RCCrawler Forums

RCHunter · 10-19-2005, 02:45 PM

Has anyone used 2 micro servos the steer their rig? One per tire was my thought. You have 2 more failure points but you can can hide and tuck that servo out of the way.

I also thought of using a low profile servo and retract servo. The low pro servos lack torque. The retract servo is non-proportional so it goes lock to lock. Maybe a servo brain transplant could make it proportional?

I've seen a bicycle cable system on a juggy somewhere. It used the brake cable to connect to the steering knuckles. I'm unsure how much arctculation would interfere with the steering geometry. If it worked, the servo could be chassis mounted and out of the way of rocks.

Any more suggestions?
RCHunter

ILoveRCRockCrawlin · 10-19-2005, 03:05 PM

well the problem with using a sevo for each wheel, exspecially 4ws, is that it will cause your batteries to die in minutes. it would be easiest to just do a normal setup or try that break cable idea.

RCHunter · 10-19-2005, 03:13 PM

I didn't even think of battery draw.
Thanks
RCH

JohnRobHolmes · 10-19-2005, 08:40 PM

battery draw isnt too much of a concern, unless your running four robot servos on a 10 pound rig with 1500mah cells. I for one think that 30 minute run times are awesome, and the 2.2 rigs go even longer on sub c batteries. Throw lipo on and we are talking up to 2 hours or more. At this point I should have broken parts already.

Two cheaper, less powerful servos will draw little more than a servo that is twice as powerful as one. Therefore, if you can afford the extra weight and physical room, run a servo on each wheel

But I digress. The biggest issue to me is that you will have to link the steering knuckles anyway. With no drag link the tires wander all over and it becomes difficult to hold a line with toe in/ out changing constantly. I do like the idea of running brake cable, but deraillier cable might be more precise. On this scale I doubt the difference would be much. Using cables, the servo could be mounted at a wider range of locations. Making cable stops to hold the housing could get interesting.

wheelhaus · 10-19-2005, 10:36 PM

There's a bunch of different ideas, but in the end the single high power servo with standard links can't be beat.

I don't think a bicycle brake or derailleur calbe will work well enough to eliminate enough slop to be worth it... Both are tension-cable compression-housing designs. They aren't designed to push.. The derailleur housing would be more suitable as its a little stiffer, but the cable is a smaller diameter. Anyways, I think a solid wire heavy duty aircraft pushrod system would work better.

toyofast · 10-19-2005, 11:00 PM

Quote:

Originally Posted by bigdsti

I don't think a bicycle brake or derailleur calbe will work well enough to eliminate enough slop to be worth it... Both are tension-cable compression-housing designs. They aren't designed to push..

Who says it has to only push? Why not pull on one knuckle while trying to push on the other knuckle?

It worked really well in this rig.... One 1/4 scale servo hooked to cables made for a clean setup.

edit: From way back in 11/2003

wheelhaus · 10-20-2005, 09:04 AM

Ah, i was thinking of the cable only hooked up to the knuckle, I didn't think of a rod connecting the two knuckles. thats a superb idea, its got me thinking now...

boxedjuice87 · 10-20-2005, 11:23 AM

Quote:

Originally Posted by RCHunter

I've seen a bicycle cable system on a juggy somewhere. It used the brake cable to connect to the steering knuckles. I'm unsure how much arctculation would interfere with the steering geometry.

With a normal brake cable there might be a little change with articulation depending on how it is setup. If you use a linear cable like THIS ONE from Odyssey you would be able to mount it where you would like without suspension cycing changing the steering. I have this cable on my bmx bike and I can wrap the bars around until the cable wont allow it anymore and I still have full motion of the brakes. With a normal cable one time around and the brakes would lock.

I have actually thought about doing this since I saw the juggy on rcmt years ago, I remember it had two servos mounted on the front of the chassis.

RCHunter · 10-20-2005, 12:47 PM

boxed, I thought it was on rcmt. Been so long since i've seen rcmt.

You would need a drag link on both setups, but mounting that servo on the chassis would be great. I have a 1/4 servo sittin around. The mounting would be the hardest part for cables but not impossible. It has been done.

JohnRobHolmes · 10-20-2005, 05:02 PM

if you used one servo, a Pull-Pull setup like planes use for control surfaces would be best.

RCHunter · 10-21-2005, 02:20 PM

On the bmx cables, you have the metal caps (ferrules). How do you mount the ferrules? I'm thinking a capture nut / compression fitting of some sort, like on a brake lever, the barrel adjuster. Kinda difficult without the parts in front of you.

JohnRobHolmes · 10-21-2005, 03:45 PM

I would go with the shifter ferrules, they are thicker.

You could just solder them or braze them to a mounting bracket.

RCHunter · 10-21-2005, 04:34 PM

Sounds easy. How far away from the knuckle should the ferrule be? How would you attach the cable itself on the knuckle? A crimp on clamp or something like a pushrod connector?

wheelhaus · 10-21-2005, 07:14 PM

Quote:

Originally Posted by johnrobholmes

I would go with the shifter ferrules, they are thicker.

You could just solder them or braze them to a mounting bracket.

the ferrules are the metal "caps" that you crimp onto the end to preveny fraying.

brake cables are thicker, and so are the die cast plugs. I'd reccomend a mountain bike (or bmx) brake cable. the die case plug is a horizontally opposed barrel. (imagine an upright berrel with a wire coming out of one side). this would be easy to drill through vertically for a bolt. like this...

the servo side of things could use an aircraft pushrod connector. like this...

or a clevis such as this...

after that, you'd need to mount the cable housing to something at each end to prevent the whole deal from shifting around. the cable is supposed to slide back and forth under tension. the housing should be mounted flush at each end to something immobile (an anchor point).

I would use an aluminum plate with a 2.5mm hole for the cable and mount the other end to any bolt or pair of bolts i could find near the servo. for the housing, find a 5mm ID aluminum tube and cut a piece that is about 1/4" deep. JB weld it around the hole. this will act as a "socket" to capture the end of the housing. cut the housing and cables to the appropriate length and install.

RCHunter · 10-22-2005, 01:52 PM

Use the 5mm ID alum tube as the ferrule? The clevise might fit better on the maxx knuckle. The pushrod connector thread may be good on the servo end. I'll get in 3d. Welding a steel ferrule to a bracket on the axle is the way to go on something in progress. Retro fitting my alum solid axles would be harder. Then you would need to use a bracket drilled to fit an adjuster barrel?

JohnRobHolmes · 10-22-2005, 02:30 PM

using an adjuster barrel would be sick. It would allow fine tuning of toe in and out, as well as limited side to side.

if you did that, all you would need is a threaded bracket for your stop, the barrel adjuster, and ferrules to cap the housing. It would be so much better than a welded ferrule, but I can understand welding it just to get you going.

edit, he is saying to jb weld the 5mm aluminum and use it as ferrules instead of getting some shift or brake ferrules.

wheelhaus · 10-22-2005, 02:56 PM

yeah, you're on the same lines as I am now.. would you try to run this wi or without a knuckle to knuckle crosslink? if its a pull/pull cable system going to each knuckle you'll need something to wedge between the knuckles (steering link) to avoid compressed cable slack/slop.

RCHunter · 10-22-2005, 03:53 PM

My solid axles are being built so it would be easier to weld a bracket on now. You could glue the adj barrel to the ferrule and mount it to a bracket and shim the barrel to adjust the cable.

RCHunter · 10-22-2005, 03:58 PM

You would need the steering link. That link doesn't get in the way like the servo does.

sparko · 10-22-2005, 04:43 PM

You could always use ally tubing to house the cable, it wouldnt bend like the plastic would.....

10-19-2005, 02:45 PM	#1
RCHunter Quarry Creeper Join Date: Mar 2005 Location: Florida Posts: 216	Steering Setup Thoughts Has anyone used 2 micro servos the steer their rig? One per tire was my thought. You have 2 more failure points but you can can hide and tuck that servo out of the way. I also thought of using a low profile servo and retract servo. The low pro servos lack torque. The retract servo is non-proportional so it goes lock to lock. Maybe a servo brain transplant could make it proportional? I've seen a bicycle cable system on a juggy somewhere. It used the brake cable to connect to the steering knuckles. I'm unsure how much arctculation would interfere with the steering geometry. If it worked, the servo could be chassis mounted and out of the way of rocks. Any more suggestions? RCHunter

10-22-2005, 02:30 PM	#16
JohnRobHolmes owner, Holmes Hobbies LLC Join Date: Nov 2004 Location: Volt up! Gear down! Posts: 20,290	using an adjuster barrel would be sick. It would allow fine tuning of toe in and out, as well as limited side to side. if you did that, all you would need is a threaded bracket for your stop, the barrel adjuster, and ferrules to cap the housing. It would be so much better than a welded ferrule, but I can understand welding it just to get you going. edit, he is saying to jb weld the 5mm aluminum and use it as ferrules instead of getting some shift or brake ferrules. Last edited by JohnRobHolmes; 10-22-2005 at 02:36 PM.

10-19-2005, 03:05 PM	#2
ILoveRCRockCrawlin RCC Addict Join Date: Dec 2004 Location: Central NY Posts: 1,980	well the problem with using a sevo for each wheel, exspecially 4ws, is that it will cause your batteries to die in minutes. it would be easiest to just do a normal setup or try that break cable idea.

10-19-2005, 03:13 PM	#3
RCHunter Quarry Creeper Join Date: Mar 2005 Location: Florida Posts: 216	I didn't even think of battery draw. Thanks RCH

10-19-2005, 08:40 PM	#4
JohnRobHolmes owner, Holmes Hobbies LLC Join Date: Nov 2004 Location: Volt up! Gear down! Posts: 20,290	battery draw isnt too much of a concern, unless your running four robot servos on a 10 pound rig with 1500mah cells. I for one think that 30 minute run times are awesome, and the 2.2 rigs go even longer on sub c batteries. Throw lipo on and we are talking up to 2 hours or more. At this point I should have broken parts already. Two cheaper, less powerful servos will draw little more than a servo that is twice as powerful as one. Therefore, if you can afford the extra weight and physical room, run a servo on each wheel But I digress. The biggest issue to me is that you will have to link the steering knuckles anyway. With no drag link the tires wander all over and it becomes difficult to hold a line with toe in/ out changing constantly. I do like the idea of running brake cable, but deraillier cable might be more precise. On this scale I doubt the difference would be much. Using cables, the servo could be mounted at a wider range of locations. Making cable stops to hold the housing could get interesting.

10-19-2005, 10:36 PM	#5
wheelhaus Pebble Pounder Join Date: Jul 2005 Location: Denver Posts: 182	There's a bunch of different ideas, but in the end the single high power servo with standard links can't be beat. I don't think a bicycle brake or derailleur calbe will work well enough to eliminate enough slop to be worth it... Both are tension-cable compression-housing designs. They aren't designed to push.. The derailleur housing would be more suitable as its a little stiffer, but the cable is a smaller diameter. Anyways, I think a solid wire heavy duty aircraft pushrod system would work better.

10-20-2005, 09:04 AM	#7
wheelhaus Pebble Pounder Join Date: Jul 2005 Location: Denver Posts: 182	Ah, i was thinking of the cable only hooked up to the knuckle, I didn't think of a rod connecting the two knuckles. thats a superb idea, its got me thinking now...

10-20-2005, 12:47 PM	#9
RCHunter Quarry Creeper Join Date: Mar 2005 Location: Florida Posts: 216	boxed, I thought it was on rcmt. Been so long since i've seen rcmt. You would need a drag link on both setups, but mounting that servo on the chassis would be great. I have a 1/4 servo sittin around. The mounting would be the hardest part for cables but not impossible. It has been done.

10-20-2005, 05:02 PM	#10
JohnRobHolmes owner, Holmes Hobbies LLC Join Date: Nov 2004 Location: Volt up! Gear down! Posts: 20,290	if you used one servo, a Pull-Pull setup like planes use for control surfaces would be best.

10-21-2005, 02:20 PM	#11
RCHunter Quarry Creeper Join Date: Mar 2005 Location: Florida Posts: 216	On the bmx cables, you have the metal caps (ferrules). How do you mount the ferrules? I'm thinking a capture nut / compression fitting of some sort, like on a brake lever, the barrel adjuster. Kinda difficult without the parts in front of you.

10-21-2005, 03:45 PM	#12
JohnRobHolmes owner, Holmes Hobbies LLC Join Date: Nov 2004 Location: Volt up! Gear down! Posts: 20,290	I would go with the shifter ferrules, they are thicker. You could just solder them or braze them to a mounting bracket.

10-21-2005, 04:34 PM	#13
RCHunter Quarry Creeper Join Date: Mar 2005 Location: Florida Posts: 216	Sounds easy. How far away from the knuckle should the ferrule be? How would you attach the cable itself on the knuckle? A crimp on clamp or something like a pushrod connector?

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10-22-2005, 01:52 PM	#15
RCHunter Quarry Creeper Join Date: Mar 2005 Location: Florida Posts: 216	Use the 5mm ID alum tube as the ferrule? The clevise might fit better on the maxx knuckle. The pushrod connector thread may be good on the servo end. I'll get in 3d. Welding a steel ferrule to a bracket on the axle is the way to go on something in progress. Retro fitting my alum solid axles would be harder. Then you would need to use a bracket drilled to fit an adjuster barrel?

10-22-2005, 02:56 PM	#17
wheelhaus Pebble Pounder Join Date: Jul 2005 Location: Denver Posts: 182	yeah, you're on the same lines as I am now.. would you try to run this wi or without a knuckle to knuckle crosslink? if its a pull/pull cable system going to each knuckle you'll need something to wedge between the knuckles (steering link) to avoid compressed cable slack/slop.

10-22-2005, 03:53 PM	#18
RCHunter Quarry Creeper Join Date: Mar 2005 Location: Florida Posts: 216	My solid axles are being built so it would be easier to weld a bracket on now. You could glue the adj barrel to the ferrule and mount it to a bracket and shim the barrel to adjust the cable.

10-22-2005, 03:58 PM	#19
RCHunter Quarry Creeper Join Date: Mar 2005 Location: Florida Posts: 216	You would need the steering link. That link doesn't get in the way like the servo does.

10-22-2005, 04:43 PM	#20
sparko Newbie Join Date: Sep 2004 Location: England Posts: 46	You could always use ally tubing to house the cable, it wouldnt bend like the plastic would.....

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Thread: Steering Setup Thoughts