Brake Assisted Steering
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Re: Brake Assisted Steering
Actually, it would be easier to use one of the off-the-shelf single lever units! Set up some stops on the right hand tie rod (LHD), and tie the lever to the tie rod. The ratio can be set by varying the length of the lever and mounting the cutting brake body on a similarly movable mount. Much simpler and less expensive than the convoluted method I had envisioned earlier... Just have to get a car to try this out on.
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Re: Brake Assisted Steering
If I understand what you are proposing you would be working against the steering wheel; not smart. Kind of likea grabby brake I would think.spectre6000 wrote:Actually, it would be easier to use one of the off-the-shelf single lever units! Set up some stops on the right hand tie rod (LHD), and tie the lever to the tie rod. The ratio can be set by varying the length of the lever and mounting the cutting brake body on a similarly movable mount. Much simpler and less expensive than the convoluted method I had envisioned earlier... Just have to get a car to try this out on.
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Re: Brake Assisted Steering
I don't understand what you mean by working against the steering wheel. By adjusting the leverage ratios, you can make it more or less "grabby". Unless you try to make it brake full on immediately though, it should be on the edge of transparent from the driver's perspective outside the tighter turning radius.
Like this.
Maybe it'll load up the steering a bit more, but there's nothing really intrinsically wrong with a heavier wheel. The way the load would build might also be beneficial. The leverage ratio will counter some of the loading. Is that what you meant?
Like this.
Maybe it'll load up the steering a bit more, but there's nothing really intrinsically wrong with a heavier wheel. The way the load would build might also be beneficial. The leverage ratio will counter some of the loading. Is that what you meant?
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Re: Brake Assisted Steering
Lets say you are making a right turn; you turn the steering wheel to turn right and then, because you want to turn faster, you pull on the turn right handle which pushes on the left spindle. Your steering wheel is then going to want to turn more to the right based on the pressure applied to the left spindle whether you like it or not, assuming I am understanding what you want to do correctly.
To be perfectly honest, I personally would want to mess with the steering end of the car. Power assist steering is OK (but there were been problems with some of the early designs that made things pretty touchy steering wise; the same for power assist brakes.
Off-road is one thing, DOT controlled things like steering or braking systems are another. If you had an accident and your insurance company got wind about your futzing with the steering or braking I would suspect that you would find yourself alone in court. Off-road, you might find out that your street driven car insurance stops at a certain point. That is why they now have off-road policies and not all insurance companies have them. That is basically what is going on in Oregon and maybe other states in the near future. Based on conversations I and others in our group has had with insurance companies, I think things are going to change quite a bit in the future.
To be perfectly honest, I personally would want to mess with the steering end of the car. Power assist steering is OK (but there were been problems with some of the early designs that made things pretty touchy steering wise; the same for power assist brakes.
Off-road is one thing, DOT controlled things like steering or braking systems are another. If you had an accident and your insurance company got wind about your futzing with the steering or braking I would suspect that you would find yourself alone in court. Off-road, you might find out that your street driven car insurance stops at a certain point. That is why they now have off-road policies and not all insurance companies have them. That is basically what is going on in Oregon and maybe other states in the near future. Based on conversations I and others in our group has had with insurance companies, I think things are going to change quite a bit in the future.
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Re: Brake Assisted Steering
OK, but is the assumption here you're saying that lower speeds mean more turn of the steering wheel and more brake applied to that caliper, and higher speeds mean less turn and less braking applied to the caliper--like in a linear fashion depending upon speed?
I would not say that you definitely need more turn-in under all situations. There's several I can think of. Example at higher speeds and you're on the brakes before a long sweeping turn, I would not want the car to turn-in more than I expect it to because I am trying to follow a specific line. The cutting brake was designed for off-road cars that run open diffs on short courses and are bouncing around so much with varied traction that it doesn't cut down on speed much, they just want to get the front end whipped around though.
Go ahead and try it, it may work out for you. This is not a new idea though and Porsche probably dumped a few gazillion to get it right. The last thing they would do is hamper performance. I've had quite a few modern cars over the last few years and wound up turning the traction control off on all of them in an autocross because they felt weird and definitely hurt my times. The late 80s Honda Prelude? had four-wheel steering, basically just changed the alignment of the rear end when a lot of g-force was applied and the car would turn in more. The early 90s Mistubishi Galant VR4 had four wheel steering also, a rack and pinion in the rear and separate power steering pump, but most guys wound up disconnecting it though because the car got sketchy over 90 mph.
It's not that technology isn't getting better though, far from it. A few years ago Car and Driver? did a road course test with the newest Nissan Z car and the newest Mistubishi Evo. On paper the Nissan was far better, weighed 200lbs. less, more hp, and just sleeker all around. Guess who won on the track? Yep, the Evo. The control of the 4WD systems on the Evo was so advanced it was pulling that car through to shave off time. Saw a similar test of an Evo vs. a mid 80s Audi GT on the show Fifth Gear. The same thing happened, the Audi had like 50 more hp, but couldn't keep up around the track.
I would not say that you definitely need more turn-in under all situations. There's several I can think of. Example at higher speeds and you're on the brakes before a long sweeping turn, I would not want the car to turn-in more than I expect it to because I am trying to follow a specific line. The cutting brake was designed for off-road cars that run open diffs on short courses and are bouncing around so much with varied traction that it doesn't cut down on speed much, they just want to get the front end whipped around though.
Go ahead and try it, it may work out for you. This is not a new idea though and Porsche probably dumped a few gazillion to get it right. The last thing they would do is hamper performance. I've had quite a few modern cars over the last few years and wound up turning the traction control off on all of them in an autocross because they felt weird and definitely hurt my times. The late 80s Honda Prelude? had four-wheel steering, basically just changed the alignment of the rear end when a lot of g-force was applied and the car would turn in more. The early 90s Mistubishi Galant VR4 had four wheel steering also, a rack and pinion in the rear and separate power steering pump, but most guys wound up disconnecting it though because the car got sketchy over 90 mph.
It's not that technology isn't getting better though, far from it. A few years ago Car and Driver? did a road course test with the newest Nissan Z car and the newest Mistubishi Evo. On paper the Nissan was far better, weighed 200lbs. less, more hp, and just sleeker all around. Guess who won on the track? Yep, the Evo. The control of the 4WD systems on the Evo was so advanced it was pulling that car through to shave off time. Saw a similar test of an Evo vs. a mid 80s Audi GT on the show Fifth Gear. The same thing happened, the Audi had like 50 more hp, but couldn't keep up around the track.
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Re: Brake Assisted Steering
I don't think you are. There is no handle, and the secondary calipers are on the REAR wheels. The steering and regular brake systems are completely unmodified. My crappy little diagram is just the actuation side (the black lines from the blue cutting brake setup are supposed to be tie rods). Brake lines would run from the cutting brake setup to the rear brakes alongside the stock brake line along the chassis tunnel.Ol'fogasaurus wrote:Lets say you are making a right turn; you turn the steering wheel to turn right and then, because you want to turn faster, you pull on the turn right handle which pushes on the left spindle. Your steering wheel is then going to want to turn more to the right based on the pressure applied to the left spindle whether you like it or not, assuming I am understanding what you want to do correctly.
@Jadewombat, I haven't given much thought to different braking force at different speeds, but you're right that you're probably not going to be turning a full 90° at 60mph. In my mind this is going around all the canyon twisties between me and civilization. You're going a max of maybe 45 mph in the sweepers and there are a number of switchbacks. In the sweepers (and most driving, the wheel never turns more than 10°), but on switchbacks a little tighter turning radius with the effect of a shorter wheel base could definitely come in handy. I can see taking tight turns on city streets could result in actuation of the system, but I imagine you'd get used to the extra assist pretty quickly.
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Re: Brake Assisted Steering
spectre6000. I think this is a pretty cool idea. The concern i see (this has been mentioned i think) is that when you are maneuvering a parking lot you will be locking up an inside tire.
However as for proof of concept if you needed it, I raced a CRX Si once that had one caliper that began to stick about 2 laps in. By the end of the race it would lock up with anything more than 80% force applied. The locking caliper was on the right rear, so all of my left hand turns I would brake a little earlier, then at my turn in point I would jab it locking the RR tire, the car would rotate and I found myself on the gas way sooner than before. This was all fine and well but the end result was no faster as I had to be careful not to brake to much even more so on the right hand turns as it would have sent me off into the grass. If it could have been controlled then I think it could have helped.
Another example:
Anyone ever drive a tractor? On the farm we use cutting brakes all the time to spin a tractor around and we can pivot on the inside rear tire, but they are desiged with 2 brake pedals that you can lock together or unlock to aid in steering.
So here is my off the cuff idea on how to make this work, and be able to disable it without crawling under the car. Mount two single cylinders to the underside of the dash with necessary reinforcements, run parking brake cables from each spindle/tie rod etc. then through the firewall and hook onto the cylinders. If I'm not missing something here (very exhausted at the moment) when you turn one way a cable will pull one cylinder activating one caliper and providing "slack" to the other and visa versa. Make the handle with multiple holes to hook the cable and there is your variability.
Disconnect the cable to "turn off" the system
As for the calipers and brackets For a different purpose I was going to get two pair of the "universal steel" conversion brackets, cut and weld those to facilitate the second caliper for a different idea I had, the same could be done in this case.
All in all i think it's a neat idea that could work, but I would just ease into it a little at time, this is certainly not something to jump into with both feet all at once.
However as for proof of concept if you needed it, I raced a CRX Si once that had one caliper that began to stick about 2 laps in. By the end of the race it would lock up with anything more than 80% force applied. The locking caliper was on the right rear, so all of my left hand turns I would brake a little earlier, then at my turn in point I would jab it locking the RR tire, the car would rotate and I found myself on the gas way sooner than before. This was all fine and well but the end result was no faster as I had to be careful not to brake to much even more so on the right hand turns as it would have sent me off into the grass. If it could have been controlled then I think it could have helped.
Another example:
Anyone ever drive a tractor? On the farm we use cutting brakes all the time to spin a tractor around and we can pivot on the inside rear tire, but they are desiged with 2 brake pedals that you can lock together or unlock to aid in steering.
So here is my off the cuff idea on how to make this work, and be able to disable it without crawling under the car. Mount two single cylinders to the underside of the dash with necessary reinforcements, run parking brake cables from each spindle/tie rod etc. then through the firewall and hook onto the cylinders. If I'm not missing something here (very exhausted at the moment) when you turn one way a cable will pull one cylinder activating one caliper and providing "slack" to the other and visa versa. Make the handle with multiple holes to hook the cable and there is your variability.
Disconnect the cable to "turn off" the system
As for the calipers and brackets For a different purpose I was going to get two pair of the "universal steel" conversion brackets, cut and weld those to facilitate the second caliper for a different idea I had, the same could be done in this case.
All in all i think it's a neat idea that could work, but I would just ease into it a little at time, this is certainly not something to jump into with both feet all at once.
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Re: Brake Assisted Steering
JWP, you're on the right track. Now imagine that CRX was like that on both sides consistently, with a known and controllable amount of actuation, and manipulated passively with the steering wheel as the input versus the brake pedal. You're used to it doing this and expect it, so the danger of "WTF IS GOING ON!??!?!" is fully mitigated. Your brake brakes are untouched, so there's no danger of unknown results from braking a certain amount, and the turning brake is tuned so that it doesn't lock up at all (unless you want it to, that is).
The current iteration in my head has an off the shelf cutting brake unit with a two part handle where a smaller tube fits into a larger tube and can slide (like a trombone). The brake itself mounts on a set of tracks on top of the center tunnel (this will most likely need to be run through the firewall to get an appropriate amount of adjustability for prototyping). The tracks are slotted with some wing nuts. The cutting brake is mounted on its side for visualization purposes. a dual set of hard lines are run along the passenger side of the tunnel with a set of SS soft lines between the rig and the start of the hard lines to allow for adjustment. To keep costs low for prototyping, it might not hurt to just use the cutting brake in line for the rear brakes, but I think ultimately a reservoir would need to be mounted on top somehow for redundancy and to keep the regular brakes in their safest known configuration. If you set the rig all the way at to where it butts up against the shifter, you're really not going to have ANY actuation at all as the base of the triangle gets longer and longer, the angle of actuation gets smaller and smaller. Maybe even cut the rod just short of full aft adjustment and provide some sort of hold down for disabling the system entirely... The farther from the tie rod the rig is positioned, the less actuation you get. The closer it is, the harder you get until you're actually locking up the brake. I would imagine you'd want to set that point to where it locks up at precisely full steering wheel articulation. If constructed using stock parts versus an off the shelf aftermarket unit, specifically two sets of single circuit masters and push rods with a homemade lever setup, the play in the push rods can be adjusted to provide for dead action on center...
The current iteration in my head has an off the shelf cutting brake unit with a two part handle where a smaller tube fits into a larger tube and can slide (like a trombone). The brake itself mounts on a set of tracks on top of the center tunnel (this will most likely need to be run through the firewall to get an appropriate amount of adjustability for prototyping). The tracks are slotted with some wing nuts. The cutting brake is mounted on its side for visualization purposes. a dual set of hard lines are run along the passenger side of the tunnel with a set of SS soft lines between the rig and the start of the hard lines to allow for adjustment. To keep costs low for prototyping, it might not hurt to just use the cutting brake in line for the rear brakes, but I think ultimately a reservoir would need to be mounted on top somehow for redundancy and to keep the regular brakes in their safest known configuration. If you set the rig all the way at to where it butts up against the shifter, you're really not going to have ANY actuation at all as the base of the triangle gets longer and longer, the angle of actuation gets smaller and smaller. Maybe even cut the rod just short of full aft adjustment and provide some sort of hold down for disabling the system entirely... The farther from the tie rod the rig is positioned, the less actuation you get. The closer it is, the harder you get until you're actually locking up the brake. I would imagine you'd want to set that point to where it locks up at precisely full steering wheel articulation. If constructed using stock parts versus an off the shelf aftermarket unit, specifically two sets of single circuit masters and push rods with a homemade lever setup, the play in the push rods can be adjusted to provide for dead action on center...
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Re: Brake Assisted Steering
I follow that completely, in fact i thought about this when I had the CRX. In the idea that I proposed the variability would come from hooking the cable in different holes in the handle. Ie further away from the pivot would be less active than closer to it.
Maybe I can draw up a paint picture later that shows what i'm referring to.
Instead of a cutting break, i'm looking at using something more like a drift car rear brake.
So two of these essentially one for each side.
If i had a parking brake cable tied to the tie rod, then each one could operate one lever
Maybe I can draw up a paint picture later that shows what i'm referring to.
Instead of a cutting break, i'm looking at using something more like a drift car rear brake.
So two of these essentially one for each side.
If i had a parking brake cable tied to the tie rod, then each one could operate one lever
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Re: Brake Assisted Steering
I think I have partly caught up with what you are talking about but some of it is still beyond me.
If I understand part of it correctly, and I am not sure I do, you are still dealing with the dual calipers but are you talking about them front and rear or still on the rear only? If it is front and rear then are you going to put an adjustable proportioning valve in to keep the pressure on the front less than the rear or am I still missing a lot. I gotta re-read the whole string again I think.
I don't understand the "like a trombone" tube or what/where/why of the adjustable plate but yet especially with the wing nut bit... most of them aren't made for pressures/loads and fitment that I would suspect you might be dealing with but there may be other options out there like the sliding mount that pedal assemblies fit on in rails (for example... conceptually of a sliding mount [I haven't looked at them for a while and these are getting pretty sophisticated, more than what used to be our there]: http://www.mooreparts.com/store/search.asp). I just ran into this while looking for something else: http://www.pacificcustoms.com/mm5/merch ... ange_high=
Lee
If I understand part of it correctly, and I am not sure I do, you are still dealing with the dual calipers but are you talking about them front and rear or still on the rear only? If it is front and rear then are you going to put an adjustable proportioning valve in to keep the pressure on the front less than the rear or am I still missing a lot. I gotta re-read the whole string again I think.
I don't understand the "like a trombone" tube or what/where/why of the adjustable plate but yet especially with the wing nut bit... most of them aren't made for pressures/loads and fitment that I would suspect you might be dealing with but there may be other options out there like the sliding mount that pedal assemblies fit on in rails (for example... conceptually of a sliding mount [I haven't looked at them for a while and these are getting pretty sophisticated, more than what used to be our there]: http://www.mooreparts.com/store/search.asp). I just ran into this while looking for something else: http://www.pacificcustoms.com/mm5/merch ... ange_high=
Lee
Last edited by Ol'fogasaurus on Mon Nov 04, 2013 9:01 am, edited 1 time in total.
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Re: Brake Assisted Steering
Do you mean actuating a set of hydraulic handbrake-style brakes (as pictured) by means of a cable, or actuating parking brakes by means of a cable tied into the tie rods?
This is the sort of setup I had in mind, either off the shelf or replicated using VW single circuit masters.
This is the sort of setup I had in mind, either off the shelf or replicated using VW single circuit masters.
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Re: Brake Assisted Steering
Using cables to actuate a hydraulic cylinder like you have shown, but utilize a 2 handle model to keep the circuits separate.
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Re: Brake Assisted Steering
Rear only as per Porsche design.Ol'fogasaurus wrote:If I understand part of it correctly, and I am not sure I do, you are still dealing with the dual calipers but are you talking about them front and rear or still on the rear only?
Link doesn't work.Ol'fogasaurus wrote:I don't understand the "like a trombone" tube or what/where/why of the adjustable plate but yet especially with the wing nut bit... most of them aren't made for pressures/loads and fitment that I would suspect you might be dealing with but there may be other options out there like the sliding mount that pedal assemblies fit on in rails (for example... conceptually of a sliding mount [I haven't looked at them for a while and these are getting pretty sophisticated, more than what used to be our there]: http://www.mooreparts.com/store/search.asp).
Look at the image I most recently posted, and imagine that the rod with the blingy blue ball is tubular with another tube slid over it and the whole shebang is attached to a pivot on the right hand tie rod where it passes over the chassis tunnel. The inner tube OD is oil film thinner than the outer tube ID such that they slide over each other like a trombone slide to make it longer or shorter. This is to account for the change in length that would be required as the lever travels along the arc that would be required to actuate it with the tie rod (left to right with a bit of fore and aft movement). The whole assembly with the lever is on its side versus the typical upright mounting position.
By this connection, the lever is actuated left/right (up/down in standard orientation) to actuate the secondary left/right rear brake calipers according to steering input (driven by the movement of the tie rod). The amount of actuation is determined by the length of the lever which affects the amount of pivot angle available at the lever across the range of motion of the tie rod. The shorter the length of the lever, the greater the angle of lever actuation (recall high school trigonometry). This allows for tuning of the system to allow for more or less braking at greater or lesser degrees of steering lock.
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Re: Brake Assisted Steering
If I understand correctly, you can use a two cylinder cutting brake with a pivot/lever instead of the cable actuated set of single cylinders, you can simplify the rig considerably. I may not be picturing it how you are though.JWP wrote:Using cables to actuate a hydraulic cylinder like you have shown, but utilize a 2 handle model to keep the circuits separate.
I did my best to illustrate the two cylinder lever setup above. The blue crappy squiggle is supposed to represent the type of cutting brake I linked to above, the black crappy squiggle it's touching is the RH tie rod, and the red arrow-looking crappy squiggles are supposed to represent the motion of the blue crappy squiggle that would be the lever of the cutting brake if I had any abilities for making it more readily recognizable.
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Re: Brake Assisted Steering
I'll try to draw something up tonight and post it to convey what i'm thinking of