RCCrawler Forums

ILoveRCRockCrawlin · 11-23-2005, 11:45 AM

i need to know how far a servo travels in inches. im planning on blowing all my christmas money away on pnuematic steering for my tlt/maxx and i need to know how big of a cylinder im going to need.

Frakk · 11-23-2005, 11:51 AM

servos dont travel, they rotate. the longer horn you put on it the more its end will travel but you will loose torque.

ILoveRCRockCrawlin · 11-23-2005, 12:01 PM

o yeah i forgot about that.

anyway heres what im planning on getting
the kit
http://www2.towerhobbies.com/cgi-bin...?&I=LXET22&P=7
i might buy everything individially so i dont get the valve because that vavle is the wrong valave and its an extra $20.
the valve i need (2 way):
http://www2.towerhobbies.com/cgi-bin...?&I=LXET30&P=7
and the cylinder:
http://www2.towerhobbies.com/cgi-bin...?&I=LXET28&P=7

xjnation · 11-23-2005, 12:20 PM

iS IT GOING TO BE PROPORTIONAL??? How long do you think a tank of air will last?? Cool idea but there might be some problems. I think you will lose the ability to only turn the wheel halfway instead of fully. Even if you close the valve at halfway, there will be nothing supporting the piston and it will have freeplay in it. Thats what I'm guessing, at least.... I might be wrong. If you get it working, be sure to post pics and a video.

chafey · 11-23-2005, 12:44 PM

air compresses, hydraulics dont. servo travel would depend on how hard you throw it and if it's still in the truck. huh grizz.

ILoveRCRockCrawlin · 11-23-2005, 12:44 PM

the valves have a control, the less air you put in the piston the less it will travel but that air stays in there not allowing the piston to move. this is experimental still. it has been done before so i know there is a way to get it to work. there are valves that control how far the pistons move so im going to one and plus its a two way. the wait tank should last for a good amount of time seeing that they have the pressure to hold up 20-30 pound planes and retaract/put out the landing a gear a few times before needing refilling. plus i plan on getting a few tanks.

ILoveRCRockCrawlin · 11-23-2005, 01:51 PM

i got the final list and the total is about 70 after tax. not bad.

this kit http://www2.towerhobbies.com/cgi-bin...?&I=LXET21&P=7
with this cylinder http://www2.towerhobbies.com/cgi-bin...?&I=LXET28&P=7
and there other stuff like threaded rod and rod ends but thats included in the $70.

if i do go with the pneumatic steering, its only going to be 2ws. maybe 4ws if i get the money and intelligence to do it.

WestCoastPJ · 11-23-2005, 03:05 PM

Hmm..Why not stick with the conventional servo with links?

Frakk · 11-23-2005, 04:06 PM

because that is just plain. some of us want to do something outstanding from the rest and some just lay back and go with the flow and do the old tricks over and over again.

AdamF · 11-23-2005, 04:13 PM

I thought of doing this a while back too, using some robot pneumatics, but I don't have the balls to actually go through with it! Good job. I hope it works out well.

chafey · 11-23-2005, 04:26 PM

Quote:

Originally Posted by Frakk

because that is just plain. some of us want to do something outstanding from the rest and some just lay back and go with the flow and do the old tricks over and over again.

beady eyes and flapping head!

ILoveRCRockCrawlin · 11-23-2005, 05:56 PM

Quote:

Originally Posted by WestCoastPJ

Hmm..Why not stick with the conventional servo with links?

like frakk said its just too boring.

i remember seeing someone else's rig with the pneumatic steering and since then ive always wanted to try it. it doesnt really seem that hard as long as you stick with 2ws. if forget whos rig it was but it had 4ws and each axle was controlled indiviually. the pneumatic steering also has A LOT more torque. the hitech 645 servo puts out about 6.625 pounds of torque and the pneumatic and the 1" cylinder ill be using (http://www2.towerhobbies.com/cgi-bin...?&I=LXET28&P=7 ) puts out 11 pounds of torque at 100 psi

ILoveRCRockCrawlin · 11-23-2005, 06:50 PM

i found it, but his was done with hydrolics. its JIA's rig
http://www.projecttwin.com/Scorpion_...awler_5081.cfm

ILoveRCRockCrawlin · 11-23-2005, 06:59 PM

o yeah and looking at the steering setup on JIA's crawler, it looks as if im going to need 2 cylinders. so its actually going to cost about $90 which isnt bad seeing that itll have a lil less than twice the amount of torque as a 645 servo.

TwistedCreations · 11-23-2005, 07:16 PM

ummmmmmmmmm ok

ILoveRCRockCrawlin · 11-23-2005, 07:33 PM

i know im babbling, but i just wanted to let people know that are interested, if anyone is interested.

ILoveRCRockCrawlin · 11-23-2005, 08:08 PM

i need to know if this is correct.

if you were to pretend that the cylinders were mounted to the front of the axle and you were looking at the axle straight on, they would be turning to the left, am i right?

JasonInAugusta · 11-23-2005, 09:37 PM

I used two cylinders per axle because hydraulic cylinders are stronger when pushing than they are when pulling. Putting two on the axle gives me a rated output of 14lbs of linear force @ 100psi. I've upped the psi (easy to do on the pump itself) so I'm looking at 150-200psi in the system.

I've seen pneumatic systems work in other applications...one guy had a set of four cylinders that lifted his computer case off the desktop.

I'm not sure how many left/right cycles you'd get with the Robart system. Might want to search google to see what you can find out.

I don't think controlling the system will be an issue. As far as control it should work exactly the same as the hydraulics on my Scorpion. The pressure from the canned air (my pump) is constant, you're just manipulating the volume of air and the rate at which it travels. You will end up giving more steering input than you ever have. With the type of system you're thinking about running, it will not return to center. It'll stay pointed in whatever direction until you give the opposite input. It'll be like flying a helicopter, you'll have to counter every input you give to keep it moving straight.

The main (and it seems only) problem I see is that air compresses. Hydraulics work because the fluid is incompressible. Pneumatic setups work great for airplane retracts because there's very little work to be done. On a crawler it takes a good bit of force to steer with authority.

Then again...that dude did lift his computer case with 4 cylinders.

I say give it a shot...but put the cylinders on a behind the axle setup. No sense in beating them against the rocks.

Can't hurt to try.

If it helps, here's the plumbing diagram for my Scorpion. There's a couple of things missing, but you won't need them on your pneumatic system anyway.

JasonInAugusta · 11-23-2005, 10:36 PM

After reading the topic which is "How far does a servo travel?" I'm thinking this..

Servo travel isn't important in your system.

What is important is how much linear travel you'll need to move the steering knuckles from one point to another. If I remember right, it's ~ 34mm

Then you'll need to know the stroke of the cylinders, as well as their eye to eye length when extended and compressed.

This will tell you if the cylinders will even fit the axles.

ILoveRCRockCrawlin · 11-23-2005, 10:39 PM

Quote:

Originally Posted by JasonInAugusta

After reading the topic which is "How far does a servo travel?" I'm thinking this..

Servo travel isn't important in your system.

What is important is how much linear travel you'll need to move the steering knuckles from one point to another. If I remember right, it's ~ 34mm

Then you'll need to know the stroke of the cylinders, as well as their eye to eye length when extended and compressed.

This will tell you if the cylinders will even fit the axles.

yea ik all that this tread wasnt supposed to get into such detail.

11-23-2005, 11:45 AM	#1
ILoveRCRockCrawlin RCC Addict Join Date: Dec 2004 Location: Central NY Posts: 1,980	how far does a servo travel? i need to know how far a servo travels in inches. im planning on blowing all my christmas money away on pnuematic steering for my tlt/maxx and i need to know how big of a cylinder im going to need.

11-23-2005, 09:37 PM	#18
JasonInAugusta 06 Super National Champ Join Date: Jun 2004 Location: Stark Industries Bar and Grill Posts: 11,361	I used two cylinders per axle because hydraulic cylinders are stronger when pushing than they are when pulling. Putting two on the axle gives me a rated output of 14lbs of linear force @ 100psi. I've upped the psi (easy to do on the pump itself) so I'm looking at 150-200psi in the system. I've seen pneumatic systems work in other applications...one guy had a set of four cylinders that lifted his computer case off the desktop. I'm not sure how many left/right cycles you'd get with the Robart system. Might want to search google to see what you can find out. I don't think controlling the system will be an issue. As far as control it should work exactly the same as the hydraulics on my Scorpion. The pressure from the canned air (my pump) is constant, you're just manipulating the volume of air and the rate at which it travels. You will end up giving more steering input than you ever have. With the type of system you're thinking about running, it will not return to center. It'll stay pointed in whatever direction until you give the opposite input. It'll be like flying a helicopter, you'll have to counter every input you give to keep it moving straight. The main (and it seems only) problem I see is that air compresses. Hydraulics work because the fluid is incompressible. Pneumatic setups work great for airplane retracts because there's very little work to be done. On a crawler it takes a good bit of force to steer with authority. Then again...that dude did lift his computer case with 4 cylinders. I say give it a shot...but put the cylinders on a behind the axle setup. No sense in beating them against the rocks. Can't hurt to try. If it helps, here's the plumbing diagram for my Scorpion. There's a couple of things missing, but you won't need them on your pneumatic system anyway. Last edited by JasonInAugusta; 11-23-2005 at 10:42 PM.

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11-23-2005, 11:51 AM	#2
Frakk Pebble Pounder Join Date: Sep 2005 Location: Canada Posts: 171	servos dont travel, they rotate. the longer horn you put on it the more its end will travel but you will loose torque.

11-23-2005, 12:01 PM	#3
ILoveRCRockCrawlin RCC Addict Join Date: Dec 2004 Location: Central NY Posts: 1,980	o yeah i forgot about that. anyway heres what im planning on getting the kit http://www2.towerhobbies.com/cgi-bin...?&I=LXET22&P=7 i might buy everything individially so i dont get the valve because that vavle is the wrong valave and its an extra $20. the valve i need (2 way): http://www2.towerhobbies.com/cgi-bin...?&I=LXET30&P=7 and the cylinder: http://www2.towerhobbies.com/cgi-bin...?&I=LXET28&P=7

11-23-2005, 12:20 PM	#4
xjnation Rock Stacker Join Date: Oct 2005 Location: Springfield Posts: 50	iS IT GOING TO BE PROPORTIONAL??? How long do you think a tank of air will last?? Cool idea but there might be some problems. I think you will lose the ability to only turn the wheel halfway instead of fully. Even if you close the valve at halfway, there will be nothing supporting the piston and it will have freeplay in it. Thats what I'm guessing, at least.... I might be wrong. If you get it working, be sure to post pics and a video.

11-23-2005, 12:44 PM	#5
chafey Rock Crawler Join Date: Aug 2004 Location: woods cross utah Posts: 523	air compresses, hydraulics dont. servo travel would depend on how hard you throw it and if it's still in the truck. huh grizz.

11-23-2005, 01:51 PM	#7
ILoveRCRockCrawlin RCC Addict Join Date: Dec 2004 Location: Central NY Posts: 1,980	i got the final list and the total is about 70 after tax. not bad. this kit http://www2.towerhobbies.com/cgi-bin...?&I=LXET21&P=7 with this cylinder http://www2.towerhobbies.com/cgi-bin...?&I=LXET28&P=7 and there other stuff like threaded rod and rod ends but thats included in the $70. if i do go with the pneumatic steering, its only going to be 2ws. maybe 4ws if i get the money and intelligence to do it.

11-23-2005, 03:05 PM	#8
WestCoastPJ Quarry Creeper Join Date: Jun 2005 Location: NOrthern Cali Posts: 312	Hmm..Why not stick with the conventional servo with links?

11-23-2005, 04:06 PM	#9
Frakk Pebble Pounder Join Date: Sep 2005 Location: Canada Posts: 171	because that is just plain. some of us want to do something outstanding from the rest and some just lay back and go with the flow and do the old tricks over and over again.

11-23-2005, 04:13 PM	#10
AdamF RCC Addict Join Date: Apr 2004 Location: Cincinnati Ohio Posts: 1,673	I thought of doing this a while back too, using some robot pneumatics, but I don't have the balls to actually go through with it! Good job. I hope it works out well.

11-23-2005, 06:50 PM	#13
ILoveRCRockCrawlin RCC Addict Join Date: Dec 2004 Location: Central NY Posts: 1,980	i found it, but his was done with hydrolics. its JIA's rig http://www.projecttwin.com/Scorpion_...awler_5081.cfm

11-23-2005, 06:59 PM	#14
ILoveRCRockCrawlin RCC Addict Join Date: Dec 2004 Location: Central NY Posts: 1,980	o yeah and looking at the steering setup on JIA's crawler, it looks as if im going to need 2 cylinders. so its actually going to cost about $90 which isnt bad seeing that itll have a lil less than twice the amount of torque as a 645 servo.

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11-23-2005, 07:16 PM	#15
TwistedCreations Colt Python/SR9c Join Date: Feb 2004 Location: out in the shop, reloading ammo! Posts: 8,626	ummmmmmmmmm ok

11-23-2005, 07:33 PM	#16
ILoveRCRockCrawlin RCC Addict Join Date: Dec 2004 Location: Central NY Posts: 1,980	i know im babbling, but i just wanted to let people know that are interested, if anyone is interested.

11-23-2005, 08:08 PM	#17
ILoveRCRockCrawlin RCC Addict Join Date: Dec 2004 Location: Central NY Posts: 1,980	i need to know if this is correct. if you were to pretend that the cylinders were mounted to the front of the axle and you were looking at the axle straight on, they would be turning to the left, am i right?

11-23-2005, 10:36 PM	#19
JasonInAugusta 06 Super National Champ Join Date: Jun 2004 Location: Stark Industries Bar and Grill Posts: 11,361	After reading the topic which is "How far does a servo travel?" I'm thinking this.. Servo travel isn't important in your system. What is important is how much linear travel you'll need to move the steering knuckles from one point to another. If I remember right, it's ~ 34mm Then you'll need to know the stroke of the cylinders, as well as their eye to eye length when extended and compressed. This will tell you if the cylinders will even fit the axles.

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