Traxxas UDR Driveshaft Angle

[KnowAir]

Blasphemy!!! Most likely you're correct, but I'd just get the custom adjustable links because I'm nerdy like that.

Fair enough, nothing wrong with that.
I'm the guy whose just trying to keep my crap running, upgrades are a luxury that I generally can't afford. Only when necessary for me.✌

 

[WickedFog]

Adjustable 4-links on drag cars are used to adjust the pinion angle and get the rear end tracking properly. It helps with locking up the rear tires when you launch, because as the suspension compresses on launch, your pinion angle changes due to the upper and lower links being different lengths. The upper link mounts of the axle housing rotate about a different arc and fulcrum than the lower mounts do. So you want your rear end housing to counteract the effect of the tires hooking up and trying to rotate your axle housing backwards. You do that by adjusting upper/lower links.

As for crawlers, alinging the vehicle track and getting a pinion angle in the median of it's rotation to be as best you can get it inline with (pointing at) the transmission output at the median of suspension travel would be the only reasons for having adjustables I csn think of. And both of these issues technically should already be nominal if the engineers did a good job at Traxxas designing the chassis components. So I don't see any benefit to using adjustable links. But I could be missing something.

 

[MVRCA]

Adjustable 4-links on drag cars are used to adjust the pinion angle and get the rear end tracking properly. It helps with locking up the rear tires when you launch, because as the suspension compresses on launch, your pinion angle changes due to the upper and lower links being different lengths. The upper link mounts of the axle housing rotate about a different arc and fulcrum than the lower mounts do. So you want your rear end housing to counteract the effect of the tires hooking up and trying to rotate your axle housing backwards. You do that by adjusting upper/lower links.

As for crawlers, alinging the vehicle track and getting a pinion angle in the median of it's rotation to be as best you can get it inline with (pointing at) the transmission output at the median of suspension travel would be the only reasons for having adjustables I csn think of. And both of these issues technically should already be nominal if the engineers did a good job at Traxxas designing the chassis components. So I don't see any benefit to using adjustable links. But I could be missing something.

Yes, tolerance stacking. Measure 10 UDR's and I bet there is more than a bit of variation in the parts. Does it matter, eh, probably not, but it doesn't make the math incorrect.

This: "So you want your rear end housing to counteract the effect of the tires hooking up and trying to rotate your axle housing backwards. You do that by adjusting upper/lower links." Sorta. It's where the links are mounted ( location ) on the chassis which does this, and the final length of a link is the byproduct of the placement. This is why crawlers have many link locations on the chassis, and adjustable links. You adjust link length based on where it connects to the chassis for the optimal anti-squat levels, specific to that particular car / truck / crawler. This is also why you have riser blocks on the rear axle of a crawler. They do things that link length cannot solve by changing where the links connect the rear axle to the chassis.

With fixed links, you much run the suspension height the manufacturer sets the truck up to. So if you want to run slung lower for speed, or taller for jumping, then your pinion angle suffers, placing undue stress and vibrations on the driveline and bearings.



In a nutshell, you are actually talking about traction and the amount of torque applied to traction and not "hop", ect. Suspension sag is a part of this, but we are already in the weeds pretty deep.

Links are designed to be the adjustable part; they are far easier to dial in than drilling countless holes in chassis and dealing with all the other nonsense which may be in the way ( transmissions, ect).

This is why every high-quality RC platform has adjustable links, and low quality has fixed links. Just because Vitavon is charging a small fortune for their fixed links doesn't make them correct; they make plenty of stuff that is designed poorly.

If the RC comes with fixed links and it performs well, then you may indeed not need to replace them. If you are in the position of replacing them, I cannot fathom any reason to buy a fixed link unless there was a budget issue and pricing forced you to use fixed links. Technically, is absolutely no gain and only downsides. If you're bashing and launching into low-Earth orbit, then all bets are off and I'm not sure what to advise. But don't be fooled; fixed links are the cheap way to go by the manufacturer and they are hoping that any tolerance stacking isn't enough to make the RC perform poorly.

Final parting idea; if the links are heavy duty and fixed, then something else will need to give under impact. Most likely it will be a more costly part to replace.

s.

 

[WickedFog]

Yes, tolerance stacking. Measure 10 UDR's and I bet there is more than a bit of variation in the parts. Does it matter, eh, probably not, but it doesn't make the math incorrect.

This: "So you want your rear end housing to counteract the effect of the tires hooking up and trying to rotate your axle housing backwards. You do that by adjusting upper/lower links." Sorta. It's where the links are mounted ( location ) on the chassis which does this, and the final length of a link is the byproduct of the placement. This is why crawlers have many link locations on the chassis, and adjustable links. You adjust link length based on where it connects to the chassis for the optimal anti-squat levels, specific to that particular car / truck / crawler. This is also why you have riser blocks on the rear axle of a crawler. They do things that link length cannot solve by changing where the links connect the rear axle to the chassis.

With fixed links, you much run the suspension height the manufacturer sets the truck up to. So if you want to run slung lower for speed, or taller for jumping, then your pinion angle suffers, placing undue stress and vibrations on the driveline and bearings.



In a nutshell, you are actually talking about traction and the amount of torque applied to traction and not "hop", ect. Suspension sag is a part of this, but we are already in the weeds pretty deep.

Links are designed to be the adjustable part; they are far easier to dial in than drilling countless holes in chassis and dealing with all the other nonsense which may be in the way ( transmissions, ect).

This is why every high-quality RC platform has adjustable links, and low quality has fixed links. Just because Vitavon is charging a small fortune for their fixed links doesn't make them correct; they make plenty of stuff that is designed poorly.

If the RC comes with fixed links and it performs well, then you may indeed not need to replace them. If you are in the position of replacing them, I cannot fathom any reason to buy a fixed link unless there was a budget issue and pricing forced you to use fixed links. Technically, is absolutely no gain and only downsides. If you're bashing and launching into low-Earth orbit, then all bets are off and I'm not sure what to advise. But don't be fooled; fixed links are the cheap way to go by the manufacturer and they are hoping that any tolerance stacking isn't enough to make the RC perform poorly.

Final parting idea; if the links are heavy duty and fixed, then something else will need to give under impact. Most likely it will be a more costly part to replace.

s.

That makes sense. I didn't even think about adjusting your ride height interfering with the pinion angle. But as far as that goes, the UDR suspension is already setup pretty darned good from what I have seen.

 

[MVRCA]

That makes sense. I didn't even think about adjusting your ride height interfering with the pinion angle. But as far as that goes, the UDR suspension is already setup pretty darned good from what I have seen.

I agree and I think Traxxas did a pretty good job with the overall layout. It's a pain to work on; we tore one down to screws for a major overhaul and it wasn't fun.

 

[KnowAir]

I agree and I think Traxxas did a pretty good job with the overall layout. It's a pain to work on; we tore one down to screws for a major overhaul and it wasn't fun.

I haven't experienced a UDR,though I am interested in it. IMO, TRX has the best engineers, even QC is very good, where they fail for me is cheaping out on materials, such as the 4mm links discussed here. Could have easily made them 5mm.. Not knocking, I own a half dozen TRX rc's, just wish they weren't so profit oriented and sue happy. Is what it is.

 

[WickedFog]

I haven't experienced a UDR,though I am interested in it. IMO, TRX has the best engineers

Whichever Traxxas Engineer that designed the Jato transmission case and rear shock tower mounts on it is a complete idiot

 

[Beer_Goggles_RC]

Whichever Traxxas Engineer that designed the Jato transmission case and rear shock tower mounts on it is a complete idiot

Let’s design a nitro rc that can do 60+ but lets make sure the brakes never work also!

 

[WickedFog]

Let’s design a nitro rc that can do 60+ but lets make sure the brakes never work also!

Yeah. My Jato brakes are only on the car to add weight I assume. Because they damn sure don't slow it down.

 

[KnowAir]

Whichever Traxxas Engineer that designed the Jato transmission case and rear shock tower mounts on it is a complete idiot

I'll take your word for it, definitely have seen some blunders as well. I think a lot of times the engineering gets circumvented for production cost savings. I look at the Maxx trucks and while overpriced, they defy what I ever expected from a plastic truck. But I also have worked on my bro's E Revo and thought, WTF? All this to change shock fluid/springs? Grr.. LOL

 

[Chubaka]

I'll take your word for it, definitely have seen some blunders as well. I think a lot of times the engineering gets circumvented for production cost savings. I look at the Maxx trucks and while overpriced, they defy what I ever expected from a plastic truck. But I also have worked on my bro's E Revo and thought, WTF? All this to change shock fluid/springs? Grr.. LOL

Try changing a spur gear on a tmaxx. Better yet, a nitro stampede.

 

[Beer_Goggles_RC]

Try changing a spur gear on a tmaxx. Better yet, a nitro stampede.

I replaced the one way bearing on a tmaxx for my neighbor. What a pain in the absolute . That was my first Traxxas experience too so for the longest time I thought they were all just junk lol

 

[KnowAir]

Try changing a spur gear on a tmaxx. Better yet, a nitro stampede.

Pretty sure I have, been a minute, more like 10 years, LOL. I have a Tmaxx.. buried under the bottom shelf of my workbench on the garage floor amongst all the other miscellaneous debris I've dropped but didn't care to retrieve. A turd indeed. Just to clarify, I'm not a fanboy of TRX. They don't need or deserve my allegiance. But I do own and enjoy several. They're like mopeds and fat girls..

 

[AjDale]

I’m running vitavon upper rear links, vitavon halve diff housing, vitavon sway bars front and rear