External hydro assist on stock toyota steering rack

Blender

Swiftie
Joined
Oct 4, 2018
Messages
2,772
Location
Chandler, AZ
I don't know about you guys, but I've broken off the stock rack mounts a few times now. My shit's way too heavy for the steering/skid plate layout that's pretty much identical to a 1G taco and 3G 4runner.

Minimum fix it adding a crossmember behind the steering rack to keep the tranny skid from tearing off the steering rack. That's boring. Why not add an external hydraulic cylinder to gain ~1000 LBs of steer force? This can also function as a rack-slider to help alleviate some of the stress at the rack and rack mounts.

Rough specs:
  • +1000 LBs of steer force. Stock should be around 1600 LBs+ manual contribution. This will end up at ~2600 Lbs of assist + manual contribution.
  • Requires 60% more fluid flow, so it might drive like shit.
  • Retains 100% stock rack for easy off the shelf rack swaps. No custom work or seals on anything that can wear out.
  • Inner tie rods replaced with 3/4" heims, outers could be stock toyota outers or 80 series LC TREs (requires reduced droop travel)
  • passive upper bar acts as rack slider which reduces vertical deflection of stock rack ~50% by initial simulation. Not as good as a purpose built, but not horrible
  • Systems are synchronized with the beefy clevis adapters (green). They need to transmit high loads so they're pretty huge.
  • Ties into stock sway bar mounts and also supports the transmission skid to avoid future damage
  • No decrease in ground clearance

So far everything is floating where it needs to be. Initial cradle from sheet metal wasn't to my liking, so I'm starting fresh. Geometry is far from ideal. Fitment of everything is really tight and needs to allow structure around it and fitting access. Transmission pan isn't shown.

I think I tracked down all the fittings for the lines. Still unsure how much room i'll need at the rack high pressure port to do a 90 deg bend. Could end up with a custom fitting.

vcOPgve.png

Dashed line is where the cradle goes.
2U9nYDz.png



Needs to somehow tie into the rack or rack mounting itself to prevent relative movement. Still working on a few options. As of now I have no way of reinstalling any kind of bellows over the stock rack. I think all the aux stuff will be fine, but the stocker needs to be protected from grit.

Now is when you guys poke holes in this idea.
 

AssBurns

will wheel for beer
Staff member
Joined
Oct 1, 2018
Messages
7,959
Age
31
Location
Yucaipa, CA
While I like the idea, are there any concerns about the hydro assist basically ripping the rack out of the frame? Seems like the assist and sliders would work really well, but I’d be a little worried about how the rack handles the push/pull force from the assist. It might not be an issue at all, but definitely the first thing that comes to mind.
 

Blender

Swiftie
Joined
Oct 4, 2018
Messages
2,772
Location
Chandler, AZ
While I like the idea, are there any concerns about the hydro assist basically ripping the rack out of the frame? Seems like the assist and sliders would work really well, but I’d be a little worried about how the rack handles the push/pull force from the assist. It might not be an issue at all, but definitely the first thing that comes to mind.

I sure am worried about that. The assist cylinder adds some fore/aft bending to the stock rack bar which I can't really stop. I'm hoping a tie in from the stock rack housing to the cradle will protect the factory mounts.

I'm also concerned about tearing the lower arms off the truck in a bind. I specified a small cylinder with low-ish output, but there's not a lot I can do on this one.
 

PCTaco

36 Hour Build
Joined
Apr 26, 2019
Messages
509
Age
35
I don't work on these trucks, but I do work on a ton of hydraulics.

If your flows aren't damn near perfect you're going to be either yanking the rack into position with the cylinder or pushing against the cylinder trying to turn the vehicle.

https://www.womackmachine.com/engin...calculations/hydraulic-cylinder-calculations/

This is a pretty nifty site, make sure your flow/inch works out to keep the rack and cylinder running at the same speeds.
 

AssBurns

will wheel for beer
Staff member
Joined
Oct 1, 2018
Messages
7,959
Age
31
Location
Yucaipa, CA
I'm also concerned about tearing the lower arms off the truck in a bind. I specified a small cylinder with low-ish output, but there's not a lot I can do on this one.
I wouldn’t be too worried about the lowers ripping off. I think the tie rods or rack will rip off first.
If you can figure out the right flow rates like @PCTaco is saying, I think you can make this work.
 

Blender

Swiftie
Joined
Oct 4, 2018
Messages
2,772
Location
Chandler, AZ
I don't work on these trucks, but I do work on a ton of hydraulics.

If your flows aren't damn near perfect you're going to be either yanking the rack into position with the cylinder or pushing against the cylinder trying to turn the vehicle.

https://www.womackmachine.com/engin...calculations/hydraulic-cylinder-calculations/

This is a pretty nifty site, make sure your flow/inch works out to keep the rack and cylinder running at the same speeds.

I've been all over the place on synchronization. My cylinder volumes will never match for a 50:50 fluid split since the rack is metric and I can only get english bore cylinders. I found some flow dividers which have adjustable dividers but also 10% internal leakage.

Loader arms use mechanical synchronization, but they also have equal cylinders. Solid axle hydro assist uses the draglink and tie rods to sync unequal cylinder bores in the steering box and external ram. Certainly not an ideal design. It's a bandaid in every sense. Road feel will likely dissappear. I'll have to account for everything fighting eachother

Looked around for a cheap HPU and OTS double ended cylinder to do a benchtop test. They're around, but it'll cost as much as just going for it :noidea:
 

Arcticelf

Head BFH Operator at Gray Man Fab
Joined
Apr 23, 2019
Messages
1,167
Location
DelCo PA
I don't work on these trucks, but I do work on a ton of hydraulics.

If your flows aren't damn near perfect you're going to be either yanking the rack into position with the cylinder or pushing against the cylinder trying to turn the vehicle.

https://www.womackmachine.com/engin...calculations/hydraulic-cylinder-calculations/

This is a pretty nifty site, make sure your flow/inch works out to keep the rack and cylinder running at the same speeds.

An easier solution is just to disconnect the hydraulics on the rack, and put all the fluid into the ram.
 

Blender

Swiftie
Joined
Oct 4, 2018
Messages
2,772
Location
Chandler, AZ
An easier solution is just to disconnect the hydraulics on the rack, and put all the fluid into the ram.

true. In that case I'd swap the cylinder to be in the stock rack's position to keep the high loads inline with the tierods. I'd need to move the stock rack backwards and upsize the aux ram to 2.5"bore. Let me play around in CAD this evening and see how it fits.
 

AssBurns

will wheel for beer
Staff member
Joined
Oct 1, 2018
Messages
7,959
Age
31
Location
Yucaipa, CA
true. In that case I'd swap the cylinder to be in the stock rack's position to keep the high loads inline with the tierods. I'd need to move the stock rack backwards and upsize the aux ram to 2.5"bore. Let me play around in CAD this evening and see how it fits.
I've been considering this. If you put in an load reactive orbital valve, you can still have a little bit of road feel.
 

Blender

Swiftie
Joined
Oct 4, 2018
Messages
2,772
Location
Chandler, AZ
I've been considering this. If you put in an load reactive orbital valve, you can still have a little bit of road feel.

I don't really want full hydro on a street legal truck although it would probably be easier and cheaper. I'd like something that can be defeatured back to stock if it's a total disaster.

the minor internal leakage of full hydro would annoy me with a crooked steerwheel. Could cost me the horn airbag and cruise control if I run out of clockspring travel which is a no-go
 

Dukestaco

Stirring the pot 24/7
Joined
Oct 3, 2018
Messages
7,472
Location
Tucson
Georgie you can’t do full hydro on a street truck. The zuk had hydro assist of the power steer Toyota box. One line was tapped in to the right side and one on the left side. I’ll look and see if I have any pics of it. Like mentioned before I also think that would be the way to go. Some how tap into the power steering pump pressure to assist the ram instead of a separate hydro system.
 

Arcticelf

Head BFH Operator at Gray Man Fab
Joined
Apr 23, 2019
Messages
1,167
Location
DelCo PA
Georgie you can’t do full hydro on a street truck. The zuk had hydro assist of the power steer Toyota box. One line was tapped in to the right side and one on the left side. I’ll look and see if I have any pics of it. Like mentioned before I also think that would be the way to go. Some how tap into the power steering pump pressure to assist the ram instead of a separate hydro system.

You should be able to use the valving in the OEM rack to run fluid into the hydro/assist ram then use the OEM rack ram to keep the road feel and mechanical safety.
 

Blender

Swiftie
Joined
Oct 4, 2018
Messages
2,772
Location
Chandler, AZ
Looked at the geometry to place a cylinder in the current rack position. Stock rack will not fit if moved rearward due to exhaust/cat/frame interference. Didn't bother to look at steering shaft routing issues since there were so many other problems. Too extreme for my end goal.

Keeping the original layout to de-feature the system back to stock if it sucks. I'm still chugging along on it when i have time. Now im certain I cannot use the stock high pressure/return lines, but some modified adapters and hardlines should get me there.
 

Blender

Swiftie
Joined
Oct 4, 2018
Messages
2,772
Location
Chandler, AZ
Ordered the cylinder last week. Longer lead time and higher cost than I hoped, but whatever. Also found shorter adapters into the rack ports. Less stickout at the steer tube lines.

Modified the rack inlet/outlet to accept an M10 Banjo fitting. Might have enough material to upsize to M12. Looked around for any details on the minor losses of the banjo, but couldn't find what I needed. Wanted to do some rough fluid flow calcs to see if I'll be constricting the flow too much.
5Ks1IVxh.jpg

o8ICxaah.jpg

45dwgrFh.jpg

Top: aftermarket ITR, Hamburg LT steering extension
Bottom: Camburg 3/4" Clevis adapter, custom adapter, stock outer tie rod. Missing jam nut.

Received my tie rod adapters. They are my "minimum repair" solution. swaps the ITR to LH 3/4" heim with camburg's clevis. These keep a stock outter tie rod since the head is canted 7deg. I need this cant to prevent binding at full droop. They're 17-4 SS, so they can technically be heat treated. Lively only marginally stronger than what I had before.

QOYOoDXh.jpg

Better part uses LC 80 series outers. The taper, and castle nut matches my LBJ which is nice. Since the head is straight, not canted, I'll lose a little downtravel. Not sure how much, but if it's ~0.5" I'll probably limit the suspension to be able to run these beefier parts.
 

Blender

Swiftie
Joined
Oct 4, 2018
Messages
2,772
Location
Chandler, AZ
80 series outer will rob me of >2" downtravel. Stock LBJ has the steer arm canted the opposite direction I expected. Maybe to maximize the effective length of the stock tierod? To get double shear heim at the outer guys weld a tab to the LBJ. Since it's a wear item I don't wanna do that. As it turns out BBM makes a uniball conversion. Instead of running the welded cup, I'll have a solid cup/steer arm cut with double shear provisions and an un-canted perch:
LBJ uniball and SCAN annotated.jpg
Uniball becomes the service point and BBM can figure out all the uniball adapters and hardware for me. All I need is one custom part per side. Pic shows a stock LBJ and a concept integrated cup with wrong arm geometry.



As for the hydro assist, Technically this was fully designed and I slapped some hard-mount bushings in the stock rack to see where the rack really sits before ordering any parts. As it turns out everything is in pretty rough shape. Pass side of the stock rack is an inch high. Not a straight edge anywhere

Scope creep: Rebuild the rear crossmember to better incorporate my steering needs and fix the rack mounts, diff mount and alignment cams at the same time. I'd like to rebuild the front crossmember too which would allow the lower arms to be relocated forward a-la JD fab to make room for the set of 37s I've been sitting on. Initial napkin doodles show it's maybe ballpark possible for 0.5". I can't move the diff forward because of the oilpan, i can't move the rack forward because of the diff's pinion flange. Worst case I leave the arm mounts where they are, but beef up what's needed.

New lowers would probably be easier and reversible. Gotta see what the most achievable solution is.

Cradle concept rough in.jpg

Caved, and got a scanner to verify where everything is. Been getting the hang of it on smaller stuff for now and verifying its accuracy. I don't have the big-baller reverse engineer software, so I gotta slum it with featureless mesh surfaces. So far they're workable.
comparison to scan.JPG
Comparison of my initial rack measurements to the scanners output. Main tube is spot on, most angles are pretty close. Control valve is noticeably taller. That gives me way more room for the lines and fittings. Point to point measurements lead me to believe the scanner is right.

tundra crawlbox raw.JPG

Inchworm crawlbox. Really hard to scan because of the shine from the machined adapters. Lots of holes in the model. Coated key areas in baby powder to help the scanner, but still couldn't get the deep crevasses. Learned some good techniques though.

This shit will never get finished :deadbanana:
 

Blender

Swiftie
Joined
Oct 4, 2018
Messages
2,772
Location
Chandler, AZ
Now that you've got a scanner, go to a couple taco meets and scan everyone's front frame where the LCA mounts are. I really want to know how much variation there is between frames in that area, especially on trucks the get wheeled.

It's a rental thru Monday. I dunno any 2G taco guys, but if the trucks were available the front section would be pretty quick.
 

Blender

Swiftie
Joined
Oct 4, 2018
Messages
2,772
Location
Chandler, AZ
Initial report is I can't move the rear crossmember forward. Front diff and CVs aren't gonna make it easy.

I do have a plan B: Increase alignment adjustment to allow the arms to be placed such that the LBJ is 0.25-0.5" forward. I have heimed lowers, so there will be no binding. Would also be reversible I run into problems.

Any suspension gurus wanna poke holes in that idea? It's essentially adding a shit tonne of caster which is fine by me, but will it have any negative affects since everything is altered? Still need to figure out the geometry to even do it.

Diagram isn't to scale yet:
increase Caster below annotated.jpg

raw scan of front sus 1.jpg
 

Stairgod

Two bad decisions away from buying a bulldozer
Joined
Apr 22, 2019
Messages
2,438
Initial report is I can't move the rear crossmember forward. Front diff and CVs aren't gonna make it easy.

I do have a plan B: Increase alignment adjustment to allow the arms to be placed such that the LBJ is 0.25-0.5" forward. I have heimed lowers, so there will be no binding. Would also be reversible I run into problems.

Any suspension gurus wanna poke holes in that idea? It's essentially adding a shit tonne of caster which is fine by me, but will it have any negative affects since everything is altered? Still need to figure out the geometry to even do it.

Diagram isn't to scale yet:
View attachment 57823

View attachment 57824
No guru, but moving the lbj forward a half inch should only add about 1.25° more caster.
 
Top Bottom