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Old 08-26-2019, 01:53 PM   #1 (permalink)
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Dual Single Ended Steering Cylinders

can somebody point me in a direction? i think i'm spinning my tires again

dual single ended steering rams: is there any reason why i can't use 8" travel cylinders and simply use "the other side" ram as my steering stop to accomodate 6" travel knuckle/arm combo?

why? i'm not confident i'll be on toyota axles forever, but i don't want to buy a bunch of steering stuff over again. i've been hung up lately on valve sizing because i'm trying to get a cylinder size that will work with 6" stroke and then be rather similar for 8" stroke for steering feel.

but hell, why not just snag 8" travel rams now, then the only difference would be a bit more wheel input lock to lock, but the degree of travel per rotation feel would be the same

don't want to use a sindle double ended ram because...i dunno, 2 rams just seem easier to mount and locate
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Old 08-26-2019, 02:07 PM   #2 (permalink)
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Internal stops in both cylinders FTW.

You talking about mounting them monster truck style with each going to a knuckle and a side to side tie rod or ?

Last edited by SLOWPOKE693; 08-26-2019 at 02:08 PM.
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Old 08-26-2019, 02:13 PM   #3 (permalink)
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Internal stops in both cylinders FTW.

You talking about mounting them monster truck style with each going to a knuckle and a side to side tie rod or ?
yeah that is what i was thinking, one to each steering arm and then a tie rod to keep them 'timed'

i guess yeah, internal stop would be easy and accomplish the same thing.

i'll start looking for some 8" cylinders then and shoot for and orbital in between. i think changing my view from maximum input from steering wheel into output of degrees of steering is the more relevant calculation/measure than the simple lock to lock that i've been stuck on for so long
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Old 08-26-2019, 02:21 PM   #4 (permalink)
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follow on question would then be, what would be considered the minimum shaft size for that kind of setup?

http://www.pscmotorsports.com/pdf/te.../calculate.pdf

2ea 1.75 dia 0.75 shaft would net more joint steering force than a single DE 2.5 dia 1.5 shaft, but will a 3/4" shaft survive or at least be stronger than a knuckle?

stout tie rod and an extra cylinder should help with the shock
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Old 08-26-2019, 04:18 PM   #5 (permalink)
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had duals in one of my rigs.
had them set up only to push towards knuckle. rod sides was just wented together.

they where 40mmpiston 20mm rod
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Old 08-26-2019, 04:43 PM   #6 (permalink)
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The big rods on double ended cylinders are mostly because they get side loaded, not because they "need" to be that big for the forces involved. Once you move to a strict tension/compression model and get rid of side loading, smaller shafts are fine. So yes, two 1.75/.75 cylinders, a decent tie rod, a means to protect those cylinders from rocks, and you're good (probably break knuckles or tie rod ends before hydro parts).

I would connect the two cylinders in parallel, opposing directions, not just vent/couple the can sides, as that will allow you to use smaller/cheaper cylinders and still have the power of two vs. only the power of one in each direction.

Personally, I'd set it up with rod side stroke limit stops, one on each cylinder, and place the cylinders such that the can side stroke limit when the piston hits the end is where you need it to be. Depending on cylinder construction, it should add to less disassembly to put them in or take them out later, it lets you have less exposed rod during use (less risk of buckling/bending/damage), and keeps the overall extended length shorter, which means easier mounting.

Last edited by [email protected]; 08-26-2019 at 04:45 PM.
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Old 08-26-2019, 05:55 PM   #7 (permalink)
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had duals in one of my rigs.
had them set up only to push towards knuckle. rod sides was just wented together.

they where 40mmpiston 20mm rod
thats a good thought for keeping the required flow volume down.
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Old 08-26-2019, 05:58 PM   #8 (permalink)
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The big rods on double ended cylinders are mostly because they get side loaded, not because they "need" to be that big for the forces involved. Once you move to a strict tension/compression model and get rid of side loading, smaller shafts are fine. So yes, two 1.75/.75 cylinders, a decent tie rod, a means to protect those cylinders from rocks, and you're good (probably break knuckles or tie rod ends before hydro parts).

I would connect the two cylinders in parallel, opposing directions, not just vent/couple the can sides, as that will allow you to use smaller/cheaper cylinders and still have the power of two vs. only the power of one in each direction.

Personally, I'd set it up with rod side stroke limit stops, one on each cylinder, and place the cylinders such that the can side stroke limit when the piston hits the end is where you need it to be. Depending on cylinder construction, it should add to less disassembly to put them in or take them out later, it lets you have less exposed rod during use (less risk of buckling/bending/damage), and keeps the overall extended length shorter, which means easier mounting.
looking at the arms i have now, the cylinders will end up mounted fairly high. guess i'll do some more digging to see how small i can get away with.

i'm also trying to keep my cylinder volume for 8" stroke around or under 20 cu in (320 metric)
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Old 08-26-2019, 07:17 PM   #9 (permalink)
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alright, some notes so i don't have to do the math again. looks like if i go with double acting cylinders, the 1.5x8x1" shaft will give me a total volume of just under 22 cu in. seems to be as small bore and large shaft for net smallest displacement
@2k psi it would net 3532 (piston side) + 1962 (shaft side) = 5494 lbs of force max
~$90 ea at surplus center

for single acting cylinders or DA with shafts tied together; 1.75x8 (shaft size irrelevant) nets 19.23 cu in and at 2k psi nets 4808 lbs of force - harder to find cylinders though
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Old 08-27-2019, 04:54 AM   #10 (permalink)
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Quote:
Originally Posted by Provience View Post
alright, some notes so i don't have to do the math again. looks like if i go with double acting cylinders, the 1.5x8x1" shaft will give me a total volume of just under 22 cu in. seems to be as small bore and large shaft for net smallest displacement
@2k psi it would net 3532 (piston side) + 1962 (shaft side) = 5494 lbs of force max
~$90 ea at surplus center

for single acting cylinders or DA with shafts tied together; 1.75x8 (shaft size irrelevant) nets 19.23 cu in and at 2k psi nets 4808 lbs of force - harder to find cylinders though
If you're trying to keep total volume down look at single acting snow plow cylinders. A nice bonus with single acting is that the tie rod will always be in tension, never compression.
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Old 08-27-2019, 07:11 AM   #11 (permalink)
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If you're trying to keep total volume down look at single acting snow plow cylinders. A nice bonus with single acting is that the tie rod will always be in tension, never compression.
oddly enough those seem to only be 10" stroke as the shortest, yet the collapsed length shows 16" where a DA 8" stroke from the prince catalogue shows same length as 20-1/4"

1.5 limited to 8" travel would put disp around 14 cu in, which is my next step down in steering valve size, which makes everything just a touch easier

https://www.northerntool.com/shop/to...ct_21002_21002
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Old 08-27-2019, 07:12 AM   #12 (permalink)
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the tie rod will always be in tension, never compression.
well, until i hit a rock at 60 mph
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Old 08-27-2019, 08:01 AM   #13 (permalink)
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well, until i hit a rock at 60 mph
good reason to use two dual acting ones. when you fuck one up just swap the hoses and you can drive home
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Old 08-27-2019, 01:57 PM   #14 (permalink)
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good reason to use two dual acting ones. when you fuck one up just swap the hoses and you can drive home
seems lots of the smaller cylinders also use small fittings, -4 or -6.

i can't think of any reason to not cut those off, redrill and enlarge those to -8 or -10 or whatever hose size i can actually end up with.

https://www.surpluscenter.com/Hydrau...der-9-6845.axd

2x8x1.25 DE DA Cylinder disp volume 15.36 cu in @2k psi is 3840 lbs of force


https://www.surpluscenter.com/Hydrau...-9-4410-08.axd

1.5x8x0.75 DA single cylinders with shaft sides tied together disp volume 14.13 cu in @2k psi is 3532 lbs of force

meaning i can use the OSPU 60/240 valve. displaces 3.66 cu in/rev minimum and 14.65 cu in per rev max at max flow of 6.38 gpm. using a 10 bar load sense priority valve would put about 11 cu in per rev amplified flow available for initial input from static, ramping up to full shortly after.

i think that gives me a direction to start saving for and spending money on. if the dual cylinder thing is no bueno, then i can go to a "standard" tandem cylinder without a huge change in steering feel
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