LocostUSA.com

Learning how to build Lotus Seven replicas...together!
It is currently July 19, 2018, 3:33 pm

All times are UTC - 5 hours [ DST ]




Post new topic Reply to topic  [ 11 posts ] 
Author Message
 Post subject: Pedals Don't Move
PostPosted: April 11, 2015, 11:34 am 
Offline

Joined: April 15, 2014, 1:54 pm
Posts: 397
I was reviewing Lonnie's pedal setup. His setup would work perfectly if he didn't have to move his feet.

Suppose the foot pedals didn't have to move, but were fixed and merely sensitive to pressure only. This would be like the joy sticks in military aircraft that don't move physically but sense the pilots pressure only and activate the control surfaces accordingly. Essentially this is how brakes work after you use up the pedal travel.

Then you wouldn't have to wear ballet slippers to drive these cars and have to explain that every time you got out of the car. "Cool car, Mister, but why are you wearing those funny slippers? Do you think you are Dorothy in the Wizard of Oz? If you click your heels twice, will you car turn into a Ferrari?".


Top
 Profile  
Reply with quote  
 Post subject: Re: Pedals Don't Move
PostPosted: April 11, 2015, 12:36 pm 
Offline
User avatar

Joined: April 12, 2010, 5:40 pm
Posts: 2081
Location: san francisco bay area
I think the lack of feedback would take some effort to get used to. .. I also think you would be more likely to experience muscle cramps.

_________________
"There are times when a broken tool is better than a sound one, or a twisted personality more useful than a whole one.
For instance, a whole beer bottle isn't half the weapon that half a beer bottle is ..." Randall Garrett


Top
 Profile  
Reply with quote  
 Post subject: Re: Pedals Don't Move
PostPosted: April 11, 2015, 12:57 pm 
Offline

Joined: August 19, 2014, 5:17 pm
Posts: 685
Location: England
There is enough room to spread the pedals and still have room to get your clogs off the pedals in you use all the space available. Pan the gear tunnel to within a few mm of the bellhousing/gearbox in the footwells and it all starts to look like it would accommodate a guys feet rather than one of snow whites followers.

Bob

_________________
Build Log viewtopic.php?f=35&t=16640&p=187700#p187700

Mancave http://s1116.photobucket.com/user/mypic ... ow/mancave


Top
 Profile  
Reply with quote  
 Post subject: Re: Pedals Don't Move
PostPosted: April 11, 2015, 1:37 pm 
Offline
User avatar

Joined: April 26, 2008, 6:06 pm
Posts: 2952
Location: Under the weather. (Seattle)
My first thought would be to try oversized power assisted master cylinders that just get the pedal effort vs stopping force similar to unassisted levels. The more assist, the bigger the master cylinders can be, the less travel is required. Then using extreme mechanical linkage ratios to get the throttle pedal movement minimal. It would probably require a pretty clever system of mechanical assist that keeps the actuation smooth and linear with increased force at very small travels. The less Locost route would be to develop/modify a computer controlled drive by wire system that uses load cells rather than potentiometers at the pedals.

_________________
-Justin

Also follow my build on blogspot, tumblr, or instagram and twitter (GarageOdyssey)


Top
 Profile  
Reply with quote  
 Post subject: Re: Pedals Don't Move
PostPosted: April 11, 2015, 2:01 pm 
Offline
The voice of reason
User avatar

Joined: January 10, 2008, 4:47 pm
Posts: 7546
Location: Massachusetts
I believe the brake pedal in the Citreon from the 60's - 70's work that way. You could look into it. Hydraulics can work that way. power steering doesn't require much movement to provide assist.

It will add complexity though which doesn't help use get our projects done. The pedal space problem is caused by the tapering of the frame. If you buy a body for the car, like a Lalo etc., then you don't have this problem. I think that is a more cost effective way to approach this. Then you get some actual foot room which is a plus.

_________________
Marcus Barrow - Car9 an open design community supported sports car for home builders!
SketchUp collection for LocostUSA: "Dream it, Build it, Drive it!"
Car9 Roadster information - models, drawings, resources etc.


Top
 Profile  
Reply with quote  
 Post subject: Re: Pedals Don't Move
PostPosted: April 11, 2015, 2:33 pm 
Offline
User avatar

Joined: April 12, 2010, 5:40 pm
Posts: 2081
Location: san francisco bay area
I was under the impression he meant piezo force sensors
Bobber wrote:
...pedals didn't have to move, but were fixed and merely sensitive to pressure only.

_________________
"There are times when a broken tool is better than a sound one, or a twisted personality more useful than a whole one.
For instance, a whole beer bottle isn't half the weapon that half a beer bottle is ..." Randall Garrett


Top
 Profile  
Reply with quote  
 Post subject: Re: Pedals Don't Move
PostPosted: April 11, 2015, 8:13 pm 
Offline
User avatar

Joined: July 17, 2008, 9:11 am
Posts: 4623
Location: West Chicago,IL
In order for this to work, you would have to have brakes-by-wire, either electrically actuated or electric over hydraulic. Hydraulic brakes currently work this way, sort of. The "Sort of" caveat is the movement of the piston(s) that move back into the caliper when pressure is released, the slack in the pedal linkage(s), the master cylinder piston closing up the "fill hole" before pressure builds, the flex of mounting brackets (sorry JD) and hydraulic flex lines, no matter how little each contributes.

_________________
Chuck.

“Any suspension will work if you don’t let it.” - Colin Chapman

Visit my active Cushman Truckster resurrection log: over HERE
or my archival Locost build log: over HERE


Top
 Profile  
Reply with quote  
 Post subject: Re: Pedals Don't Move
PostPosted: April 12, 2015, 12:01 am 
Offline
The voice of reason
User avatar

Joined: January 10, 2008, 4:47 pm
Posts: 7546
Location: Massachusetts
This can be done electrically or hydraulically.

If you do this electrically, you measure the strain on a crystal and duplicate it in the hydraulics. You can also do this hydraulically. You measure the force on the pedal and replicate in the brake system. That's different, but related, to how the typical power brakes work now. The pedal doesn't really have to move much in either case to measure a force on it. It could feel solid to the driver.

In the Citreon car, the brake pedal does not move when you use it. I've never driven one, but have a read a description 30 years ago. :rofl:

Compared to things like making the entire car wider or moving the engine forward a bit, it's a lot of work when you decide to be really creative like this. Might as well just make that your hobby and forget the car part. I think this is an area of current research for hydraulics because it's actually fairly difficult and tiring to use large hydraulic equipment like excavators etc. So real proportional controls would be a good thing.

_________________
Marcus Barrow - Car9 an open design community supported sports car for home builders!
SketchUp collection for LocostUSA: "Dream it, Build it, Drive it!"
Car9 Roadster information - models, drawings, resources etc.


Top
 Profile  
Reply with quote  
 Post subject: Re: Pedals Don't Move
PostPosted: April 12, 2015, 5:21 am 
Offline

Joined: February 20, 2015, 12:04 pm
Posts: 281
Location: Cotswolds - UK
horizenjob wrote:
In the Citroen car, the brake pedal does not move when you use it. I've never driven one, but have a read a description 30 years ago.


Like you, I've never driven a Citroen SM, but in period road tests the feature seemed to be heavily criticised - apparently it was difficult to judge pressure alone (as opposed to pressure and movement), so you tended to spend quite a lot of time pitching your passengers through the windscreen when you thought you were just check-braking.

The TVR Tuscan used the opposite principle as a caveman version of traction control - they gave the car a reeeaaallly looooong throttle pedal travel, to make it easier to modulate power delivery. The approach on that car (which I have driven) worked well - it made it considerably less evil than the preceding Griffith 500.


Top
 Profile  
Reply with quote  
 Post subject: Re: Pedals Don't Move
PostPosted: April 12, 2015, 11:48 am 
Offline

Joined: October 19, 2009, 9:36 pm
Posts: 2070
Location: meadview arizona
i have driven citroens, some with pedals and some with a big tit on the floor, the system works very well.

the driver application problem is soon overcome, just like left foot braking.

it relies on a pumped system with accumolators, normal braking is done by tapping the line pressure and hard braking is done by adding the accumolator pressure to the line pressure which still fluctuates with application pressure.

the same system is used on rolls royces and before the introduction of air brakes, london double decker buses.

the answer to a variable throttle pedal is to make it hydraulic and use different sized cylinders.

the clutch, well just throw it away and fit a tiptronic trans, this will give you 30% more foot room.

i personally chose when panelling my tunnel to put the panel in the drivers foot well on the tunnel side of the chassis tubes giving me an extra inch of space.

i have size 13 shoes and can drive my car in normal footwear.

i do however have a 442 chassis but my engine/trans is set back a long way, so far that my radiator is in the engine bay.

_________________
this story shall the good man teach his son,
and chrispin chrispian shall ne'er go by,
from this day to the end of the world.
but we in it shall be remembered.


Top
 Profile  
Reply with quote  
 Post subject: Re: Pedals Don't Move
PostPosted: April 12, 2015, 12:51 pm 
Offline

Joined: February 8, 2014, 10:47 pm
Posts: 489
Location: Cornholio OR "Where the magic happens"
Hydroboost has been around a long time, not for the weight conscious.

_________________
Yaaaaaaay! The profile link is fixed!


Top
 Profile  
Reply with quote  
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 11 posts ] 

All times are UTC - 5 hours [ DST ]


Who is online

Users browsing this forum: No registered users and 1 guest


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
Jump to:  
POWERED_BY