One servo for 4WS

[xtremraptor]

i had an idea pop into my head of a way to get 4WS with just using one servo.

to start use the normal steering rod set up from knuckle to knuckle (blue line)

next find a way to mount a cantilever type set up at the top of each diff assembly or on the arms somewhere (red bloch on diffs)

use a rod or cable (i have cable shown) to go from the cantilever to the knuckle (fuscia line)

run the cable (lawn mower throttle cable or bike shifting/brake cable) (fuscia line) from where ever the servo is mounted to the cantilever. i've shown it in the servo in the chassis area but i think i could mount it to the front diff for wieght and still use the cable to run the back

i know there will still be some figuring to be done to make sure the rear wheels turn opposite from the front for proper steering. i think one will have to be run backwards from the other.

i was thinking that the lawn mower cable would be heavy enough to turn the wheels under pressure. the bike cable might be. i would use mountain bike cable not road bike cable. it's a little stronger. but it can stop me and a bike flying down a hill so why would it not have enough strength to turn these wheels. myself and a bike wiegh almost 225lbs, the truck is only 10lb(ish). it should be strong enough and a little more flexible than the lawn mower cable. the lawn mower cable would obviously be stronger but maybe to stiff to bend where i need it too

anyone else had this idea or actually tried it? let me know what you veterans think, please

would be a good way to eliminate some wieght i think

[gregrocks90046]

it looks like it would work, but connecting your servos directly will give you so much more control.

also, if you are going to have 4 wheel steering on a crawler, don't you want to have independent control of the front and rear?

the combination of cable, links and all the other hardware would probably weigh more than another servo.

[JohnRobHolmes]

Originally Posted by gregrocks90046

the combination of cable, links and all the other hardware would probably weigh more than another servo.

yep

not to mention the time that it takes to figure it all out, in that time you could make the money to buy another servo. But, you could try it for the fun factor.

[flexntj2001]

I would definetly go 1/4 scale. I personally think that anything less than 200oz (front and rear) on a crawler is just a waste of time and money to install. I want to see the rig move when the side of a wheel is pushed against a rock and you hit the steering control.

It does sound like a fun challenge to setup though.

Let us know how it goes.

[jetboat]

good idea but, you're going to have a problem when you need to push on the cable.... the cable will mover and you will never straighten out, I would recommend using a pull-pull set up like is used on rc boats. or replace that cable sheething with a metal tube something rigid

[xtremraptor]

this is completely a concept. i have seen a couple othere threads that have talked about this, but they were trying to use links. i was just curious for the most part.

i was at home depot today checking out some of the lawn mower cables. they would deffinately work better than a bike cable. alot stiffer cable there. but as asked "what is it gonna do when it's up against a rock?" my guess right now is bend, same as yours.

would definetly go 1/4 scale. I personally think that anything less than 200oz (front and rear) on a crawler is just a waste of time and money to install. I want to see the rig move when the side of a wheel is pushed against a rock and you hit the steering control.

i am running 1/4 scale servos (fr n rr) on my build up right now. they are fairly heavy. i'm not sure everything would weigh more. although the cable i was looking at at home depot did have a metal sheathing around it.

maybe this is an idea i should link with a 2.2 crawler (smaller tires to turn) and a digital servo (for wieght savings)

not to mention the time that it takes to figure it all out, in that time you could make the money to buy another servo. But, you could try it for the fun factor.

the thoughts been at me off and on for a month now (that's about 160 CS-80's) i have bought two in that time

hell every idea in here takes more time to come up with than it would to just take the conventional route and buy stuff. creation and inginuity(?) are a large base for building your own crawler

besides, it's better than sniffen paint fumes, smokin crack, and chasing your own tail around the room. (no this is not personnal experience )

[xtremraptor]

Originally Posted by jetboat

good idea but, you're going to have a problem when you need to push on the cable.... the cable will mover and you will never straighten out, I would recommend using a pull-pull set up like is used on rc boats. or replace that cable sheething with a metal tube something rigid

the sheating will deffinately have to be clamped down somehow. same idea as the mower. doesn't work right if it's not solid

[gregrocks90046]

nobody is saying not to try your idea. you have to try new things to find out what works, but your idea kills three objectives-

one-the additional hardware will weigh significantly more than a additional servo.

two-it will never be as strong turning the wheels as a servo mounted on the axle with direct linkage. remember, the shortest and fastest path from point A to point B is a straight line.

three-you have no independent rear steer. a crucial feature for a large scale rig.

[flexntj2001]

Originally Posted by xtremraptor

but as asked "what is it gonna do when it's up against a rock?" my guess right now is bend, same as yours.

Actually, when I have one of my wheels up against a rock and I try to steer into that rock.....the front of my rig moves in the opposite direction. I have yet to bend anything that I have built, but I might not be trying hard enough.

Originally Posted by gregrocks90046

nobody is saying not to try your idea. you have to try new things to find out what works, but your idea kills three objectives-

one-the additional hardware will weigh significantly more than a additional servo.

two-it will never be as strong turning the wheels as a servo mounted on the axle with direct linkage. remember, the shortest and fastest path from point A to point B is a straight line.

three-you have no independent rear steer. a crucial feature for a large scale rig.

That is all I was trying to say. If all our rigs were the exact same.....what fun would that be. You have to keep challenging yourself with new ideas, or try to reinvent old ones.

[xtremraptor]

Actually, when I have one of my wheels up against a rock and I try to steer into that rock.....the front of my rig moves in the opposite direction. I have yet to bend anything that I have built, but I might not be trying hard enough.

i didn't mean YOUR stuff bends. i meant that i too think the cable (from my idea) will bend when it is pushed. this is kind of what you were thinking too isn't it?

nobody is saying not to try your idea. you have to try new things to find out what works,

i know you guys aren't trying to kill my idea. i am only asking for opinions and wisdom here. besides when it comes down to it i'm not really the kind of guy that cares what others think. but i do value others input when i venture into new projects and unknown areas of thinking

to answer your 3 issues:

1- your right the weight might be more. i have not checked into this yet

2-when i posted i had not actually checked the cables i was thinking of using. after taking a look at a few different kinds of cables yesterday and how they looked for strength i do tend to agree with you

3-independant steering crucial- yes i agree again. but like i said i have seen several posts on this subject and just thought i would throw an idea out there that popped into my head after reading those posts

there are alot of good thinkers in here and i was just trying to pick some brains that's all. i probably will go ahead and try the idea (next project). if it doesn't work ah well i'll only be out $20 or so for the parts.

if it does work, you guys can pay me for the new system (LOL as if)

thanx for the input guys/gals(must be one here somewhere)

[DISTURBIN' tha PEACE]

Originally Posted by xtremraptor

i had an idea pop into my head of a way to get 4WS with just using one servo.

to start use the normal steering rod set up from knuckle to knuckle (blue line)

next find a way to mount a cantilever type set up at the top of each diff assembly or on the arms somewhere (red bloch on diffs)

use a rod or cable (i have cable shown) to go from the cantilever to the knuckle (fuscia line)

run the cable (lawn mower throttle cable or bike shifting/brake cable) (fuscia line) from where ever the servo is mounted to the cantilever. i've shown it in the servo in the chassis area but i think i could mount it to the front diff for wieght and still use the cable to run the back

kinda like a stock clod

[xtremraptor]

i didn't think the idea was original, but i didn't think a RC company did it.

have you driven a stock clod? i have not. how do they steer?

[gregrocks90046]

the stock clod has horrible steering even with a 1/4 scale servo. at least mine did.

post some pics when you get your steering fabbed!

[xtremraptor]

will do.

[microgoat]

I'll share my cable experience, using a plastic airplane pushrod to shift my E-Maxx tranny. The pushrod is a semi-rigid plastic tube that will flex, similar to lawnmower cable, but lighter. I thought it would be just the ticket, but holding it in place proved to be a hassle. Even using a micro servo, the cable would deflect instead of moving the shift fork. Using a cable for steering, your load will be 100 times greater.

Now, if you can support the cable along its entire length (like they do in model airplanes) to prevent deflection, then you have a shot at making this work. A big problem is going to be trying to push with the cable, as noted previously. Using a pull-pull system will be much more effective, and won't weigh that much more. You shouldn't have too much trouble finding a 1/4-scale pull-pull system. I'm pretty sure Dubro makes one. How you'll link two of them together to make both axles steer is another story, but you'll figger it out

[xtremraptor]

http://www2.towerhobbies.com/cgi-bin...?&I=LXD859&P=0

is this what you are talking about?

[TwistedXT]

i tried the whole canti's on the axle with remote mounted 1/4 scale on a txt i built... it sucked! the only way that this works is if the steering geometery falls inline with the suspensions rotational axis, other wise when you try to turn it will either raise or lower the chassis. Even with the canti falling in line like described above, there is alot of force involved at the axle mounting point of the canti, tends to bend alot of stuff... if you figure something out, let us know... it is a great idea and reallt frees up room on the axle.. happy building. oh yeah, one more thing... your steering links have to be the same lenght as your suspension links or you will have bump steer. just my 2 cents... doesnt much but its somethin... i hope this helps.