprights and diagonals to the frame to prevent flexing IRL because we are trying to “model” something to make IRL. This is just “old school” 3D modeling, with actual physical pieces getting cut and built in actual physical space. And also because I like cutting material and gluing stuff together. So, indirectly thinking about the Mini Sprint-T is actually thinking about the full-size Sprint-T, just thinking in more achievable circumstances. I have the skills to make a presentable engineering model, but it might not be a display quality model. And what I really want is a display quality engineering model. But I will accept an ugly engineering model in lieu of a display quality engineering model if it means I have a representation of the Sprint-T in physical form.

Along those lines I bought new model-building tools as I can’t use the tools I did have because age has hampered my abilities and the new ones will fit my hands better (I hope). At any rate what I have now are jury-rigged from tools made for other things, or just flat out never intended to use for making models but can be forced into the role if you have the physical dexterity, which I don’t anymore. As an example there’s this one cut I need to make that requires rolling your wrist just right while holding the razor blade to get the desired curve, and my wrist no longer moves that way while imparting enough force to make the cut. When the tools get here I’m hoping I can make that cut. That’s the thing I’m dealing with because of my accumulated damages over the last 60 years. It’s not the tools, it’s the fact that I can’t make the tools do the thing any more. And this is why I’m sad/angry, sadgry? What is the word for that emotion. And Amazon was of no help in finding equivalent bits that I can spend my gift cards on…

And I just got a box the size of a shoebox containing a few plastic rods and sheets and lots of paper padding. Which was the first of the many packages I’m getting from the same order. I guess this is to prevent damage to the rods from bending as they can develop a permanent set if held in a flexed position. And now I need to find my butane torch and a can of fuel to use it so I can bend the rods without breaking them. This seems like a good place to stop writing and maybe start doing again.

Opus did not survive Christmas

And who knew ghosts could blog? 🤣 Seriously I think I ate myself to death yesterday, and my eternal punishment is to continue to feel stuffed for all eternity. My daughter got a spiral cut ham as a gift and I might have gone definitely went overboard loading my plate with the ham, on top of the hors d’oeuvres served in the hours before dinner. I never even touched my pound of Reese’s peanut butter cup which was actually two half-pound cups that my son gave me for my wrapped present. All told I made out like a bandit again this Christmas what with the engine hoistshop crane, $100 in gift cards for a famous online shopping destination, cash from the in-laws, and a pound of Reese’s peanut butter cups.

Mrs. the Poet did well with the upright vacuum cleaner, a cooking device that can either be a panini press, or one or two griddles, gift cards, two tea pitchers and more gift cards.

Getting back to the gift cards to the online shopping destination I bought more raw stock for the Mini Sprint-T, because when you are scratch building something you don’t have detailed plans for you will make mistakes about dimensions, especially for things like bends and clearing other components. So I bought enough rod stock for at least 3 frames, to allow for many mistakes. And some sheet for making brackets and linkages, because those things need to be on the car.

In the meantime boxes were opened and contents were unpacked and assembled.

Note the weight limit markings

And I may not be able to unpack some boxes.
This is his box and he loves his box.

And the fur babies were not ignored either.
A filtered recirculating water bowl, the end of the nasty water bowl.

I have recovered enough for coffee and breakfast partially because I don’t want to insult Mrs. the Poet’s cooking, but lunch was beyond my abilities and I’m not banking too much on eating dinner, either