DIY electric power steering

[jaybee]

Not sure if anyone else has looked into this, but some folks have put a fair bit of effort into figuring out how to retrofit salvaged electric power steering units into cars which didn't come with them originally. This retrofit seems to be particularly interesting to people who build cars which use the Bendix ram-based steering assist system.  Some of the columns only work in cars with modern, Canbus-wired electrical system, but some of them work without Canbus or a VSS speed signal.  This first video is a look at some units which work without access to computer control.  

Here's a bench test of a salvage unit and a partial disassembly of the system to show how it works. A torsion bar in the column operates a pair of magnetic rings to sense when torque is being applied through the steering wheel.

Now, as to how to splice one of these setups into the middle of a steering column. Several options are considered here, but I'm scratching my head a little. Surely there must be ways to do this that don't involve welding steering shafts, wouldn't you think?  

Here it is installed in the car.  

If you'd prefer to see this stuff on a page (and I do) the same guy has posted his information on a couple of forums.

https://www.therangerstation.com/tech/toyota-electric-power-steering-eps-conversion/

https://ls1tech.com/forums/suspension-brakes/1848775-35-electric-power-steering-fail-safe-no-ebay-module-no-caster-issues.html

Here's another take on the same Toyota Prius unit built into a full column instead of turning it into a column with no tube at the bottom. As it notes in here you need to use a modern wheel alignment with plenty of caster to make sure the steering self centers properly. This guy also built into a steering quickener.

Unlike the other guy this one is using the entire Prius upper column, which gets you a tilt/telescope column in the process.

Here's a bloke who made some nifty, 3d printed parts to put it all together.  

[kb426]

I have looked into it and watched other's efforts. I found the DCE Microsteer that had a simple controller that most anybody could connect. I was looking for something small enough to be used with manual trans pedal hangers. On older vehicles with shallow cowls and no room next to the firewall, it gets real difficult to install. The last 2 cars my wife has had have epas.

[WZ JUNK]

This is distantly related to this topic.  My neighbor just built a dune buggy.  He started with a used conventional tube chassis type rail dune buggy with VW front end,  At the rear he grafted the frame to Chevy Impala front subframe and used the complete drivetrain of the Impala.  He kept the steering rack and added a small electric motor to it.  He has four wheel steering.  It looks good, runs really strong, and cost him a fraction of what building a VW based buggy would cost.

Today I am working on a circuit using relays and a micro switch to automatically center the steering when you want to return the rear wheels to straight ahead.  The circuit will work much like the park feature of an electric wiper circuit.

[enjenjo]

All of the places where the shaft was welded could be changed with the right pieces from another column, or with aftermarket parts. Flaming river makes a coupler the is 11/16" 36 spline on one end, and 3/4" DD on the other that could go from the lower splines shat on the EPS to a 3/4" DD U-joint on the other end.

On the upper shaft, you could shorten it, turn the top end and machine it for a 3.4" DD coupler to a DD machined on your stock top shaft. I have not welded a steering shaft in 40 years.

[jaybee]

I think that's the way to go with it, Frank, find the right couplers, rag joint or whatever. The origin cars all seem to have a collapsible U jointed shaft at the bottom, something to do with that would be good. In a rear steer application it might reach all the way through the floor so it could hook to the steering box directly. Where you put the motor would be be a factor in that. As you said, KB, older cars tend to have limited space under the dash.

Looking at some more YouTube videos there are some people who've done some really scary welding of steering shafts on these things. I wouldn't put my life on the line with some of that stuff even if it's a comparatively slow moving tractor...and these things are also gaining a foothold with old tractors.

Ideal, IMO, would be to graft the top end of a traditional column above the the tilt/telescope mechanism that seems to be in every new car in one form or another. I like my wheel to be fairly close and in almost every late model car I pull the wheel all the way back where my elbows have a lot of angle. Maybe you'd have to go to a dash-mounted ignition switch in that case, that would be something to work out or maybe there's be room for the column-mounted switch above the tilt joint. Probably, since GM had a lot of tilt columns in their cars quite a few years ago.

Here's a page on the DCe electronics systems including Microsteer. They have a lot of information on their page. Their stuff looks nice but of course it's pricey.  https://www.dcemotorsport.com/Home/EPAS

I like the sound of the four wheel steer project you're working on, WZ, very cool stuff.

[jaybee]

Looks like there are plenty of possible solutions for sealing where the steering shaft goes through the firewall. Chevy Luminas and like cars used a "coupling shaft seal" which was a sort of boot effectively extending the interior of the car all the way down to the rack. I used to have one of these from a Lumina I partly dismantled. I disposed of that steering column in the last move, but with well over 100,000 miles and 15 years old everything in the intermediate shaft assembly was completely without slack like it was brand new.  https://www.gmpartsclub.com/oem-parts/gm-coupling-shaft-seal-10283587?c=Zz1zdGVlcmluZyZzPWxvd2VyLWNvbXBvbmVudHMmbD0xMiZuPUFzc2VtYmxpZXMgUGFnZSZhPWNoZXZyb2xldCZvPWx1bWluYSZ5PTE5OTcmdD1iYXNlJmU9My0xbC12Ni1nYXM%3D

Fox Body Mustangs run a bare shaft through the firewall. It has a rubber seal that just rides against the shaft. That's probably the easiest solution.  https://lmr.com/item/LRS-3611B/mustang-5-0-resto-steering-column-firewall-seal-79-93

Someone got clever and used a rubber shifter boot as a steering shaft seal. Seems like overkill.  https://www.google.com/imgres?imgurl=https%3A%2F%2Fi.pinimg.com%2Foriginals%2F47%2F7f%2F37%2F477f378617016e6c664808ebd7cb1680.png&imgrefurl=https%3A%2F%2Fwww.pinterest.com%2Fpin%2F310889180528384782%2F&tbnid=qlGhyJFfk-wIKM&vet=10CAkQxiAoCGoXChMI6KD44OGV7wIVAAAAAB0AAAAAEAs..i&docid=aeNTjeBB17UMmM&w=714&h=960&itg=1&q=floor%20seal%20for%20u%20joint%20steering%20shaft&ved=0CAkQxiAoCGoXChMI6KD44OGV7wIVAAAAAB0AAAAAEAs

A lot of race cars use a simple flat seal with a hole through it.  https://timmcamis.com/shop/ajax/index/options/product_id/2395/

Chevelles, Camaros, at least some Jeeps, and I'd imagine a number of other front steer cars enclose the intermediate shaft U joint in a bellows. A seal like this would sure work. https://www.musclecarcentral.com/1968-1977-Steering-Column-Shaft-Rubber-Boot-Seal-p/ste-137.htm

[jaybee]

This is a smart way to do it. Connect everything with couplers. This unit has an adaptor on the wheel side of the EPAS unit so the column shroud can be cut off and slid over. At least one of the DIY setups I looked at did more or less the same thing, but by using an exhaust pipe adapter to connect the two sizes. The EPAS hangs off the end of the column shroud on one end and is stabilized at the firewall by a shaft bearing. The motor is clocked to tuck up behind the dash on the left side, modifying the cowl vent duct to make room. The video doesn't show how they did that, but surely they just cut one side out to get it out of the way. No big deal.

[Beck]

How big of a vehicle could these be used on? I'm just dreaming on this one. I like the late 60's early 70's Chevy 1.5 and 2 ton trucks. These didn't normally come with power steering. For my usage it would be a tow rig, not a heavy hauler. Would these EPAS type units be heavy duty enough? It would be easiest to use the stock steering box, however, swapping to a rack may make it easier to slam the front suspension.

[jaybee]

I'm not sure where this guy Waid found time to do his conversion, he's all over the place on the internet. He sure kept good notes and pictures though, so here's another. As I suspected the top of an older car steering column adapts easily to the top of the EPAS column.  https://www.fordmuscleforums.com/threads/100-power-steering-yes-you-can-use-column-electric-power-assist-system-epas.538585/

It is possible to build these into the middle of a full length steering column.  https://www.vintage-mustang.com/threads/best-200-mod-ever-eps.787114/page-5#post-6037649

I think the earliest version of this setup used a Saturn column, but it work without CANBUS or a special box which doesn't seem to be that available in the US...probably liability issues for the guy who's building them and used to ship them to this country from somewhere else. New Zealand, maybe?

I looked, but couldn't find a link to fitting these into pickup trucks. I suspect it would work. People are putting them on antique tractors, and the steering on those can get to be darn near impossible if you're standing still.

[jaybee]

One more. This video is a pretty long one, but the builder is working out all the kinks as he goes and it comes out pretty nice. He also welds a steering shaft, but as we've already discussed that really isn't necessary.  

[enjenjo]

I talked to an engineer today and the subject of electric power steering came up, and how big a truck you could use it on. His take was that anything that uses a 3/4" steering shaft could probably use the electric power steering safely because the electric units are for the most part based on a 3/4" or 19mm shaft He also pointed out that they fail safely, you lose the boost, but you don't lose steering input.

[kb426]

One other option is the electric pumps that modern vehicles have. I just started looking into this. There is a Volvo that is commonly used but many of the newer units have pumps. If you have space problems on the column, this should be an answer.

[jaybee]

It makes sense to me these units should work on anything with a 3/4" steering shaft. I picked a model out of thin air and see that's the shaft size on a 200 Dodge Ram 1500, which can weigh over 5000#. Applying steering assist through the shaft instead of at the box shouldn't matter in that calculation, because it has to be strong enough to allow steering with broken p/s. In OEM applications they do all sorts of tricks with increased steering assist at parking speeds, and there are ways to dial the steering effort up and down. I guess I'd consider that an after the fact add on if you decide the steering assist is inappropriate.

The key to retrofitting one of these to a car without canbus and skipping the add on box (required with the Saturn unit) is that you're in a first stage failsafe mode. Without power at all I think these still provide better steering feel than a hydraulic system because you aren't pushing fluid through the system like a shock absorber.

The more I think about this the more I think the way to go is with a telescoping straight shaft off the bottom of the unit for crash safety, through a floor mount bearing, to a u joint on the engine side of the firewall...meaning right on the steering box in a rear steer configuration.

I've seen the electric hydraulic pump as well but haven't looked into it in nearly as much detail. It seems to work pretty well, and from what I've seen these are good for about 950psi. At parking speeds they draw a lot of power, up to 75amps, but the pump can be packaged anywhere you need it and you don't have constant parasitic drag from a conventional p/s pump.

[jaybee]

Since there was interest in an electric power steering pump I found something on that at all. This is pretty clear and self explanatory.  

[jaybee]

I'm back on this one due to questions of whether this can be used on a larger truck. Here's an installation on a 1977 Ford F250 and it seems to work fine.  

I'm not sure I'd put the motor in the engine compartment. that would take some careful consideration of whether or not the equipment is truly weather tight.