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01-21-2014, 12:31 PM | #41 |
RCC Addict Join Date: Mar 2013 Location: Oklahoma City
Posts: 1,685
| Re: Does a bend in a link effect the geometry of the suspension?
With the link bends facing downward, can you flip the rig over and replicate the suspension behavior from the first video? Essentially, using the forces applied during "reverse" rotation/axle wrap? (I know you don't use reverse, I'm curious...) |
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01-21-2014, 01:06 PM | #42 | |
Pebble Pounder Join Date: Nov 2013 Location: Here
Posts: 150
| Re: Does a bend in a link effect the geometry of the suspension? Quote:
https://lh6.googleusercontent.com/-M...ity_offset.jpg | |
01-21-2014, 01:37 PM | #43 |
Suck it up! Join Date: Mar 2008 Location: Arkansas
Posts: 11,652
| Re: Does a bend in a link effect the geometry of the suspension?
Cool. Now give it a crazy bend like what was seen in the videos.
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01-21-2014, 03:05 PM | #44 |
Rock Crawler Join Date: Feb 2013 Location: york
Posts: 707
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After watching the video it dawned on me that with the bend towards the uppers the longer straight part of the link attached to the axle the forces of the axle transfer through the long straight part first which turns the bend into a lever on the shorter straight part of the link connected to the upper. So in short the force doesn't travel in a straight line from rod end to rod end. Sent from my C811 4G using Tapatalk |
01-21-2014, 03:59 PM | #45 |
Pebble Pounder Join Date: Jan 2014 Location: In the Middle
Posts: 135
| Re: Does a bend in a link effect the geometry of the suspension? |
01-21-2014, 07:00 PM | #46 | |
RCC Addict Join Date: Apr 2009 Location: Token's life matters
Posts: 1,836
| Re: Does a bend in a link effect the geometry of the suspension? Quote: Completely wrong. Not exactly a nice cad drawing, but the idea is there. If the black dots were exactly the same distance apart as in link ends, both links would behave the same if there was no flex and no binding. The suspension does not care if the links are bent, straight, curved, etc. The axles will follow the same path all things being equal. Now the zig zag link would need to be 100x stronger because of all the forces involved, but the axles would follow the same path no matter the shape of the link as long as they are the same length. Straight bars have the advantage of no bends to weaken the bar. That is why the upper links on most cars can be a lighter design because they are usually straight and shorter than lowers. It is basic design. I would venture to say the first video there is some sort of binding going on. Not that I would say shaking a car by the rear axle is a scientific way to design and test a suspension 4 link. | |
01-21-2014, 07:00 PM | #47 |
RCC Addict Join Date: May 2012 Location: Folsom
Posts: 1,867
| Re: Does a bend in a link effect the geometry of the suspension? This maybe more liquid dynamics than geometry, but isn't more force (suction) required when using a crazy straw than a straight one?
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01-21-2014, 07:04 PM | #48 |
I wanna be Dave Join Date: Dec 2009 Location: .
Posts: 7,967
| Re: Does a bend in a link effect the geometry of the suspension? Quote: |
01-21-2014, 07:26 PM | #49 | |
Rock Stacker Join Date: Jan 2008 Location: Victoria BC
Posts: 94
| Re: Does a bend in a link effect the geometry of the suspension? Quote:
But that doesnt help here. | |
01-21-2014, 07:51 PM | #50 |
RCC Addict Join Date: Apr 2009 Location: Token's life matters
Posts: 1,836
| Re: Does a bend in a link effect the geometry of the suspension? Nope, that would be the years of building hot rods. Hot rods that actually get driven. And drive down the road straight, handle well, and launch straight without a ton of wheel hop. And reading the books I listed earlier. The ones pictured are the 2nd set I bought. The first spent years in the shitter of my shop being read over and over. It is amazing the things that can be learned while dropping Novaks. I worked for a guy who raced pro stock drag cars and learned as much as I could from him on set up, and how to make a car hook up. It is amazing in the real world how a 1/2 a turn on a 4 link can make the .01 second difference between going to the next round and packing up and heading 1000 miles home. Jeremy is a numbers guy, he runs his designs through lots of modeling software to see what things are happening. I personally do not think it makes that much difference on these cars, they tend to be so loose anyway, but it makes sense to start out with a design that you know has a shot of doing things you intended them to do. When i see designs that stagger the upper link mount holes back and forth it makes me laugh. There is no way to account for all the things that happen when you not only move the upper links back but also up just a hair. Poor design for having any consistency, IMO. |
01-21-2014, 07:53 PM | #51 | |
Pebble Pounder Join Date: Jan 2014 Location: In the Middle
Posts: 135
| Re: Does a bend in a link effect the geometry of the suspension? Quote:
The only way a bent link would pull the same force when mounted either way is if both attaching points are on the same horizontal plane, but in this case it looks like the mounting point on the car is higher than the mounting point on the axle. Looking at the pic below, remember that force the upper link "sees" is a pulling tension force, not any type of downward weight compression force. No weight has been applied, only a twisting motion that will pull the link away from the frame. In the top illustration the point of pull is on the same plane as the point of resistance, so it wouldn't matter the orientation of the link as each situation is identical. Now in the bottom illustration, the lower black dot is the axle mount point and the higher black dot is the car mount point. Looking at the bottom illustration you can see the green link will pull down on the black dot with more force than the red link. It all has to do with vectors when the direction of the pull is on a different plane than the point of resistance. [/URL] | |
01-21-2014, 07:54 PM | #52 |
Shelf queen Join Date: Aug 2008 Location: Internet
Posts: 5,857
| Re: Does a bend in a link effect the geometry of the suspension?
Theoretically, I believe the forces should be the same upon a bent or straight link. the issue however though, is that links bend, and the forces applied to the links will differ greatly upon the whether or not a link is bent or not. Therefore the bends in the inks will absorb/deflect some of the energy applied to them. Simplest way I could describe it would be if you had a straight link between point A and pont B and had direct lnear force applied between the two points. Very little energy would be absorbed by link deflection. However, if the link between point A and point B were shaped like an "S" and the same linear force used in the first example was applied, the link would compress (whether you can visually notice it or not) and absorb some of that energy, and in the end rebound and redirect the force. Last edited by TSK; 01-21-2014 at 11:38 PM. |
01-21-2014, 08:10 PM | #53 | |
RCC Addict Join Date: Jul 2009 Location: Reno, Nv
Posts: 1,964
| Re: Does a bend in a link effect the geometry of the suspension? Quote:
1-WOW That sure is a sexy axle in the pic! 2- get that guy some paint, his motors all rusty and crap. 3- who runs rodends like that on the upper link? | |
01-21-2014, 08:18 PM | #54 |
RCC Addict Join Date: Jul 2009 Location: Reno, Nv
Posts: 1,964
| Re: Does a bend in a link effect the geometry of the suspension?
But really, the links obviously changed something in the video. I can't understand why, but it did. I am thinking that because the lower links are mounted above the axle centerline of the axle and by holding the truck by the rear axle, it puts so much pressure on the upper links it causes them to flex. Weather you can see it with the eye or not. When they flexes it might be letting the lower link mount at the axle push the lower link up causing? Could that cause squat?
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01-21-2014, 09:29 PM | #55 | |
RCC Addict Join Date: Apr 2009 Location: Token's life matters
Posts: 1,836
| Re: Does a bend in a link effect the geometry of the suspension? Quote:
The forces would act exactly the same on both diagrams. The force is going to act as is it is a straight line between the 2 black dots, no matter the path of the link. Again the 4 link bars do not care about their shape, bends, etc. As long as they do not bind, etc. They are like Rowdy, they act straight even if they are not. The bends only introduce weak spots. | |
01-21-2014, 10:18 PM | #56 |
RCC Addict Join Date: Mar 2013 Location: Oklahoma City
Posts: 1,685
| Re: Does a bend in a link effect the geometry of the suspension?
Apparently it does matter bent or straight. Wrap your minds around that! Unfortunately we aren't dealing with straight line physics, the axle is applying 2 forces on the chassis using a rotational force. However small, it's still there. Now look at the angle both setups leave the axle, that force will be altered as seen. So, IF everyone agrees it doesn't matter how they are bent or even straight, the force acts between A-B, then nothing should change. As seen in Erik's videos, crappy yes, something has changed. With the first comment accepted, rule that out and consider another variable which is what he is trying to determine to begin with. I propose a revision to the first question.....does a bent link affect performance characteristics on a crawler? That should be a resounding "YES"....it's been proven, you figure out why. P.S. What if C.A.T. Really spelled.....Dog? |
01-22-2014, 01:25 AM | #57 | |
Rock Stacker Join Date: Jan 2008 Location: Victoria BC
Posts: 94
| Re: Does a bend in a link effect the geometry of the suspension? Quote:
Another thing I was thinking. And this is purely coming from my own experiance. I realize noone runs metal rod ends, but how would the same "test" be affected by swapping to them? I'm willing to bet that it tightens right up. And along those lines, its a possibility that the tolerances between the rod ends was differant, being that they where differant links? | |
01-22-2014, 01:37 AM | #58 |
Pebble Pounder Join Date: Jan 2014 Location: In the Middle
Posts: 135
| Re: Does a bend in a link effect the geometry of the suspension? |
01-24-2014, 02:10 PM | #59 |
Rock Crawler Join Date: Dec 2005 Location: East Texas
Posts: 870
| Re: Does a bend in a link effect the geometry of the suspension?
Gotta say Erik, this is the awesome stuff I like to see on this board. Challenging math and physics to try and explain why things are what they are. I'm no engineer but I believe the geometery and motion is only related to the distance from eye to eye in this situation. The bend should produce no factor other than binding. Yes, this angle is extreme and not likely my go to on future builds . But I love this test and something does need to be explained there! Maybe one of you masterminds will come up with a way to test in another controlled way? There's a reason you guys are the best at this, never leave it alone |
03-02-2014, 10:25 AM | #60 |
Quarry Creeper Join Date: Feb 2014 Location: Chapel Hill, NC, USA
Posts: 191
| Re: Does a bend in a link effect the geometry of the suspension?
I am starting a 2.2 build using the YTC DA chassis and RC4WD Bully 2 axles. The hardest thing for me to figure out being new/b to 2.2 crawlers is the lengths needed to order from VP for each suspension link. If they were all perfectly straight, roughly what lengths would be a good starting point to order? Since I will have to bend the lower links myself, which makes me nervous, what is a recommended angle and starting length for the lower fronts and then the lower back links? What should the final point to point length be after a bend? I tried to find a source for pre-made bent links in the vendor's section, but have not had any luck yet. Any advice or links to other threads would be most appreciated! |
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