Tuning with Shock Angle - Part 3: PROGRESSION
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- Опубликовано: 25 июл 2024
- This is the ADVANCED version of tuning by shock angle. Learn what all those chassis mount options do to your performance!
00:00 Intro
00:33 Review
03:09 Purpose
03:32 Specialized Demo
04:30 KTM
05:48 Basics
07:17 Weight Distribution Example
10:42 Progression
11:17 Regression
13:10 Progressive Wound
13:24 Air Springs
14:35 Software
20:58 Traxxas
25:22 Associated RC10
26:52 Axial Capra
30:31 Ideal Tuning Design
30:56 RC Crawlers are Unique
31:22 What Did We Learn
31:48 Outro
Tuning Part 1
• Tuning with Shock Angl...
Tuning Part 2
• Tuning with Shock Angl...
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I am fully appreciating all the time and energy you’re putting into this, as well as the information involved
Much appreciated! It does take a surprising amount of effort. Happy you enjoy it.
A lot of people might not like this stuff but I do I think it's cool as hell
Thanks! I hoped some people would like to nerd out with me.
Fully agree 👍🏻
Great...as always.
Thanks again!
I’ve not seen many options in crawlers (mine anyway) for laying down the shock laterally. Seems maybe that could be helpful. Thanks for your excellent videos.
You can space the top of the shock inboard or outboard with thicker spacers, but you’re right it’s not a primary option on rail chassis with solid axles.
Whew! Stayed with you through most of that, lol! Shock angle is probably the most dynamic change you can make in a crawler, that is, it has the most profound effect. Add link risers and the like but you will see (and notice) the biggest change in handling following a change to the shock angle (especially considering limited spring choices in crawlers). It's why a chassis design with multiple holes, to address parameters individually, is sooo important.
Also, important to note that, in the buggy example, laying the TOP of the shocks down reduces leverage on the spring and creates a softer feel. Moving the shock out on the arm also lays the shock down but essentially has the opposite effect (something many people don't understand). This is not especially relevant on a crawler where mounting on the axle is typically not adjustable.
Then, there is preload and its affect on spring rate. Most people understand it doesn't change spring rate but not that it does change the force required to move the spring and hence, the stiffer 'feel'. It CAN be used to compensate for springs that are too soft or too hard but generally creates other issues that adversely affect handling. A subject for another day, though, for sure. Keep up the great work. 👍
Great point - moving the shock mount at the swingarm side has a very pronounced effect on spring rate and travel - more so than shock angle. That might merit it's own video and I focussed just on the top mount in this one.
No - you cannot change the force required to move a spring with preload - it's still X-force/mm no matter what the preload. All you are doing with preload is changing the ride height and the corner balance. I got into a big debate with Crawler Canyon trying to tell me about Nascar cross weight balance. This will get a dedicated video for sure (preload, not Nascar lol).
@@BoomslangSussBeg to differ with you but preload affects more than just ride height and corner weights. A preloaded spring takes more force to initiate movement resulting in a harsh ride with poor small bump absorption (i.e. 'stiffer'). Not sure what your rationale is here, it is a principle widely accepted in all industries and backed up with real world experience?
@@jerryvolpini7987 Rewatch the video at 5:48. Lets say a coil spring is rated at 1 lb / in. It takes 1lb of force to move 1in. That is the same 1lb to move 1in at all points in the springs compression. 10-20% = 1lb/in. 40-50% = 1lb/in. 90-100% = 1lb/in. If that were not true, you would not have a linear spring.
If you are sitting with your spring 0% compressed, i.e. fully extended, with preload, you first have to overcome the preload for the spring to move. If you add more preload, then you have more force to over come. BUT...this is where people get confused - no suspended vehicle is sitting on shocks that are fully extended at 0% compression. Let's say a vehicle is at 20% droop for example. At that point, any pre-load has been over come. The force to move from 20% to 30% is still 1 lb/in. The difference in additional preload is simply that you are sitting with less dropop, say 15% for example.
If you draw a graph of compression on the X axis and force on the Y axis, the slope (rise over run) is mathematically the spring rate. If you add pre-load, the slope of the graph stays the same. It shifts vertically, but the slope is unchanged. You simply cannot transform a 1 lb/in spring into a 2 lb/in spring with preload.
If this doesn't make sense I can draw said graphs and put on them on the Facebook page.
You know I got your back @jerryvolpini7987 . I will make a video on this topic shortly. For sure it's misunderstood, even by some experienced individuals.
@@jerryvolpini7987 No, sorry, but thats not true ....springrate is springrate on a linear spring...no matter what.
Hey, another awesome video, thanks! It's pretty clear how the perceived spring ratio changes when you adjust the upper shock position. I'd like to see how the leverage ratio changes when you switch to a different lower shock position while keeping the upper position the same. Intuitively, when the shock is mounted closer to the wheel hub, it has less leverage, but the shock angle also decreases, resulting in a lower spring ratio.
So, which one has more impact on the final suspension stiffness: the lever distance or the shock angle? I'm particularly interested in double wishbone suspension like on the Traxxas Slash from this video.
Great question. On double wishbone suspension, the leverage position on the swing arm has a more pronounced effect on wheel travel and stiffness. The upper chassis position is for finer tuning. On a typical crawler all you have is the chassis mount position to tune with.
Excellent, excellent video. I’m not a crawler guy but I have a B74.2 and I’m interested in setup theory at least as much as driving itself.
I’ve thought the shock angle (as adjusted at the tower) to be a significant change because of the progression rate but it appears to be a lot more about the effective rate through the whole travel.
This shouldn’t be a surprise because all of the shock positions are fairly upright in relation to the arm and the angle doesn’t seem to change a lot through the travel.
As a funny comparison, I have a Kyosho Scorpion and the front suspension is ”progregressive”, for lack of a better word. It starts with the shock leaning toward the lower arm hinge but the angle reaches 90 degrees when compressed and goes beyond that when compressed further. The arms are relatively short so the angular change is pronounced. This is a terrible design for this application because the damping and spring rate soften and make the suspension ”bottomless” when you would really want things to ramp up before the chassis hits the track.
P.S. I fully agree with the observation that Traxxas has the rate change backwards.
Sounds like the Kyosho has a RE-gressive setup - rarely ever a benefit on any vehicle.
Yes. It starts out as progressive but passes 90 degrees and becomes regressive.
I’m looking into ways to fix that as I don’t mind not being ”period correct” and you could have done the same thing in the ’80s if you understood geometry.
Thank you for this video! i was waiting with excitement for you to post it :)
You covered it so well and in a very digestible manner. And i liked you showed some actual measurements of progressions from actual cars, it was very helpful.
You didnt cover WHY the angle effects progression, i guess not to over-complicate too much, and this is the area i feel i have gaps in my understanding.
Let me share how i currently understand the reason of how the geometry effects spring progressiveness, by imagining whats going on, and i think its a combination of 2 geometrical effects:
1. The shock angle changes to a more stood-up angle (compared to the arm) as the suspension compress, which adds progression
2. Depending on the relative lengths of the shock compared to the length of the arm (from the base to where it meets the shock), it can either
- add progression if the shock is longer, which is compounded with the progression from the point i described above.
- be the same length so it has no effect and only the first point is adding progression.
- the shock can be shorter than the arm (like on most crawlers) which adds regression, which together with the first point it can either cancel out the progression or go into regression, which i think is what happens on your Capra example.
Again thanks for the info you share!
Short links and long shock produce the pronounced curvature that creates progression (moto and mountain bike). Long links and short shocks produce the straight line lever curves (crawlers). The Capra is in sort of a weird zone where it goes regressive and it's not totally intuitive unless you look at the full 4-bar linkage in software because there are a lot of variable at play.
I figured 30 min was more than most could handle! 💀
@@BoomslangSuss And when the link/shock length are the same?
@@yonicozac Generally speaking, if the angle between the shock and link is obtuse (>90 deg) it will be regressive. If it is acute (
I'm not a crawler person but wouldn't you want the spring rate to be progressive or regressive depending on whether you were climbing or descending in order to keep the centre of mass as low as possible?
That’s an interesting thought exercise. You can’t change progression regression on the fly, but it would probably make sense to have your rear wheels be progressive when climbing and regressive when descending to somewhat counteract the weight bias at different pitches.
Are you related to Ned Overend?