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Thread: Unequal length links, looking for feedback

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Old 10-31-2020, 06:01 PM   #1
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Default Unequal length links, looking for feedback

I'm working on a Tube buggy and I'm running out of space for my front upper links. Right now I have it mocked up with upper links that are 3/4 the length of the lowers.







My concern is this being bad for geometry, but I cant seem to find a good answer for whether its bad geometry or if the main concern is how the pinion angle is effected.


I've had a look at the shifting pinion angle an I'm okay with it, it only shifts a tiny amount.



I'm trying to mount it in a location that puts it inline with where it would be mounted if it were longer. I'm also planning to space it inwards to match the angles of the lower links.


A few more details, if I shifted the tranny to the left I could clear the links and use a full length upper link.



But If I do shift the tranny to the left I have driveshaft clearance issues.



My alternative plan is a set of long kinked links, like a gradual S bend. Though these will not match the angle of the lowers as they will be spread farther apart.



TLDR: Are unequal length links to be avoided for any reason other than its effect on pinion angle?



Any feedback would be appreciated

EDIT: I think I found a pretty good video from busted Knuckles that goes over differences and Anti squat values stay the same and the main difference is in caster changes and pinion angles. So I think I'll stick with the setup I have mocked up.


Both of these a great videos:
https://www.youtube.com/watch?v=BTWZgVx8Y6o
https://www.youtube.com/watch?v=UzayUxQCWaY

Feedback is still welcome though

Last edited by HumboldtEF; 10-31-2020 at 07:11 PM. Reason: Made some corrections
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Old 10-31-2020, 07:57 PM   #2
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Default Re: Unequal length links, looking for feedback

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Old 10-31-2020, 09:09 PM   #3
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Default Re: Unequal length links, looking for feedback

I think it makes sense that the angle of the uppers matters for squat/antisquat and not so much the length. I’d send it as well.

That video was interesting, I’m going to need to go back and watch the rest of it.
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Old 10-31-2020, 09:53 PM   #4
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Default Re: Unequal length links, looking for feedback

Quote:
Originally Posted by Topher Builds View Post
I think it makes sense that the angle of the uppers matters for squat/antisquat and not so much the length. I’d send it as well.

That video was interesting, I’m going to need to go back and watch the rest of it.

right on, thanks for chiming in.


This should be my last stumbling block, tomorrow progress
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Old 10-31-2020, 10:19 PM   #5
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Default Unequal length links, looking for feedback

Quote:
Originally Posted by HumboldtEF View Post
right on, thanks for chiming in.


This should be my last stumbling block, tomorrow progress

Hey man, you have a build thread for this? I’d like to follow along


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Old 11-01-2020, 07:14 AM   #6
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Default Re: Unequal length links, looking for feedback

That's pretty much the out of the box setup on the TRX4 - the front upper link is much shorter than the lowers. Seems to work decent enough.
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Old 11-01-2020, 12:59 PM   #7
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Default Re: Unequal length links, looking for feedback

It was my understanding that the lowers were for position and the uppers were for pinion angle. Their length relative to each other shouldn’t matter. The lowers will dictate what length the uppers need to be with the only variable being mounting points of the uppers. Obviously moving the frame mounts closer to center will allow for a longer link, but again in the world of cause/effect the constraint there is available real estate on the frame or skid.

I wanted my upper and lower links to be set at the same angle/parallel so I messed around with both length and mounting point until that was achieved, while also keeping an eye on pinion angle to minimize drive shaft bind.

Not sure if that helps...honestly sometimes I think there is some over-engineering on these little trucks and you can get away with things you couldn’t on a 1:1 just because they weigh almost nothing and don’t have the whole “ride quality” factor.

Last edited by Phildirt; 11-01-2020 at 01:03 PM.
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Old 11-02-2020, 08:36 AM   #8
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Default Re: Unequal length links, looking for feedback

Quote:
Originally Posted by ScaleLifeNewbie View Post
Hey man, you have a build thread for this? I’d like to follow along


Sent from my iPad using Tapatalk

Not yet but It will be up eventually.




Quote:
Originally Posted by OSRC View Post
That's pretty much the out of the box setup on the TRX4 - the front upper link is much shorter than the lowers. Seems to work decent enough.
Quote:
Originally Posted by Phildirt View Post
It was my understanding that the lowers were for position and the uppers were for pinion angle. Their length relative to each other shouldn’t matter. The lowers will dictate what length the uppers need to be with the only variable being mounting points of the uppers. Obviously moving the frame mounts closer to center will allow for a longer link, but again in the world of cause/effect the constraint there is available real estate on the frame or skid.

I wanted my upper and lower links to be set at the same angle/parallel so I messed around with both length and mounting point until that was achieved, while also keeping an eye on pinion angle to minimize drive shaft bind.

Not sure if that helps...honestly sometimes I think there is some over-engineering on these little trucks and you can get away with things you couldn’t on a 1:1 just because they weigh almost nothing and don’t have the whole “ride quality” factor.

Thanks guys! Yeah this is definitely going to be one of those "over thinking it" builds lol
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Old 11-02-2020, 11:08 AM   #9
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Default Re: Unequal length links, looking for feedback

It's been my observation that unequal length links will cause a slight pinion angle change as the suspension articulates. I think this would be because the upper and lower links are traveling in a different arc. Generally not enough angle change to worry about but becomes more noticeable as the link length difference increases. I check mine to make sure the pinion angle change is acceptable to me. Once the axle is set for the wheelbase, adjust the top link length to get a pinion angle you are happy with through the whole suspension travel. Maybe I'm just too particular about this but it keeps me busy and out of trouble.
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Old 11-02-2020, 11:55 AM   #10
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Default Re: Unequal length links, looking for feedback

Picturing that in my mind the uppers would have to be dramatically shorter than the lowers to alter pinion angle enough to create a bind, but that 's a great observation. Made me go to the garage and cycle mine again lol.
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