Your opinions on two servos

[Josh_Br]

I have an AX-10 RTC. I'd like to have a greater range of steering. I already made my own tie rod that adds a little toe-out, and now I'm looking at servos. Can you tell me what you think of these two servos?

Henge MD260 180-260 degrees Metal Digital Servo for FPV pan tilt control MD180 S | eBay

SR403P 180 Degree Metal Gear Robot Servo Double Bearing | eBay

Thanks,
Josh

[DRV KRAWLER]

Hey Josh,

Actually a longer swing servo is not really what you need. I see in your future is serious binding issues. I would suggest a High torque servo and some quality High clearence Knuckles and some C-hubs with additional caster angle. You may want to consider a Behind the axle steering set up.

You have a Axial so my information is based on Axial design axles.

Just my 0.02 .

[SINister]

The robot servo has outputs on both sides and no ears on the case so you would need to modify your servo mount. The other one has a low torque rating. There are others in that price range with a lot better specs.

Have you tried a longer servo horn?

[Josh_Br]

I do not have an aluminum servo arm, but I did super glue the servo saver so it is solid. I have an aluminum arm on the way; it should be here in a few days. I do have aluminum steering knuckles already installed. I set up the suspension so there is a very slight amount of caster.

I just want to have more steering. I want the steering knuckle to hit the screw on the c-hub when I turn the whole way in one direction. Any advice is appreciated. Here is a link to a few photos I took so you can see my set up and what is going on: AX10 steering - a set on Flickr

[Grizzly4x4]

Originally Posted by Josh_Br

I want the steering knuckle to hit the screw on the c-hub when I turn the whole way in one direction. Any advice is appreciated. Here is a link to a few photos I took so you can see my set up and what is going on: AX10 steering - a set on Flickr

If you have the stock dog bones then all you will do is bind them up and cause breakage if you try to make the arm touch the screw head. You need to clearance the cups for more steering or run some type of CVD (not Axial CVDs, they break).

Take your tie rod off, push the arm against the screw head, and then turn the tire. You will feel the bind.

[Josh_Br]

Originally Posted by Grizzly4x4

If you have the stock dog bones then all you will do is bind them up and cause breakage if you try to make the arm touch the screw head. You need to clearance the cups for more steering or run some type of CVD (not Axial CVDs, they break).

Take your tie rod off, push the arm against the screw head, and then turn the tire. You will feel the bind.

CVD's sound like a worthwhile mod. Say I get CVD's, what else can I do to get more steering?

[Grizzly4x4]

Originally Posted by Josh_Br

CVD's sound like a worthwhile mod. Say I get CVD's, what else can I do to get more steering?

You need a long servo arm to make the tires turn more. A long arm makes the servo weaker though so you need a strong servo.

I like the Hitec 7955TG because it is a good bang for the buck servo. 333 oz/in of torque at 6V and only $109. Any 3/4" servo horn should work well, I even use the black pastic one that comes with the Hitec servo, on my 1.9 top truck rig.

Oh, and you need a CC Bec to run that stronger servo because of the amps it pulls.

Servos and accessories*-*-Electronics*-*The Crawlers Store LLC

[Josh_Br]

Awesome, that's great info. I actually do have a CC BEC....forgot to mention that above. Thanks!

[Grizzly4x4]

Originally Posted by Josh_Br

Awesome, that's great info. I actually do have a CC BEC....forgot to mention that above. Thanks!

Gitcha some steering.

[SINister]

It doesn't take much to touch the screws on the axials. The arm in the pic doesn't look to short but it's hard to tell in the pics. Do you have a way to adjust the steering throw or EPAs on the TX.

[hoghead5150]

go to the ax10 section and look at my thread "steering angle" it will give you lots of tips and tricks.

[Josh_Br]

Originally Posted by SINister

It doesn't take much to touch the screws on the axials. The arm in the pic doesn't look to short but it's hard to tell in the pics. Do you have a way to adjust the steering throw or EPAs on the TX.

The transmitter is a little basic, as it is the one that came with the RTC package. It does have an adjustment to turn up or down the amount of movement the servo has, and I have it turned all the way up. The servo seems to have about 90* of total movement.

[SINister]

Originally Posted by Josh_Br

The transmitter is a little basic, as it is the one that came with the RTC package. It does have an adjustment to turn up or down the amount of movement the servo has, and I have it turned all the way up. The servo seems to have about 90* of total movement.

Ok a longer servo arm will get you where you want then. As mentioned above if it binds you can open the end of the cup up a little with a dremel tool to smooth it out.

[tiny2085]

If that picture is full lock, you need to change your steering knuckle, so that the arm on the knuckle sits 90* perpendicular to the axle when the truck is pointed straight, the way it sits now its at 45*, sooo the maximum amount of travel regardless of axle bind is only 45*. If the arm were 90* to the axle, then you could have up to 90* of travel. Did that make sense ?

[Josh_Br]

Originally Posted by tiny2085

If that picture is full lock, you need to change your steering knuckle, so that the arm on the knuckle sits 90* perpendicular to the axle when the truck is pointed straight, the way it sits now its at 45*, sooo the maximum amount of travel regardless of axle bind is only 45*. If the arm were 90* to the axle, then you could have up to 90* of travel. Did that make sense ?

I want to understand what you are saying. Do you mean the part of the steering knuckle that the tie rod attaches to?

[Charlie-III]

Originally Posted by tiny2085

If that picture is full lock, you need to change your steering knuckle, so that the arm on the knuckle sits 90* perpendicular to the axle when the truck is pointed straight, the way it sits now its at 45*, sooo the maximum amount of travel regardless of axle bind is only 45*. If the arm were 90* to the axle, then you could have up to 90* of travel. Did that make sense ?

Ehhhhh.....not quite, unless you notch the axle housing & axle.

The angle of the connection points has some bearing on the amount of steering, but once "hard parts" hit something else, all movement stops.

What you are describing is Ackerman angle, that has more to do with what each steering tire does relative to the other steering tire when you move the steering servo.

The link angle from the servo arm/horn to the knuckle attach point has some relevance as well, but is also separate from Ackerman angle.

Josh, if you disconnected the steering stuff from the knuckle, the max steering angle you could get is based on when hard stuff hits other hard stuff (or, you max out your flex joint of the axle within the steering knuckle).

[Josh_Br]

Ok that makes sense. My problem is that hard stuff is not hitting that other hard stuff. Maybe I need a longer servo arm. Seems like the whole steering system needs more movement.

[Charlie-III]

Originally Posted by Josh_Br

Ok that makes sense. My problem is that hard stuff is not hitting that other hard stuff. Maybe I need a longer servo arm. Seems like the whole steering system needs more movement.

Griz & Sin already stated that, yes, a longer servo arm/horn will give more movement.
Keep in mind that if you double the arm length, you ~halve the torque available.
Hey, it's engineering, typically when you fix one thing, you FUBAR another.

Make sure the steering moves freely with the servo disconnected. If not, fix that 1st, then move on to more travel from the servo (maybe a longer servo arm/horn).

[tiny2085]

Originally Posted by Charlie-III

Griz & Sin already stated that, yes, a longer servo arm/horn will give more movement.

I disagree, and here is why, the arm(part that the tie rod attaches to on the knuckle) will only turn to 0*, which is where the arm is at now at full turn. Adding more movement on the servo end won't make the knuckle turn past 0* Try disconnecting the tie rod from the servo and cycling the steering on the same plane as the servo, if you do, please take pictures so we can all see. Adding a longer servo arm will increase the turning rate of the steering, and if the steering geometry were better, would increase movement.

[SINister]

Originally Posted by tiny2085

I disagree, and here is why, the arm(part that the tie rod attaches to on the knuckle) will only turn to 0*, which is where the arm is at now at full turn. Adding more movement on the servo end won't make the knuckle turn past 0* Try disconnecting the tie rod from the servo and cycling the steering on the same plane as the servo, if you do, please take pictures so we can all see. Adding a longer servo arm will increase the turning rate of the steering, and if the steering geometry were better, would increase movement.

I missed that but your right. The servo horn sticks out so far that it can't hit the screws because of the angle of the link. Moving the rod to the back side of the servo arm would help but a lower profile alum horn would be the best option. Look at the 3rd pic to see what tiny is saying.

Good eye newbie