Engineers

wagonist · Post by **wagonist** » Fri Dec 09, 2005 2:37 pm

There's been use of the 200SX rear calipers. Apparently because they'll bolt straight onto the L series (or it might be XT6) backing plate.
I can't see why though (unless they're using the twin spots or the caliper is used as the handbrake.

subarursliberty · Post by **subarursliberty** » Fri Dec 09, 2005 6:45 pm

Reason i'm asking is why not just get a new backing plate made up to a different caliper. Should be a heap easier than adapting the subaru one with handbrake.

wagonist · Post by **wagonist** » Fri Dec 09, 2005 7:43 pm

I completely agree.
These are the cars which I know have calipers with built in handbrakes:
Toyota Sprinter
XF Falcon
Subaru before Liberty (front caliper)
early Saabs (front caliper)

Just had another thought:
If we're going to make up a custom backing plate, why not get the backing plate to be the mount for TWO calipers.
One of those above for the handbrake only & another for the hydraulic system.
Should work & would also look pretty sick

I'm sure we all have access to the front Subaru caliper, just need another one at the back.

Ben · Post by **Ben** » Sun Dec 11, 2005 7:31 pm

wagonist wrote:Your are correct in that you are taking a lot of material off the edge of the drum.
But you are also removing a lot of the weight of the braking part of the drum (which is the thickest part)
The EJ disc also fits snugly around the hub as well, its not just sitting on the outside face.
To apply tension on the wheel studs, you do need the wheel to either part company or slowly move around (something that could happen if there is no centre ring)

Here is some pictures, with description of some work I did to an MY rear drum that I was modifying to fit MY front discs to the rear of an MY.

The drum chucked up on the lathe.

The braking surface cut off and just finishing to the right diameter.

Machining a flat on the back of the drum to give a nice bolting plane.

Getting ready to drill the disc mounting holes using the milling machine.

Finished part

So why didn't I put it into service? Everything worked how I wanted it to, and everything lined up and fitted on the car. What it came down to is the mounting points of the disc. See how close the 90mm pcd is to the edge of the structural part of the drum? The rest of the drum is quite thin, and as I said cast iron isn't particularly good at tension - this is especially so when you machine off most of the hard crust that forms on the outside of cast iron parts.

This next picture is just an interest piece - at one stage I made an adaptor to bolt the big disc onto an L series - the disc is from a Nissan Patrol and is freaking heavy and huge. You'd need 300kw to warrant it

wagonist wrote:Out of curiousity, what do you do for a living? You seem to display a lot of technical knowledge.

I work for the Commonwealth Bank, however I have had an interest in metallurgy for a fair while and started machining at tafe three years ago. I have been learning as much about metallurgy as much as I can since then and to paraphrase Carroll Smith, "Parts don't fail, people do" - essentially the only time something breaks is because the engineer that designed the part, didn't do a good enough job. I am studying to become a Mechanical Engineer and hope one day to be able to do authorised automotive engineering work.

wagonist · Post by **wagonist** » Sun Dec 11, 2005 8:01 pm

Now I understand where your comments come from.
That MY drum looks puny compared with the equivalent piece from an L series.
I've got a pic, but can't get to hosting it from my home computer.
The studs are a bit closer to the edge, but the material is approx 10mm thick.

Does the fact that the hub is sandwiched hard up against the cast disc make a difference?
ie by being bound by the rotor will that help with structural strength?
I'm a civil engineer, so I reckon it would whilst stationary, but I'm not completely upto date with moving parts.

wagonist · Post by **wagonist** » Sun Dec 11, 2005 8:05 pm

Oh, & I was at the local wrecker yesterday.
Had a look at the rear caliper on a ZF Fairlane.
It fits over a vented 22mm odd thick disc (need to confirm the specs as that one was worn).
But because it has an integral handbrake with the caliper, which looks as big as a RS liberty version, it coud be used over an RS rear disc (or I'm now looking at R32 GTR as its a bigger diameter, 290mm vs 260mm) with a custom backing plate & not needing to worry about the internal drum handbrake.

Ben · Post by **Ben** » Sun Dec 11, 2005 8:49 pm

wagonist wrote: Does the fact that the hub is sandwiched hard up against the cast disc make a difference?
ie by being bound by the rotor will that help with structural strength?
I'm a civil engineer, so I reckon it would whilst stationary, but I'm not completely upto date with moving parts.

Yeah, I agree that stationary it would be fine until the rust finally took over. In practice the metal used in braking will flex whilst cornering (I have seen video of discs and wheels flexing. Where my concern lies is that the stud is secured in 10mm thick of cast iron, with maybe 4mm of material on the outside of the pcd, even if this is bolted into a sandwich situation there still exists the ability for the stud to flex against the cast iron which will eventually crack a section that small. When one cracks it allows a little more movement, and in turn another will crack.

So many times you hear "I have had this on my car for so long and haven't had a problem" People don't realise that every piece of steel will behave differently. Look at the paperclip test that all engineers (should) do at uni. Take 100 paperclips and for each one bend it back and forth until it breaks, count how many cycles were required. For the minimum cycling for breakage, take that and include a 10x safety margin - thats how many times you can safely bend a paperclip without it breaking. Even if a single clip out of that 100 has to be cycled 1000 times before breaking, reality is that most will break in one or two cycles.

Being an engineer yourself you'd understand the need for safety margins - in the machined drums, there may be enough steel to support the vehicle and physically work, but there is not enough margin for error as far as I am concerned. L series drums aren't that much better than an MY one, slightly different ribs in the back. But these get machined off anyway...

If you are going to the effort of having stuff machined, get hubs made from 4340 or EN26 and do it properly.

Guest · Post by **Guest** » Sun Dec 11, 2005 9:11 pm

4340 should really be forged after you've machined it shouldn't it?

An you can't exactly go down to Metaland and ask for a bar of 826M40.

Ben what are your thoughts on 4140?

wagonist · Post by **wagonist** » Sun Dec 11, 2005 9:16 pm

You make some valid points there.
I've got a big problem with the way the backing plate is re-drilled to suit the L series.
That's plate steel, but on the one that was already done on my car, the holes have about 2mm to the inside edge.
That's way too small for something that's holding a caliper.
I believe the other kit being developed doesn't really address that issue.

subarursliberty · Post by **subarursliberty** » Sun Dec 11, 2005 9:46 pm

This is what I want to see. A rear caliper capable of a thick disc. That way I can buy a rotor and make an alloy hat for it like DBA 5000 series. ZF is not listed but ZG,H,J,K,L is and its a 24mm wide disc.

So what I can do is just order a front rotor off a 4 pot WRX. The 294mm rotors in the 5000 series and throw that on the back. only parts that will have to be made is the hub, newer backing plate, then the handbrake cables. Sounds easy I know

The front I was planning on using the subaru 4 pot or better still the nissan 4pot if I can get it to fit. At the least a VT caliper. The later 2 use a 30mm disc.

Any chance you could take a dimension off your 4 pots for me wagonist? I need from the mounting point (where it bolts to the backing plate) to the most outer front part of the caliper. I will take the measurment to the wrecker and I will hope fingers crossed I will walk away with a pair of nissan calipers. They are $200 cheaper than the subaru ones but I can kiss that money good by in making up adapters for them. Don't forget 30mm disc is the advantage while on a track pulling up after pulling over 200ks down eastern creek straight.

If I am using the nissan 4pots I will defonatly need 17's, a 300-330mm rotor. That should pull it up nice a quick.

Ben · Post by **Ben** » Mon Dec 12, 2005 8:50 am

MUDRAT wrote:4340 should really be forged after you've machined it shouldn't it?

Not really sure what you are talking about here - Forging is the operation of shaping a material with a hammer or stamping machine. I think you mean Stress Relieving - the part is heat soaked at about 600° for a period depending on the section sizes and realigns the structure of the steel so that stresses in the part caused by different section thicknesses are reduced.

MUDRAT wrote: An you can't exactly go down to Metaland and ask for a bar of 826M40.

No you can't, but http://www.interlloy.com.au will get you pretty much anything you want and is happy to post. There is also an office at Albury which is close enough to Tumut, and also offices in the major capitals.

MUDRAT wrote:Ben what are your thoughts on 4140?

4140 is fine for this application, I prefer to machine 4340 as it comes away nicer. 4340 is also stronger than 4140, but not enough to make a difference in this application. I like EN25 the most, for its machiniability and strength - that stuff comes off the tool so shiny!

wagonist · Post by **wagonist** » Mon Dec 12, 2005 9:37 am

The rear discs have a lot bigger offset to the fronts, that's why I mentioned the R32 GTR rear calipers.
Very similar offset to the Subaru (63mm vs 67.5) but bigger diameter at 290mm.

Though if you use a front disc, then the conversion may be as simple as using an original disc brake backing plate off an L series (finally a use for the rear disc brakes off a FWD Vortex) with an adaptor plate for the Fairlane calipers.

I'll get some measurements for you tonight, though if you've already got EJ front hubs, my 294mm 4 spots bolted straight onto the twin spot hubs.

I decided to stick with the Subaru 4 spots because I still wanted to be able to run the 15s I got for motorkhanas, etc.

You're worried about the cost? Try Toyota 4 spots. I ended up paying $600 just for a pair of calipers. Cost me $1500 all up to get 300mm discs, 32 mm thick onto my Caldina.

subarursliberty · Post by **subarursliberty** » Mon Dec 12, 2005 11:43 am

I'm not worried about cost that much. But a caliper that takes the same pad thats $200 cheaper and it uses a 30mm thick rotor instead of 24mm. My money is on the bigger one.

wagonist · Post by **wagonist** » Mon Dec 12, 2005 12:03 pm

Do a search of the DBA site.
It gives a list off all the dimensions of the rotors they have available.

Searching through the specs, I'm going to get a stuffed 4 spot front disc from a 99-01 WRX. These are 294mm dia, 57mm offset (giving 10mm to play with for adaptor brackets), 5x100 stud pattern, 24-22mm thick like the Falcon/Fairlane rear caliper.

Going to get a sample caliper & see what's needed to fit it up to an L series rear disck backing plate.
Also need to find out what size hub goes into it.
There may be a lot more cast metal left behind meaning a machined drum might work (though still doesn't have centre locating ring

)

Ben · Post by **Ben** » Mon Dec 12, 2005 12:04 pm

Theres every chance that you'll find Nissan Patrol, Toyota Landcruiser, prado etc front calipers are the same as the subaru and skyline 4 pots.

For the rear I wouldn't worry with an adaptor. Just get a piece of 8mm bisalloy plate laser cut to be what you need. I am sure you would be handy with autocad

wagonist · Post by **wagonist** » Mon Dec 12, 2005 12:51 pm

Probably a good idea, though I have been trying to do this on the cheaper side.
The L series disc backing plate is going to be nowhere big enough anyway.

subarursliberty · Post by **subarursliberty** » Mon Dec 12, 2005 1:41 pm

If you want something drawn in AutoCAD let me know. I can only try.

Yeap a new laser cut backing plate with a ford caliper. I'm not to worries about the offset. You can make alloy hats to make the offset you want. Just buy a rotor from the DBA 5000 series without hats etc and have them custom made.

Bare in mind to with your 15in wheels. There is only a couple that will go on. No Subaru 15in wheels will go over 4 pots that i know of. But i'm sure you know all of this in the first place.

wagonist · Post by **wagonist** » Mon Dec 12, 2005 2:24 pm

Got autocad already.

It'd be cheaper to just get some 4000 series (or even normal) discs as they'd be a heck of a lot cheaper (& they'll be on the back anyway)

Already got the 15" wheel thing sorted

And you're right. There's only 2 types AFAIK.

Guest · Post by **Guest** » Mon Dec 12, 2005 6:57 pm

wagonist wrote: I believe the other kit being developed doesn't really address that issue.

Do you mean my kit?
Why would you make that assumption.
I have addressed that problem if you mean my kit. It was a real hurdle in the development.
The finnished product is easily as strong as the original fitting to a Liberty and much stronger than the standard L/my set up, it requires no welding and will breeze through ADR certification.
The rear hubs were a walk in the park. They have a locating "Ring" for the disk and the wheel as per "ej" series hubs and are cnc machined from crmo billet and the splines, in fact the whole hub is case hardened.
I have spent the last 12 months developing the backing plate and handbrake set up. It is now sorted and is very simple for the end user to install. Including new brake lines center post supports. Handbrake lever (Magna for L series, Civic for my) and cables(standard Lib) are also easy to install.
The ADR guys were particularly impressed with the backing plate fitting mod/method. Its actually the centre piece of the kit.

If you don't mean my kit sorry for being defensive.

Gee

wagonist · Post by **wagonist** » Mon Dec 12, 2005 7:37 pm

I was talking about it, but while you're watching in, can you explain how you've fixed that problem of the Lib having a bigger hole through the centre of the backing plate than the L series?
I have another person's conversion here, & it's well dodgy. Hence the reason I want to modify it.

From reading through you're description of parts supplied, it seems like you do an exchange on this part for your kit.
There's a lot of people on here who haven't seen your kit, or remember what it looks like. I know I'd appreciate it if your could find the time to re-post the pics.

Please don't take offense at my comments, there are merely my thoughts & aimed to provide some constructive criticism.

Out of curiousity, does anyone know what Subaru made the front hub from (the bit we're replicating by machining down a drum)?
I compared the parts on my car today, & the machined drum has a bigger diameter & is thicker than the factory subaru front part.