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With the clutch activation, I'll still need the manual clutch for launching / stopping. If I did it hydraulically I would need to set it up with a parrallel master driven by pneumatics feeding into a tee. But then if I hit the gear down button whilst my foot is on the clutch it will either damage the slave / pressure plate or push my foot back. I could have a clutch switch so that the clutch pneumatics don't fire if my foot is on the clutch.
I could also do it mechanically so that either the pneumatics or the clutch pedal pushes onto the master.
I think first stage is just replacing the manual gear selection. Second stage is optimising it for speed.
Currently shifts are very fast when I'm confident.... but due to the layout of the box with 1st in 5th position I'm a bit tentative going from 3rd to 4th especially whilst cornering. I know if I hit that 3rd gate by mistake its all bad.
Yeah clutch would be pnuematic, like the rest. Have the solenoids setup to connect each side of the cylinder to atmosphere when not firing so the pedal is still easy to use like before. I would just have the pnuematics operate the clutch pedal directly. Have a button where the deadpedal is that you mash with your foot to enable the pnuematic clutch control. Moment your foot comes off the deadpedal, it's back to regular clutch. That would be simple and fairly safe.
It's right on the limit of these little cylinders but I also had the air pressure down at 50PSI. I could crank it up too 100 and the shift speed would increase a lot. Still, it's pretty damn awesome!
It's right on the limit of these little cylinders but I also had the air pressure down at 50PSI. I could crank it up too 100 and the shift speed would increase a lot. Still, it's pretty damn awesome!
That is looking awesome! The only thing I will mention is that if you watch your video, those steel brackets that hold the cables are being way too much to be reliable. Those will fatigue fail bending that much with every shift. I would make those from thicker steel, especially the front one. Otherwise looking very solid!
The brackets are temporary... I'm just using some bend ally to lay it out. The entire assembly will be flopped to the alternate side and I'm going to move it down towards the tail shaft another 50mm for final. I'll machine some nice billet brackets out of aluminum or weld some out of plate steel.
There isn't massive amounts of room in the tunnel so that little nub will be trimmed back.
I think I have a solution to handle auto blip. I'll basically make a servo driven large port idle control valve. It will be a port from after the intake filter that bipasses the throttle and feeds directly into the plenum. I'll make a rotary valve that will open up via the servo motor when I need to blip the revs. I'll have to have a search and see if I can find something that will work. I don't think a standard idle control valve will allow enough air through at 6000rpm to lift the revs.
what about a waste gate or bov or something like that? There is no pressure from the intake to drive it but I will have compressed air onboard.
Superchargers often have a small "bypass valve" that's effectively a 1" to 1.5" diameter throttle valve with a vacuum diaphragm on it to actuate it. You could likely modify one of these to act as a throttle blipper. A small electric push/pull solenoid to replace the diaphram would be pretty easy to construct and control such a device.
I could probably just use peumatics to open the throttle. Close it when I'm at target revs.
There us a haltech idle valve which would hook up via 4 dedicated outputs on the ecu. Its a stepper motor with 19mm ID ports so will be fast and flow a decent amount of air.
Last night I set up the gear indicator. Its a 38mm 16 segment display driven by a controller chip that only requires 2 pins on the arduino. I couldn't use the standard libraries so I'm manually turning on the individual leds based on there addresses which works well enough. I'm using a 16 segment display so that I can display 'N' and 'R'. I've also set it up to show 'P' when the pressure is low and 'E' if there is an error.
The shield on top is a CAN bus shield with logging and GPS (if I solder to it). I'll see if I can get this receiving ecu data.
I'm another former FSAE guy who did a simple pneumatic shifter and I have to say that I really like the progress you've been making on this. I have had this idea in my head for a while now but I might start to look into it more with your success.
I'm surprised how easy it has been so far. The part I was most worried about has been fairly simple so far. Its simply awesome how easy it is to add modules and fuction to arduinos.
Today I spent an hour setting up the CAN-BUS shield. The libraries supplied with the shield didn't have a 1mbit option so I had to add it. I then wired into my existing CAN loom in my car and first go it was reveiving data. So I added some filters for RPM, TPS and MAP from the Haltech and the data streams through super fast. I think I'm seeing around 50 packets per second so thats around 20ms delay from the ecu to the ardunio.
I'll use the rpm data to make sure the revs of the target gear are under a threshold to avoid money shifts. I'll also use the manifold pressure to data log whatever auto blip mechanism I use.
I've just ordered a 150psi pressure sensor for the air supply and also a 4L aluminium tank. I still need to order my final air cylinders which will be custom 3 position tandems so that I don't have complicated pivots and arms driving things.
Final layout on the shifter cables. The entire assembly is now mounted on my dog box and flopped to the other side to clear the ppf.
I'll remake the base aluminium plate and the side to side bracket once I get the final pneumatic cylinders. The dog box does shift easier than the stock 5 speed so I'm wondering if I should order 20 or 25 mm bore cylinders. I'm currently testing with 16mm bore so a 25 will be over double the power.
The multi position cylinders cost a lot more but they will also package far better with the cylinders solidly mounted rather than moving like my piggy backed design. The are around 80€ so I want to get them right. They even have magnetic sensors that pick up the cylinder position which saves me from having to set up the potentiometers.
I've designed a simple paddle shift mechanism for my steering wheel. It will use two momentary limit switches on each side to give a nice solid feel and a bit of redundancy. I'll bridge the connections so that either switch will trigger to ground.
This design is the simplest I could come up with that requires the least amount of work for a good function and adjust-ability. It's basically a couple of aluminum blocks bolted either side of the mounting plate, with just the paddle itself needing a bit of machining. I'll bolt the handle to the main body of the paddle so that i can easily readjust if the position isn't working.
One made... the shift feel is brilliant! By using two switches the paddle has a nice solid click to it and a feel similar to a mechanical keyboard. I still need to make a moon shaped carbon fibre handle.
Very cool project. Are you using any debounce code for the paddle shifters? I see you have two switches, is that so you can have them in parallel for redundancy, or in series to act as hardware debounce?
It's winter here in Australia and my entire family has been sick, so I haven't done much in the last few weeks other than coding and wiring. I'm also waiting for my 3 position air cylinders and 3 way valves to rock up before I can start to finalise things and test it in my car. I have ordered 5 x magnetic reed switches which I'll use to detect successful gear changes. These work on air cylinders with a ferrous strip around each piston so that the magnetic sensors pick up the movement of the piston. My current code relies on these sensors to display the gear as well as enable the next shift, so I can't really test it all until everything rocks up.
I have also ordered a air cylinder that I'll mount directly to a secondary clutch master slave. It's single action (return spring) 50mm bore air cylinder so it should be able to put out around 180lbs of force, which I think is enough to punch the twin plate clutch. That should rock up in a couple of weeks and then I'll be able to fire that off on down shifts.
Here is a 3D mockup of the various parts I'll be running. I already have the compressor (I'm nicking it from my 4x4) and I have just received my 3L (1Gal) ally air tank. The 3 position cylinders directly connect to the shift cables making for really nice packaging. My old system of piggy backed cylinders meant the pneumatic air tubes all jump around with each shift which isn't really ideal for long term use. I've calculated that the air tank will hold enough air for most of my events, but the compressor can keep topping it up as the pressure drops if I need.
I had a bit of a play with my car's ECU and managed to get shift cut working in principle. So basically I earth an analog input and the ECU stops ignition so I should get a nice pop once the gear shift completes. I'll test this with the arduino next time I start up the car.
I also managed to figure out how to connect all 3 switches on my paddle shifter to my ecu with only two wires. This means I can use the inbuilt horn connections in my quick connect steering hub to transfer all my button presses to the shift computer. Not only that but I can also test for connectivity and short using the same process. So basically I have 3 different resistors hooked up in parrallel, plus a pull up and an inline resistor. This ends up giving me the following:
This is a really nice elegant way of connecting multiple buttons to a single analog input, plus I can add more if I want. I can even query multiple button presses, eg button 1 + button 2 to enable launch control...
Really the last component now is the auto blip. I'm thinking I'll use a generic 4-wire stepper idle control valve found on most modern cars which can connect to my ecu via dedicated inputs. I'm pretty sure they open and close quickly plus I'll be able to use it for idle control which is nice as it's hard to drive through the pits at low speeds as it is. I might even hook up a switch on my center console to idle up the engine when cruising in the pits.
Really the last component now is the auto blip. I'm thinking I'll use a generic 4-wire stepper idle control valve found on most modern cars which can connect to my ecu via dedicated inputs. I'm pretty sure they open and close quickly plus I'll be able to use it for idle control which is nice as it's hard to drive through the pits at low speeds as it is. I might even hook up a switch on my center console to idle up the engine when cruising in the pits.
Just a random thought: with the compressor and air tank in place, you could also put a bit of compressed air into the IM for it to blip.
05-30-2017, 01:07 AM
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