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MG Midget and Sprite Technical - Moss parts check

Just taken delivery of some odds and ends from Moss, but need confirmation from someone who knows.

I ordered a clutch pipe to go between the mastercylinder (dual type) and the slave. What has come is packaged and labelled as a brake pipe, and is just 3/16". Have they sent the wrong item?

I thought that the clutch pipes were larger bore than this. I have yards of 3/16" pipe and ends and could have made one up, but thought they were different, which is why I ordered a ready made one.

AND, not from Moss this time but can someone remind me the slave cylinder bore size for a later 1098 clutch. I have a selection to choose from!
GuyW

As long as the ends fit in the slave and M/C and it's the right length I think the pipe bore is fairly irrelevant Guy. It makes no difference to the displacement or pressure after all.
Greybeard

I think it does make a difference to the speed of clutch release, which is why itís bigger.
Dave O'Neill 2

Fair enough Dave. That sounds reasonable after all.
Greybeard

It's certainly bigger on my 1275, but I built that and wasn't sure about the earlier cars with the coil spring clutch covers. Maybe Horler lists a change date. I will check when I get home unless someone knows for sure?
GuyW

Itís 3/16 on mine. Had to get a fancy adapter to get it to fit the 1275 slave. It seems to work fine. I think mine will be the same as your Moss one and you have loads spare to form the coil to dampen out vibration.
John Payne

If you use a 1275 slave you need to use the thicker pipe because the connection to the slave requires the bigger union. If you need to use the thicker pipe you need the adaptor to screw into the master cylinder.
When I first put a 1275 into my Frog I copied the 948/1098 clutch pipe. i.e. I put a few (2 I think) loops in the pipe as it drops down to the slave and screwed it direct to the slave. This worked OK but it was really hard to put the loops into the pipe. I used an aerosol can but even that ended up with a few dents.
Later I changed it to the proper way with a flexi, one end secured to the chassis, the other into the slave.
Rob
MG Moneypit

As John Payne says works also but the adaptor at the slave end is harder to obtain. Having the adaptor at the master end and bigger pipe is the normal way.
Rob
MG Moneypit

Ok, a 3/16" pipe should be fine then with my 1098 clutch, which I presume needs to use the early slave. But then it shouldn't need an adapter to get it to match.

I will fit the pipe with the coiled vibration damper next to the footwell side.
GuyW

Hereís mine:




John Payne

Heres a thread about finding the right adapter in case you need one:

http://mg-cars.org.uk/cgi-bin/or17?runprog=mgbbs&access=3&mode=archiveth&subject=97&subjectar=97&thread=2019032922171321994
John Payne

Iím useless at posting links that work!!
John Payne

That link works just fine if you copy and paste. Thanks John.
Mine differs of course in that I am using a 1098 with a spring clutch, not the 1275 with diaphragm clutch cover like yours.

Now for a negative! One of the bits that I ordered from Moss was an air duct tube - the short one that goes between the fan housing and the heater box (early frogeye style). If you are considering getting one from Moss then don't bother! The item that came is sufficiently undersized to make it impossible to fit. I persisted, but eventually the thing just split.
Fortunately I still have the original which fitted very easily and just needed a bit of a refresh with some black shoe polish.
GuyW

Modern parts that donít fit? I donít believe it!
Dave O'Neill 2

Forgot the photos!

Maybe I should have soaked the new one in water, but it's only made of paper and I think would just disintegrate.





GuyW

I've come to the conclusion that, wherever possible, it's best to renovate old parts. Rubber is the problem. I suppose 50 or more year old rubber is past it but new rubber, as often reported here, isn't good.
Bill Bretherton

I agree Bill, I have over the years collected NOS when I see it at autojumbles and the like.Its just decent quality, even rubber parts tend to be better. for example, I have a set of TRE's, which have got to be 30 years old, and the rubber gaiters are still nice and supple with no cracks.
Bob Beaumont

Also, while talking about clutch pipes, I intend to fit a 1275 slave (and 1275 clutch) so I was going to get the same pipe as you Guy but adapt it at the slave end. However John says the slave end adaptor is hard to get BUT if I were to use a 1275 pipe wouldn't the routing be difficult at the older dual master end? Also pipe size must surely matter - a wider pipe will result in shorter slave throw but softer pedal, a narrower pipe longer throw but harder pedal (for same amount of fluid displacement).
Bill Bretherton

That's strange Guy, I'm sure mine was from Moss and it appears to be different in that it has an aluminium core. It was a tight fit but it went on ok. Not sure if the Frog heater is exactly the same as the Mk1 midget though.




John Payne

Bill

The diameter of the pipe has no bearing (no pun intended) on the throw. Itís the relationship between the diameters of master and slave cylinders that does that.
Dave O'Neill 2

Bill, if you use a 1275 pipe then you've got thr same problem but at the master cyl end. The adapter is easy to get for the slave end, it was just a case of finding the right one - thanks to Willy who put me on to Automec.

As for the pipe size affecting it I'm not sure. I've done loads of theory and practical stuff with hydraulics in my job but I'll leave it to the more scientific minds to discuss that one! All I know is that mine seems to work ok (1275 engine, box and clutch) with dual master and 1275 slave - though only done about 50 miles!!
John Payne

Pretty certain that the diameter of the pipe has no impact on the throw of the slave. A thinner pipe will require a bit of additional foot pressure to get the fluid to flow but the distance travelled depends only on the ratio of master cylinder to slave cylinder. And conversely when releasing the clutch pedal it may not rise quite as fast.
I am going to use this 3/16" pipe now that I have it, but may in the longer term replace it with a 1/4" one if gear changing is too sluggish.

GuyW

You're right Guy. No difference at all, other than in resistance to fluid movement which I suppose will cause a momentary pressure drop, probably too small to measure.
Greybeard

Guy, just checked through my restoration receipts (well hidden from Mrs P!) and found that I got the snail to heater duct from AH Spares. Part number is XCHT165 and was cheap enough at less than £5.
John Payne

John, this air duct pipe does have an aluminium core, - a sort of card/ally/ card sandwich.
Photo shows how I cut a strip off the end that had split and tried it for size, pulling it firmly around the heater pipe. You can see how it is way too short. And on my car the plastic fan housing is just a tad bigger again so there was no way it would fit around that.!


GuyW

Dave, I stand corrected, you're right! However, a narrower pipe is moving the fluid more quickly and might create a harder pedal, I'm not sure. Maybe coefficients of friction and viscosity come into it.

John, sorry, it was Rob who mentioned the slave adaptor. Actually the older pipe makes sense for the older dual master cylinder so Guy has the right one it seems although it must be annoying if you already have 3/16" pipe and a flaring tool.
Bill Bretherton

I used the 3/16 pipe on my 1275 Frog with the 1275 slave and brass adaptor supplied by Powertrack. Absolutely fine. I had the engine out in February to change the faulty cam followers ( more poor quality) and there was no evidence of any overthrow or markings on the clutch plate. Previously I had the 948/1098 slave and this produced a much heavier pedal and the occasional overthrow.
Bob Beaumont

I started with routing and bending the clutch pipe, but then ground to a halt! Where exactly does the double loop bit hang? I have started from the mastercylinder, gone down the outer side of the pedal box and then across the top of the footwell. But where next? I thought there was a photo in Horler showing the coiled pipe but cannot now find it.
GuyW

Across the top of the footwell then down slightly then the coil. The pipe then runs to a clip on the panel to the inside of the triangular section. I must admit I did away with the coil some years ago and nothing untoward has happened!
Bob Beaumont

So the coil is a double loop, with a horizontal axis across the width of the car?

Given the length of pipe I have from Moss, I need to put a coil in if only to use up the excess!
GuyW

Try page 48 in Horler - not the clearest.

R.
richard b

Thanks, I hadn't interpreted the two red lines as part of a copper pipe coil!
GuyW

This thread was discussed between 10/04/2020 and 12/04/2020

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