Clutch problem.

[Forumadmin]

I was called out by Ken Brown to get his engine started but after doing that I then had to sort out a clutch problem. On investigation, the clutch pressure plate actuating fingers were seen to be fully depressed towards the engine. This meant the clutch release bearing had about 3 cm of travel and was clearly useless. So the engine and gearbox were removed. I removed the pressure plate and friction plate but could not find anything wrong. The friction plate had been fitted the correct way around with the flywheel side facing the flywheel. On reassembly as soon as the bolts were tightened on the pressure plate the fingers moved right in towards the flywheel meaning that any further movement needed to release the clutch was not possible.

I deliberated for many minutes and looked at a working assembly but can only think that the reason is the friction material is too thick. Any ideas? I will go back on Friday with a known good assembly and a micrometre and hopefully cure the problem.

There were three previous attempts by Ken and Bill Lock to fix the clutch so a fresh pair of eyes will hopefully solve it.

Anyhow it was a great day out in the SA helping get another Jowett on the road.

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[Forumadmin]

I studied the manual this morning and seem to need Borg and Beck gauge plate Part number CG12916. Does anybody have one or has a drawing of it?

Also used on MG Y http://www.mgcars.org.uk/imgytr/pdf/mot0457.pdf and Riley https://jowettnet/forum/download/file.p ... &mode=view

[David Morris]

Hi Keith,

I measured two Javelin/Jupiter clutch covers this morning, after reading your post.

One was used and the other new. Both gave a measurement from the outer tip of the fingers to the surface of the pressure plate of almost exactly 2". I could discern no appreciable difference in the heights of the three fingers on each plate.

Hope this helps?

All the best,

David

[Forumadmin]

The height of the fingers was tested with a set square across the concave top of the plate and vernier zeroed to accommodate thickness of set square. The friction plate was installed and tightened down.

IMGP2617 (768x1024).jpg

The first readings were taken with a partly worn disc (0.283 / 7.16mm) on pressure assembly part number 43638A.
0.214"/5.44mm
0.195"/4.97mm
0.167"/4.24mm
were the depths of the three fingers.

next with the new friction plate

0.296"/7.51mm
0.265"/6.75mm
0.248"/6.31mm

IMGP2619 (1024x768).jpg

You may notice the plate has red and white springs as opposed to the standard blue, but the thickness is the same as standard (0.323"/8.21mm). It also has a shorter splined boss (0.795" v 1.083" /20.2mm v 27.52mm). This friction disc is also ventilated so more suitable for competition. part number 47238.

So you can see that the 1mm extra thickness gives 2 mm of travel in the fingers.

The test was repeated with the new friction disc on 3 other pressure assemblies all part number 43638.
The one removed from the SA on 8/2012 gave 7.55mm/7.85mm/8.19mm
The one removed from the SA on 03/1992 gave 11.13mm/10.26mm/11.67mm
And a very worn one gave 11.74mm/11.23mm/11.33mm

IMGP2620 (1024x768).jpg

Although this should be enough to fix Ken Brown's problem it does not give the definitive set up for the pressure plate fingers. I do not think a gauge is necessary but it would obviate need for vernier and take out risk of differences in the friction plates. So look out for one of those Borg and Beck gauges!

[David Morris]

Hi Keith,

I have just been out to the shed to measure the friction plates that I have in stock.

There are three. Two are used, and although I assume they came from a Javelin/Jupiter, I cannot be certain. However, I am on much firmer ground with the third one. This is NOS and is boxed, with the Borg and Beck reference number on the box and actually printed on the plate. The reference number is 45589/14 and the fitting list on the box shows it being suitable for quite a few cars of our age, including a Jowett 10hp, 1943/45, Javelin RHD (!) 1946/53 and a Bradford Van 1948/54. However, I recollect that there are different types of plate, according to the number and rating of the take-up springs, which have different colours.

The plate we have here, in the Ferodo box, has six springs, all black, but I suggest the critical measurement is the height of the centre boss. This is 1.345". The other plates that I have give centre boss heights of 1.299 and 1.280. These seem considerably different to the plates that you have, which I believe you have quoted centre boss heights of 0.795" and 1.083". Could this be the clue we are looking for?

Hope this helps?

David

[Forumadmin]

I went around to Ken's place again yesterday armed with new knowledge, some spares and measuring kit. I checked the failing clutch to find it was the wrong part number, so this was discarded and another one found by Ken which had also failed apparently and this I checked out. I noticed the peening on the adjustment screws was not in line with the slots and, after some thought, Ken admitted he had 'set it up', however I think this was by guesswork and not using any gauge or measurement.

A test on my flywheel jig with Ken's friction plate showed this plate to have finger depths of 11.4mm,12.2mm and 13.4mm which was more than desired. However the friction plate part number 45589/53 had a thickness of 9.44mm which was 1mm more than my plate used for testing. The fingers were close to the plate but I thought it would have enough clearance. I was wrong because the clutch would just about disengage to allow starting in gear but would not disengage enough to stop the input shaft moving slightly. Also the fingers touched the friction plate on fully depressing the pedal. So is this the wrong friction plate as well or is it just a bad pressure assembly?

45589/53 CLUTCH PLATE AUSTIN, HILLMAN, STANDARD ETC TO SUIT.. AUSTIN A40 DEVON & DORSET. A40 CAMBRIDGE (UP TO ENG. CE 152790.. A40 CAMBRIDGE. (from car? engine SERIAL NO. CE 152791.. NASH METROPLITAN, SERIES 1 & 11 UJP TO ENGINE NO. 2G 10000. SERIES 11 FROM ENGINE NO 2G 10001.. AUSTIN 10 HP 1939-48.. 1946-48.. COMMER COB 7CWT.VAN 8 CWT EXPRESS DELIVERY VAN FROM CHASSIS NO, D447179... HILLMAN MINX MK V11 INCLUDING CALIFORNE OHV. MINX MK V111 MINX SPECIAL, NEW MINX SERIES 1.. HUSKY 1956-57. SINGER 9 HP 1939 , 9 HP ROASTER 1938-40 1946-51. 10 HP POPULAR & 10 HP SUPER 39-40. 10 HP SUPER 1946-49... .. MORRIS OXFORD 10HP SERIES M 1938-40, OXFORD SERIES 1 SALOON & TRAVELER, HINDUSTAN 1948-56,, .. STANDARD A10 1935-36... SUNBEAM TALBOT 10HP & 80.... TRIUMPH MAYFLOWER 1950 - 53 ... WOLSELEY 10 HP WASP & HORNET, 1935-36 10HP 36- 40.... JOWET 10HP 1943-45.. JAVELIN RH DRIVE 46.55. LH DRIVE 48-55.. JUIPTER 50-54.. BRADFORD VAN 48-54.... MG 10 HP MIDGET ( ENGINE SYMBOL XPAG) 1939. & 1939-46, 1 1/2 LITRE (Engine SYMBAL XPAG) 1945-47 & 1 1/2 LITRE 48-50.... ALPINE TRIALS 51-56... TG MIDGET (to engine 9048) 49-51.... THIS IS A NEW BORG & BECK CLUTCH PLATE.. PART NO RS.35589/53

Comp tuning notes

Clutch – It is desirable to replace the Clutch Friction Disc with one of a woven type having a greater coefficient of friction, this is available under our Part No. 52420/A.

j) NOTE: This Clutch Plate 52420/A is the deluxe type available from most retailers. The Pressure Plate normal for Javelin is Borg and Beck B2 with Blue Springs – however a stronger Pressure Plate with White Springs can be obtained from Motor Traders Ltd. The reconditioned Pressure Plate Assemblies from some suppliers are not recommended as the balancing is very suspect.

The engine was not running well. I found that one spark plug lead was not attached properly to the plug. All other plugs had their screw on tops removed but this one had not. I then thought it was because the head cover plate prevented the elbowed plug caps from seating, in desperation I removed the plug to find it was a good 1cm shorter than the other three. I suggested to Ken he buy some new spark plugs, leads and cap as there were 4 different makes of plug on the engine, cracked leads and an old cap.

Anyhow I drove the car out of the garage but the engine had no power. So I drove it back in again with Ken and Janet helping by pushing! I suspect the petrol is old. So my next visit I will be armed with known working clutch and friction plate, distributor, leads and ignition coil and some fresh petrol.

This takes me back to the days of a support engineer where you were called to a seemingly small problem to find a litany of issues. Establishing the history of anything is very difficult, even after some very pointed questions.

[Forumadmin]

Item No. 19. Clutch Assemblies – Borg & Beck, PA and PB Models

All replacement clutch cover and pressure plate assemblies, Part Numbers 50844 (RHD) and 52420 (LHD), are now treated with 'Lanoline' as a precaution against corrosion. When replacing clutch assemblies it is most important that all traces of the Lanoline are removed, before assembly.

This will apply to replacement clutch assemblies, Part Number AS6622, for Bradford CC Models.

Above from bulletins so what is the difference between the RHD and LHD assemblies and, if there is a difference , why?

[robert lintott]

Keith, some parts of the clutch mechanism on LHD cars will be different because the pedal is further away from the clutch than it is on RHD. So the operating lever and connections to the pedal will differ, but why the plate and pressure plate --all listed in the Parts Book as LHD-- should change seems odd! regards Bob

[Forumadmin]

I spent some of yesterday building a jig to test the clutch assembly and made some measurements on some of the 14 assemblies I have!

I first inspected the friction plates. Seven of which looked the same and had the same part numbers. Of the others, three had red springs and had different spline offsets but carried the same part number. Two of the other four had six springs and the other two had no part numbers . All were presumed to have come out of a Jav or Jup.

Anyhow I assumed the seven that looked the same and had blue springs were the correct part.
So I started measuring. Clutch diameter is 7.257 " (184.3mm) this varied on some to 183mm.

Spline boss height 1.304" (33.14mm) Height to number side .769" (19.5mm) Height to name (BORG and BECK) side .95" (24.1). This offset is certainly something that varies even on the same part number but NOT on the seven with 4 blue springs that I had. Whether this is a critical dimension could only be proved by looking at clearances when assembled on the spline shaft. The boss could hit the brass cover of the gearbox bearing, or it might hit the flywheel. In either case the symptom would be the clutch would not disengage. More research here needed.

Friction plate thickness across both linings and gap I think should be about 7mm when new. I had one non-standard over 8 and the one I took out of Ken Brown's car today was 9.5mm. This plate would not disengage even after modifying the clutch operating shaft to take up all the free play. The pedal was then so depressed the fingers hit the friction plate springs.
I have some new linings but not sure if they are for Jowett plates. These were between 3.5 and 3.1mm thick which added to the gap between plates gives about 7.8mm.
A friction plate 7.4mm thick and slightly worn was put in the test jig. When bolted down the fingers were 20mm above web of the friction plate.

The jig bolt was then tightened until it was just possible to move the friction plate. The gap between the finger and the spring was then measured with various sizes of nuts as I had no other tool! This clearance was 6mm. Note that over depression of the clutch will reduce this to zero causing the springs to be hit and a clattering will result.

With an 8mm friction plate this clearance was reduced to less than 3mm meaning that it was highly likely clattering would be heard.

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My interim assessment is that the friction lining thickness is very critical. Just .6mm thicker from the optimum 7.4mm will reduce spring clearance by over 3 mm. Note I have not done this test on all new and properly set up components, I have used the units taken out of a known working system and compared to many others from presumed working systems and from units taken out of known non-working systems showing spring interference.

There are many friction plates and pressure plates available which will 'fit' and I have a number of these as the 7.25" clutch was quite common. But there can be problems with certain combinations. Having taken Ken's engine out now three times, I will now test the assembly before fitting!

I left Ken very happy as his car now works.

[Forumadmin]

Back to the test rig today with the extracted clutch from Ken's car.
Firstly assembled 'good' 7.4mm thick friction plate with the 'faulty' pressure plate.
Measured distance from top of fingers to web of friction plate on Peter Pfister's old engine as it is accessible in the rack. That was 34mm, 33m, 31mm whereas on Ken's it was 24mm. So I adjusted the three fingers with a 5/8" AF ring spanner so they were level with casing, so setting to 33mm. This increases the gap between spring and finger hopefully stopping any clattering. It might put strain on assembly though, but without Borg and Beck tool I do not know what it should be set to.

To release the friction plate the fingers needed to be depressed by 3.8mm.

Next the 'faulty' friction plate of 9.5mm thickness was assembled. The fingers now were 6.4mm lower, that is 26.6mm above friction plate. This assembly needed 5.8mm of depression to release friction plate, but at least there was still plenty of space between fingers and springs.

So is this a conclusion? Well no, but I do know to adjust the fingers to stop them hitting the friction plate. I do know that the friction plate thickness needs to be checked and the pressure plate adjustment needs to be checked prior to installation. What we need are drawings for the adjustment tool and details on the differences of springs and plates and list of suitable part numbers and sources that can be made to work. We also need to be aware that adjustment and wrong combinations might compromise reliability.

The color of the clutch springs indicates roughly at what rpm they should engage (or the stiffness of the spring). Depending on the manufacturer the white is the softest (will engage at the lowest rpm), red the stiffest (will engage a higher rpm), and yellow and blue somewhere in between. The problem is that the color signification may not be standardized between the various manufacturers.

or here

or the MGA forum

I also revisited this Riley maintenance Manual where it reiterates the fingers cannot be adjusted without the special tool because of differences in the driven (friction) plates. But looking at the diagram the adjustment is below the cover top by about 6mm so perhaps with a new plate of say 8mm thickness my adjustment may be correct. (I used a 7.4mm plate).

clutch tool.jpg

[Forumadmin]

Jack and I removed the engine and gearbox out of Amy's Jav last night so as to investigate the lack of clutch.
I have added the relavant couple of pages with OCR into the Gallery as I will need to dismantle the offending pressure plate.

[Forumadmin]

Removal showed a worn friction plate, so that was the cause of the slipping as copper does not grip very well. However, one of the fingers was not level with the others , so I disassembled the unit. One of the screws' heads came off with the nut and had been sheared for some time.I did some tests and measurements with the press before disassembly to see the movement in the pressure plate. I clamped the unit to the press cross member as it would be on the flywheel. My calculations prior to this suggested that 4.2mm of movement of the fingers once contact was made with them should be enough to release the pressure plate from the friction plate. I tried it with different thicknesses of friction plate, from the 4 mm that the removed worn plate had , through 7mm which seems to be standard, to the 8 mm which seems to be the modern 'possible' replacement and which I had so much trouble on Ken's (now Chris's car).

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The calculations based on the info in the old maintenance manual :
Pedal Free play 1 inch (25mm) plus Travel to floorboard 2.75 inch (70mm) = total pedal travel 95mm.
Thrust bearing travel 1/16inch (1.5mm) gap before engage plus 0.172inch(=2.75/16) or 4.2mm (=70*1.5/25).

This could explain why the fat friction plate had problems disengaging on Ken's car as the below test showed that between 4 and 5 mm was needed to free the plate which might be over the travel available at the pedal.
This is the arrangement used to check travel. The friction plate can be checked for freedom by sticking your finger through the hole in the flywheel from underneath.

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I forgot to say above that the height of the fingers was checked with different friction plates inserted and on different pressure plate units which were tightened (evenly ) onto a flywheel. I placed a ground bar so that it was flat across the depression just above the fingers (avoiding the wire spring hooks) and measured how far each finger was below this. Some considerable variation occured on used units ranging from 12 to 3 mm. I chose a standard 6.94mm thick friction plate to set up the new unit to 3mm +/- 0.1mm on all three fingers. Then inserted the non standard 8.26mm plate taken from Ken's car which moved the fingers down to give 6.24, 6.19 and 5.28 mm . I am not quite sure why this variation on one occured but it might have been a high bit of friction material as it was unused.

More experiments today which will check to see the clutch operates without fouling the bell housing or that the rotating unit does not hit the operating arm or finger.

[Forumadmin]

Amy helped put the engine back in yesterday after I tested the clutch operation like this.

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The plate holds the lever peg in place and the jack pushes the lever to operate the clutch.


We then connected up the clutch pedal and did a quick test with Amy turning the end of the gearbox output shaft whilst I depressed the clutch pedal. All seemed OK so today we connect up the engine.

Note the small amount of gap with such a thick clutch plate. This gap will increase as the plate wears. There is enough of a gap for the plate to disengage. It is most important to maintain the 25mm free play at the clutch pedal. That is the pedal should be able to be depressed an inch before all but the lightest resistance is felt. This is when the thrust bearing starts to touch the clutch fingers. The clutch pedal return spring provides that light resistance! If this is not done the thrust race and the fingers will wear as they are in contact, and worse you will start to get clutch slip and the whole unit will wear. As the plate wears the rod length needs to be adjusted. There is at least 30mm of adjustment and you might need all of this as the friction plate wears. So check the free play regularly!!!

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[Keith Clements]

Engine in and clutch works fine, but unfortunately the radiator sprang a leak where the top pipe enters. A bit too much strain when fitting the fan, as the soldered joints are not very strong! Nothing a bit of solder cannot fix, but it is a rad out job and will have to wait till August, if I am to do it, as I am off to Queensland tomorrow.