Weber and Coulomb's MX-5

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Post by PlanB » Wed, 12 Oct 2011, 23:11

I nearly got run over in Coles a while back by a dear old soul on her electric ride on. Those things are so stealthy, you can't hear them at all above the in store promos. No power steering obviously.

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Post by T1 Terry » Wed, 12 Oct 2011, 23:51

$240 for that :shock: I hope the pump doesn't run continuous, there is no provision for oil cooling, this is usually done through a lingh of steel pipe run across an area where there is air flow. Without it the oil will over heat and burn destroying the pump and the power steering rack seals.
The noise issue is a nasty one, perhaps the pump and drive belt may have been better after all. I had been looking at using an electric hydraulic pump for a power steering conversion for kombis, this is a very timely warning so thanks heaps.

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Post by Squiggles » Thu, 13 Oct 2011, 00:40

The mazda 3 has an electric power steering rack, maybe that's a chance?
Also I think Honda has some and maybe VW.....so probably just about any current manufacturer.

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Post by mcudogs » Thu, 13 Oct 2011, 03:10

The pump I have installed on my auto transmission made a lot of noise when I hard mounted it to the transmission. I then mounted it with rubber vibration mounts and it is now very quiet. I can't hear it at all with normal traffic noise but I can just feel a slight vibration through the steering when it runs.

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Post by weber » Thu, 13 Oct 2011, 03:18

mcudogs wrote: The pump I have installed on my auto transmission made a lot of noise when I hard mounted it to the transmission. I then mounted it with rubber vibration mounts and it is now very quiet. I can't hear it at all with normal traffic noise but I can just feel a slight vibration through the steering when it runs.

Hi mcudogs. Can you tell us what make and model the pump and mounts are? Any photos? Thanks.
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Post by coulomb » Thu, 13 Oct 2011, 04:25

weber wrote: Can you tell us what make and model the pump and mounts are?

Er, I think he's talking about a Shurflo pump for Auto Transmission oil, not a steering pump.

Per this DIY Electric Car thread: The Reasons why Automatic Gearboxes WILL Work with EV's & how to do it..

[ Edit: So I think he was making a general statement about noisy pumps, not about steering pumps in particular.

Also, maybe it will make less noise when the power steering system is properly bled. Maybe a lot less noise, I really don't know. ]

[ Edit: spelled Shurflo ]
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Post by coulomb » Thu, 13 Oct 2011, 04:28

Duplicate post. Duh.

So as not to totally waste this space, Mcudog's pump may be this one:

Image

From http://www.diyelectriccar.com/forums/sh ... post250520

I turn, possibly from http://www.dultmeier.com/products/0.851.857.4045/7405
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Post by Johny » Thu, 13 Oct 2011, 15:20

weber wrote: Hi Mr B. My mum is pleased that you lick^H^Hke her paint job.
I hope Mr B's saliva isn't corrosive...

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Post by mcudogs » Thu, 13 Oct 2011, 19:07

Hi Weber,

Sorry I didn't elaborate on that. Coulomb has it right and that is the pump I have used complete with picture. Unfortunately it doesn't come standard with a suitable diaphragm for ATF but I managed to buy a replacement Geolast diaphragm that did the job. It is not suitable as a power steering pump as it only develops 150psi.

If you are looking for vibration mounts Element 14 has a range that may suit, try order code 1303906.

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Post by weber » Fri, 14 Oct 2011, 02:32

Thanks for all the info and suggestions guys.

Auto Transmission Fluid is what is used in power steering systems. But yes, the diaphragm pump at 1 MPa, would be too low in pressure. The MX-5 workshop manual says the standard PS pump does 8 MPa into a blocked line, or into the steering system when turned hard at full-lock (which amounts to the same thing).

The manual has dire but inconsistent warnings about not turning it against the stops for more than a few seconds at a time. In two places it says 5 seconds max, in two others it says 15 seconds max. It seems this is the time when it most needs cooling.

Yes I am a little worried about my decision to leave the cooling loop out of circuit. But the pump has a large reservior and a heavy aluminium manifold block that I'm hoping will allow it to run without overheating for the approximately 90 minutes maximum that the car can run on a single charge. That, and the fact that we will run the pump lower than its design speed.

I have bled the air out of the system. According to the manual, this consists of turning the steering wheel several times from lock to lock while the pump is running and the wheels are off the ground.

Here's some engineering eye-candy to break up the text. The inside of the PS pump's motor.

Image

I notice that EVWorks part number is STE-MOC05D01-006 while it says 05D01-007 on the pump. But this seems unlikely to be significant, as the specs written on the pump agree. It appears the "05" means 500 watts, the "D" is for DC and the "01" is the hydraulic circuit as shown here:
http://www.mocen.cn/mocen/hydraulicpowe ... .asp?mm=05
The hydraulic symbols are explained here:
http://www.freestudy.co.uk/fluid%20powe ... ndards.pdf
The -006 and -007 are not explained, but they could be tenths of a mL per rev.

There's a good explanation of how power steering works here:
http://auto.howstuffworks.com/steering5.htm
I understand what the rotary valve has to do, but I still can't visualise it, despite the two projections and the animation.

I notice it says at the end, that this type of system is pretty inefficient. It does sound like an electric system would be much better. But the chance of finding such a rack that fits the MX-5 seems slim, and the cost unacceptable after what I've spent on it already.

Interesting thread here, that also mentions the Mazda 3 rack as a possibility.
http://forum.miata.net/vb/showthread.php?t=235374

I'm almost ready to concede that this was all a big mistake on my part and I should have stayed with the "armstrong" system, as they say in the above thread, i.e. the manual steering rack.

Image

Here's what I learned about the noise through some experiments today:

Using a PWM speed controller (at least the ATA one I have) doesn't significantly reduce the noise level. It just changes the nature of the noise. I now hear the approx 5 kHz PWM frequency as well as the original pump/motor noise. I suppose I need an ultrasonic PWM frequency like 20 kHz.

Without the PWM controller, turning the steering against the stop caused the motor speed to drop alarmingly. With the PWM, but turned to 100%, it caused the motor to practically stall and popped the 30 A fuse on the PWM controller. It makes one wonder whether it really has a pressure relief valve. Or maybe it could use one with a lower rating than the 10 MPa that I assume it is.

Mounting the pump on rubber mounts (at least via the provided mounting holes) will make no difference to the noise. I know this because I unbolted it from the traction motor and held it in midair and it was just as noisy.

With the pump mounted solidly to the traction motor, wrapping a towelling rag around the pump's motor significantly reduced the high frequency noise. Wrapping it around the pump manifold-block made no difference.

Grasping the pump motor at different positions produced radically different amounts of quieting. But it never seemed to be repeatable. It seems that the node moved around a lot with very small changes in speed.

A big soup can full of glass wool over the whole motor would probably quiet it a lot. But then the motor would overheat. Maybe some kind of muffler could be made, with a fan blowing through it, but it sounds difficult, particularly since we only have 15 mm in which to do it.

Any further brainstorms gratefully received.
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Post by weber » Fri, 14 Oct 2011, 03:40

Here's the result of the latest PS pump noise-reduction experiment, as suggested by Newton (Jeff Owen):

Running it off two LiFePO4 cells (about 6.5 V with no PWM noise) reduces the pump/motor noise by maybe half (whatever that means) and it sounds like it might have reduced the speed to about a third.

Without being able to drive it, I can't tell how that will impact on the steering. So I guess I'll just get on with other things and wait until we can test it while driving. But the noise level at 6.5 V may just barely be acceptable.

Running it off one cell, it was hardly going at all. Running it off 3 cells it was maybe 2/3 as noisy and half the speed.
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Post by KDRYAN » Fri, 14 Oct 2011, 04:13

By chance I installed a 1997 Holden Astra electric power steering pump ( it was the only pump the wreckers had)into my Seat Ibiza conversion. I had seen a u-tube video using a earlier version of the Astra pump which was very noisy, the later version I used to my surprise only puts a hum and only slightly louder at full lock. I have no way of checking it but it seems to be a very high reving motor located in the fluid reservoir. At full lock it draws 16amps
Image

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Post by weber » Sat, 15 Oct 2011, 01:35

Thanks for that, KDRYAN. I saw (or rather heard) that video too, before I bought the EVWorks PS pump. Here it is.



Both Newton and Coulomb visited today, and when I tried to demonstrate the horrendous shrill ringing noise I had experienced when running the power steering pump at full voltage, it didn't happen, and they thought I had been exagerating. They agreed it was too noisy, but not 72-point capital letters noisy. Of course this was rather frustrating for me.

I had chosen to demonstrate it using 4 LiFePO4 cells in series (about 13 volts), because I also wanted to demonstrate 3 and 2 cells. We all agreed that when running off two cells the noise was acceptable (I added "just barely").

Then I reconnected the pump to the MX-5's 12 V lead acid battery (via the PWM module turned to 100%) and still the extra noise that I had experienced failed to happen. Then, as I adjusted the speed downward I heard it "chirp". So I adjusted it up to full again and was able to back it off ever so slightly so that it "sang", or rather shreiked. I think Coulomb and Newton both said something like "WHAT IS THAT!". It's one of those noises that seems to be coming from inside your head.

I had a battery charger connected, which I had not had on other occasions. So it appears that there is a high-pitched mechanical resonance of the pump's motor-casing (or something) that occurs at a very narrow range of speeds, which just happen to correspond to the voltage of a 12 V lead acid battery at an ordinary state of charge.

That may also explain the non repeatability of damping various parts of the casing with the hand. The position of the node may change rapidly depending on how far down and what side of the sharp resonance peak we are at.

So if we get a PWM controller that doesn't add a horrendous noise of its own, and we ensure that the pump always runs slower than the resonant speed, we should be OK. Hoorah!

I also did some more reading and it seems that the best kind of hydraulic pump for low-noise power steering is a rotary vane pump. I wonder if that's what the new Astra pump is. Apparently gear pumps are notorious for being noisy, unless they use helical gears that are cut very precisely. I expect our unit has straight gears.

BTW, the vaccum pump we have for the brake booster is marvelously quiet. We couldn't be happier with it. We bought it from Goombi, but now it is available from Suzi Auto Sevices.
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Post by Nevilleh » Sat, 15 Oct 2011, 16:57

I used the pump from a Toyota MR2. It normally runs from a driver that drops the voltage to about 8V for full PS and down to about 5 or 6 above a certain speed (I think about 80 kph) for less PS at high speeds. I find it gives adequate assistance at 6V and I shut it right off once the car gets moving. That makes it very quiet! It draws about 15A when running, rising to about 25 when the steering is on full lock.
I used a PWM driver, a kit from somewhere, that allows me to adjust the drive voltage.

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Post by coulomb » Sat, 15 Oct 2011, 17:31

Nevilleh wrote: It normally runs from a driver that drops the voltage to about 8V for full PS and down to about 5 or 6 above a certain speed (I think about 80 kph) for less PS at high speeds.

I wonder how it determines the voltage to run at. Maybe it's as simple as vehicle speed, which I suppose would work well enough. Hopefully full lock steering at high speed would be rare Image
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Post by Nevilleh » Sun, 16 Oct 2011, 17:08

Yes, it is that simple. I found the wiring diagram and the computer outputs a signal when the speed gets above 80 kph. Its not a very noisy pump but you can hear it when stopped at the lights or whatever. But I only turn it on now when parking, or other low speed manoeuvres. The power assistance isn't really needed for normal driving.

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Post by weber » Sun, 16 Oct 2011, 19:01

Shutting the PS pump off when you're moving at a reasonable speed doesn't help the noise problem. You won't notice it then anyway. What we need to do is get the speakers installed making the V8-with-the-lumpy-cam idle sound to mask it. Image

I modified the ATA PWM controller to run at 20 kHz and with this putting out 6 volts the PS pump noise is acceptable. But the PWM controller was only designed to work at 1 kHz and doesn't have enough MOSFET gate drive current to operate at 20 kHz for more than a few seconds. The switching losses are too high and the MOSFET overheats.

Neville -- the PWM kit you used -- does it operate at an inaudible frequency. If so, what make and model is it and where can I buy one?
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Post by Nevilleh » Sun, 16 Oct 2011, 20:54

It came from that Aussie electronics outfit that sells surplus stuff, etc. The name escapes me for the moment. I'll dredge around and see if I can find it. Same name as the bloke that owns Hamilton Island! And yes, it is inaudible - but my hearing is pretty bad anyway.

Edit: It was Oatley electronics, they have quite a range of motor speed controllers now, can't recall which one I used but you'll find one if you look at their website.
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Post by weber » Sun, 16 Oct 2011, 22:53

It was straightforward to decode that to Oatley Electronics, using Google, thanks. But I can only find two that work at 12 V (one 20 A, the other 50 A) and they both only PWM at 250 Hz which is slower than the one I have, and definitely audible. They suffer from the same design limitation as the one I have, which is that they drive their MOSFET(s) directly from the output of op-amps or comparators with a piddly 40 mA or so.

The simplest mod would probably be to insert a complementary pair of TO92 or E-line package MOSFETs as an inverting driver and swap the op-amp inputs to compensate for the inversion. I'd also need some positive feedback to give a schmidt trigger action so they can't stay in shoot-thru. The ZVP2106 and ZVN2106 or ZVN3306 look good (from Element14).
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Post by coulomb » Mon, 17 Oct 2011, 00:31

weber wrote: The simplest mod would probably be to insert a complementary pair of TO92 or E-line package MOSFETs as an inverting driver and swap the op-amp inputs to compensate for the inversion.

Or use an actual dual MOSFET driver chip, like this one:

http://au.element14.com/microchip/tc442 ... dp/1332311

There are also inverting versions (TC4426) that are half the price. Schmitt inputs built in.

Arguably easier to connect, since it's one package, verses two.

I use a higher voltage version of these (and non dual; can't get dual drivers that run at 24 V) at work.
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Post by Nevilleh » Mon, 17 Oct 2011, 12:17

I don't recall which one I used, but it is more than adequate for the job, its been running my PS pump for the best part of a year. It doesn't make enough noise to be a concern, no matter what frequency it works at. Maybe it isn't "state-of-the-art" but what the hell, it does the job. Which was to get an electric car on the road!!

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Post by weber » Mon, 17 Oct 2011, 14:10

Nevilleh wrote: I don't recall which one I used, but it is more than adequate for the job, its been running my PS pump for the best part of a year. It doesn't make enough noise to be a concern, no matter what frequency it works at. Maybe it isn't "state-of-the-art" but what the hell, it does the job. Which was to get an electric car on the road!!
Hi Neville. I'm very grateful for whatever help you can give. I'm sorry that my question, whether it used an "inaudible frequency", was ambiguous. It may be that your pump motor doesn't act so much like a speaker for the PWM pulses as ours does. But I was also concerned that maybe I had not yet found the controller you are using.

Whether it is state-of-the-art is of no concern (for example we're currently designing some logic circuits using relays). But whether it will run at 20 kHz or above, is of concern, because our pump motor is such a good tweeter.

[Edit: That driver chip looks ideal, Coulomb]
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Post by bladecar » Mon, 17 Oct 2011, 14:15

I've occasionally thought of that idea with an electric car. Have an effective sound system and have programmed or dial-up sound effects to amuse yourself and occasionally the listeners.

Lumpy-cam v8, jet engine start-up, mr magoo bop pop pop, solid lifter noise, mixmaster whine, freight train at high speed, failing starter-motor start-up, and possibly a coughing bout, or a sneeze.

I think, maybe, this type of sound system should be a standard component of the electric car until there are enough of them on the road to prompt anyone within ear-shot of these sounds to throw projectiles in their general direction.

I'm keen to find out how quiet the Blade is from a bystander's point of view. My Vectrix has a whine like "I'm a real boy" by Pinocchio in
Shrek and should be hard to miss. The whine has enough sounds to form an orchestra depending on where the throttle is and what work is required. On low load at low speed, it sounds like a manual car transmission with stuffed gear-shaft roller bearings. Some people stop and look in my approaching direction from quite early on and others don't appear to ever notice anything out of the ordinary. Here, the difference is probably between those people who buy a red car or a blue car when buying new, and those who forgo 4 doors for 2 because they want that special trim.

With modern, reasonably expensive petrol cars running as quiet as they do (heard a volvo c60 lately?), they shouldn't pick on the electric car as being unusually dangerous in this regard.
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Post by Nevilleh » Fri, 21 Oct 2011, 14:10

Sorry I can't tell you the model number of that driver, its inside a black plastic box screwed to my car and not so easy to remove!

I was in a gas station (used to be called a "Service" station) the other day checking my tyre pressures and I very nearly ran over a fellow as I was leaving. He had just finished filling the tank (he, he) and stepped in front of my car as I took off. Didn't hear, didn't look, taken completely by surprise. Even the noise from my power steering pump wasn't enough for him to notice - I had it switched on at that speed. So there is obviously a need for a gadget to simulate the sound of a big V8 at the appropriate times! Whoever suggested that recently, get to it, I need one!

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Post by Tritium_James » Fri, 21 Oct 2011, 14:20

I like the idea that GM used on the EV1, which had a sounder kind of like a cross between one of those tin 'clicker' things that are quite often in showbags, kids toys, etc, and a small bell. Electrically actuated, and it made a 'ting ting' sort of noise when you flashed the high beam lights. Perfect for alerting pedestrians (you get the flash of light too) and not offensive like a horn.

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