Tag Archives: technical stuff about building cars

A little late, but here it is

Sorry to take so long but I finally got a decent picture saved someplace I can use to post it to the blog.
See that teardrop opening?
There’s a wrinkle that doesn’t show well in the picture because of the angle, but is glaringly obvious IRL. So this part is Just Practice while I perfect my technique. Also I have been looking at pictures in catalogs and online of turnouts that used this method and they have egg-shaped openings, not teardrops. That means I have to work on my technique even more to get the opening right every time.

Since I spent so much time trying to get a good picture today after trying to get a good turnout yesterday I’m up past my bedtime and I really need to be awake when the stormdoor installation team shows up in the morning, I’m putting this to bed and then myself. Hasta la Friday. Which I know is ungrammatical Spanglish, but anyway, Mañana

I spent hours practicing

Last night I did the bender again and started trying to do the “sliced tangent to the inner radius” exhaust tip. Now while I was building my tool and practicing bending the raw stock I was listening to YT Music on my phone, which ran the battery down so I couldn’t take pictures after I was done. But I promise pictures for tomorrow after the phone gets charged.

The tricky part is the heating of the raw stock to make it soft enough to bend without causing the tube to collapse. I ruined many bends because I overheated the tube and collapsed it. I also discovered that heating the stainless steel bolt I’m using as a bending post doesn’t work for tubing at all, unlike solid rod. If the post is warm enough to soften the plastic, the wall of the tube next to the post collapses before the outer radius starts to bend. In retrospect I should have expected that, but I was thinking in metalworker mode not plastic model builder mode. The way to go for the plastic tube is to spin the tube on its long axis with the intended bend area in the heat source (butane torch flame) until it gets soft but not floppy, then put it in the bender and make the bend. This has to be done extremely fast because the temperature spread between floppy and rigid is very small and soft enough to bend and too cold to bend smoothly is even smaller.

Anyway I discovered another reason for using the sliced bend exhaust tip, it leaves a delightful teardrop shaped opening besides directing exhaust away from the car, similar, shorter, but not exactly like when the reverse technique is used for side-exit exhaust. But I wasn’t expecting this shape from the inside bend, I was expecting a more oval shape opening. Maybe when I get a better quality bend the shape of the opening will be more oval than this attempt. But better quality requires more practice and there is a limit on how much raw stock I can waste on practice. I really need to reserve one stick of tailpipe material for the final build so I have enough length. But I will get a picture of the pretty practice tailpipe for tomorrow’s post

Here’s the link to that lean-burn Corvette

Lean burn Corvette testing video.

You can see what it does IRL on real roads. This video was done last week and uploaded Saturday 12/7 so cold weather which is very bad for gas mileage because of increased aero drag and rolling resistance. Now my car is going to have horrible aero especially compared to a 1999 Corvette. If I’m lucky I’ll get about 30 MPG highway because of that, but that is still about as good as I got with my 1987 Hyundai with the non-overdrive 4-speed transmission. My best Dallas-Nashville mileage was about 31-32 back in the early ’90s partially because I was driving at night and missed everybody’s rush hours for all the cities I hit. Again, 1980’s technology and no overdrive with a carburetor but I did have an external oil cooler running as low viscosity oil as was available at the time, I think 10W-30 non-synthetic because synthetics were like 3 to 4 times as much as petroleum-based oils and as always we were Not Rich even then.

So, now that we know what’s possible, let’s see what we can do with what we have.

I have been practicing on raw stock

This is a technique I haven’t used since the last time I was building models for/with my son when he was a child, who will be 42 next birthday. So to say I was out of practice would be a gross understatement. So I decided some practice on some of the raw stock I’m using for the exhaust would be in order. I decided to start on the hardest exhaust end first because if I could a decent job on that the others would be a piece of cake.

Well the pictures didn’t turn out so good because the new phone doesn’t do macro very good, the old phone used to do macro real good, but this one stinks. Also it’s all white plastic so while I can see it, the camera just doesn’t pick it up well at all. But given the limitations of the technology here’s a before pic. Actually the other end of the tube that hasn’t been worked yet, but you get the idea.
that's a thick-wall tube if I'm trying to emulate exhaust tubing
And after, notice the thin edge looks like the whole tube is really thin.can you see how much thinner the tubewall looks now?
On a different background and lighting to make the difference more noticeable.That's really thin now
And before really needs a contrasting color on the edge but the tube wall is still discernible.needs better lighting and a better photographer

So this was the straight-cut tip, the tip I’m going to be emulating in plastic is the turn-out tip, where the tube is bent around a radius and then cut tangent to the inside of the bend right where the bend begins. This is a classic hot rod design motif that forces the exhaust in a different direction without enlarging the width of the exhaust in tight confines. The normal use is to turn the exhaust down in front of the rear axle when a combination of no ground clearance and not enough floorpan clearance when the axle is at full bump prevents routing the pipe over or under the rear axle. Or like I’m doing putting a side exit exhaust where there isn’t a lot of room to the side and you don’t want to hang a sharp edge out on the side of the car.

And if a picture is worth a thousand words then I have posted enough for today. Next step is to fire up the bender and make that turn-out tip.

Waiting on the door installation people

OK I have selected storm doors to replace the ones installed when the house was originally built in 1985, now I’m waiting for the installers to arrive and measure the door to get the right size storm frame. As this is one of the few standard size things on the house, I don’t expect too much hassle getting it installed.

One thing I have to say, it’s easy to get through the door once it’s open, the frame is 3′ x 6′. Looking through the Lowe’s listings this is the largest standard door available. There are taller doors, but they are only available by special order. There are lots of doors that come narrower, but I didn’t see anything wider. So 3 by 6 is as big as you can get without spending buttloads of money. But the installation people have to verify that in person so they get the right thing.

I have been practicing with the bender for the plastic stock of the frame and exhaust for the Mini Sprint-T, as the exhaust in particular requires lots of work to get right and there is a bend for the muffler/tailpipe in particular that really needs to be done right. To simulate the thin wall exhaust tubing of the 1:1 scale vehicle the end of the exhaust tip needs to be filed to a knife edge from the inside and the inside painted matte black or matte silver. That’s something I’m going to have to research, does E85 leave a carbon deposit when tuned for best power? I already know that the highway mileage tune for 87 octane won’t, as it is about as lean as the engine will run right with, emulating a tune that let a ZO6 Corvette get just over 38 MPG in a real-world highway test. For airplane drivers this is the car equivalent of tuning 150° lean-of-peak on the EGT. And for people not aware this is over 40 MPG steady-state from an engine that displaces 427 in3 (7 liters) and put out ~500 HP at the rear wheels back in the day. But anyway the highway tune will not remove carbon deposits at the end of the exhaust, so if the tune for E85 carbons up the exhaust then I need to emulate that in the model. And I just checked the E85 forum and there are 3 posts that say they don’t get any carbon from running E85, and one that said he still has carbon in his tailpipe from the 87 octane the dealer put in when he first bought it, but nothing more than that in 5000+miles since he bought the car, so I’m going with the matte silver for the inside of the tube.

The fuel map is going to look really strange when I get this tune done, because most of the map will be slightly rich except for the RPM block and throttle setting for steady-state freeway cruise at 60 MPH which will have a “hole” that leans the engine as far as it will go and still run right. On 87 octane this will be leaner than the max NOx point so low CO, CO2 and middling NOx.

And I have been sitting here writing for about 3 hours waiting to hear from these people, and it’s about 1630 CST so I’m going to assume they aren’t going to answer today. And this is a good word count to stop at, because I don’t want to bore anyone today. So, I have to go out again tomorrow to deposit a check, which means going on the bus again. But not as bad as Black Friday in the rain.

Still stuck on imagi-building that A-MOD car

I have a mind that must chew on problems to solve, not social problems, physically solvable problems like bicycles or race cars. And the one that’s occupying my mind is the A-MOD car. Like all good engineering problems it has a simple premise: Make the quickest car possible on an autocross course within these constraints; 72″ minimum wheelbase, 42″ minimum tread, 900 pounds minimum weight with driver and full fluids, and 10″ minimum wheel diameter. There are safety rules common to every car in the series, and because having a really stiff suspension is a huge advantage you have to have sprung suspension, not that actual springs are required, there are cars that are riding around on actual hockey pucks between the suspension and the frame, but something that isn’t a solid piece of metal against another non-moving piece of metal.

Anywho, working through those minor strictures I have evolved literally thousands of cars with uncountable variations of “suspension” over the last few weeks. But what I keep coming back to is a single-pivot rear suspension with a solid axle and a single disk brake halting the axle. It’s simple, strong, and fairly lightweight. And relatively easy to adapt to a chain drive. Another thing is it works extremely well with a common trope in cars this size, mounting the engine on the rear suspension. Basically this is done to simplify the drivetrain and shorten the chain on chain drives. It’s really bad for unsprung weight so I’m only doing the designs as due diligence to make sure I’m covering all the bases, and because researching this adds to the knowledge base for other designers, and what I learned to pass on to other designers is the unsprung weight is pretty close to zero if the Center of Mass of the engine is mounted right at the pivot point of the suspension which is physically impossible unless the rear swing arm is mounted in such a way as to create a virtual pivot point in or near the CG of the engine, which kinda negates the purpose of mounting the engine on the swingarm in the first place, simplifying the rear suspension and drivetrain.

Another suspension I have been looking at is the classic 4 link and panhard rod with the forward pivot of the 4 link even with the front drive sprocket of the chain drive and the rear pivot right on the centerline of the rear axle so the chain and the suspension swing through very close to the same arc and making having the same chain tension through the suspension travel simple.

Another thing I have been looking at is mounting the rear part of the chain drive solidly to the rest of the frame and using CV axles to run the power to the wheels as shown in a book I bought, How to Build Motorcycle-Engined Race Cars by Tony Pashley. and in this video by Vasily Builds where he modifies his swingarm buggy into IRS. Way more complex to build but less unsprung weight than almost anything else, but the 4 link is lighter overall, allowing weight to be added where it will do the most good, making the final decision a tossup or a painstaking virtual build of both to see which would be better. I have the time but not the software to do the virtual build, and the 4 link is both cheaper and easier. And since I have more time than money, cheaper is the way to go on this one.

But I would still rather be building the Sprint-T. This is just something to keep my mind occupied so I don’t build a doomsday device and just destroy everything. Speaking of which, I can’t find my yellowcake, I have the lemon and the cinnamon, but not the yellowcake. (Mad scientist in-joke, you don’t have to laugh if you don’t get it, but if you don’t get it and want to get it google “Nigerian yellowcake” for the source of the joke.)

Nothing much to write about since putting my head through the door

Basically my mind won’t stop building A-MOD cars and it’s been keeping me awake at night. How much of that is related to last week’s adventure in DIY home-wrecking and how much is just frustration at not being able to build anything (or even able to type anything as I will explain later)?

I have been thinking about taking the driveline out of one of those AWD quadbikes and stretching it out to the required wheelbase and track for an A-MOD car. Basically that would require making one new drive shaft and 2 new axles to put everything on one side of the car so the driver could sit beside the engine instead of over it, and get everything as close to the center as possible. Quadbikes are literally available all over the place out here because nobody can find parts to fix them so when they break they get thrown away, and because nobody does routine maintenance on them they break with appalling frequency. So they are literally available for towing fees or “How much you wanna pay me to haul that off?” If you get one that has good parts support they are somewhat fixable but those are not the kind that get thrown away, otherwise you try to find a bunch so you fix one and use the rest for parts. So the build process is basically find a quad, cut off the front end and build new pickup points for the front suspension that moves the wheelbase out to 72″ and the track to 42″ and widen the rear to match the front. Then move the controls to the side and down so that the CG is close to centered on the new layout with the driver and because the driver is on the same plane as the rest of the vehicle the vertical CG is lowered a bunch. Swap out race slicks for the all-terrain tires of the quad and semi-instant A-MOD car!

The other idea that has been prancing through my mind is a variation of the sidewinder build trailing A-arm rear suspension that puts the pivot point of the suspension next to the output shaft of the transmission so that chain tension wouldn’t change much as the rear suspension traveled through its range. Basically the design change was a single structural member from the pivot point of the A-arm to the rear axle bearing support next to the chainline, to prevent flex from the chain pulling the axle forward, and one diagonal that runs from the pivot behind the engine to the far support bearing while another runs from the chainline support to the support on the driver’s side of the axle, with another running in front of the rear axle sprocket to the engine side bearing support on the axle to prevent flex when cornering. The best way I can describe this is it will look like a flattened A with one leg missing and a line up the middle and another leg to the center on the side away from the driver from overhead. Because I plan on running the same size tire on both ends it will have only one spring and shock absorber on that center bearing support, as close to the axle as possible to get what is technically a “zero roll stiffness” suspension so that all the roll stiffness is in the front and the car will corner on the outside front and both rear tires to prevent massive oversteer under power. Having the full length and width support only on the side away from the driver allows the driver to sit further back in the car while still allowing for suspension travel.

Now, about that typing issue mentioned earlier. Basically what it comes down to is stuff from the cuts on my hands got all stiff and I couldn’t hit the keys with my fingers. Long story is some of the cuts opened up and started bleeding so I had to put bigger bandaids on them with more antiseptic, leaving me with two fingers that couldn’t bend, the index and third fingers, and typing became a single-handed operation of hunt and peck. And slowly because sympathetic pain every time I moved the fingers of the other hand because I use both hands to type and I kept trying to use the injured hand. So no new posts until the hand healed enough that I could type. But now I’m better (or as the saying goes “good enough”) I’m doing another post.

I had a trip to the Lab Rat Keeper

I keep wanting to add “and the Feed” to headlines like that, except I don’t do that any more. Any bike wrecks I see online are incidental these days, instead of being the result of a deliberate search.

Anywho I gained 5 pounds since Mrs. the Poet’s return, and we may have figured out why I’ve had high blood pressure since I was a kid. Way back in 2002 I had to get my BP under control for an operation, so calcium channel blockers were prescribed and they did what can only be described as a “bang up job”. Also one of the identifying characteristics for my other condition is a high blood calcium reading that leads to the extreme bone density, which in my case is something between “concrete bridge support” and “actual rock”. I think I might have mentioned getting tested for this by a guy studying the condition, and that one of the things tested for was blood calcium level and that mine was in the range that defined the condition but he didn’t tell me the exact reading. Which is typical of doctors they run tests and say it indicates this or that but they never give me the actual numbers unless I press them on the subject.

So, next trip I’m going to bring up the subject with the Lab Rat Keeper and see if we might get some other kind of treatment for my hypertension, to go with the current diuretic. The guy studying the super thing said that diuretics are part of the standard treatment for the condition to prevent kidney stones. I need to bring the blood calcium levels and calcium channel blockers up because this could be a key to why I still have high blood pressure.

As for the other “stuff” I found out that the 4.8l crank and rods in 6.0l and larger LS blocks is popular for building higher RPM middle-displacement engines to run on 87 octane. The theory is the longer dwell at TDC gets a more complete burn and more expansion of the burned gasses with less spark advance to heat up the combustion chamber and cause detonation or pre-ignition, and has been proven to generate more power per pound of fuel burned. That’s a fuel economy thing, moving the car the same speed with less fuel, but it also is a performance thing. I guess it also would work with a standard stroke LS (3.622″) with shorter piston compression height and longer rods, but the effect is amplified with the 3.26″ stroke and 6.275″ rods from the 4.8l engine because there is a limit to how short a compression height you can get imposed by the separation between the second ring and the oil control ring on the piston. The oil ring can intersect the piston pin location, but that is as high as you can go and still have a functional engine with current piston ring technology. Also the increased rod ratio (rod length/stroke) of 1.932 for the 4.8l crank and rods means significantly less piston wear from side loads regardless of the RPM range and still allows the use of standard pistons for the size block chosen. As a point of comparison the 383 SBC has a rod ratio of 1.52 with stock SBC rods, and the 350 SBC has a rod ratio of 1.638. This is a substantial improvement for the 4.8l crank and rods. I’ll have to do “something” to bring the compression ratio back up after installing the 4.8l crank and rods reduces the displacement of the cylinder compared to the original crank and rods. “Something” in this case is reducing the combustion chamber volume by the same ratio as the change in displacement from the 3.622″ crank to the 3.26″ or about 11%. That’s a major change in volume, for the smallest factory LS head that would be more than 6cc (6.829). That’s a large cut to the head combined with a thin head gasket to get the combustion volume to the point that the same place it was before the crank change. I guess I can live with the 11.3:1 with the stock heads and the 0.027″ compressed height Cometic composite (not MLS) head gasket.

Well that’s enough rambling about a fantasy engine, time to put this post to bed and eat the dinner Mrs. the Poet has been working on. Oh yeah they just announced that the total number of twisters that hit the area on Sunday was 10 as they found another damage track in an unpopulated part of the area.

Another update without real information

First of all the good news, Mrs. the Poet has lumbago and can be treated by a combination of steroid injections and physical therapy. That means she might stop yelling every few steps as her back locks up and her feet go to sleep at the same time as her back goes wonky. Her TBF is about 6 feet now when it was 10-12 feet just a few weeks ago. She also has an issue where here spinal column is smaller than it should be where the actual nerves pass through which also contributes to her pain and feet going to sleep.

The “meh” news I was awake all night last night thinking about alternative rear suspension/engine mounting for the A/MOD car and I’m writing sleep-deprived again. Also was thinking about alternative front suspensions for the same car because why only change one thing? This was because I changed the engine from the cruiserbike V-Twin to a Predator 670 V-Twin and the exhaust and the drive are on the same side meaning the engine has to go on the left of the car to keep the engine from blowing exhaust right in the driver’s face. The cruiserbike engine has exhaust on the front of the front cylinder and the back of the rear cylinder meaning it can be run out the right side of the car and the drive is on the left. All this means is the jackshaft for the 670 has to be longer than for the cruiserbike because it has to go all the way across the engine while the bike engine just has to go far enough to reach the drive chain from the transmission.

I also thought about a mount on the rear suspension like the old Malibu Virage cars and some Chinese kart style dunebuggies and some RC cars, but I discarded the idea as having too high an unsprung weight with the engine bouncing around with the rear axle. It sure did simplify the drive to the rear axle though and lightened the car up a bit.

I have been having bad brain days for a while

This is normal right after my death day, and it doesn’t matter if there’s a big shindig, or I’m all by myself like this year. The difference is when there’s a big shindig it doesn’t last very long, and when I only have the cats to be with I get down for much longer. This year the cats didn’t show up either but they did come back in the morning, but I still got way down. This was a bad year for this particular problem. The only social group I interact with any more is the RPG Group. And nobody responded to my Twitter invite or my FB save the date. I never saw the FB thing go live so that might have been a mistake on my part setting that up.

But anyway, the end result was a lack of desire to write anything more complex than a grocery list, or work on the Mini Sprint-T, or the Sprint-T. I knew I was starting to come out of it when I started thinking about building a car for SCCA Solo racing A-MOD using a V-twin engine from a cruiser motorcycle and a setup that was basically a scaled-up shifter Kart with the suspension and brakes needed to be a legal A-MOD car. I planned on using Midget or Micro-sprint spindles (pretty much the same thing) with pavement brackets for big brakes on both sides (dirt spindles have a smaller brake on the left side only), hung on an axle made from wrapping carbon fiber around a foam core and steel inserts for the kingpins to ride in. The idea was to use a beam axle to keep the tires pointed in the right direction for camber and then make that sucker as light as possible for the lowest unsprung weight. I was going to use a rear axle from the mini- or micro-sprint to connect to the chain drive from the motorcycle engine with a jackshaft for initial gear reduction and moving the final drive to the center like on the Grind Hard Plumbing Princess Jeep only with much less articulation because pavement racer instead of dirt crawler/buggy like the Princess Jeep. But what they did prove was that using a small sprocket on the axle prevented chain bind or jumping when the axle was twisted through a range much further than an A-MOD Solo racer would ever see outside of a wreck. So Imma steal that idea for my car.

Also the reason I’m stealing the jackshaft idea is I’m mounting the engine way off center to balance the driver weight and to keep the polar moment as low as possible by keeping as much mass in the center of the car as possible. Driver to one side, engine to the other with both as close together as physically possible given the need to balance left-to-right and the need for the final drive chain to ride in the center of the axle. I’m leveraging my skinny butt to get as close to the centerline as the chainguard will allow, because I’m only 13″ wide at the hips. This reduces my moment arm from 11.25″ in the Sprint-T to 7″ leaving clearance for the chain and chainguard because I don’t have to leave room for another person, just the engine. I have really wide shoulders and a really skinny butt, like my Dad, and that’s the main reason why the driver moment is so large in the Sprint-T because I have to leave room for a passenger by the rules for Goodguys.

I also knew I was getting better when I started looking through the Hoosier tire catalog looking for the right tire to use when racing the Sprint-T in SCCA Solo events. Basically I was looking for short, wide and sticky that would fit a 15″ X 8″ or X 10″ wheel because there are light, strong, and cheap wheels in those sizes available in several different offsets that fit one or the other of the bolt circles on my hubs. I also used more than just the road racing tires and went into the pavement oval listings to see if there were any tires that came close, and I found a couple in the section for Modified class, and pavement sprint and Supermodified classes which despite being vastly different in layout use pretty much the same tires. Those tires were larger in diameter than my ideal of <23", but were considerably wider than most of the road race offerings with tread widths of 11-13" compared to the 8-9.5" of the road race catalog. The suitable tires for the pavement oval racers were 24-25.5" in diameter compared to the road race tires in the 22.5-23.5" diameter but much narrower as the diameter decreased. Also the oval racing tires are bias-ply while the road race tires came in a mix of bias and radial depending on the size, which tosses another variable into the mix. Radial tires have higher peak grip given the same size and compound, but bias tires are much more controlable at the limit and come in wider tread widths with stickier compounds, so ultimate grip becomes a wash. Also, the reason why there are so many size and compound choices in the oval tire section of the catalog is oval cars run different size and compound tires at each corner in the sprint and Supermodified classes to balance the handling or to use different diameter tires to force the car to turn left when running a locked rear or a solid rear axle (same thing, just built differently) so the right tire drives the car to the left.

It has been a bit difficult to type this in as Clint has decided to lay on my lap on his back demanding tummy rubs which means I have to type with one hand while holding the cat with the other to keep him from sliding off my lap and grabbing me with his claws to keep from sliding. That usually results in long deep scratches. And now he lost interest and has left the room.

Which makes for a good time to end this and hit "Post"