Tag Archives: problem solving

Can’t stop, won’t stop, thinking about building the Sprint-T

Sometimes it’s a bummer when you get caught in a rut, trying to solve a problem that ultimately can’t be solved. That’s a little like what I’m dealing with on the Sprint-T. Absent a change in the build budget from zero the problem is unsolvable. But that doesn’t keep me from trying to solve it. I mean I have been working on this problem since 1968, why stop now? I’m as close now as I was when I was 10.

With the loss of access to the Subaru transmission the Subaru build got more expensive but still not as expensive as a V8 build, so right now the engine of choice remains the EJ20X at $1K. If I can find a decent Subaru transmission at a good price then I’m ahead of the game, if not I have to figure out how to get a bellhousing and starter to fit so that a good T5 transmission can be installed. Weight wide that would be the way to go, but building the bellhousing might be too much work without access to a 3D printer. I thought I might be able to hydroform a bellhousing, but while I could build the mold and baseplate I don’t have access to the kind of pressure needed to force steel or aluminum thick enough to work as a bellhousing into the mold. If I’m reading the literature right I would need pressures on the order of 3k-4k PSI (207-275 bar) for that deep a stretch, while what I have access to tops out at 1700 PSI (117 bar) That would work for about half the thickness I need in either metal, not good enough.

But this being DFW with lots of aerospace manufacturing going on I might be able to either get equipment to stretch 3/16” steel that far, and a quick Google search shows 2 local companies that can 3D print in several aluminum alloys or in Chromemoly steel, but at “not cheap” costs that are still much less than DIY hydroforming if I try to do it in one pass with materials that are thick enough to pass inspection at the race track (0.25″ at the thinnest point for aluminum, or 0.1875″ in steel). Now the problem here is will a 3D printed bellhousing even pass tech at any thickness. Tech inspectors can get pretty leery of unconventional manufacturing techniques especially on parts that are both structural and safety-related like a bellhousing. The bellhousing has to partially support the weights of the engine and the transmission, making it a structural component, but also has to contain the shrapnel of a potential clutch or flywheel explosion. That would mean making more than one bellhousing and then deliberately exploding a clutch or flywheel inside it and proving nothing made it outside the bellhousing.

Now something that used to be done back in the early ’70s was to make the bellhousing out of aluminum but then put a thin steel liner to contain the exploded bits using the aluminum to support it. That is the liner alone would not contain the explosion because it wouldn’t be strong enough while the aluminum was strong enough but not hard enough to contain the explody bits, so the liner prevents the bits from contacting the aluminum while the aluminum holds the liner together, and the pumps I have access to could hydroform the aluminum and the steel liner using the aluminum as the mold for the steel liner without removing it from the mold used to hydroform the aluminum. In other words it would be a two part process of putting the aluminum sheet in the mold, forming it to the mold, splitting the mold and putting the steel sheet in place inside the aluminum, then forming it to the combination of the mold and the aluminum. The tricky part for the Subaru engine is the starter bolts to a flat spot on the back of the bellhousing which has to be at a certain depth from the block and flywheel for the starter to engage, while the transmission also bolts to that same area and also has a distance from the flywheel it needs to be to function.. The added problem is that T5 transmissions were used in many applications with different mounting depths, so I would need to find a Subaru transmission case and cut off the bellhousing to get the starter depth right, then rig up a plate to mount the transmission at the right depth, fill in the gaps and smooth out the differences and pull the mold off that. The mold would not have to be super strong, just strong enough to hold together for two forming cycles, and the second cycle would put most of the forces on the aluminum outer layer.

And it’s getting late and I got extreeeemely wordy, so time to put the post and the writer to bed.

Advertisements

Another wild idea about the Sprint-T

I was looking at the shifter location on the T5 transmission and I was thinking I would have to use the furthest aft shifter mount and extend the handle back and to the left by about a foot to be able to reach top gear at the far top right of the shift pattern. Then I started thinking that mounting the engine further back would help, but that I would need to cut the body for clearance. Then I let my imagination go wild and tried to imagine the entire engine mounted behind the original firewall and sticking out the side of the cowl on the right, moving everything 28″ to the rear from the ahead-of-the-firewall position. This position would allow installing the shifter in the middle mounting point as far as fore-and-aft positioning, and only slightly longer than the Camaro/Mustang short shifter to reach 5th gear because of the radical engine offset.

Now the body modification needed to get that much rear mounting are pretty severe what with the right side cylinder head sticking out about 2″ from the passenger side door. I know I had posted a much further extension in a previous post but my calculations used an erroneous premise that doubled the offset for right side measurements and subtracted double the offset for left side. That was a mistake. The correct way is to add on the right side and subtract on the left side only once. But be that as it may, the body will basically be cut away from the left side of the firewall to the base of the windshield and level across the base to the right side and about 20″ behind the original firewall to clear the cylinder and exhaust pipe. The parts of the intake system that stick up higher than 20″ are basically the intercooler and ducting that guides the outside air into it, so following the upper flange of the body at 22″ will clear all the intake runners. As far as the internal sheetmetal is concerned there would be a shelf above the bellhousing that would give footroom for the driver while leaving room for the intake plumbing. The offset leaves over 8″ of foot room on the left of the engine behind the cowl pinch and almost 5″ ahead of the pinch. That leaves room to get to the master cylinders for fluid checks and fills, which also applies to the car with all of the engine ahead of the firewall.

On that, seriously the engine offset with the Subaru leaves a ton of room between the engine and the body for access to the master cylinders no matter which place I put the engine. With the huge space behind the engine because of the intake plumbing combined with the offset there is an acre of empty real estate between the firewall and the left side of the engine block and head for master cylinders. This is great, I love it when packaging problems solve themselves.

All said and done, I think I would go with the option of mounting the entire engine in front of the as-molded firewall on the body and work with the long shifter handle rather than cut up the body and fabricate a ton of interior sheetmetal, because the engine is so light it doesn’t put much weight on the nose of the car and also because the large offset leaves room for the master cylinders. Now all I need to do is win the lottery so I have the $$ to buy an engine and transmission to install.

Black Friday deals on Witch on a Bicycle merchandise

Exclusive deals on plenty of nothing. Nine years at this URL and I still haven’t managed to even make a T-shirt. So I’ll tell you what. Make something with a WoaB logo and send me a picture of it to post here.

Getting back to the original purpose for this blog for a paragraph or two I have been checking out the parking lots of the local stores and strip malls, and as I suspected they are mostly empty, even though the stores are packed. The Beautiful Suburbs of Hell have way too much parking for retail, or to put it another way we could have tons more retail space without needing any more parking. We are zoned for tons more parking than we need. And in the current economy we have way more retail space than what we need, so making getting to the retail we have that much worse and more car-dependent. The stand-alone retail is over-supplied with parking so you can imagine what the half-empty strip malls look like.

The swelling is down on the broken toe and the bruising is starting to fade, and unless something presses against it the pain is mostly gone too, unless it gets cold. So I have been making sure I don’t get cold feet.

Fuzzy slippers FTW!  No painfully cold toes

I have been thinking about a custom cooking tool I need, a 2/3 dry cup measuring cup for making Beans and Rice. The problem is the 1/3 cup measuring cup likes to go walkabout when I’m trying to make beans, and I need 2 dry cups total of 3 kinds of beans. Going equal volumes of each kind keeps the black beans and the small red beans lasting about the same, while the lentils are on their own schedule especially since I’m also making lentil stew. But back to the problem at hand perusing Google gives me a dry cup is 14.4375 in3 so multiply by 2 and divide by 3 to get 9.625 in3 and ¼πd2*h for a cylindrical representation of the volume, solve for d=h. So 9.625 = ¼πd3, multiply both sides by 4 gives us 38.5 = πd3 divide by π gives us 6.1275 = d3 and ∛ both sides gets us 2.31″ base and height internally. Sioux you have permission to use this as a word problem for your adult math class, complete with showing the work. “Work” in this case consisted of pushing buttons on the calculator app on my phone, and moving things from one side of the equals sign to the other. The hardest part of the problem was getting the formula for volume of a cylinder correct.

I really need to have the traditional spaghetti after-Thanksgiving dinner now, so this is the end.

Still thinking about the rear suspension on the Mid-Bucket

Yes I was being dangerous again, thinking and all. Basically I’m thinking about details now, how to arrange the heim joints on the plate so they don’t interfere with other bits and are still adjustable for what needs to be adjusted.

My first thoughts were they needed to be set up in an equilateral triangle with one located center bottom. Then I ran some adjustments in my mental model in that configuration and there too many interactions in that configuration. What it came down to was every adjustment would change another parameter that did not need changing (or maybe it did but not at the same time and maybe not in that direction). So, change to a right triangle with the sides adjacent to the right angle located vertical and horizontal. Changing the camber will change the toe slightly but changing the toe doesn’t affect the camber. The longer the distance between the vertical pair of heims and the toe heim the less a camber change would change the toe. Thinking about it more putting the toe heim on the horizontal centerline of the rear axle with the camber heims equally spaced in relation to that line would give the least toe change with camber adjustments, especially if the camber heims were adjusted in equal and opposite directions. So, maybe not equilateral, but isosceles with the point on the horizontal center of the axle and the short side vertical.

Now that that part is decided how to connect it to the de Dion truss? The reason the equilateral triangle first suggested itself was using the horizontal part of the truss to support two of the joints and a side support off the vertical for the third. And as I think about it I can get zero interaction with the right triangle by leaving one joint fixed, and adjusting the other two for toe or camber, depending on which axis they are on. Which tells me that the horizontal pair mount to the horizontal truss, and the vertical pair the vertical, and the heim that is on both axis is the fixed one.

See how problems can be solved if you just put them in words while thinking in 3 dimensions? I know, not everyone can do that, I have what amounts to a 3D CAD program in my head. What frustrates me is I can’t just copy and paste from my head to my computer like I do when I write stuff on my phone. I mean I can see it perfectly, but I can’t reach in and pull what I see in my head out where everyone else can see it, and I lack the skills to enter what I see into a real CAD program, and the patience to learn how. I know, that last one is on me, my problem. But I can even see how the flanges for the various heims interact to add support to the mount for the hub bearing with minimal added weight. Just connect them around the bolt pattern for the hub bearing and they have enough vertical depth to keep the mount from flexing. I just need to leave enough room for the bolt heads and a socket to drive them into the holes on the flange on the hub bearing. All the major forces go directly into that hub mount, bypassing the de Dion truss which has been reduced to keeping the wheels pointed in the right directions on two axis and the same distance apart all the time.

Speaking of the same distance apart, it looks like this is gonna be a very wide bucket, about 6′ 3″. The front axle is going to be 56.5″ wide compared to the usual 48″. That’s because the hub-to-hub width on the donor vehicle is right at 65″± compared to 56″± for the usual hot rod axles. This solves a lot of problems with the suspension, while introducing others. But mostly it solves problems or makes them tiny. And tiny problems are either easily solved or ignored.

And on that note it’s time to say buh-bye until next time. Opus the Unkillable