Undertaking Tough: DIY Nook Steadiness Take 2 – With Physics!

Nook balancing a automobile has been a type of issues that appeared off-limits to the typical automotive DIY fanatic.

Yow will discover a variety of digital scales from a velocity store like Summit Racing; nonetheless, a ‘respectable’ set will set you again at the very least $1,000, and a higher-quality set will value double that.

You should utilize the toilet scale hack, the place you jack the automobile up and decrease it on a set of low-cost rest room scales. I even tried this again in 2020 with Undertaking Tough, my ER34 Nissan Skyline GT-T, and had… average success.

To do that accurately, you will need to guarantee you’re engaged on a wonderfully flat floor. The automobile must be as stage as doable whereas on the scales –  i.e., on some kind of platform – and also you want a method to chill out the arms after jacking the automobile as much as transfer the scales into place.

It’s fairly the dance, and there are a number of variables the place issues can go improper. One among my scales broke on account of going far past the utmost weight restrict of 130kg (286lbs).

So, measuring the load in any respect 4 corners, making any changes, and having to carry out the entire circus once more made this system removed from sensible. It appeared like devoted digital scales had been nonetheless the one viable method.

Or Is It…

Quick-forward a number of years, and I found a YouTube channel known as SuperfastMatt. Matt’s movies are as humorous as they’re insightful, and one known as I Invented a Higher Strategy to Weigh Your Automotive. And it’s Cheaper, Too. discusses how you should utilize leverage and a little bit of math to calculate the load at any given nook.

You’ve a supporting block during which a beam rests on. The supporting block is a ‘X’ distances away from the toilet scale. You’d then place the tire on the beam, and that weight transfers throughout the beam to the size. The burden shall be considerably smaller, which shouldn’t max out the size. If you already know the space from the supporting block and the space to the size, you possibly can calculate the precise weight with the worth proven by the size.

Seeing that I nonetheless had my analog scales from the primary try and a workable platform I designed for aligning vehicles, I figured I’d let my internal engineer again out to play and provides this a shot. Earlier than going full ship, I made a decision to check it on a small scale with an previous battery from the household Honda Stepwgn.

I first weighed the battery to know my goal— roughly 9.8kg (21.6lbs). The decision on these scales go away quite a bit to need.

I subsequent created a platform that will have the beam stage with the toilet scale. I recorded the size (92.2cm). We are going to name this ‘L’.

Then I positioned the battery on the beam and bought a studying of two.9kg (6.4lbs). Nice! I’ll name that ‘Fa’ for now. Now, to calculate the distances.

Not like the drawing, the drive of the battery isn’t a single level on the beam, thus I made a decision to take the typical of utilizing a distance from in entrance of and behind the battery – one closest to the size (L2) and one closest to the supporting block (L1). I’d subtract the 2 and divide it by 2.

(L2-L1) /2 = Lm

(39cm-15.5cm) / 2 = Lm

11.75cm = Lm

With what I’m calling ‘Lm’, you possibly can subtract that quantity from L2 and get the battery’s ‘heart’ level of drive. I’ll name this worth ‘Lf’.

L2-Lm= Lf

39cm-11.75cm= Lf

27.25cm= Lf

With Lf now decided, I can divide it by the overall size of the beam. If you already know the space relative to the beam, you possibly can divide that quantity by the load on the size to calculate the load. I do know it’s getting a bit wild right here…

Fl=Lf /L

Fl=27.25cm / 92.2cm

Fl=.2955

I discovered this on the full-size take a look at, however I attempted to maintain as many numbers after the decimal place as doable to extend accuracy. It does make a distinction. With Fl, we will lastly calculate the load of F.

F= Fa / Fl

F= 2.9kg. / 2955

F= 9.81kg

That is an error of 0.10%, which greater than proves the accuracy of this mathematical take a look at. With this strong proof of idea, it was time to scale up.

Full Steam Forward

With Undertaking Tough able to go, I made a decision to do an alignment, as I’d use the identical platform rig for the nook balancing.

For shaken, I needed to reinstall some OEM components, which threw my alignment out of whack.

Bringing the automobile to my home from its storage spot was one of many sketchiest drives of my life. I adjusted my laser stage to stage the platform with shims.

I used to be now able to nook steadiness Undertaking Tough. I bought my rest room scale out and ensured the beam and platform had been stage…

…And instantly bumped into an issue. Though I had calculated that if my bar had been 184cm lengthy, I’d have loads of area to drive on the beam and never max out the toilet scale, the load deflected the beam a lot that it touched the bottom. Two extrusion bars weren’t going to work.

However how about three? Seeing that I had further extrusions from varied tasks at that very same 184cm size, I made a decision to attempt that earlier than chopping the beams to a smaller measurement. I used to be nonetheless afraid that if I had minimize the beams too quick and pushed too far on the beam, it will max out the size, and I’d danger breaking them.

Even with three beams in place, they nonetheless bowed like loopy. This wasn’t going to work. I then remembered that I might transfer the size nearer to the automobile and use a wedge piece of wooden for the beams to relaxation on to switch the load, successfully shorting the size of the beams. All I wanted to do was zero out my scale and check out it.

With my present size (L) now shortened to 108.3cm from 184cm, the beam hardly deflected and will proceed with the experiment. The studying on the size was 42.5kg (93.7lbs) (Fa).

It was now time to calculate the assorted lengths as I had achieved with the battery. Nevertheless, it was harder to inform the place the contact patch was on the beam. I used a small sq. ruler and slid it underneath the tire till it couldn’t transfer anymore, after which marked the beam. I did this for each side to get my L2 and L1 calculations.

(L2-L1) / 2 = Lm

(20.5cm-1.1cm) / 2 = Lm

9.7cm = Lm

It wasn’t till I completed measuring all the pieces that I spotted there was a neater method to decide the tire’s contact patch…

You may press a chunk of flat scrap wooden anyplace in opposition to the tire and mark out the L2 and L1 of the tire contact patch utilizing the identical technique. Amazingly, this technique matched my numbers for the entrance tires (9.7cm) however was barely increased within the rear (10cm). These could be the Lm values used within the calculations.

Seeing that I can straight calculate Lm from the tire contact patch, my new equation is now this.

L2-Lm = Lf

20.5cm -9.7cm = Lf

Lf = 10.8cm

We now take Lf and calculate the drive relative to the space on the beam.

Fl=Lf / L

Fl=10.8cm / 108.3cm

Fl=.0997

Once more, hold as many locations as doable within the calculations. I saved your complete quantity on my calculator (0.099722992). Then, we will calculate the drive of the automobile at that nook.

F= Fa / Fl

F= 42.5kg.0997

F= 426.18kg

And identical to that, one nook is finished! Subsequent, roll the automobile again a bit, transfer the size to the subsequent tire, drive up, and crunch these numbers.

When you get the hold of it, every nook takes about 5 minutes. In fact, in case you have a number of scales and beams (I used to be nonetheless cautious and determined to not get extra beams to do that), you would do that complete course of in a single shot.

Listed here are the values that I got here up with after all of the calculations. In line with the shakensho, my Skyline ought to weigh 1,460kg (3,218lbs). I’m unsure how they bought that quantity (moist, dry, full tank of fuel, and so on.), however I shouldn’t be too far off.

Think about an excellent light-weight (learn: barely flimsy) FRP entrance hood, no spare tire, and some different bits right here and there, and the overall calculated weight is fairly rattling shut. Ideally, I’d take Undertaking Tough to a spot the place I can drive and weigh the automobile, however that should wait till it’s handed its shaken inspection.

What can we do with this newfound details about Undertaking Tough‘s steadiness? A nook steadiness exhibits your automobile’s weight distribution, which might then be manipulated to optimize dealing with. For many who are useless critical about getting the most effective lap time, you’ll manipulate this distribution by bodily eradicating weight or including ballast in strategic places to get nearer to that ‘very best’ 50/50 distribution entrance to again and left to proper.

We are able to manipulate how a lot weight a nook receives by elevating or reducing it. Nevertheless, as one motion impacts all the opposite corners on the similar time, it isn’t doable to alter the entrance, rear, left, and proper weight percentages. So until I bodily take away, shift, or add weight, Undertaking Tough could have these values.

Entrance Weight % =54.06% 

Rear Weight % =45.95%

Left Weight % =53.23%

Proper Weight % =46.77% 

Word: I didn’t simulate my physique weight (84kg/185lbs) or disconnect the sway bars. In good observe, you completely ought to do that when organising a race automobile or a automobile with extremely stiff springs. Minor tweaks could have a much bigger impact, and also you don’t need unintentional preload within the sway bars. Though Undertaking Tough has adjustable sway bar finish hyperlinks, and I’ve dialed them in for no preload, it isn’t a race automobile. We’re nonetheless doing this with rest room scales no matter what number of variables we restrict.

What we can do is get our cross-weight to a really perfect 50/50 scenario. At the moment:

(Entrance Proper (kg) +Rear Left (kg))  / Whole Weight (kg) = Cross Weight % 

 (351.83kg+340kg)  / 1439.27kg =Cross Weight % 

48.07% = Cross Weight % 

Anytime you have got a cross weight above 50%, you have got a wedge. Something under 50%, like Undertaking Tough, is a reverse wedge. Realizing this, you possibly can comply with these guidelines to regulate the journey top to get nearer to a 50/50 distribution.

RAISING anybody nook will INCREASE the load on that nook and barely have an effect on all different corners.

LOWERING anybody nook will DECREASE the load on that nook and barely have an effect on all different corners.

Cross weight ABOVE 50% = DECREASE weight (top) on FR/RL or INCREASE weight (top) on FL/RR. – Wedge

Cross weight BELOW 50% = INCREASE weight (top) on FR/RL or DECREASE weight (top) on FL/RR – Reverse Wedge

Thus, I ought to work on rising the peak on the Entrance Proper – Rear Left or lowering the peak on the Entrance Left – Rear Proper. That is the place all the pieces turns into hella-tedious. You additionally have to determine how set you’re within the automobile’s journey top. Once more, the stiffer the springs, the stronger the influence minor changes will make. Nevertheless, in case you are useless set on how the automobile seems, you may need to compromise that fifty/50 distribution.

And that’s so that you can determine. For me, as soon as I get Undertaking Tough again on the street, I’ll do that once more and intention to get that fifty/50 cross weight distribution. I additionally need to take a look at a number of extra suspension tasks and experiments.

This goes to indicate that if you happen to’re not afraid of a little bit little bit of math, you possibly can unlock potential and knowledge that will in any other case be locked behind costly tools. It did take some refinement, and this nonetheless received’t be as correct as set of digital scales, however in contrast to my first try at nook balancing with scales, it was successful.

Digital scales would nonetheless be glorious, although…

Ron Celestine
Instagram: celestinephotography