Planetary gearbox "power" steering

[MB750]

I realize this is probably some very outside the box thinking but hear me out.

Planetary gearboxes are used in many applications where increasing torque is needed in a small, inline package. Many cordless drills use them.

My manual steering goes lock to lock in three full turns. 1.5 turns from center to lock. I would easily take 3 turns (6 lock to lock) if I could increase the torque on the rack side of the shaft.

You'd have the high torque side of the planetary gearbox on the steering wheel side, and the high RPM side of the planetary gearbox on the rack side. Assuming you can source a 2:1 planetary gearbox, that would double the number of turns on the steering wheel, but it would also double the torque applied to the manual rack.

I've been running 7 degrees of castor and it's driveable, but you really have to be purposeful on the wheel at all times. I've seen those electronic steering kits, but I also know a thing or two about mechanical engineering design and I believe a planetary gearbox could work. Anyone ever pursued something like this?

[OSU Cowboy]

Matt - I think your idea has serious potential - power steering with mechanics rather than hydraulic or electric. I'm a mechanical engineer by education.

David Peck

[rich grsc]

You are going to create a steering system that is so slow to react as to be dangerous?

[Mike.Bray]

You are going to create a steering system that is so slow to react as to be dangerous?

I was thinking it would be like driving a Greyhound bus.

[MB750]

You are going to create a steering system that is so slow to react as to be dangerous?

Not exactly. That's the beauty about gear ratios. I can dictate the output based on the input and by using a specific ratio. 3:1 would mean 3 input turns would equal 1 output turn. It would also triple the torque.

Power steering adds leverage through hydraulic means (or electric) before the steering box. I'm saying add leverage by increasing torque through mechanical advantage of a reducing geartrain.

In my idea, reverse the gearbox so 1 input - 3 output. That way instead of 1.5 turns center to lock it would be 4.5. But you would reduce the leverage (torque) required to turn the wheel by a factor of 3. If it takes 45 ft-lbs to turn the wheel, now it only requires 15 ft-lbs.

I think 2:1 would be the sweet spot but I'm having trouble finding planetary gearboxes in that ratio.

I mean, technically there's already gear reduction down in your steering box. I'm saying alter the input between the steering wheel and the steering box. Older Mopars came with a 24:1. Now most of them are 16:1.

[JJK]

Interesting idea, but I have to agree with the others. With power steering, a turn of the steering wheel results in the same angle change of the tires as would be achieved without power steering. It just reduces the torque to make the turn. With gearing as you suggest, you would have to turn the steering wheel more than 'typical' to achieve the same angle change of the tires. Even at a modest 1.5:1 gearing, you would have to turn the wheel quite a bit more for minor steering adjustments. I would think this would be very unsafe, especially in high speed adjustments.

[Mike.Bray]

With gearing as you suggest, you would have to turn the steering wheel more than 'typical' to achieve the same angle change of the tires. Even at a modest 1.5:1 gearing, you would have to turn the wheel quite a bit more for minor steering adjustments.

It would certainly take the sports car feel out of it. A nimble quick reacting car turns into a lumbering slow reacting car. Not for me but it's probably easy for the OP to test. As an engineer I would want to be extremely careful when selecting the hardware since it's between the wheel and the rack. Lose the planetary and lose your steering.

BTW, I was originally going to go with manual steering but this forum convinced me otherwise. And I absolutely love my power steering now, I cannot imagine not having it.

[MB750]

I hear y'all, for sure. Yes it's a snappy car with 3 turns lock to lock. Even more snappy if you take some caster out of it.

And you're right about the safety of it all. Planetary gearboxes are a tried and true technology but it is another failure point. If power steering goes out, you've got manual steering.

I'm not giving up on this, but I am gonna keep it in the research phase. I've found some 3:1 planetary gearboxes online for $90 that are large enough to handle the shafts and torque applied, but 9 turns lock to lock is a lot.

[Mike.Bray]

I've found some 3:1 planetary gearboxes online for $90 that are large enough to handle the shafts and torque applied, but 9 turns lock to lock is a lot.

Just remember it's not the torque so much as it is the shock loading. Think pot holes.

[GoDadGo]

My car has the manual rack and requires around 3 turns to go from lock to lock.

1. I find it steers spot on perfect at speeds between 5 MPH and 125 MPH.
2. The car is easy to turn except when I am stopped and I need to turn the steering wheel.
3. With fairly sticky NT-05's tires (255/40-17 @ 200-TW) on the front the car is well planted and stable.

Why reinvent the wheel by creating a non-engineered solution for a problem that does not exist?

NOTE:.. The caster angle for Manual Racks should be between 3.0 - 4.0 degrees not 7.0.

[MB750]

Just remember it's not the torque so much as it is the shock loading. Think pot holes.

That's a good point. Very hard to calculate the shock load even making valid assumptions.

[MB750]

My car has the manual rack and requires around 3 turns to go from lock to lock.

1. I find it steers spot on perfect at speeds between 5 MPH and 125 MPH.
2. The car is easy to turn except when I am stopped and I need to turn the steering wheel.
3. With fairly sticky NT-05's tires (255/40-17 @ 200-TW) on the front the car is well planted and stable.

Why reinvent the wheel by creating a non-engineered solution for a problem that does not exist?

NOTE:.. The caster angle for Manual Racks should be between 3.0 - 4.0 degrees not 7.0.

Ok, for YOUR specific set of parameters and expectations. Not everyone wants YOUR expectations. Same goes for your problems. Mine might be different.

And for what it's worth, everything you touch was "non-engineered" at some point.

[Jeff Kleiner]

I can tell you that when I've gotten into customer cars with 18:1 manual racks I've hated them. Like Mike said earlier the slow steering makes them feel like driving a bus. I can't imagine how bad it would be if the steering was even slower :eek:

Jeff

[rich grsc]

By all means, go head and do this. Then have fun trying to drive it

[Jeff Kleiner]

You're going to want one of these:

https://www.ecklers.com/image/chevy-steering-wheel-spinner-traditional-with-photo-frame-in-knob-1955-1957-57-331491-1.EK-57-331491-1.jpg?wid=400&hei=300&op_usm=0.8,1,10,0

Jeff

[GoDadGo]

I can tell you that when I've gotten into customer cars with 18:1 manual racks I've hated them. Like Mike said earlier the slow steering makes them feel like driving a bus. I can't imagine how bad it would be if the steering was even slower :eek:

Jeff

I forgot about the 5 turns lock to lock manual rack.
I was lucky enough to get the 3 turn rack system which was offered shortly after.
For those of you you have not seen it, attached is that unit as demonstrated by Dangerous Dan when he was much, much young:

https://youtu.be/B5zGnHExZuA?list=PLWvfrZxPoPnbmHRjXTlVS-CVcPoK4x6lB

[GoDadGo]

Ok, for YOUR specific set of parameters and expectations. Not everyone wants YOUR expectations. Same goes for your problems. Mine might be different.

And for what it's worth, everything you touch was "non-engineered" at some point.

FYI.. Please know that I didn't mean to offend you.
........I couldn't comfortably steer my manual rack at 7.0 so I've got it set at 3.5 degrees.
........You must have much stronger arms than I do to handle a manual rack at that caster angle.
........Regarding my specs, it is true that my car is like no other Factory Five and can cruise at 125 MPH @ 3,000 RPM in 6th gear.
........It also ran a best time of 11:30 @ 124 MPH with a really sad, sad, sad 60' time of 2.57 seconds because we all know that spinning ain't winning.

We Embrace The Power of The Dark Side!
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383 Small Block Dart (SBC) 10.3-1 Somewhat Pump Gas Friendly Compression Ratio.
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Standard Front End Set Up With Mustang Brakes & Forte’s .75” Sway Bar.
Standard 3-Link Moser Dana 44 (TSD 500) Rear With 3.73 Gears & Explorer Brakes.
The wheelbase has been shortened by .875″ to better center the rear wheels within the wheel arches and improve pinion angle adjustment.
The fuse block has been moved to the passenger side of the car which allows the car to have an uncluttered foot box and to better protect it.

At Least You Liked My Door Fix So You Are Welcome!

[Avalanche325]

I am all for innovation. But there is also the principle that if everyone does things a certain way, there is usually a good reason for it. I cannot remotely imagine that it hasn't been tried in the history of the automobile....

Here you go:
https://www.researchgate.net/figure/Schematic-of-BMWs-planetary-gearset-for-active-front-steering-source1_fig1_356913079

I agree the 3:1 is right for these cars. Yes they feel twitchy when you first get them on the highway. You should get used to it fairly quickly. However, the steering ratio isn't going to change what the car /road interface are doing. The short wheelbase, lightweight, and wide tires make it tramline and want to dart everywhere. You are just going to have to chase it more with a slower rack. And you better stay away from the track. Even further from autocross.

[kgkeys]

Regarding my specs; it is true that my car is like no other Factory Five and cruises at 125 MPH @ 3000 RPM in 6th gear.
It also ran a best time of 11:30 @ 124 MPH with a really sad, sad, sad 60' time of 2.57 seconds because we all know that spinning ain't winning.


Apropos of nothing, but that actually sounds a LOT like my AOD car with 3.07 gears... 80mph @ 2000RPM in OD. 0-32mph in 60ft @2.5s, 60mph in 5.3s. I've yet to go try it at the drag-strip for a full 1/4 mile. I do really love your dark-side cobra, GoDad...

Kyle

[MB750]

FYI.. Please know that I didn't mean to offend you.
........I couldn't comfortably steer my manual rack at 7.0 so I've got it set at 3.5 degrees.
........You must have much stronger arms than I do to handle a manual rack at that caster angle.
........Regarding my specs, it is true that my car is like no other Factory Five and can cruise at 125 MPH @ 3,000 RPM in 6th gear.
........It also ran a best time of 11:30 @ 124 MPH with a really sad, sad, sad 60' time of 2.57 seconds because we all know that spinning ain't winning.

We Embrace The Power of The Dark Side!
https://youtu.be/GpqvBPwIbzI

383 Small Block Dart (SBC) 10.3-1 Somewhat Pump Gas Friendly Compression Ratio.
Eagle Internally Balanced Rotating Assembly With 6″ H-Beam Rods With Short Skirt Floating Forged Flat Tops.
Dart Iron Eagle 215 CC Tall Port Heads with 2.05 Intake & 1.60 Exhaust Valves.
Harland Sharp Roller Rockers & Other Go Fast Goodies.
Comp Cam Extreme Energy 288 Hydraulic Roller Tappet Cam
Edelbrock AVS 800 Feeding A Weiand 7530 Team-G Single Plane Manifold.
Schoenfeld IMCA Modified Headers & They Really, Really Fit, But Stuff Had To Move A Bit!
New Old Stock Corvette ZF 6-Speed Transmission With Hydraulic Clutch. (.75 and .50 Overdrives)
Standard Front End Set Up With Mustang Brakes & Forte’s .75” Sway Bar.
Standard 3-Link Moser Dana 44 (TSD 500) Rear With 3.73 Gears & Explorer Brakes.
The wheelbase has been shortened by .875″ to better center the rear wheels within the wheel arches and improve pinion angle adjustment.
The fuse block has been moved to the passenger side of the car which allows the car to have an uncluttered foot box and to better protect it.

At Least You Liked My Door Fix So You Are Welcome!

And I do appreciate that. And I do appreciate this forum for all its guidance. Like Jeff said above, I'd hate a Cobra with anything less than a 3 turn lock to lock. Honestly though, sometimes I need to learn on my own. I may try this, or not. Depends on whether or not my ambition overrides my physical abilities.

One thing I really love about these builds is they allow me to really chase my mechanical dreams. Sometimes I dream too big though. It's like a Twin Cam Harley when it comes to making it my own (mechanically and cosmetically).

[Joel Hauser]

Can we install a 15" or 16" steering wheel on these cars? Wouldn't that increase the torque without changing the number of lock-to-lock rotations? It would increase the distance your hands travel around the arch of the steering curve, but not by so much that we wouldn't get used to it. I've briefly searched the internet but was unable to find an old school style 15 or 16" steering wheel with the English style (non equally spaced holes) steering hub bolt pattern, so that could be a reason it can't be done. But I also agree with godadgo; manual steering has not been a problem for me unless I'm moving at less than 5 mph.

[Jphoenix]

I was thinking it would be like driving a Greyhound bus.

Well, mine is not a Greyhound bus - but the steering is similar, except it does have power steering. After a weekend of racing, I get in this bus and the first few turns out of the paddock are a bit of a shock.

:rolleyes:

207853

[CraigS]

I think the planetary gear set could work. But, no matter what type gears you use, if you trade off more turning the wheel to get reduced effort, I don't think you will enjoy the result. I'd rather you look into some of the electric assist options to see if any of them give you decent steering feel. I say that because some of the early attempts created steering w/ no feel at all.

[Avalanche325]

Can we install a 15" or 16" steering wheel on these cars? Wouldn't that increase the torque without changing the number of lock-to-lock rotations? It would increase the distance your hands travel around the arch of the steering curve, but not by so much that we wouldn't get used to it. I've briefly searched the internet but was unable to find an old school style 15 or 16" steering wheel with the English style (non equally spaced holes) steering hub bolt pattern, so that could be a reason it can't be done. But I also agree with godadgo; manual steering has not been a problem for me unless I'm moving at less than 5 mph.

Depending on your anatomy, a larger steering wheel could get in the way of your knee when you go for the brakes.

Moss Motors has steering wheels for most British cars. I would start by looking there.

[MB750]

I went for a little spin last night, around 7 miles with some 45 mph zones and roundabouts. Total on the car now is 26 miles.

I think it's just taken some getting used to. With almost 30 years of driving all manner of vehicles I guess I just got used to power steering (and power brakes). Now that I've got a car with manual everything I just need to acclimate to the car sometimes rather than vice versa.

[lance corsi]

If one did decide to employ a planetary gearbox, a simple locking mechanism could effectively lockout the the gearbox and cause the entire gearbox to rotate as a solid shaft might do? Just spitballing here.

[MB750]

If one did decide to employ a planetary gearbox, a simple locking mechanism could effectively lockout the the gearbox and cause the entire gearbox to rotate as a solid shaft might do? Just spitballing here.

It kinda depends on what part of the gearbox you use as the input and output, and if the ring gear is mounted to the chassis or not.

In my head I was thinking the ring gear part wouldn't need to be mounted to the chassis to work, but I'm not 100% sure on that.

I like your idea though. It's an easy fix, assuming the failure doesn't take place at highway speeds.