Weber and Coulomb's MX-5

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Post by Johny » Tue, 02 Aug 2011, 19:36

That's some very tidy hacksawing. Leave it clear - it looks great.

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Post by htial » Thu, 04 Aug 2011, 22:56

I agree...   ...Leave the clear top on it...
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Post by weber » Sat, 06 Aug 2011, 17:15

It has been a big week for the MX-5. On Wednesday night I hosted a Nerds Nite, where any nerd who wanted to, got to drive the MX-5 on the fire-break. Nerds Nite is a venerable tradition started and maintained by Eddie Matejowsky. Thanks also to Ross Pink and all the Electronic Innovations staff for coming along. Ross got me started on AC EVs with his eVan.

On Thursday, my dad "Kiloweber" and my uncle "Oersted" (he's a CGS unit because he's old-fashioned) came to give me a hand with some steel work. Of course they had to have a drive before they started work. And it's about time we showed some video of the MX-5 going properly. So here they are driving the MX-5 at break-neck speed. Image My uncle decided it was so quiet there must be a big wound-up rubber-band powering it.



Then they got to work cutting some 3 mm steel plate to reinforce the front shocky-tower gussets, to take a 90 kg battery box at 20 gees. The steel plate came from a modification to the deck of this picture-postcard yacht, that my mum and dad used to own and live on. The 10 m Roberts Spray, "Augusta Marie". [No, not rich. They sold their house to buy her, just for the experience.]

Image

Man we had some good times on that boat. So it's nice to have a piece of her incorporated into the MX-5, ... by my dad. <sniff>

[Edit: Spelling and minor wording changes]
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Post by weber » Sun, 07 Aug 2011, 04:52

On Friday Coulomb, Newton and I had a very productive EV day.

The following photos show the drilling, clamping, tacking and welding of the reinforcing plates for the front shocky towers.

Image Image
Image Image
Image Image
Image

Coulomb single-handedly completed the required cutting and rewelding of the passenger-side lower-middle battery box, to clear the larger diff -- one of the world's most complicated battery boxes. It was a relief to find we had already allowed for losing a cell there.

Newton and I worked on finishing the battery box to go over the motor, and the details of how we are going to mount it. After Coulomb finished the diff battery box he joined us. Here you can see where we were trial-fitting the battery box, with blobs of blutak on top to check clearance from bonnet ribs, to get the optimum tilt angle and maximise the clearance from the motor's cut-down junction-box lid (that will be staying transparent).

Image
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Post by weber » Tue, 23 Aug 2011, 05:28

We're getting close to finishing the welding of all the battery boxes. EV day before last, Coulomb built the basic frame of the last one, the 13-cell box that goes at the bottom of where the radiator used to be. We still have to design and weld the mounting tabs for that box, and for the 19-cell box behind the rollbar, and prepare and paint them.

Last EV day we got serious about where we're going to fit all the vacuum contactors, fuses, shunts and precharge resistor. These things, and the enclosures for them, take up an awful lot of space in a high voltage conversion like this. As you go up in voltage the space required for conductors reduces while the space required for insulators increases. It's amazing how much space a vacuum can occupy, and we have twenty of them. Image

Here's the beginning of one of the more difficult contactor boxes, the one designated "A5" on the diagrams below.

Image

The boxes we have chosen, after searching far and wide, are from Jaycar/Electus and are made of ABS. They are of two sizes: Large (designator has uppercase letter) 240 x 160 x 90 mm (HB6134) $38, and small (lowercase letter) 171 x 121 x 80 mm (HB6129) $22. To fit an EV200 contactor into the 80 mm high box, with a 3 mm clear polycarbonate baseplate (or "false floor") inside, one has to cut 5 mm off its terminal bolts, which brings them flush with the nuts when these are tightened onto crimp-lug and washers.

The following diagram gives an idea of the physical placement of these contactor boxes, with the front of the car to the right.

Image

We have tried to design things so we can easily change from the parallel 375 V setup to a series 750 V setup if and when a 900 V version of the controller becomes available. I think we've got it figured out, but we'd be very grateful for any criticism or suggestions regarding the following schematics for 375 V and 750 V setups respectively, particularly in regard to safety from shock or fire.

Image

Image

Ideally we'd switch both sides of every load, to ensure that in the event of an undetected fault to chassis, an unswitched side can't become live wrt chassis. But we don't have the space for that many EV200s and anything smaller than an EV200, even if you only want it to break 10 amps (at 450 Vdc), costs at least three times as much as an EV200 ($65 on eBay). But at least we switch both sides of the battery when the key is off and we're not charging. In fact we break it up into segments which are nominally 92 V or less.

Because of the single-pole switching of the loads, we need to change the switched side of the loads on Bus B from positive to negative when we go from parallel to series. This is so that the unswitched sides of A and B loads remain connected together and so cannot have a potential between them.
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Post by weber » Fri, 09 Sep 2011, 19:12

There has been progress over the last few weeks. All 8 battery boxes are complete and all but one have been painted.



Image   Image   Image

The radiator battery box has three tabs, one cutout and one strengthening rib (around the cutout). The two mounting brackets, made partly from existing mounts for the radiators; parts for mounting to the engine radiator have been removed.

Image   Image

The "rollbar" battery box attached to the rollbar:

Image

Now we're concentrating on getting enough cells installed for the EV festival, and aesthetic items. Here is the rear of the MX-5 with its bumper bar, and a black (almost dark purple) garnish (trim around the rear number plate). We intend to spray it red eventually, but decided it looks good enough to leave as it is for the festival.

Image
Last edited by weber on Sat, 10 Sep 2011, 12:00, edited 1 time in total.
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Post by evric » Fri, 09 Sep 2011, 20:22

Excellent work guys. I look forward to meeting you at the EV Festival next month.
By the way, I have a hint for painting bolt and screw heads... just poke them through a decent size piece of cardboard, leave them just proud of the surface and spray.
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Post by coulomb » Sat, 10 Sep 2011, 20:51

I visited mx5plus again today; see this post in the Lounge.
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Post by coulomb » Sat, 10 Sep 2011, 23:11

After a comment from Jeff Owen, who kindly visited again last EV day, I've edited the rear MX-5 photo (three posts back, here and scroll down), to put the classic number plate into the photo. We actually used the old number plate holder from the front of the MX-5, with two pieces of blank paper and held on with blue-tack, so that we could visualise the back of the car without the distraction of the holes behind the number plate area.

Feasibly, I may fail forever to become a fantastic fotoshop fraudster. Foo!   Image

Edit: More fabled alliteration; sp'ling
[ Edit 2: I should point out that we don't have the "XXX-AUD" number plate any more; registration was cancelled on the car years ago. It just seemed to me that it had to be there, in place of the two pieces of paper that were there in real life. ]
Last edited by coulomb on Wed, 28 Sep 2011, 18:08, edited 1 time in total.
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Post by weber » Thu, 29 Sep 2011, 03:09

This work of art (cubist sculpture?) has a function in the MX-Image. Actually 3 functions. Can anyone guess any of them? The large slot in the foreground is vertical when the part is in use.

Image

Pascal (Warrick Beatie), who designed and made the adapter plate and designed the taperlock flywheel, was going to design and make this part from aluminium plate etc, but he will be out of action for some time due to surgery on his spine. We wish him a speedy recovery.

So this version, made from steel angle, SHS and stainless rod, was designed by Newton (Jeff Owen) and myself and fabricated by Coulomb, my father and myself. I must also thank the support staff: my wife, my mother and my sister for tea, coffee, wonderful meals and detailing work on the MX-Image to have her looking good for the upcoming EV festival.
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Post by coulomb » Thu, 29 Sep 2011, 04:02

weber wrote: I must also thank the support staff: my wife, my mother and my sister for tea, coffee, wonderful meals and detailing work on the MX-Image to have her looking good for the upcoming EV festival.

I have seen Weber's sister on a few occasions, and I didn't think that she needed much work to be looking good for the festival. Image

No takers on the sculpture? I have to say it looks lovely finished and in its almost-ABB-blue colour. Hint: what are slots used for? Adjusting something? Where would there need to be an adjustment in a car? My part in this thing was extremely minor. I wish I had more time to devote to the project, over and above the statutory one EV day a week.

[ Edit: resolved an ambiguity of my own making :-O Also trimmed the joke. ]

[ Edit 2: Hint 2: The stainless steel rods are very smooth. They might even be oiled in final use. Does that constrain the possibilities any? ]
Last edited by coulomb on Thu, 29 Sep 2011, 04:01, edited 1 time in total.
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Post by weber » Thu, 29 Sep 2011, 19:55

The following photo shows how we have turned a low cost encoder, intended to be mounted by its case and to have a flexible coupling to the motor shaft, into a shaft-mounted encoder.

Image

We have Araldited a radial stainless rod to the case and we will place its outer end between two stainless pins mounted to the motor body, parallel to the shaft. That way we lock up only the single degree of freedom required to prevent the encoder body rotating, hence it is called an anti-rotation arm.

This allows the encoder shaft to be solidly mounted to the motor shaft, in this case by being a friction fit in a hole drilled in the end of the motor shaft. If the other 5 degrees of freedom were not still available the slightest misalignment would cause a massive load on the encoder's bearing and it would soon fail.

It would generally be better to attach the anti-rotation arm to the other end of the case, nearer the shaft, but in this case the encoder is inside a pulley which drives the pulley of the original air-conditioning compressor (via a belt with an idler for adjusting tension). So the arm has to get past the pulley. The cable has to get past the pulley too, so it will be tied to the arm.

[Edit: Added last paragraph]
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Post by weber » Fri, 30 Sep 2011, 16:17

Ok, to those of you who figured it out but didn't want to show off by posting the answer, congratulations!

It is of course a bracket to mount the air conditioning compressor, along with its idler/adjuster pulley. It was convenient to also hold the anti-rotation pins for the encoder, and the brake vacuum pump as well.

Here it is installed:

Image

Edit2: The above photo shows a 4PK815 belt, but this was too long and has since been replaced with a 4PK800 belt from http://eziautoparts.com.au.

Image

Edit3: Here's a closeup of one of the rubber standoffs that came with the vacuum pump. It's tapered like a rubber stopper, has a hole through it for an M6 bolt and a shoulder so part of it projects through the larger (10 mm?) hole in the motor foot. I also cut some rubber sheet to put on top of it, between the head of the bolt (with flat washer) and the foot.

Image

[ Edit: added second photo for context ]
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Post by weber » Sat, 01 Oct 2011, 20:48

BTW evric, I used your poke-it-thru-cardboard trick when painting the bolt-heads blue above. Thanks.

Here is the "engineering drawing" of the aircon compressor bracket -- a snapshot of our whiteboard. We'll need this when we come to make a similar one for the other side of the motor, to mount the power steering pump from EVWorks. Even though it's not driven by the traction motor but has its own 12 V motor, we'll be mounting it on the traction motor for noise reduction, as recommended by EVWorks.

Image

You may remember back in December 2010 we made up a cradle that mounts the motor and gearbox to the original engine mounts (which has since been approved by our engineer). We "test fitted it" unpainted, and it has been there ever since, quietly going brown with rust. So yesterday we unbolted it and lifted/jacked the motor and gearbox up just enough to get it out to paint it.

I'm using a five stage process now. Degreaser (orange oil), rust-converter (phosphoric acid), Penetrol, metal primer, enamel. The primer and enamel are the quick dry spray can kind from White Knight (I was using Dulux, but White Knight dries faster). Even with quick dry paints this is incredibly time consuming. And I don't enjoy multi-tasking -- too stressful. And you've heard the expression "about as exciting as watching paint dry".

So I've been accellerating the process at the expense of filling the kitchen with solvent fumes and turning my brain cells to mush.

The photo below shows the mounting-cradle parts going into the oven for the fourth and last time (the degrease stage dries fast enough by itself). Paint, wait about 15 minutes for it to be touch dry (longer for the penetrol), then 15 minutes in the oven on the lowest setting (starting from cold, not preheated), then maybe 15 minutes to cool down to below 30°C ready for the next coat.

Image
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Post by T1 Terry » Sat, 01 Oct 2011, 20:56

Congratulations to all involved, that is lookin very neat under the bonnet. Can't get over the size of that motor, it's near the size of block of the ICE that came out of there.
I wish I had your faith in the mounting method for the encoder, my industrial and plant equipment background would have forced me to the classic over build of 2 pieces of hollow square to make a stand off each side of the pulley and a piece of flat bar across the centre line to mount the encoder, a piece of flat plate with studs glued to the encoder and adjustment slots for location adjustment. 2 bits of rod and you have achieved the same result Image
Just a quick question, why are there still 2 heater core pipe sticking through the firewall if you have made an electric heater?

T1 Terry

EDIT: You have an extremely understanding wife, letting you use the oven for paint baking. I tried it once, the oven was then donated to the workshop and I had to buy a new stove/oven, rangehood, fit exhaust extraction through the roof ...... would have been cheaper nd a lot less stress to give it to the local spray painter Image
Last edited by T1 Terry on Sat, 01 Oct 2011, 11:03, edited 1 time in total.
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Post by weber » Sun, 02 Oct 2011, 04:15

Hi T1 Terry, Thanks for the kind words.
T1 Terry wrote:I wish I had your faith in the mounting method for the encoder, ...
I'm a bit worried about it myself. The problem is in the "friction fit" of the encoder shaft in the motor shaft. The squirel cage rotor with its shafts was too long to use a drill bit in the tail stock of the lathe we used and so we used a cordless drill. Bad idea. It wobbled on the way out and made the hole a bit conical. Newton came up with the idea of wrapping the encoder shaft with plumber's teflon tape before wedging it in. It works, and it will do for testing, but we need to come up with a more permanent solution. Ideas welcome.

If you're reading, Tritium_James: What happens if the encoder suddenly stops spinning, or becomes intermittent, as we're driving along?
2 bits of rod and you have achieved the same result Image
3 bits of rod and some epoxy, but yes, we hope so.
Just a quick question, why are there still 2 heater core pipe sticking through the firewall if you have made an electric heater?
Good question. Basically because we'd have to completely dismantle the dash and the HVAC unit to get them out. And I should add that we haven't actually made the electric heater yet.

But I agree they look untidy. I have now put some black rubber caps over them (made for the ends of chair legs). I suppose I could try to cut them off flush.
You have an extremely understanding wife, letting you use the oven for paint baking.

I passed on your praise. Now she's worried. Image

My story is that the solvents used in modern paints are far less offensive than they used to be.
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Post by weber » Sun, 02 Oct 2011, 06:38

Newton came by this afternoon to check out his brainchild (the compressor bracket) in 3D feely-vision. While here he helped me reinstall the motor/gearbox mounting cradle. It looks much better now. Call me old-fashioned but I really prefer blue paint to surface-rust for some reason. Image

Then Newton pointed out how easy it will be to mount the power steering pump (on the other side of the motor from the compressor). It will only require the vertical piece, made from 50x50x5 angle, that bolts between the lifting hole and the foot below it. But for this to be as simple as possible the pump needs to bolt to it in what appears to be a non-standard orientation.

The pump can be mounted with motor up and tank down, as in this photo from the EVWorks website.

Image

But we can't fit it in that orientation.

Or it can be mounted as in this drawing from the EVWorks site.

Image

Here it is in the above orientation, but seen from the other side, and with the tank removed to show the pump intake (with sintered bronze strainer) and the tank return hose (clear reinforced hose).

Image

What we want is different again. Here's the orientation we want.

Image

The only problem I see here is that the tank return hose is now near the top of the tank and will tend to entrain air bubbles. So we'd need to replace it with a hose that bends down. The intake can be rotated to be nearer the bottom of the tank again and the filler/breather cap can be swapped with the plain plastic plug.

Anyone see any problems with this idea?

[Edit: Added white space above and below images. Gave credit where due re simple PS pump mount. Added question at end.]
[Edit: Uploaded two broken images that were no longer on the EVWorks site. Found by coulomb in the Internet Archive. Thanks.]
Last edited by weber on Fri, 28 Jul 2017, 07:50, edited 1 time in total.
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Post by T1 Terry » Sun, 02 Oct 2011, 19:41

You could go one step further and add a hydraulic filter to the return line. This would stop rubbish build up in the tank and stop the oil foaming problem. Alternately a longer hose or a 90deg fitting will redirect the oil to the bottom of the tank.
The encoder problem, here's one out of left field, what about a flexible cable drive like a speedo cable and mount the encoder in a convenient position away from the motor shaft. There are a number of different drive options for a flexible cables, this mob http://www.powertransmission.com/news/1 ... _Products/ or this mob http://www.fdrive.com.au/products/02/speedometer.php can make up just about any sort of flexible drive cable or with a bit of oxy brazing skills you can make one from an old speedo cable sourced from the wreckers.

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Post by weber » Mon, 03 Oct 2011, 00:04

T1 Terry, That flexible shaft mounted encoder idea certainly is out of left field. It sounds like more work than the standard method you described earlier. And I'm afraid the rotational springiness would screw up the control loop. But thanks for brainstorming.

The return hose off the original power-steering tank happened to have a nice bend in it. I gave the outside of it a good scrub with orange oil, then detergent and hot water, then I realised what I really needed to clean it with -- hydraulic fluid. So that lets us use Newton's simple mounting bracket idea.

Image
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Post by weber » Mon, 03 Oct 2011, 02:46

The EVWorks site tells us that the 4 mounting holes we are looking at in the above photo are 3/8" UNF. It doesn't tell us what size the 4 mounting holes are on the vertical face we can't see, surrounding the motor. I can screw an M8 into them, but that doesn't mean they aren't really 5/16" UNC, whose diameter is essentially the same and whose pitch differs by 10%.

The chinese manufacturer's website is utterly useless, as usual.
http://www.mocen.cn/mocen/hydraulicpowe ... .asp?mm=05

I'm tempted to drill them out and retap them with the next larger metric thread rather than sully the metric purity of the MX-ϟ. But it's stainless, so that's scary.

[RANT]I detest non-metric stuff. For example: If I want to know what the tap drill size is for a standard M8 thread, which has 1.25 mm thread pitch, it's simple -- subtract the pitch from the outer diameter. 8 mm - 1.25 mm = 6.75 mm. So I need a 6.75 mm drill (which, irritatingly, is typically still sold, even in Australia, as 17/64" in big letters, 6.75 mm in small letters in parenthesis). Fa cryin' out loud. Australia went metric 41 years ago!

Now take the 5/16" UNC. That has 18 threads per inch. So the tap drill size would be 5/16" - 1/18" = (5*18 - 1*16)/(16 * 18) = 74/288" = 37/144". Now quickly -- is that more or less than 17/64"? So I need a 37/144" drill right? Or maybe a 0.257" drill? Wrong on both counts. The answer is in fact "F". I have to look up a table to find that what I need is an "F" drill, whatever the F that is![/RANT]

Oh well. Off to the Blackwoods catalog to order some countersunk 3/8" UNF and 5/16" UNC. Sigh. Perhaps I should just try to think of them as M9.525 x 1.058 and M7.938 x 1.411. On second thoughts, that's just silly.

[Edit: Turns out I don't need countersunk because there's a convenient indentation in the motor fins, an alternative position for the nameplate. So I just went and got ordinary bolts from Supercheap Auto. But it turns out the smaller ones are not 5/16" UNC. It seems they really are M8.]
Last edited by weber on Tue, 04 Oct 2011, 06:42, edited 1 time in total.
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Post by Tritium_James » Mon, 03 Oct 2011, 15:35

Heh, that photo two posts above is great - Monet or Van Gogh or something - "Still life with pear and pump".

Regarding the encoder mount, any difference in the speed of the motor and the speed of the encoder is really bad news. The complex D/Q current type control we run ends up in a single output: slip. This gets added to the current motor speed (from the encoder) to effect the control we desire, where positive slip = acceleration, negative slip = regen. A quick example of what happens if the encoder stops would be the motor rotating at say 100Hz, with a slip of 5Hz, so the output frequency from the controller will be 105Hz. Now the encoder stops, so the controller thinks the motor is doing 0Hz, so the output frequency will now be 5Hz. In fact, because the motor is still doing 100Hz (inertia, etc), the actual slip is -95Hz. This will give an insane amount of regen, and in theory one of the other control loops (motor current, bus upper voltage limit) will take over, but in practice it probably can't react fast enough and you'll get an overcurrent fault and it will shut itself down. It should be fast enough to do this before anything gets damaged.

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Post by T1 Terry » Mon, 03 Oct 2011, 16:33

You could always helicoil the holes with 8 mm 1.25 pitch thread to be sure to be sure :lol: Loctite on the 8 mmm bolts will make up for any possible difference between 5/16UNC and 8mm 1.25 thread. The tricky part of thread tap/drill size is the thread pitch, metric didn't really help, is it 1.00 pitch, 1.25 pitch, 1.5 pitch or 1.75 pitch, at least the old standard only had course or fine thread and it wasn't too difficult to identify which was which. Witworth, UNC, BSC 1.5, 1.75..... that's when it becomes a tad tricky in larger diameter threads.

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Weber and Coulomb's MX-5

Post by coulomb » Mon, 03 Oct 2011, 18:53

The small yellow tag that that says "connect only to positive (+)" came off our vacuum pump recently. The pump has blue and brown wires. It looked like the tag must have come from the blue wire; there was sticky goo there which looked like it came from the tag. But that seemed counter intuitive to us: the "colder colour" (blue) would then be the positive lead. The "manual" that came with the pump is a single slip of paper about 40 x 120 mm, and doesn't indicate which wire is positive. The pump doesn't seem to have a brand or model number on it.

I did a search, and could not find any photos or other clues to tell us which wire is positive. These pumps came from Eugen Goombi, who has retired from importing EV components; Graeme of Suzi Auto has taken this over. Unfortunately, the pump on the Suzi Auto web site seems to have changed, and has red and light blue wires.

I sent a message to Suzi Auto via the "contact us" form, and Graeme responded this morning with "BLUE IS POSITIVE". Thanks again, Graeme. I post this information here in the hope that someone else in this situation might be able to find it.

This is the pump that the information refers to; it may not be a "Chinese standard" that blue is always positive:

Image
Last edited by coulomb on Mon, 03 Oct 2011, 16:46, edited 1 time in total.
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Weber and Coulomb's MX-5

Post by weber » Mon, 03 Oct 2011, 19:53

Thanks TJ, you made my day. Image
T1 Terry wrote: The tricky part of thread tap/drill size is the thread pitch, metric didn't really help, is it 1.00 pitch, 1.25 pitch, 1.5 pitch or 1.75 pitch, at least the old standard only had course or fine thread and it wasn't too difficult to identify which was which.

You say the old standard, but there are two. USA and British, UNx and BSx. Although, in another sense, they are all BS as far as I'm concerned. Image

So assuming you've identified that the major diameter is a dyadic inch fraction rather than millimetres (impossible in the M8 5/16" case) you may still have a choice of up to two coarse threads and two fine threads.

There's a great chart here from Maryland Metrics which includes the pipe/taper threads too. It has been very helpful in identifying not only the pump mounting threads but also the hydraulic port threads on both the pump and the car (1/4" NPS and M16 x 1.5 respectively).

Considering the common automotive sizes, and ignoring the uncommon extra-fine threads and the pipe threads, for imperial we have the following (u = USA, b = British, f = fine, c = coarse):

       28   26   24   22   20   18   16   14   13   12 TPI
1/4"   uf   bf             c                                 6.35 mm
5/16"            uf   bf         c                           7.94 mm
3/8"             uf        bf         c                      9.53 mm
7/16"                      uf   bf         c                11.11 mm
1/2"                       uf        bf        uc   bc      12.70 mm
      0.91 0.98 1.06 1.15 1.27 1.41 1.59 1.81 1.95 2.12 pitch (mm) 
But even the apparent uniformity of (most of) the coarse sizes above is misleading because there are two different thread flank angles. 60° for USA and 55° for British.

For metric we have the following (all 60°):

   x  0.75 1.00 1.25 1.50 1.75 pitch (mm)
M6      f    c
M8           f    c
M10               f    c
M12                    f    c
Of the approximately 200 countries in the world, only the USA, Burma and Liberia have not gone metric. The USA with its economic power is pretty much responsible for maintaining this confusion of different systems throughout the entire world.

There are a lot of American's who hate this as much as I do. For an entertaining rant, visit this page and scroll down about two screenfulls to item (i) "Metric system (SI)".
http://euler9.tripod.com/bolt-database/22.html
Not what you expect to find in an otherwise technical document!

Possibly the most famous single example of why this mix of systems is a bad idea was the loss of NASA's Mars Climate Orbiter in 1993.
http://en.wikipedia.org/wiki/Metricatio ... _incidents

I guess I'm getting a bit off-topic here. But I just love to make fun of imperial measurements. Image

[Edit: Made last URL into a clickable link]
Last edited by weber on Mon, 03 Oct 2011, 09:44, edited 1 time in total.
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Weber and Coulomb's MX-5

Post by T1 Terry » Mon, 03 Oct 2011, 22:07

There are a lot of American's who hate this as much as I do. For an entertaining rant, visit this page and scroll down about two screenfulls to item (i) "Metric system (SI)".
http://euler9.tripod.com/bolt-database/22.html
Not what you expect to find in an otherwise technical document!

Quite a laugh, seems they can see the issues from inside as well as we can from the outside.

T1 Terry
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