Linear Actuator To Control Clutch?

[pope_face]

Alright, I've got a 1970 521 with the original J13 engine and transmission... Unfortunately, I can't use a stick shift (I have issues with the clutch pedal), and AFAIK there is no automatic available for that engine. I originally intended to do an engine/transmission swap, but now I'm considering just using the stock drivetrain.

 

So, I was wondering: Would it be possible to use a linear actuator to control the clutch? I'm thinking of putting a bicycle brake lever on the shifter stalk and having it control a potentiometer. The potentiometer would be connected to a linear actuator, which would then operate the clutch (probably at the transmission). Has anyone tried anything like this? It seems like it should work in theory, but I'm not sure about the practice. I managed to find a couple short-throw, high force (500 lbs and half-ton) 12VDC linear actuators locally, so it seems like the main issue would be in wiring and setting it up to properly work the clutch. Anyone have any thoughts on a project like this? What should work in theory doesn't always go that way in practice...

[datzenmike]

Have it work the peddle and you would only need 20-30 lbs. Also it moves over a longer range so more sensitive for clutch slipping on starts... not so jerky.

[ggzilla]

Never heard of anyone doing that.

 

But since the clutch is hydraulic, you could use a small, simple hydraulic motor and perhaps a computer to control the force and timing.

 

But what most people do if fit hand controls, don't they?

[pope_face]

Mike: That's a good point, although I'd like to keep the pedal itself mostly free... It would be pretty intrusive if I had to mount it under the dash. However, I suppose I could mount it in the engine bay, and use a cable to attach it to the back of the clutch pedal.

 

gg: I know there are actuators available for people with disabilities, but the ones I've heard of are simple on/off types, so the clutch is either fully engaged or disengaged. I'd prefer to be able to slip the clutch, as Datzen mentioned... Still, I'm sure it's doable. As for the hydraulic motor... Yes, that is possible, but the costs and difficulty might be greater than simply moving the piston in the master cylinder. I'd like to come in under $500 for this, if possible. Even then it's not a cheap modification, but it'll let me keep my original drivetrain.

 

I did, however, realize that a linear actuator may not be what I'm looking for... It seems that the linear action is controlled by a worm gear (or something similar), so it'll move in one direction when power is applied, and simply stop when the circuit is opened. I need something that'll return to its starting position when I remove power... I guess an electromagnetic solenoid or something is more accurate, although I don't know if that's quite the appropriate term. Something similar to electric door lock solenoids, but more powerful, and with the ability to control how much force/distance is exerted based on current.

[oldschool90]

http://www.magnet-schultzamerica.com/

 

They even do custom.

[Laecaon]

Could you run a cable from the backside of the pedal into the engine bay and then back into the cab somewhere connected to something like a ebrake handle?

 

 

New idea, use a hydraulic e-brake handle m/c to control the clutch...

 

Just not sure how that could work with also needing a hand to shift...

[pope_face]

Laecaon: Hydraulic or cable operated was actually my original idea... I'd hoped to do the same thing with the brake lever on the stalk, but running a cable down and connecting it to something, either a mechanical linkage to the clutch (which would be the cable operated version) or a master cylinder (for the hydraulic version). I don't think actually having the hydraulic cylinder on the shifter itself would be a good idea, as the constant motion might cause it to spill all over the place.

 

My big concern would be the amount of torque needed on the lever in order to get the right amount of force on the clutch... The cable end of the lever only moves about 3/4", if that, and I think I need at least an inch of travel at the clutch master cylinder to fully engage it. I might be able to work it out somehow, but I still think it'd require some 40+ lbs of force on the end of the hand lever to get it to work. Then again, I haven't done the math on it, so I may be off.

 

However, another possibility would be to use a brake booster in between the hand lever and the master cylinder... I could possibly swap an entire brake booster and master cylinder into the car, and use that as the clutch master cylinder. Depending on the size of the booster, I might be able to get it to work with a hand lever.

 

As for the e-brake style: Yes, I've toyed with that idea as well, but it'd be much more of a PITA to use. If I had an extra hand, it'd be perfect, but I'd like to keep at least one hand on the wheel.

 

The huge benefit of using a mechanical style of operation, instead of the electronic, would be the amount of control I'd have... I suppose a mechanical linkage would be a hell of a lot cheaper to build and "tune" than an electrical one, although I'd have to work out all the math on it.

 

Oldschool: Thanks for that link... I'll send them an email and see if they can recommend anything. I checked out their site, but didn't really see any pricing, so I hope it's not outrageous.

 

In any event, there are a couple possibilities... Given the responses I've gotten from a couple computer/electrical engineers, it seems that the mechanical route might be a better idea.

[Laecaon]

So what type of lever are you thinking, where at, how is it used?

 

It seems all options require an extra hand... Unless you had some way to pull it, lock in place, shift, release lever...

[oldschool90]

Little somethin I thought up. One possible problem would be seat in the way

 

 

 

It'd be interesting to drive though, and it's more of a permanent thing.

 

Unless you put pull pins in it and make a regular shift handle, then just pull the handle off, shove it out of the way and put the knob on.

 

[pope_face]

Here's what I was hoping to do:

 

 

Hopefully it's clear enough how it works... I'd use a standard bicycle style cable and lever. If I decide to go with a brake booster for a bit of extra power, I'd mount the other end of the cable to the "pedal" side of the booster. If I can pull on the end of the brake booster, that'd be the best, otherwise I'll have to convert the pulling action into a pushing action using a lever. Then I just have to figure out what to do with the other end of the brake booster... Ideally, I'd like to mount another cable to it and have it operate the clutch pedal (like Datzen mentioned). The best way to do this would be to mount it on the engine side of the firewall and have it pull the pedal towards the firewall. This setup would allow me to operate both the clutch and shifter with one hand... I could use my palm and thumb to hold the shifter, and my fingers to operate the lever.

 

I'll still have to work out whether or not a brake booster would give me enough power, but I think that depends on the diameter of the booster... IIRC, larger boosters offer a larger increase in power, so something out of a domestic pickup/SUV might be good.

 

Oldschool: I appreciate the suggestions... The first one seems pretty good, I hadn't considered doing it that way. I don't actually mind permenant... I'm planning on keeping the truck for a while, and as long as the pedal can be used as well, it's fine.

[elmerfudpucker]

For the headache it looks like your going thru, I would just swap it out to something with an automatic. But good luck to you regardless.

[pope_face]

Elmer: I agree, just putting in an automatic might be easier, but if I were to go that route, I'd have to get a pickup and swap the entire drivetrain over... Engine, transmission, driveshaft, and rear axle. I could go with an L16 and an automatic, but they're between 30-40 years old now. A 90's Toyota or Nissan pickup might be a good route, but again, it's a lot of work.

 

In any event, the brake booster route would be cheaper, and easier to rig up... It'll require no new engine mounts, no new exhaust, no new wiring, and I can always adapt it to other vehicles in the future.

[Laecaon]

What about using a motorcycles brake lever to control the slave? I wonder if it would displace enough fluid/give enough power.

[]2eDeYe]

You could use a turning brake lever and master cylinder. Easy to mount, weird to operate. :lol:

[datzenmike]

How about a hand lever (like on the shifter) working a brake booster conneced to the clutch master to hard line to the slave? You could mount the booster/master in the trunk and it would work. Not sure if the lever would give enough 'sensitivity' and the action may be more on/off than you would like. Also the brake booster may not multiply the power enough for a clutch slave?

 

Can you use your left foot at all???? If so maybe add a brake booster to the clutch master ... in effect making it a power clutch. Almost effortless in opperation.

[pope_face]

I can use my left leg, but I already use it for braking... Unfortunately, my right leg gets pretty tired if I move it from gas to brake (I can't actually pivot my foot), I just tend to keep it over the gas pedal, and move my left foot to the brake when needed.

 

I was actually thinking about using the brake booster and master cylinder this morning too... I was thinking about trying to tap into the existing line from the clutch master cylinder. If I understand it correctly, the two master cylinders should only operate the slave cylinder, not each other. I could also just install a valve in the engine bay to switch between one clutch and the other, in case someone else wants to drive the car.

 

I agree that it would be hard to feather the clutch, but being able to do it a little is better than not at all, so I'll just have to train myself to do it. In any event, it seems like I only really need to feather it when initially engaging the clutch (that is, clutch pedal coming up off the floor). Disengaging the clutch doesn't have to be as precise... I can't really think of any reason where I'd want to feather the clutch while disengaging it. In that case, it'd be nice to set it up to work exponentially... I'm not sure how well I can explain this (it makes sense in my head), but when I pull on the hand lever, the first 50% of the distance it travels is equal to the clutch pedal moving 75% of the way down to the floor... The last 50% of the hand lever would be equal to the last 25% of the foot pedal... Does that make sense to anyone?

 

It wouldn't have to be 75/25, it could be 70/30, or 60/40... It depends on how much people usually feather their clutch. In any event, I'd like the feathering to take most of the travel on the hand lever, and the last little bit will just be to fully engage the clutch again.

 

Laecaon: I did consider that too, but I think the size of the cylinders would be an issue, and I wouldn't get enough pressure... I think motorcycle clutches are under a lot less pressure than car clutches, so I'd need freakishly strong hands to do it. Then again, I don't actually know how much force the clutch in our Datsuns requires...

 

I did some more poking around on the internet, and found another website where some folks had discussed a similar idea, but there were only six posts, and the last one was over two years ago. However, a guy mentioned that he used an air piston to push the clutch pedal down, powered by an air compressor and tank for airhorns. The only issue with his setup is that it was a simple on-off action... If it could be made to vary the force, then it might work.

 

I've got a friend who recently did a major swap on his Subaru, so I'll ask him tonight if he still has the original brake booster and master cylinder... If so, I'll grab it and start toying around with it.

[bananahamuck]

Here's what I was hoping to do:

 

 

 

 

If you could get an actuator to work correctly with your clutch ... The idea you drew up is a really good one . Kinda like a 2 speed rear end type thing, only switch is instant off.

And if not hydraulic it would be easier to use , because if handle is hydraulic you would have to grab stalk of shifter and squeeze but electric you could get a finger on it ..Also if handle is hydraulic the rubber hose set-up would be troublesome to get hose long enough to make all the gears changes in the rowboat-like shift pattern those old trucks have.

( i do realize it would be hard line down shaft ,, then a rubber connector hose at floor )

 

I dont know if it would work ( no experience with actuators ) just saying would be easier to use.

[DanielC]

I think the easiest thing to do would be to put an L-engine, with an automatic in your truck. there is information on changing J13-521 trucks to L-521 trucks. Easiest has a good chance of being the most economical, all things considered.

 

I think one thing you are forgetting it that is takes a pretty large force at the slave cylinder to move the lever that pushed the throwout bearing. Your foot moves the clutch pedal several inches. The clutch master cylinder moves maybe an inch. There is a big mechanical advantage there. It is also pretty easy to push on the clutch pedal with a force of several hundred pounds, the way you are braced, with your butt against the seat. I do not see any way a mechanical hand operated linkage would be effective in disengaging the clutch.

 

Have you looked into some of the modifications that wheelchair bound people use to operate motor vehicles? There might be some hand controlled actuators available through those sources.

 

I went for a flight, shortly after Mt. St. Helens blew her top, in a airplane flown by a paraplegic. (No muscle control below waist)

If a person who cannot even use his legs can fly an airplane, is should not be impossible to make your Datsun usable to you.

[yello620]

Pope: I have wondered about this very same idea before of hand controled clutch. I have back issues that make the clutch painful to operate sometimes.

 

 

So, one of the ideas that I wondered about was making the clutch system air powered? Butoon on shifter that controls an air actuator to the stock clutch master, or maybe an air actuator mounted in place of the stock slave cylinder.

 

Also something to think about is that the clutch master cylinder does not need mounted to the firewall if something besides the pedal is controling it.

[pope_face]

Daniel: I agree, I could put in an L-series engine and transmission, but I don't have one... There is an L20B and manual transmission for sale locally on Craigslist, as well as an automatic transmission. On the other hand, these are 30+ year old engines, so I don't know what condition everything is in.

 

I actually have looked into actuators for disabled drivers, but it seems that they're either simple on-off switches, or pretty expensive. Still, someone had to design and build the first one, so I don't see why I couldn't do the same with some assorted parts.

 

Yello: I was actually looking at some pneumatic rams and valves today... I don't know how much a compressor and tank would cost, but the ram itself wouldn't be much more than $30 or $40, and the valve might be even cheaper. I'd just have to figure out how to plumb it... I suspect an air brake valve from a truck might work for adjusting the amount of pressure going to the pneumatic ram.

[Laecaon]

Im starting to think a stepper linear actuator would be best. Need a controller, cant be too hard since RC cars use position based servos. I would then use a basic bicycle brake lever (I think Cantilever style offers most cable throw) and run the cable to the controller and have it read the location of the cable. I wonder if a basic servo controller could control a stepper motor? This would give you the most imediate control of the clutch with minimal force needed. But it would have no feel. A purely hydraulic system would give better feel.

[pope_face]

Laecaon: That's brilliant, I never thought of the RC car style of controller... You're absolutely right, when you tweak the controller one direction or the other, the wheels turn a certain amount. When you let it go, they return back to their original position.

 

I suppose I could try to just find an RC car with wired controller, tear out the switches, and try to modify them to work with a stronger motor... I'm sure it would have to provide a lot of torque though, so I wonder if a linear motor would be better.

 

EDIT: Did a bit more research on air brakes, and I think I may have come up with a very basic method of operating the clutch with a pneumatic ram...

 

 

A: Pneumatic cylinder

B: Pneumatic ram

C: Air inlets/outlets

D: Vent lines to atmosphere

E: Two-way valve

F: Air feed line

 

In this case, when the ram is retracted, the clutch is engaged (no pressure exerted on the pedal). When the ram is extended (as shown), pressure would be applied to the clutch pedal to disengage the clutch. In order to extend the ram, the two-way valve (E) would be set to allow air from the feed line (F) to enter the cylinder through the right air inlet ©. This would increase the pressure behind the ram, causing it to extend and push down the clutch pedal. Because the left air inlet is vented to the atmosphere, I wouldn't have to combat any air pressure on that side of the piston.

 

In order to allow the ram to return to its retracted position, I would turn the valve (E) into its second position, causing the pressurized air in the cylinder to vent out to the atmosphere (through D). The original clutch pedal spring would remain, so the force from the spring would push against the ram, causing it to retract. This time, atmospheric air would enter the cylinder (ahead of the piston) through the left inlet (to prevent a vacuum from occurring), and escape (from behind the piston) to the atmosphere through the right inlet/outlet (preventing it from being pressurized). This would allow the clutch pedal to return to its starting position. Having the valve in this position would also allow the clutch pedal to be used independently, as both air inlets on the cylinder are open to the atmosphere, so moving the ram itself wouldn't cause high or low pressure inside the cylinder. The compressed air would also be contained within the system, so it wouldn't overwork the compressor.

 

I could easily swap the intakes as well, so the ram retracts to disengage the clutch, and extends to engage it... That would allow me to mount the cylinder in the engine bay and work the clutch pedal from the firewall.

 

I just can't come up with a good way to apply partial air pressure to the ram to feather the clutch... In this case, if I have the valve turned halfway between the vent and feed lines, compressed air should enter the cylinder through the feed line and immediately bleed off into the atmosphere through the vent line. As the valve is turned towards the feed line, more air would enter the cylinder through the feed line, and less would vent to the air, so the ram should extend. As the valve is turned the other way, less air would enter through the feed line, and more air would vent to the atmosphere, so the ram would retract.

 

The only other thing I should mention again is that I think I only need to feather the clutch when I'm engaging it again... In this case, that would be venting the air to the atmosphere. If I bleed off the air slowly, the clutch will engage slowly. If I do it quickly, the clutch will engage quickly.

[yello620]

I agree that the air idea seems like it would operating like a switch. Either engaged/disengaged.

So what allows the air brakes in a semi to be linear? They are not a switch.. :D

 

I also wondered if this same idea would be possible using engine vacuum? I highly doubt that enough vacuum is created to work a clutch, but the idea would be that no compressor would be needed.

[pope_face]

Yeah, it really would be more of an on/off type thing... Not very effective, I suppose. I actually spoke to my Pa, who's got experience working on and driving trucks, and he told me that air brakes work differently than hydraulic brakes in how the pressure is applied... When you engage the brake pedal in a car, you force a certain amount of fluid into the calipers, and they apply a certain amount of pressure to the disc. When you push down, you force more fluid in, and the force increases. If you hold your foot in one position, you're not moving any fluid, so the pressure remains constant.

 

For air brakes, when you push down on the pedal, you open a valve which lets air from a reservoir into the brake. If you push down a little, the valve only opens a little. When you push down a lot, the valve opens further. Just like in the car, when air enters the brakes, it exerts pressure against the drum. However, when you hold your foot in one position, the pressure does not remain constant... Instead, the valve stays open, and compressed air continues to enter the brake. How fast the air enters depends on the position of the brake pedal, but if you hold it down long enough you will eventually get full pressure in the brake.

 

A vacuum is a good idea, but I think I'd run into the same issues...

 

However, there is this possibility:

 

 

In this case, the shifter is the same as before. However, instead of using a lever on a pivot to move a cable (as in the previous version), I would use a sliding "sleeve" (the white "clutch handle" in the photo) to pull the cable up. So, rather than having a cable which moves only a couple centimeters at the pivot, I'd have one that could move several inches (or even a foot, if I like). With the clutch engaged (pedal up), the handle would be low down on the shifter stalk... To disengage the clutch, I would grab the handle and pull it up to the shift knob. I can make the top of the handle into a half-sphere to fit over the shift knob at the top. If I want to shift gears, I grab the handle, pull it up until it reaches the shift knob (at the top of the stalk), select my gear, and slowly let down on the handle to release the clutch.

 

It seems like a bit more of a PITA to learn to use, but it would require less fiddling around trying to multiply the force (I could connect it directly to the clutch pedal), and it would be easy to feather the clutch when moving from a stop.

[jrock4224]

swap a ka with a utomatic on it .... u ill never buy another car