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Old 09-26-2020, 01:35 PM   #1
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Default Setting up front suspension

Is there a guide for setting up front suspension when making a custom build?

I figure you want the panhard bar on the front to be parallel to the axle line, and same with the steering link.
How important is pinion angle?
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Old 09-30-2020, 07:42 AM   #2
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Default Re: Setting up front suspension

Pinion angle setting is going to depend if your axles allow you to clock the c-hubs so you can independently set your pinion angle from your caster. I like at least 10 degrees of caster, ideally with the pinion pointing up towards the trans output. If you can't separately adjust your caster from pinion angle then just dial as much caster as your comfortable with as long as your drive shaft pivots dont hang down below the lower links and doesn't bind at full drop and your all set.
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Old 11-17-2020, 09:57 AM   #3
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Default Re: Setting up front suspension

To your panhard bar question, ideally the panhard bar would be parallel with the axle at ride heigh but this is not normally possible on a crawler given the long suspenion travel and limited space. But more important is to have the panhard bar and steering drag link as parallel as possible. This will reduce bump steer which can be pretty annoying.

Last edited by Inspector86; 11-29-2020 at 05:16 PM.
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Old 11-28-2020, 01:49 AM   #4
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Default Re: Setting up front suspension

Start with I'm not an expert by any means.



As inspector said, you want the pan hard and steering link parallel.



You can adjust the length of the upper and lower links to change the pinion angle (point it towards your transfer case). And the height of the links will change your (anti)squat and dive.



If you google 3 or 4 link calculator, there is a ton of info out there. Crawlerpedia, Jeep Forums all have similar tools. Here is a video of one of the tools.

https://youtu.be/nQMrnsOAPig



I'm not sure this scales 100% though. The reason being is we can scale the dimensions but the RCs are way under weight. If it's and 8 lb RC it wold 80 lb full size. To be true scale it would be 500-600 lbs. We also have like 1,000 HP by comparison.



When you align everything don't forget the tow. You probably want a little bit of tow out to keep it tracking straight. I'm not sure you can adjust the camber and other angles? So you are probably limited to tow and caster.


Let us know how it comes out - post some pix.
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Old 12-01-2020, 02:41 PM   #5
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Default Re: Setting up front suspension

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Originally Posted by itr1275 View Post
The reason being is we can scale the dimensions but the RCs are way under weight. If it's and 8 lb RC it wold 80 lb full size. To be true scale it would be 500-600 lbs. We also have like 1,000 HP by comparison.
I'm a relative noob and can't help much with suspension geometry, but I have given some thought to scale weights, and I actually think most rigs are probably close, maybe even a bit heavy.

The thing is that we describe the scale in one dimension - a 1/10 scale truck has a wheelbase that's 10% of its 1:1 counterpart. But, if you want "realistic scale weight," that really means having roughly equivalent density. Since density is a function of weight and volume, and volume is the product of three dimensions (length, width, and height,) you have to apply the 1/10 scale three times.

The rig is 1/10 length AND 1/10 with AND 1/10 height, so if you multiply those three 1/10ths together, you should end up at 1/1000 weight. If typical scale rigs run from 5-10lbs, that would be the equivalent of 5,000-10,000lb full size trucks. Depending on what vehicles you're modelling, I think scale weight actually isn't too terribly far from where it should be.

Mind you - this is all just theoretical junk in my head, so I could be way off base. I'd be interested in hearing other opinions on this.

Anyway, sorry for drifting off topic a bit. As for the original topic, I find suspension tuning to be fascinating, but I'm certainly still too inexperienced to help anyone with it. I've stayed pretty close to stock on my RTR SCX10.2.
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Old 12-01-2020, 03:20 PM   #6
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Default Re: Setting up front suspension

^^ correct. Scale weight would be cubic so in 1:10 scale it would be 1 lb per 1,000lbs if I’m not mistaken. Keep in mind 1:10 scale for these trucks is kind of a ball park and not always a very precise representation of the 1:1s.

As far as front axle geometry, as mentioned above have your drag link and pan hard as parallel as possible to prevent bump steer.

A longer panhard will have a larger arc and therefore less axle swing, because of this I prefer pan hard mounts on the outside of the chassis rail instead of the ones that tuck under.

Pinion angle depends on driveshafts but generally you want the pinion input on the axle to be parallel with the output on the transmission/tcase.
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Old 12-06-2020, 02:22 AM   #7
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Default Re: Setting up front suspension

Quote:
Originally Posted by ebeowulf17 View Post
I'm a relative noob and can't help much with suspension geometry, but I have given some thought to scale weights, and I actually think most rigs are probably close, maybe even a bit heavy.

The thing is that we describe the scale in one dimension - a 1/10 scale truck has a wheelbase that's 10% of its 1:1 counterpart. But, if you want "realistic scale weight," that really means having roughly equivalent density. Since density is a function of weight and volume, and volume is the product of three dimensions (length, width, and height,) you have to apply the 1/10 scale three times.

The rig is 1/10 length AND 1/10 with AND 1/10 height, so if you multiply those three 1/10ths together, you should end up at 1/1000 weight. If typical scale rigs run from 5-10lbs, that would be the equivalent of 5,000-10,000lb full size trucks. Depending on what vehicles you're modelling, I think scale weight actually isn't too terribly far from where it should be.

Mind you - this is all just theoretical junk in my head, so I could be way off base. I'd be interested in hearing other opinions on this.

Anyway, sorry for drifting off topic a bit. As for the original topic, I find suspension tuning to be fascinating, but I'm certainly still too inexperienced to help anyone with it. I've stayed pretty close to stock on my RTR SCX10.2.

No worries. I love the math stuff I have forgotten so much, and it's good to go figure this stuff out once in a while.

I think you are correct. Another way to think of it is the density would remain constant.

Full size (assumed box) -> 10 ft x 5 ft x 5ft = 250 CF. It weighs 2500 lbs and the density is 10 lbs/CF.

Scale rig (1:10) 1ft x.5ft x.5 ft = .25CF. The density is 10lbs.CF so the new weight is .25 CF*10 lbs/CF = 2.5 lbs.

It would still be cool to have a 500lb RC.

I believe the HP (Watts) and speed (MPH) are linear though.

A small ESC with 40A (random guess) draw at 11.1V is 456W or .61HP. If the rig weights 8lbs the power to weight ratio is 8 Lbs/.61 HP= 13 lbs/HP. Which if this were a car could be a pretty quick car.

And 10 MPH is 100MPH scale. I'm not sure about you, but I don't like driving 100 MPH in a 4wd truck. It gets a bit weird, sort of like jumping to light speed.

Or to put in perspective it would be like have a Landcruiser with 500 HP and a top speed of 150 MPH. I can't wait for that model.
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Old 12-06-2020, 07:54 AM   #8
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Default Re: Setting up front suspension

There is an excellent post here on the forums regarding this. I read it through and through a couple years back, but can't remember who the OP was and what the thread was titled. It was clear they intimately understood 1:1 suspension dynamics and had an innate ability to apply that information to scale crawlers. I'll dig back through my posts to see if I can find it as i'm pretty sure I commented.
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Old 12-09-2020, 08:38 PM   #9
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Default Re: Setting up front suspension

Quote:
Originally Posted by itr1275 View Post
Start with I'm not an expert by any means.



As inspector said, you want the pan hard and steering link parallel.



You can adjust the length of the upper and lower links to change the pinion angle (point it towards your transfer case). And the height of the links will change your (anti)squat and dive.



If you google 3 or 4 link calculator, there is a ton of info out there. Crawlerpedia, Jeep Forums all have similar tools. Here is a video of one of the tools.

https://youtu.be/nQMrnsOAPig



I'm not sure this scales 100% though. The reason being is we can scale the dimensions but the RCs are way under weight. If it's and 8 lb RC it wold 80 lb full size. To be true scale it would be 500-600 lbs. We also have like 1,000 HP by comparison.



When you align everything don't forget the tow. You probably want a little bit of tow out to keep it tracking straight. I'm not sure you can adjust the camber and other angles? So you are probably limited to tow and caster.


Let us know how it comes out - post some pix.
That's a good video tutorial for calculator. Gonna pass this my buddy for his new build. I might start another build after I finished installing the parts from 4Wheelonline on my current Silverado project.
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