Tag Archives: Sprint-T

I’m on my third pair of underwear tonight

I’m having hip problems that keep me from side-stepping quickly which is how I get from behind my computer. The muscles I need to move my hips from side to side are not functioning to specs the last couple of days, and that keeps me from getting up and going to the toilet as quickly as drinking lots of fluids to prevent kidney stones combined with diuretics to keep my BP down and also not get kidney stones sometimes requires. Basically I’m trapped in a bentwood rocking chair with tall arms and I need to completely stow the keyboard shelf and my laptop under the desk to have room to slide sideways out from under my desk, and sometimes there’s a bind in the sliders and I can’t get everything out of the way in time before the dam breaks and I have soggy underwear. So far I’ve managed to get my pants off in time, but my underwear doesn’t clear the waterworks before the dam bursts, and I have to put on fresh underwear. This is embarassing, but it’s a fact of life when you have hip issues and calcium metabolism issues and blood pressure issues all at the same time, so I just live with it and try to not get caught in places where someone could find out about it.

I’ve been watching YouTube videos related to building the Sprint-T and getting hopeful I might get this thing done before I won’t be able to get in and out of the car because of my hips not working, maybe. Even though I’m still missing an engine, transmission, frame, and all that kinda stuff I have to either buy or build yet. Anyway, I’ve kinda figured out how to make the clutch work so I will be able to make the car start and stop without stalling, but I really wanna know how Indycar makes the clutch on the steering wheel work, because they can slip the clutch or dump it as required from a paddle on the steering wheel where I’m looking at using a handbrake lever to do the same thing. If I could get it done from a paddle on the steering wheel, I could granny shift with the same paddle instead of having to buy a special gearset for the transmission and jam the car into gear without the clutch just lifting the throttle and sticking in the right gear. Looking at the way it’s done by Indycar, I don’t think it’s a viable method for the Sprint-T. Indycar uses an electro-pneumatic system, which has a system not on the Sprint-T to power the clutch declutching, the pneumatic system also used to operate the airjacks that are also not on the Sprint-T. I can’t find anything more than that about the system but as it allows the gradual engagement of the clutch I’m assuming there’s some kind of linear sensor in the paddle on the steering wheel that controls the clutch, and probably a PWM (Pulse Width Modulation) signal to the controlling device for the pneumatic cylinder that drives the clutch to declutch the transmission. As I stated I’m having to exercise my imagination on this because there’s nothing on how this system works beyond “electro-pneumatic clutch” “operated by a paddle on the steering wheel”, in two separate articles, but I can’t figure out any other way for it to work than as I have posted it.

As it stands I’ll have to use both hands to get the car in gear then lift throttle and jam the gearshift either up or down to get the car in the right gear, because I’ll need to use my left hand to work the clutch and my right hand to shift into gear and if the car is moving that leaves no hands to turn the steering wheel, which is illegal in some states and not recommended in most if not all of the rest. Although these same states allow putting critical engine and HVAC controls on a touch screen that requires taking eyes off the road for an extended time so apparently not having a hand on the wheel is a bigger thing than not having eyes on the road.

And I’ve been awake over 22 hours now and I’m getting clumsy at the keyboard and having to fix typos repeatedly, so maybe this is a good time to put this post to bed, and me shortly thereafter.

Another case of nothing to write but a compulsion to write something

The tl;dr version of this post is I feel the need to write, but I don’t have a topic springing to mind at the moment. I think I wanna write about the Sprint-T, but I don’t have anything to say about it, except for how frustrating it is to not have a budget for building this thing.

I have been thinking about also the dedicated A-Mod racer with the aluminum block LS engine sitting next to the driver for the lowest possible polar moment of inertia, because if you can’t do anything with the main project distract yourself with a different project that has even less likelihood of completion than your main project. The idea driving the LS A-Mod is offsetting the engine and transmission to one side and putting the driver next to it but offset the other direction so that the two moments balance out. The exhaust will run over the driver’s legs, and the driver’s butt will be right about even with the rear face of the block. This will mean the engine will be offset about 10″ away from the driver because of having to clear the physical parts of the engine specifically that bellhousing, but the driver could be offset more than the engine. Like I already know how far to move the engine when the driver sits completely behind the engine and there is some left-to-right overlap, it’s just basic algebra to use when they’re side by side. Basically the engine has a moment relative to the driver, the driver has a moment relative to the engine, and the two moments have to add up to 0 when the car is built. This kind of stuff is what I do for fun and relaxation, and I’ll say it first: NEERRRRRD! I’m literally doing a word problem, for fun. Sioux Geonz teaches remedial math to college freshmen and I’m told sometimes links to my blog posts as examples of real-world applications for what she teaches. If it helps, I’m happy with it.

Anyway part of the reason the engine is beside the driver is another moment problem. If the driver is in front of the engine like most formula race cars, it stretches the car out and results in a larger moment than if they are side by side, and for this particular style of racing this makes the car with the larger moment slower than the car with the smaller moment because the smaller moment lets the car change directions quicker. And if your car can change direction quicker then you can cover the distance the direction change has to take place in faster. And as in everything about cars this results in a tradeoff, the driver is exposed to more heat sitting beside the engine than if they are in front of the engine and not under the exhaust. There’s also the location of the cooling system to consider in the heat loading situation, in that there is a greater likelihood of the radiator blowing on the driver with the side-by-side driver-engine configuration because the cooling system is literally hung off the front of the engine and is easier to plumb if the radiator is in front.

And I’m writing right now because I’m trying to not think about the Ukraine, and dinner is ready, so I’m going to put this post to bed now.

Forcing myself to actually care about something

I think that’s something old people have a problem with, finding something to actually give a shit about as they get older. Also I’m dealing with something that’s making my damaged hip hurt, so there’s that, too.

What I have been thinking about for something to do is looking up stuff that might be useful for building the Sprint-T. The price of that upgraded T5 transmission is $3600, this week. But it only weighs 77 pounds, 2 pounds more than the stock T5. That’s pretty good for a 67% increase in rated torque capacity from 300-500 pound-feet. Most of the increase in capacity comes from upgraded materials, with the rest from slightly larger gears.

While I was it it I also looked up the weight difference between the straight axle and the independent front suspension. Actual weight on the tires is about the same, but the ratio of sprung to unsprung weight change is huge, mainly because each wheel only has half of the unsprung weight as opposed to both wheels having all the unsprung weight with the straight axle. If I got my sums right the independent suspension is 5 pounds more than the straight axle, with most of that in the frame where the suspension attaches, brackets and bracing not needed with the straight axle.

There’s also a bit more weight for the moving parts in my design because I like to have the lower arm almost a center pivot with pretty much no change in track with suspension movement. That means there will be some bump steer as the instant center moves during suspension travel and the tie rod can’t point at the point where a line drawn between the upper and lower control arms intersects so it has a different arc than the place where it attaches to the spindle. That also means the lower control arm goes halfway across the car, which makes it heavy. I’m still thinking I want to make the lower arm shorter than that just to reduce weight because it doesn’t make that much difference for the geometry of the front wheel travel. But I’ll have to buy some suspension CAD program to play around with the suspension arms to see where the crossover point between long and short control arms is for the Sprint-T.

And for everybody who reads the tags, the weather today has been wonderful, warm enough to not require heat, but cool enough to not require AC. We get about 2 to 3 weeks like this twice a year here, and we just bask in it. The electric bill is almost nothing as we only have to pay for keeping the water heater going for showers and dishes and washing hands.

Still thinking alert, take cover immediately

J/K there’s no imminent danger. I was thinking of ways to improve the front of the Sprint-T. Also still thinking about the drivetrain with a possible manual transmission.

Starting with the front suspension and related things I decided it might work better if the panhard rod (AKA track bar) was straight. That requires redesigning to the front part of the frame so there is nothing that the panhard rod has to go around to get from the driver’s side of the frame to the passenger side of the front axle. I did this by moving the front diaphragm that carries the loads from the coilovers to the rest of the frame from in front of the axle to behind the axle. This requires moving the steering behind the axle as well as the steering box back to the kit location. This also means the radiator has to be moved back and up to clear the steering shaft from the steering box to the steering wheel. This is how designing a car goes, you can’t just change one thing, it cascades across most of the car. And I forgot to mention the complete redesign of the bumper support structure because the top and bottom frame rails stop at the front axle.

The other thing I was doing was trying to find a lightweight transmission with overdrive, and basically what I found was the Super T-10 couldn’t be made to have an OD without basically redesigning the transmission because the cluster was a solid hunk of steel. Now if it had followed the path of the sister/progeny transmission that used to be called the Nash 4+1 which uses a cluster with replaceable gears, then I could just have a replacement 3rd gearset machined and installed instead of a full replacement cluster. Anywho, the mentioned 4+1 is now the Super Street Five Speed with much higher torque capacity compared with the Super T-10, and extra weight from the structure to resist loads from the increased input.

The 5 speed handles 600 ft-lbs, compared to the 300 to 375 rating for the T-10, and also has a much lower 1st gear (actually several options that are as low or lower than the lowest 1st gear on the T-10). The price for gearing this low and higher torque handling is weight. The 5 speed comes in at 105 pounds compared with 70 for the T-10. Still lighter than any of the self-shifting transmissions with overdrive, by 60-80 pounds, plus it takes up less room inside the car, especially since on the Sprint-T the inside of the floor is also the top of the bellypan and nothing hangs lower than the bellypan, that’s another design paradigm for the Sprint-T.

The top of the bellypan is attached to the bottom of the bottom frame rail, and if there were no bellypan the bottom of the bottom frame rail would be the lowest part of the car except the wheels, because that lets the car be as low as possible without dragging the road if a tire goes flat. Theoretically all 4 tires could go down and the only thing touching the road would be the tires. This requires the road to be pool table flat, but even on normal pavement I can still get both tires on an axle going flat without anything touching anything except tires. I picked this one up from off-road trucks that need to be able to keep going with flat tires.

Anyway, going from a bent panhard rod to a straight one allows a smaller size rod and also allows changing from steel to aluminum, and the combination allows for the drastic reduction in weight of about 2/3, and as half of the panhard rod is unsprung a reduction in unsprung weight as well. This results in a slight increase in grip on bumpy roads and courses as less unsprung weight improves the ability of the tires to follow bumps without leaving the road. This is why I try to reduce unsprung weight every chance I get.

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.

Got a new book

I bought Advanced Race Car Chassis Technology HP1562 for the Kindle a few weeks ago and I’ve been absorbing it a little at a time. It’s a complex subject, but from what I’ve been able to read so far, if I get it right I don’t need to make the frame all that torsionally rigid. If I’m reading this right there’s no twisting load on the frame if I have the suspension geometry right and tuned the spring rates. If my sums are close there will be about 300 pounds ± on the springs of the front corners, and about 350 ± on each rear. That’s not a good sprung/unsprung ratio, but that’s what I’m stuck with.

The front axle weighs about 65 pounds plus the hubs and brakes, because it’s a honkin’ huge chunk of iron steel with tons of thick brackets welded to it, and the spindles are likewise big chunks of forged steel. The rear axle is right at 100 with the diff and and axles (drive) but without the hubs and brakes, which are almost the same weight for both ends. The rears are a touch lighter than the fronts because the rear disks are 11.75″ and the fronts are 12.19″. All of that is unsprung (bad) weight, axles, drive axles, hubs, brakes, the whole shootin’ match all bad weight. Well none of it is good but unsprung weight is super bad compared to sprung weight. Like excess unsprung weight causes tires to lose contact with the ground over a bumpy road even if the bumps aren’t that big, bad. And a lightweight car makes unsprung weight even worse because sprung weight pushes the unsprung into the road and not having enough sprung weight means the unsprung weight is just kinda floating out in space. It only contacts the ground intermittently because the two weights, sprung and unsprung, are just oscillating independently. I’m getting close to that condition with the front of the Sprint-T. If I understand the theory right the only thing you can do with a car that has sprung:unsprung ratio approaching unity is make the dampers stiffer to prevent oscillation from setting in, assuming there’s nothing to do to make the unsprung weight less. Right now the only option I have is to use “drillium” in the front axle, that is to remove weight by drilling the front axle full of holes. Since this axle was designed for a car almost twice as heavy as the Sprint-T this is actually an option.

As far as the geometries of both ends are concerned, the front end will not have any adjustability beyond caster and toe, the roll center height will be fixed to prevent the front axle moving under load and changing the steering angle. But the rear axle will be located by a Watt’s link with the pivot located by a nut on a threaded bolt that adjusts up and down to change the balance of the car for different conditions, like understeering for highway travel, neutral for road courses, and slightly oversteering for autocross. That can be done by turning the bolt to move the rear roll center up and down.

Oh, here’s the link to the build video for the GenIII Hemi™ giveaway. Lotsa power and torque from a nearly 600 pound engine.

Wanting to make a change but stymied by sunk costs

I’m looking at the front suspension for the Sprint-T and I’m thinking I really need to go with an independent suspension for more grip on bumpy tracks, but I’m dealing with over a thousand dollars in sunk costs, just in brakes that couldn’t be put on a different front end.

I think I could do better with Pinto/MII spindles and aluminum a-arms, but the only thing I could transfer would be the rotors and maybe the calipers. Everything else would have to be a new purchase. If Wilwood makes a kit that uses the same size rotors and the same calipers for the Pinto/MII spindles then the brackets, hubs, and everything else is sunk cost. And that’s just brakes, there is also the spindles, axle, axle brackets, and frame brackets that have to be discarded or replaced. If I was independently wealthy that would be a different story, but I’m on a very small pension and Social Security, so every penny counts and comes dearly. I basically don’t have disposable income these days, everything comes at a cost of something else I can’t get.

Actually the 2″ drop version of the Pinto/MII spindle would work better than the standard because it centers the spindle better in the wheel for more angle and more travel without hitting the A-arms, not that there was any danger of there being enough travel to cause the arms to hit the wheels. Angle, maybe, but travel never. That’s one place where the solid axle shines in comparison to the independent suspension, there’s a huge amount of clearance for angle. That and camber control through body roll, solid axles don’t change camber, like ever. There is some communication from one side to the other as pavement imperfections are encountered, but aside from that the camber doesn’t change. The axle holds the camber constant, which is why building the right angles in in the first place is so important.

Anyway, IFS would be a bit better in bumpy conditions, especially with really wide tires, but because I made that decision years ago and purchased accordingly I’m stuck with a solid front suspension. In this kind of competition the tires are a much bigger variable than solid or independent suspension. And it so happens I have some really sticky rubber picked out, and the slicks for SCCA competition are specifically designed for solid axles.

And this has no bearing to the rest of the post, but I have the non-ap browser version of Youtube Music running on the laptop and it’s really nice to not have to deal with ads in the middle of pieces like the phone version. And I still have access to my mixes and lists like the phone ap. The main difference is the browser version on my computer doesn’t use up my phone battery and I can leave it running in a tab while I edit a post in another tab or window. The phone ap is a little more portable because it uses cellular data that my laptop doesn’t have so I can listen on the bus or while riding in the car. Horses for courses, sometimes one device is better, sometimes it’s a different device.

Am I under a Geas?

For those not into fantasy RPG a Geas is a compulsion spell that forces the victim to do something. I have to write even though I don’t actually have anything to write about. This is kinda what a Geas is like.

Since I’m trying to win a GenIII Hemi™ engine, I thought I would see what that does to my weight-and-balance for the Sprint-T. To put it succinctly, nothing good. The GenIII Hemi™ is physically larger and also has a cast iron block, so it adds over 170 pounds to the front end of the car, 415 pounds for the LS compared to roughly 580-590 for the Hemi™, and a similar situation for transmissions I could use.

I still have the “no room for 3 pedals” situation so I still have to use an automatic, even though I’m not going to be shifting much if at all when I race, and very little when I’m driving on the streets and highways. The Goodguys’ racing is all in first gear, and SCCA is first and second but mostly first. There are almost limitless models of transmissions, between the old Chrysler 3 speed and more recent 4, 5, 6, and 8 speed transmissions for sedans, SUVs, and trucks. There are also kits to bolt up transmissions from LS engines. This just gives more options.
3.6l Pentastar but the 360 pattern overlayed is also the GenIII Hemi

Basically any Mopar/FSA transmission built for a V8 engine works for a GenIII Hemi™ including some weird ones like the NAG1. The 545RFE weighs 238 pounds, the NAG1 has a listed dry weight of 125 pounds without the converter, fluids and a torque converter add weight of course. Other transmissions will bolt up, but those two have the widest ranges and the tallest overdrives for highway driving. They also have torque ratings that even a built GenIII won’t exceed.

And I’m starting to fade, so I’ma put this baby to bed and me shortly after.

What I was thinking about last night

I have this “problem” with thinking, especially when I’m trying to sleep. This is especially true when I have a niggling design/fabrication issue that won’t let me go until I solve it.

The issue that kept waking me up last night was there will be zero clearance for the oil and transmission pans when the belly pan is installed on the Sprint-T. That also means there will be zero clearance for the drain plugs with the belly pan is installed.

Since the Sprint-T is going to be raced frequently this is a serious problem because racing requires frequent fluid changes to maintain the performance of the drive train, especially since it will be driven to and from the races. Now transmission fluid is not as critical as engine oil, but it will still need to be changed during the racing season and at the beginning of the season. Cars that are not raced then driven on the streets or highways can usually go their entire lives without a transmission fluid change, but even street only engines need oil changes regularly because oil doesn’t last forever and oil filters don’t catch all the contaminants that get into engine oil. And race engines usually get fresh oil every race meet, sometimes during the race meet if there is a lot of dust and dirt in the air, even if the engine is using an air filter on every engine orifice exposed to atmosphere.

Now there are two problems to be solved here, the first is since transmissions don’t normally get fluid changes they don’t have drain plugs, and the second is having drain plugs that are flush with the bottom of the pan but still drain completely dry with a tolerance for cling to the sides and bottom. The solution is to install the drain on an edge with the hole being flush to the inside bottom surface of the pan, and to contour that surface to direct the draining fluid to the hole. This is obviously easier on a pan that is being fabricated from scratch, but since the vast majority of transmission pans are stamped out of thin sheet metal it can be accomplished with a little hammer and dolly work, or a ball peen hammer and a soft 2 by 4.

The first thing to do is decide where the drain is going to be, and then “massage” the bottom of the pan with the hammer and whatever you choose to back it up to make that the lowest place in the pan so the fluids accumulate there. Then drill your drain hole flush with the bottom through the side of the pan. That’s the easy part, the hard part is making a plug that doesn’t hang below the bottom of the pan.

The next step is to pick a bolt that will fit the hole you drilled, ideally that will fit snugly in said hole because it will be used to locate the part that holds it to the pan. This is going to be a nut that is compatible with being welded to the pan. You will thread the nut over the bolt you chose as the plug, then stick the bolt through the hole in the side of the pan and rest it against the bottom of the pan with the nut flat against the side of the pan, and tack weld the nut in place so you can let go of the bolt. Finish weld the nut and make sure you can thread the bolt in and out of the pan. Then comes the part that lets the pan sit flat against the bellypan of the car. Using a cutoff wheel against the bottom of the oil or transmission pan slice off the part of the bolt and nut that stick out past the bottom surface of the pan. Just for insurance you might want to run an extra bead of weld on the part of the nut that was cut where it joins the pan if there is no weld showing, to prevent seepage. Then grind the weld flush with the bottom of the pan.

Now the design of the pan for the engine oil is going to be a little tricky, since it is two pieces that bolt together on the engine and the drain will have to somehow not interfere with the function of the bottom flange that holds the bottom of the pan after the pan is bolted to the bottom of the engine, since the bolts that hold the pan to the engine are inside the oil pan when it is installed. Somehow I have to get the bottom of the nut flush and the bolt resting against the inside of the pan, with the bottom being bolted to a flange around the bottom. Or I can move that flange to the top, the part that bolts against the engine, and do the drill the hole in the side routine like it was a regular oil pan that bolted up from the outside of the engine. The bottom will have to be built like a regular oil pan instead of just a flat plate that bolts to the bottom of the pan. Still easier than welding tubes for access to the bolts that hold the pan to the block on a pan with huge kick-outs to give the engine oil room to be flung from the crankshaft. There was an episode of Engine Masters that used a pan that had the mounting bolts on the inside and that pan actually made more horsepower than a deep sump pan without kick-outs but was way deeper than the pan with the kick-outs. I would link to it but unless you have a subscription to Motor Trend On-Demand you won’t be able to see it.

So anyway, that’s the kind of stuff that sometimes keeps me awake at night, or haunts my dreams (yes I have dreams of making car parts, and no I don’t know what that means if anything). Happy Fourth of July to those who celebrate it.

Does it count as sleeping at night if you went to bed in the middle of the afternoon?

OK did the filing unemployment insurance thing for the former tenant thing and did the falling asleep on the couch right after at about 1430 thing. Got to bed about 1500 and was out almost immediately because the sleepytime cocktail hit almost immediately. I’m not sure when I woke up because it was dark outside and I normally judge time by seeing how the shadows fall on the fence around the north side neighbor’s yard. Mrs. the Poet got off the couch and in the bed at about 0230 so I got out of bed at 0245.

While I was drifting back and forth between awake and asleep but lucid dreaming, I contemplated an AWD Electric T-Bucket. The motor I mentioned for the electric A-Mod racer a few posts back is actually intended for a street vehicle and has PTO from either end, partially for ease of installation and partially to allow running as a “stack” of motors, or as I like saying “some from column A…”. Well I was thinking that if I could take power off either end why not both ends? Run the motor on the centerline and power the front wheels of the front output shaft of the motor and the rear wheels off the rear output shaft, and use some kind of decoupler to unhook the front wheels when the front axle is trying to run at a higher speed than the rear axle because of the geometry of the drive system.

Sidebar, this is a thing caused by steering the front wheels on a two axle system and had nothing to do with which end is driven. The front wheels run slightly further than the rears because of geometry, and the wheel on the outside of a turn takes a longer path than the inside wheel, and if no allowance is made for this either the tires wear out faster or more energy is consumed, and usually both at the same time. The usual allowance is to have one end or the other free-wheeling which is the natural occurrence when only one axle gets drive, and a differential on the driven axle for the inside-outside speed difference. Where it gets tricky is when both axles are driven with a solid connection between the two. Most of the time a solid connection is good, ensuring all the power gets to the road that the road surface can hold even if there is slippage at one corner. This even applies when turning, which is why welded rear differentials work most of the time except in low power and high traction situations. Ironically there is much more stress on the welds from just gentle driving on pavement than there is racing on the same surface. Back to the e-Bucket.

As I was saying, why not pull power from both ends of the motor and powering both axles, and use something to unhook the front axle when going around turns on high traction surfaces? Something like the mechanism from a locking differential? Well a big part of how that works is the different loads between the axles and we don’t have that here, we have power coming in on one side and going out the other. There is also lockers that use electric or pneumatic driven clutches to unlock one side or the other on demand that might work, since we have lots of electricity to run the electric kind. The trick would be sensing when the front is driving the system instead of being driven. The locking and unlocking is existing technology and so is torque sensing on a rotating shaft, so the trick then becomes integrating the two and running the unlock and relock fast enough to appear seamless. And some kind of logic that can tell when the front wheels are no longer trying to turn faster than the front and can be solidly connected to the output shaft again. So, the system will require torque and speed sensing from both sides of the locker, torque sensing to unlock and speed sensing to relock. Or, and this just came to mind as I was getting ready to put this to bed and do something else, adjust the logic to use the direction of torque from the sensor on the axle side of the locker to tell when the front wheels are driving the motor instead of vice-versa and only have one torque sensor in the system to reduce costs.

Second sidebar, on RC cars this is done with a one way sprag that only transmits power, well one way. While this is great for model cars that can be picked up and moved from a situation requiring travel in the opposite direction, it’s obviously no good for a real car that has to be driven in reverse. But it does provide a working mechanical solution to the problem.

The fun part comes from trying to do this on a “disposable income from SS” budget, we are literally talking years of saving just to buy the torque sensors at Ali Baba prices, forget retail in the US prices. The speed sensors are literally just a few bucks because there are like 2 of them in every LS engine sold and as many as 8 in the more exotic engine designs that have 4 cams and independently change their timing as well as have sensors watching the input and output speed of the transmission to track the health of the friction materials. I’m talking less than $100 for all the speed sensors for the system. But the torque sensors that will not twist in two under the shock loads start at a kilobuck and go up from there, and this system requires a minimum of two and a high probability of 3 total for best system performance. The controller is the easy part, an Arduino has way more processing power than this requires. It could balance your checkbook between system inputs and outputs, and still not miss anything. If anything it’s too fast and powerful, the conditions we need to track change over a few hundredths of a second, and the Arduino works at several million ops per second, literally more than a million times faster than needed or to quote the Wiki: “the ATmega microcontroller can execute up to 16 million instructions per second,” and we need to run a few hundred times a second to not get ahead of the physical system. This is why we can get good control over a mechanical system with a cheap electronic system. The old Moore’s Law “processing power per $ doubles every “x” years” (before inflation) from the mid XX century has brought us to the point that it is cheaper to use a computer than it is to depend on mechanical controls. The cost limit is now the physics of the sensors and other things needed to connect the processor to the real world.

Now the fun part of this is putting extra weight on the passenger side to balance the weight of the driver and not having it just be ballast. That can be done with a driver-weight battery pack on the passenger side of the vehicle, either an add-on, or just having that much weight naturally on the passenger side when all the bits and pieces are put in place. My preference is to have the weight balance out when all the bits are where they are supposed to be rather than adding another battery pack to go racing. Actually my preferred option is to remove a driver weight of battery from the driver’s side of the car, and call it an extended range pack to go racing, and use the BMS to pull power from the cells that were taken out to race when driving back from the race. The idea is usually to remove weight before racing, not add except to meet minimum weight rules. Since F=M*A for a given F you need to reduce M to increase A, increasing M just doesn’t make sense. The other fun part is you can make the pack low in the car to get the CG low without making the Polar Moment high, and you can build the pack around objects so they can mount as low as possible. And when objects are already as low as possible, if they don’t need to have cooling airflow it’s also sometimes possible to mount the battery underneath some things to further lower CG height. Anywho, this is what can happen when you change from an IC engine and support systems to electric power.