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Nook balancing a automobile has been a type of issues that appeared off-limits to the common automotive DIY fanatic.
You will discover a variety of digital scales from a velocity store like Summit Racing; nonetheless, a ‘respectable’ set will set you again at the least $1,000, and a higher-quality set will price double that.
You should use the lavatory scale hack, the place you jack the automobile up and decrease it on a set of low-cost lavatory scales. I even tried this again in 2020 with Mission Tough, my ER34 Nissan Skyline GT-T, and had… average success.
To do that appropriately, you need to guarantee you might be engaged on a superbly flat floor. The automobile must be as stage as potential whereas on the scales – i.e., on some form of platform – and also you want a option to loosen up the arms after jacking the automobile 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 mistaken. One among my scales broke as a consequence 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 have been nonetheless the one viable method.
Or Is It…
Quick-forward just a few 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 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 have got a supporting block by which a beam rests on. The supporting block is a ‘X’ distances away from the lavatory scale. You’ll then place the tire on the beam, and that weight transfers throughout the beam to the size. The burden can be considerably smaller, which shouldn’t max out the size. If you recognize 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 automobiles, 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 depart rather a lot to want.
I subsequent created a platform that might have the beam stage with the lavatory scale. I recorded the size (92.2cm). We are going to name this ‘L’.
Then I positioned the battery on the beam and received 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 common 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 full size of the beam. If you recognize 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 realized this on the full-size check, however I attempted to maintain as many numbers after the decimal place as potential 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 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 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 Mission Tough. I received my lavatory scale out and ensured the beam and platform have been stage…
…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 lavatory 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 strive that earlier than reducing the beams to a smaller dimension. I used to be nonetheless afraid that if I had lower 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 may 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 completed 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 below 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 the whole lot that I noticed there was a better option to decide the tire’s contact patch…
You’ll be able to 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 greater within the rear (10cm). These can 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, maintain as many locations as potential within the calculations. I saved the 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 completed! Subsequent, roll the automobile again a bit, transfer the size to the following tire, drive up, and crunch these numbers.
When you get the hold of it, every nook takes about 5 minutes. In fact, if 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 can do that entire course of in a single shot.
Listed below 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 received that quantity (moist, dry, full tank of gasoline, and many others.), however I shouldn’t be too far off.
Think about a brilliant light-weight (learn: barely flimsy) FRP entrance hood, no spare tire, and some different bits right here and there, and the full calculated weight is fairly rattling shut. Ideally, I’d take Mission 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 Mission Tough‘s steadiness? A nook steadiness exhibits your car’s weight distribution, which might then be manipulated to optimize dealing with. For many who are lifeless critical about getting one of the best lap time, you’ll manipulate this distribution by bodily eradicating weight or including ballast in strategic areas to get nearer to that ‘ideally suited’ 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 identical time, it isn’t potential to vary the entrance, rear, left, and proper weight percentages. So until 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%
Be aware: I didn’t simulate my physique weight (84kg/185lbs) or disconnect the sway bars. In good follow, 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 unintended 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 automobile. We’re nonetheless doing this with lavatory scales no matter what number of variables we restrict.
What we can do is get our cross-weight to a super 50/50 scenario. At present:
(Entrance Proper (kg) +Rear Left (kg)) / Whole Weight (kg) = Cross Weight %
(351.83kg+340kg) / 1439.27kg =Cross Weight %
48.07% = Cross Weight %
Anytime you’ve gotten a cross weight above 50%, you’ve gotten a wedge. Something under 50%, like Mission Tough, is a reverse wedge. Understanding this, you possibly can comply with these guidelines to regulate the experience peak to get nearer to a 50/50 distribution.
RAISING anyone nook will INCREASE the load on that nook and barely have an effect on all different corners.
LOWERING anyone nook will DECREASE the load 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 lowering the peak on the Entrance Left – Rear Proper. That is the place the whole lot turns into hella-tedious. You additionally have to determine how set you might be within the car’s experience peak. Once more, the stiffer the springs, the stronger the influence minor changes will make. Nevertheless, if you’re lifeless set on how the automobile appears, you might 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 highway, I’ll do that once more and intention to get that fifty/50 cross weight distribution. I additionally need to check just a few extra suspension tasks and experiments.
This goes to indicate that in the event you’re not afraid of a bit of little bit of math, you possibly can unlock potential and knowledge that might in any other case be locked behind costly tools. It did take some refinement, and this nonetheless gained’t be as correct as a great 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
