Category Archives: Daily post

Couldn’t stop thinking last night

And it kept me awake until nearly dawn thinking about getting an overdrive for the T-10 by swapping in an OD for 3rd and changing the shifter to allow it to be the new 4th.

In doing my research for this I discovered that the OE 3rd gear is already a slight OD as the ratio between the input and cluster shafts is 1.28:1, while the output from 3rd is 1.23:1, which means the ratio of the gears on the 3rd position of the transmission is already an OD just not very much of an OD, 0.96, probably just a tooth larger on the cluster than the main shaft. It’s looking like I will have to order a custom cluster with a custom gear for the main shaft that is as small as will fit. This is not an inexpensive alternative.

And it’s not like I could amortize the costs by selling duplicates at a profit until the tooling costs are covered. This application is very niche, not many people are in the market for this combination of light weight and OD top gear, and can live with only 4 speeds. Also I have been looking at the ratios in use on the transmission and most of them are not actually useful in making 3rd OD. Swapping the gear for 2nd gives an OD that is not even enough to make the output OD, the gears are 1.25:1 as they are before swapping which is less than the 1.28:1 of the input gears. So basically I’m looking at finding the smallest gear that will fit the output shaft and designing a gear to machine into the 3rd position on the cluster and hoping the resulting ratio is enough to be more overdrive than the underdrive ratio of the input shaft to the cluster. Also most of the different ratios available are just from changing the ratio of the input to the cluster, the 2.43 S cluster, and the 2.64 W cluster are the same ratios except for the input/cluster gear. In fact checking the spares list shows that most of the ratios are shared with common 2nd ratios for the S, W, CC, and Z clusters, common 3rd for S and W, and common 3rd for X, CC, and Y. So yeah, I will have to order a special cluster and gear for the main shaft if I want to hang an OD 3rd on my transmission.

And I have been going back and forth between the PDF of the spares list, the calculator app, and this post for like 4 hours, it’s time to put this one to bed.

Thinking again part googleplex

And yes that is an actual number, it’s google to the google power, an impossibly large number I’m using for humorous effect. If you are wondering exactly how impossibly large, that is a 1 followed by google zeros.

But I have already gotten on a tangent (SQUIRREL!) in only one paragraph. That’s not a good sign for the rest of the post, but I’ll be good and make it make sense. What I have been contemplating is weight reduction in the powertrain.

This takes us back to the engineering maxim of choice: Light, Strong, and Cheap; pick two. I absolutely need light, and I need to balance strong and cheap. The idea here is start with the Super T-10 aluminum case and make or modify the cluster and counter shafts to get 1st and 2nd underdrive, 3rd direct, and over drive in 4th by putting the overdrive in the 3rd position on the cluster and modifying the shifter to swap 3rd and 4th on the pattern. The effect will be a manual version of the gearing in the 4l80, except way lighter and more expensive but still lighter and maybe cheaper than the 5 or 6 speed manuals.

I’m still not sure of the best way to do it because I’m not a transmission engineer, I’m just a shlub that has lots of time doing systems. My initial take is copy the gears from 1st, and put them on the 3rd spot on the cluster, except swap them between the cluster and the main shaft so that it overdrives instead of underdrive. This compensates for the underdrive between the input shaft and the cluster, and gets me a decent amount of overdrive, without having to spend a bunch of money, hopefully.

There will have to be some money spent obviously, but I’m hoping this will reduce how much money that is. The plan is taking the 2.43 1st cluster and machining 3rd gear to the outside diameter of the main shaft, welding the main shaft gear for 1st where 3rd was, and machining the cluster gear for 1st from another cluster to install on the main shaft, or machining the profile of the gear onto a main shaft gear. The modified cluster will need to get heat-treated again because of the loss of strength from welding the new gear on it. And I won’t get a 0.403 overdrive because of the reduction between the input shaft and the cluster, I’ll get 0.403/(whatever the reduction from the input shaft to the cluster)2 because the initial ratio is reduced by the input shaft reduction and then again as an overdrive because the installed gear is driven by the reduction still.

And it’s late for me (0400) and I need to get some sleep, so I’mma pack this one to bed and me right after.

Another hint that I’m getting old

Another short post of things I noticed. I’m getting a blur at the top of my vision that I couldn’t figure out what it was. It moved with my head and obscured the top edge of my vision, and got brighter when the sun was coming from the side window on my face.

Then I had something itch in my left eyebrow and when I rubbed at it the blur went away for a few seconds. Yep, my eyebrows are hanging in front of my eyes now like I’m a Mentat from Dune, or I’m just old now. Since I’m not a Mentat, I’m sticking with the “I’m old” hypothesis.

Sorry for the radio silence

I would have posted something if I had something worth posting, but I don’t. Things around here at Casa de El Poeta have been quiet and boring. The most newsworthy thing I have is Mrs. the Poet’s bloodwork came back and her cholesterol is higher than her doctor likes. Other than that I got nuttin’.

On other venues Bubba Wallace was the second African-American to win at the Cup level in NASCAR since Wendell Scott in 1963 when I was still in kindergarten. So, good for him. It didn’t take 50-some years for Bubba to get the trophy from winning like it did for Scott.

Hip still hurts

Not too much to say today. My hip still hurts, the joint not the muscles around it. I’m getting tired and falling asleep at odd times which doesn’t help my aches and pains because I fall asleep in places and/or positions that make my hip hurt more.

The cushion on the rocking chair I sit in when I use my computer has developed a lump that holds my hip in an uncomfortable position. I can’t seem to find a place to sit in the chair that the lump doesn’t put the whammy on my hip. Basically the cushion is holding my hip at a bad angle and making it hurt, from a little to a lot.

Another thing, I’m having digestive problems. Basically my poops are messed up, and if I wasn’t drinking fluids like a fish I would be dehydrated. I’m also eating raisins because fiber, and yogurt because gut biome. That helps a little, but I haven’t completely recovered yet. And AFAIK messed up BM are not a COVID-19 symptom, so don’t worry it might be that.

Also, I’m having a budget issue that I’m trying to work out that looks like I’m taking a $100/month hit. This really annoys me because this is something that used to be free, and now I have to pony up $100 for it. And I’m pretty much just stuck with having to deal with the expense.

Barely mobile because bad hip

This time it is the actual joint that actually hurts, not just the muscles around the joint. As the headline says, I have been barely mobile most of the afternoon because of the hip pain. And FYI the joint pain is an order of magnitude (binary) worse than the muscle pain.

I have been thinking about the Sprint-T since I can’t do anything about it. I have been thinking about weight with an aluminum LS architecture engine and the Super T-10 transmission, which weighs about 110 pounds less installed than the 4l60e, which comes in at 165 without the torque converter and flexplate. Those come in at about 50-55 pounds dry, and the flywheel and clutch are about 40 pounds together for the manual transmission, while the transmission comes in at 70 pounds dry. That means that if the car weighs 1800 pounds with the 4l60e it will roll up to the start line just under 1700 with the Super T-10. I don’t think I need to explain what a 6% reduction in weight means for the performance of the car.

Angry and annoyed by life, but I’ll get over it

I am still dealing with things I can’t write about in the blog because reasons, things that are causing me emotional “problems” that I can’t deal with. I’m also dealing with some physical stuff, mostly pain and tightness in my glutes and hips. I won’t be able to deal with them until I get some money, which will be Thursday.

I’ll probably go get a massage after my birthday Wednesday because I get my SS deposit at 0001 Wednesday night/Thursday morning. If I felt actual pain instead of discomfort I would probably be out of it right now because my hips are barely mobile right now.

Enough ranting, I really don’t have anything important to say, just venting about my hips and other non-functional body parts.

No game Sunday, watched the race instead

We had a post-pandemic scheduling problem as 2 of the group were attending events rescheduled from 2020. As such they were more anxious to attend the events that they missed last year than to play a game. Also our GM has family obligations for the next three weeks and that means no games. So I watched the race just in time to catch Roman Grosjean slicing his way through the field to a third place from way back in the pack. It was one of the best drives I’ve seen at Laguna Seca. I haven’t seen every race from that track, so there very well could be a better race but not that I’ve seen.

I also checked my Lottery numbers to see if I won a comfortable retirement , but I’m still p’.

Wednesday is my birthday so I’m taking a day off from blogging even if I have something to write about.

Been thinking again about suspensions

Basically what I was thinking about was tall front uprights for camber control. Basically the taller the upright the less the suspension arms change the camber of the wheel because the side to side motion induced by the arms rotates the upright in the camber plane in inverse proportion to the distance between the ball joints.

GLOSSARY

Camber – The angle between the tire and the road surface. Positive is the top of the tire tilted away from the center of the car, negative tilts toward the center of the car. This is backwards because positive camber is almost universally bad for tire grip and is therefore a negative, but the terms were defined prior to the invention of the pneumatic tire and now we are stuck with them.

Kingpin inclination – Another term that is archaic because kingpins are from solid axles except for a very tiny number of early independent front suspensions. It refers to the angle of the axis of steering rotation for front wheels between the upper and lower ball joints.

Scrub radius – The distance between the intersection of the steering axis with the ground and the center of the wheel. Basically this is the moment arm of the force generated by the brakes through the steering system. The greater the absolute value of this number the larger the force felt at the steering wheel under braking. The direction of this force depends on the positive or negative value of the radius. If positive the steering wheel will turn in the direction of the greatest braking force, and opposite if negative. Now there are schools of thought that if the system is designed to turn away from the stronger braking force it will be self-correcting in the case of brake failure. There are other schools of thought that drivers will instinctively turn away from forces trying to steer the car so positive scrub radius is better, with the debate coming down to do you want your driver to be an active part of the car.

Upright height – The distance between the upper and lower ball joints of an independent front suspension

This is a hypothetical discussion because the front suspension for the Sprint-T has been frozen as a straight axle, and because my fabrication tools are not up to building suspension uprights. So theory only. No labs for this lesson (shoutout to my teacher friends who “get” this joke). Theory for this starts with the statement from the opening paragraph camber change is inversely proportional to the distance between the ball joints. Second is that the position of the bottom joint is constrained by the dimensions of the wheel used, because kingpin inclination and reducing scrub radius dictate the location somewhere inside the wheel. Excessive positive scrub radius has been proven bad experimentally by excessively increasing the force required to steer under braking.

And it just dawned on me this post needs a glossary to keep track of all the technical terms. We already have camber, kingpin inclination, and scrub radius besides upright height. Basically I’m assuming my reader has a working knowledge of terms used in suspension design, which is probably not the case. So I’m inserting one following the first paragraph. It’s there now but wasn’t before I started this paragraph.

Anywho, the design parameters basically dictate the lower ball joint be as far inside the wheel as possible constricted by the brake disk because of scrub radius minimization. It doesn’t matter if you want positive or negative scrub radius, you still want it to be small or variations in braking force caused by changes in road surface can tear the steering wheel out of the driver’s hands which is bad no matter how you look at it.

Also, the amount of camber change caused by body roll is proportional to the ratio of the distance between pivot points on the frame and the distance between the pivot points on the upright. Desirable geometry of defining the instant center dictate this is going to be close to unity and usually less than 1:1. There are some old GM cars that had this greater than 1:1 and they understeered excessively with the outside front wheel riding on the sidewall of the tire. Look for images of the late ’60s Chevelles making hard turns and you can see this in action, but not many of those pictures made it to the internet and the only ones I have are in paper books on suspension and my cell phone camera did not get a good picture of the picture. One of the things about having the ratio between the distance of the suspension pivots greater than unity is the front roll center is underground, which causes the body to roll excessively and further causes the car to ride on the sidewall of the outside front tire. This meant that racers using this car as a base for stock cars had to crank in ridiculous amounts of static camber and excessive amounts of roll stiffness to keep the car driving on the tire treads instead of the sidewalls. They made it work but it would have been easier if the front suspension was designed right in the first place.

Getting back on track for this essay without any more digression (squirrel!), we want to basically define a height range for the front upright. Too tall and either we get “funny” geometry in the suspension or we get the pivots for the upper suspension arm somewhere in the boonies, which technically is “funny” geometry. Too short and we get poorly controlled camber as the car goes through bump and/or roll. My personal take is I design about the same as the inside diameter of the front wheel as my max, and about 8″ as my minimum except for suspension karts. No matter what you do those are “funny” because no room.

And I seem to have lost the point of this post except that I woke up in the middle of the night thinking about front suspension uprights. So since we hit over 1000 words this seems like a good place to stop and hope I get my train of thought back on the rails for a future post.

Still thinking, remain in cover until the all clear has been given

I’m still reading my new book about suspension geometry and contemplating the information, but it hasn’t resulted in any changes to the Sprint-T. The front is still a tube with fore and aft location by parallel 4-bar and laterally by a bent Panhard rod to clear frame members, rear is still fore and aft by dual trailing links and laterally by a Watt’s link and a torque arm for control of reaction torque from the engine. And torque reaction links for the brakes. All rotational reaction forces are isolated from the suspension to prevent locking up the suspension from either engine torque or brake torque, allowing the suspension to move freely at all times. The front springs are mounted as close to the ends of the axle as will clear moving parts, and the rear springs are mounted to the trailing links originally designed for swingarm suspensions of much heavier vehicles on rough tracks. This allows easier tuning of suspension stiffness by changing the motion ratio for the springs as there is quite a bit of motion ratio to play with.

To clarify that, the bottom of the spring mount moves less than the wheel in both single wheel and double wheel bumps. This means I can get smaller changes in wheel rate than steps in spring rate which gives me finer control over wheel rate. Also the total travel of the shock is less than the travel of the wheel which reduces the amount of force per inch of wheel travel. There is a formula that gives us the effective wheel rate when the spring rate is known (mr2*Spring Rate) or the square of the motion ratio times the spring rate. On the rear suspension for the Sprint-T there are two motion ratios, the motion ratio for a single-wheel bump or body roll and the motion ratio for a two-wheel bump which is just the motion ratio of the swingarm. The single wheel bump is the swingarm ratio times (the distance from the far wheel to where the swing arm attaches to the axle housing divided by the track).