TRX4 Leafs

[Miatardo]

Interesting find of the day:

HoyFab is selling a rear leaf spring conversion on Shapeways. Looks like it uses the RC4WD red leafs.



At $170 plus the price of leafs is pretty steep, but may be a cool idea for those "totally scale" guys that want a Bronco suspension closer to that of the 1:1.

[DukeMinnix]

Thats absurdly priced....

[HumboldtEF]

Yep like all metal prints these are also crazy expensive, these are printed in matte black steel, basically sintered metal.

cool idea though

[Levi]

Interesting, a leafed trx4. Wonder how good it would do? Did they have any pictures posted with the leaf conversion?

[TheLetterJ]

I've seen how this plays out in the 1:1 world... just think of your portal box height as a lift block and say hello to massive amounts of leverage against the spring = axle wrap = broken leafs/parts. Then you'll want to add some sort of anti-wrap bar/bars to get things under control, but you'll still have the other drawbacks of leaf springs like tons of axle steer and a general resistance of the leaf pack to torsional twist/articulation. What you'll end up with is an expensive, more complicated, lower performing suspension, all for the sake of being different. Or you'll continue trying to improve it and end up with a, you guessed it, coil/link setup. I'm a leaf spring guy through and through, but I think it's generally a bad idea when combined with portal axles, but as long as you understand what you're getting into, knock yourself out! I like different.

[Miatardo]

Originally Posted by Levi

Interesting, a leafed trx4. Wonder how good it would do? Did they have any pictures posted with the leaf conversion?

They do in another post, I will see if I can find that post too and post a screenie here.


***EDIT****
Here is the screen of leafs installed. Not the best but it is the best I can find...

[Miatardo]

Originally Posted by TheLetterJ

I've seen how this plays out in the 1:1 world... just think of your portal box height as a lift block and say hello to massive amounts of leverage against the spring = axle wrap = broken leafs/parts. Then you'll want to add some sort of anti-wrap bar/bars to get things under control, but you'll still have the other drawbacks of leaf springs like tons of axle steer and a general resistance of the leaf pack to torsional twist/articulation. What you'll end up with is an expensive, more complicated, lower performing suspension, all for the sake of being different. Or you'll continue trying to improve it and end up with a, you guessed it, coil/link setup. I'm a leaf spring guy through and through, but I think it's generally a bad idea when combined with portal axles, but as long as you understand what you're getting into, knock yourself out! I like different.

Are you saying that the gear reduction at the wheels will exaggerate the normal leaf spring issues, or just pointing out the leaf spring issues in general? The only 1:1 i have ever really been around that had portals was the HUMVEE which is front and rear independent suspension and would not have many of the issues mentioned above. But I am more curious about how portals would affect an axle with leafs...

I am really new to RC crawling, but have been around some 1:1 stuffs. This being said I realize the benefit of a good 4 link over a leaf design. However being the type of guy who competes with himself WAY more than I compete with others, Being different or adding challenges can be part of the fun in RC crawling.

Either way I find it very interesting what people are doing with these crazy little things, whether it be performance or super scale. This is the real reason for posting the find... It was interesting to me and I figured may be to others.

[TheLetterJ]

It's the height of the portal box that increases leverage against the spring, regardless of gear reduction within the portal. It acts exactly the same as a lift block of the same height would (what is it, 20mm on the trx4?) Say you have 40:1 total gear reduction, that would be 40 turns at the motor to 1 at the tire, the tire sees 40 times the motor's torque no matter where the reduction happens. Sure, 40:1 at the transmission and 1:1 everywhere else will make uncontrollable torque twist of the chassis relative to the axle, and 1:1 at the trans with 40:1 in a portal box will nearly eliminate torque twist at the chassis, but ultimately the tire still sees 40:1, and the suspension still has to control that. The spring/suspension has to the resist that rotational force and hopefully turn it into forward progress. Unfortunately for leaf springs, they have to hold the car up AND locate the axle without the help of a solid link with defined pivot points, and the portal box just became a (20mm?) lever trying to twist those leafs into the letter "S". You can make a stiffer leaf pack that has more resistance to wrapping, but it's also going to have more resistance to compressing for bump compliance when you want it too. Going spring under would reduce the leverage, but then you start losing the benefit of added clearance from the portals. Not knocking the option, just trying to shed light on what is certain to cause frustration if someone were to go this route without understanding what will change.

I have seen a 1:1 Unimog 406 (portal axles) on the trail with 1/4 eliptic leafs, that guy had it figured out!

[Miatardo]

Originally Posted by TheLetterJ

It's the height of the portal box that increases leverage against the spring, regardless of gear reduction within the portal. It acts exactly the same as a lift block of the same height would (what is it, 20mm on the trx4?) Say you have 40:1 total gear reduction, that would be 40 turns at the motor to 1 at the tire, the tire sees 40 times the motor's torque no matter where the reduction happens. Sure, 40:1 at the transmission and 1:1 everywhere else will make uncontrollable torque twist of the chassis relative to the axle, and 1:1 at the trans with 40:1 in a portal box will nearly eliminate torque twist at the chassis, but ultimately the tire still sees 40:1, and the suspension still has to control that. The spring/suspension has to the resist that rotational force and hopefully turn it into forward progress. Unfortunately for leaf springs, they have to hold the car up AND locate the axle without the help of a solid link with defined pivot points, and the portal box just became a (20mm?) lever trying to twist those leafs into the letter "S". You can make a stiffer leaf pack that has more resistance to wrapping, but it's also going to have more resistance to compressing for bump compliance when you want it too. Going spring under would reduce the leverage, but then you start losing the benefit of added clearance from the portals. Not knocking the option, just trying to shed light on what is certain to cause frustration if someone were to go this route without understanding what will change.

I have seen a 1:1 Unimog 406 (portal axles) on the trail with 1/4 eliptic leafs, that guy had it figured out!

Thank you for the explanation! As soon as i read the word height I realized what you were about to discuss. For some reason that did not even cross my mind earlier.

Thank you again!