Project Rough: DIY Corner Balance Take 2 – With Physics!

Nook balancing a automotive has been a kind of issues that appeared off-limits to the common automotive DIY fanatic.

You will discover a variety of digital scales from a pace store like Summit Racing; nevertheless, a ‘first rate’ set will set you again not less than $1,000, and a higher-quality set will value double that.

You should use the toilet scale hack, the place you jack the automotive up and decrease it on a set of low cost toilet scales. I even tried this again in 2020 with Project Rough, my ER34 Nissan Skyline GT-T, and had… reasonable success.

To do that accurately, it’s essential to guarantee you might be engaged on a superbly flat floor. The automotive must be as degree as doable whereas on the scales –  i.e., on some kind of platform – and also you want a solution to calm down the arms after jacking the automotive as much as transfer the scales into place.

It’s fairly the dance, and there are a bunch of variables the place issues can go unsuitable. One in all my scales broke as a consequence of going far past the utmost weight restrict of 130kg (286lbs).

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

Or Is It…

Quick-forward a couple 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 Technique to Weigh Your Automobile. And it’s Cheaper, Too. discusses how you need to use leverage and a little bit of math to calculate the burden 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 dimensions. The load might be considerably smaller, which shouldn’t max out the dimensions. If you recognize the space from the supporting block and the space to the dimensions, you possibly can calculate the precise weight with the worth proven by the dimensions.

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 interior 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 loads to need.

I subsequent created a platform that may have the beam degree with the toilet scale. I recorded the size (92.2cm). We’ll name this ‘L’.

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

In contrast to the drawing, the drive of the battery isn’t a single level on the beam, thus I made a decision to take the common of utilizing a distance from in entrance of and behind the battery – one closest to the dimensions (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 whole size of the beam. If you recognize the space relative to the beam, you possibly can divide that quantity by the burden on the dimensions to calculate the burden. I do know it’s getting a bit wild right here…

Fl=Lf /L

Fl=27.25cm / 92.2cm

Fl=.2955

I realized this on the full-size check, 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 are able to lastly calculate the burden 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 check. With this stable proof of idea, it was time to scale up.

Full Steam Forward

With Mission 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 elements, which threw my alignment out of whack.

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

I used to be now able to nook stability Mission Tough. I obtained my toilet scale out and ensured the beam and platform have been degree…

…And instantly bumped into an issue. Though I had calculated that if my bar have been 184cm lengthy, I’d have loads of area to drive on the beam and never max out the toilet scale, the burden 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 initiatives at that very same 184cm size, I made a decision to attempt that earlier than chopping the beams to a smaller dimension. I used to be nonetheless afraid that if I had minimize the beams too brief and pushed too far on the beam, it could max out the dimensions, and I’d threat 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 dimensions nearer to the automotive 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 dimensions was 42.5kg (93.7lbs) (Fa).

It was now time to calculate the assorted lengths as I had performed with the battery. Nevertheless, it was tougher to inform the place the contact patch was on the beam. I used a small sq. ruler and slid it beneath the tire till it couldn’t transfer anymore, after which marked the beam. I did this for either 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 things that I spotted there was a better solution to decide the tire’s contact patch…

You possibly can press a chunk of flat scrap wooden wherever 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 larger within the rear (10cm). These could be the Lm values used within the calculations.

Seeing that I can instantly 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 all the quantity on my calculator (0.099722992). Then, we are able to calculate the drive of the automotive at that nook.

F= Fa / Fl

F= 42.5kg.0997

F= 426.18kg

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

When you get the hold of it, every nook takes about 5 minutes. After all, when you’ve got a number of scales and beams (I used to be nonetheless cautious and determined to not get extra beams to do that), you may 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. Based on the shakensho, my Skyline ought to weigh 1,460kg (3,218lbs). I’m undecided how they obtained that quantity (moist, dry, full tank of fuel, and so forth.), 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 whole calculated weight is fairly rattling shut. Ideally, I’d take Mission Tough to a spot the place I can drive and weigh the automotive, however that should wait till it’s handed its shaken inspection.

What can we do with this newfound details about Mission Tough‘s stability? A nook stability reveals your automobile’s weight distribution, which may then be manipulated to optimize dealing with. For many who are lifeless severe about getting the most effective lap time, you’d manipulate this distribution by bodily eradicating weight or including ballast in strategic places to get nearer to that ‘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 decreasing it. Nevertheless, as one motion impacts all the opposite corners on the similar time, it isn’t doable to vary the entrance, rear, left, and proper weight percentages. So except I bodily take away, shift, or add weight, Mission Tough could have these values.

Entrance Weight % =54.06% 

Rear Weight % =45.95%

Left Weight % =53.23%

Proper Weight % =46.77% 

Notice: I didn’t simulate my physique weight (84kg/185lbs) or disconnect the sway bars. In good apply, you completely ought to do that when establishing a race automotive or a automotive 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 Mission Tough has adjustable sway bar finish hyperlinks, and I’ve dialed them in for no preload, it isn’t a race automotive. We’re nonetheless doing this with toilet scales no matter what number of variables we restrict.

What we can do is get our cross-weight to an excellent 50/50 state of affairs. At the moment:

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

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

48.07% = Cross Weight % 

Anytime you will have a cross weight above 50%, you will have a wedge. Something beneath 50%, like Mission Tough, is a reverse wedge. Realizing this, you possibly can observe these guidelines to regulate the journey peak to get nearer to a 50/50 distribution.

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

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

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

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

Thus, I ought to work on growing the peak on the Entrance Proper – Rear Left or reducing the peak on the Entrance Left – Rear Proper. That is the place all the things turns into hella-tedious. You additionally must determine how set you might be within the automobile’s journey peak. Once more, the stiffer the springs, the stronger the influence minor changes will make. Nevertheless, in case you are lifeless set on how the automotive seems to be, you may need to compromise that fifty/50 distribution.

And that’s so that you can determine. For me, as soon as I get Mission Tough again on the street, I’ll do that once more and goal to get that fifty/50 cross weight distribution. I additionally need to check a couple of extra suspension initiatives and experiments.

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

Digital scales would nonetheless be glorious, although…

Ron Celestine
Instagram: celestinephotography