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MG Midget and Sprite Technical - 1275 rear brake backplates on Frogeye axle

I've just bolted brake backplates off a 1275 model to my Frogeye axle (axle off car) and the only position they can be fitted for correct brake pipe and handbrake alignment seems more clockwise on nearside (and more anticlockwise on offside) than when fitted to the later axle. I know some people here have done this so were there any handbrake or other issues? I now realise you have to use later handbrake rods after painting the wrong ones.....
Bill Bretherton

I did this a number of years ago and other than the slight variation of the mounting angle the only other thing was, as you've noticed, is the use of the proper later handbrake rods. And IIRC I had to twist the end of one 90 degrees for it to line up properly at both ends. This was about 12 years ago so the old memory is just that, old. And since you've got the axle off of the car you won't have to be a contortionist to get it to work.
Martin

Thanks Martin, that's reassuring. I had actually used the dreaded E clips to secure the new slave cylinders (easier off the car) but they're very close to the axle mounting flange. If I ever need to replace the cylinders I'll tap the roll pin hole like everyone else!
Bill Bretherton

Bill

Daniel's book has info in this - you can buy an adjustable brake rod.

Alternatively use the Frogeye backplates each with with a single 3/4inch rear wheel cylinder from an 1098cc Morris Minor to replace the Frogeye 7/8 inch item (Alan A tip)

Cheers
Mike
M Wood

I think these are the adjustable rods: http://www.leacyclassics.com/bta497k.html
M Wood

Mike, thanks for the link - Moss also do that adjustable rod kit. I'll try the 1275 rods initially and if they won't work properly will have to get the kit.
Bill Bretherton

Or make your own adjustable rods.
Alan


Alan Anstead

I've fitted the 1275 handbrake rods now and they actually seem ok with quite positive action.
Bill Bretherton

I just discovered another problem. The Frogeye hubs can foul the later backplates. I had to grind off the flange round the hole in the backplate, or I could not tighten the hub nut without the hub binding.

Les
L B Rose

Thanks Les, will check mine carefully tomorrow.
Bill Bretherton

Les
The hubs don't bind on the backplates on mine but the rear of the wheel stud area is very close to the slave cylinders, almost catching the rubber boots.
Bill Bretherton

Another day, another problem! I'd almost finished building up the rear axle off the car, including brakes. This is a Frogeye axle casing,1275 backplates, original Frogeye hubs with new bearings and big nuts tightened, later type slave cylinders and handbrake mechanism. Fitted second half shaft with paper gasket and O ring then tightened the brake drum against it, using washers and wheel nuts to draw them firmly together (as I'd done with the other side) and the drum was binding somewhere on the backplate - couldn't turn it. It appeared the slave cylinder E clip was slightly fouling the backplate so I reluctantly removed it together with the slave cylinder and brake shoes, then loosened and re-tightened the backplate. No difference. I checked for dints and distortion in the backplate but nothing significant. I tried the brake drum on the other side and it's fine so it must be to do with backplate. Or is it possible the hub is sitting slightly low? I don't see how this is possible with the half shaft attached to it. The binding drum seems to be sitting in the same position as the other drum.

So I've finished the day further behind than when I started! All suggestions are welcome. I really don't know what to try next.
Bill Bretherton

Are you sure the two hubs are the same? MK1 hubs are slightly different and maybe that one has pulled further onto the axle as you tightened the hub nut.
GuyW

They looked identical and each one has had same replacement bearing and seal. But is it not the half shaft which determines how far out the hub sits i.e. as you tighten shaft to hub then hub moves out to half shaft (if it needs to)?
Bill Bretherton

Quote: (But is it not the half shaft which determines how far out the hub sits."

Unless I misunderstand you, then surely not.The half shaft slides in and out on the splines in the diff. There is nothing that holds it in position other than it being bolted to the hub. The hub is clamped to the tapered end of the axle casing by the hub nut (via the bearing). If for any reason ( different dimension or taper somewhere?) The hub is pulled in further, then the hub face and therefore the brake drum will be pulled closer towards the backplate.
GuyW

Guy, thanks, I've mis-understood how it works. That all makes sense and it must be that my problem hub is too far in. But then, other than the friction between bearing and hub, what prevents the hub (and hence brake drum) from moving inwards anyway with cornering forces?
Bill Bretherton

Guy,

The end of the axle casing isn't tapered it's straight, the bearing fits onto that section and the inner race butts up against a shoulder and the nut holds it all in place. The hub should only ever fit in one position unless something has been damaged.
David Billington

David, sorry - Its a while since I fitted them.

The point remains, if the hub is different in some way, then the offset of the face of the hub flange that the drum bolts up to, from the axle and therefore from the backplate will be different.
Since David describes the face of the inner bearing clamping up against a shoulder on the axle, then it shouldn't be difficult to measure the hub depth between outer flange (that the half shaft clamps against), and the inside face of the inner bearing race. i.e. are the 2 bearings the same width?
GuyW

I don't think it can be a bearing issue unless sourced from a very dodgy maker which I think is highly unlikely. IIRC the rear wheel bearing is a standard 6207 deep groove ball bearing 35mm ID x 72mm OD x 17mm wide , no other deep groove ball bearing is an option that would fit.

I did find a bearing in my Chinese made bandsaw had a bore about 0.005" oversize so I guess they were trying to use everything they produced regardless, it got replaced with a decent one.
David Billington

Guy, David, thanks for your suggestions. I'm now inclined to think that the hub has moved inboard slightly I.e. has moved in relation to the bearing. That does seem possible and, if so, it will mean the half shaft hence brake drum are further in. Will check when time allows.
Bill Bretherton

IIRC once the hub nut is tightened, all that it really is holding is the bearing inner race. The hub itself can move in or out. When you install the half shaft and tighten the retaining screw, you're pulling the hub out a bit and holding the bearing outer race between the hub and the half shaft. Adding the drum and wheel adds to this compression of the bearing.

I would start by taking everything apart one component at a timed see what that component does to freeing up the assembly. Is there any movement at all when everything is together? Could it be one of the lug bolts hitting the wheel cylinder? There's not much else that could be causing the lockup.
Martin

Martin, the brake drum is definitely contacting the backplate which, itself, does not seem distorted. As I said above, I'm now inclined to think the hub is too far in. Although it might appear that the clamped bearing would hold the hub/ halfshaft/ drum in position I think it can move in slightly causing the bolted up drum to contact the backplate.
Bill Bretherton

I should add that if I let the drum just sit on the studs It's fine. It's only when bolted up tight that it catches.
Bill Bretherton

David will tell me if I am wrong, but would putting the bearing in the wrong way round affect the relative position of hub to axle?
GuyW

Bill,

Could it be that for some reason the bearing is too far in? Measure the drum width on both sides and the location of the hub/bearing in relation to a given point on both sides. Is the backing plate slightly bent? It may not be distorted but evenly bent outwards. I'm just clutching at straws here since I don't have the axle in front of me.

Odds are that it is something simple and very obvious once you find it.
Martin

Guy,

No it shouldn't effect the position as the inner and outer race faces are aligned to tight tolerances which can be looked up but I'm not going to. It will depend on the bearing class but overall they're considered to fit either way round, unlike dare I mention them FWBs, and I don't see this as a high accuracy application. Something must be fouling somewhere, I wasn't aware the early hubs differed from the later, maybe Bill will find the culprit tomorrow.
David Billington

Guy, you wouldn't think so looking at it.

Martin, Surely the bearing would have to be too far OUT for the drum to be too far in.
Bill Bretherton

Bill,

By too far in I meant that the inner race of the bearing had been located too far towards the center of the axle housing. That would move the hub closer to the center and therefore the drum causing it to hit the backing plate.
Martin



The brake back plate mounting flange on the 1/4 elliptical axles is set further out than on the semi elliptical. Solution that I use is to grind or turn down the edge of the drums. 10 minute job.
Trevor Jessie

That sounds like your answer then Bill.
Excepting, of course,why is one side clearing the back plate whilst the other isn't!

If there was " a foreign body" on the seat of the bearing, then with the bearing itself running in the correct position relative to the axle, the hub itself would be displaced towards the backplate. But firstly, it would have to be something quite large to make sufficient difference. And secondly, the hub and half shaft flanges wouldn't clamp up together properly and you would immediately notice that.
GuyW

The other thing to check is the thickness of the halfshaft flange.

There were three different halfshafts fitted during production, excluding the competition version, and there are also aftermarket versions out there.
Dave O'Neill 2

Thanks for all the suggestions. One side is ok and half shafts, hubs and bearings are identical so I'm still inclined to think it's the hub position. From what Trevor says it may be the clearance is minimal and the "good" side just happens to have enough. Have to go out today but may get an hour later on it. Will report back.
Bill Bretherton

An Bill, it's bodge time. Put a penny washer on each wheel stud before you fit the drum. Sorted!
GuyW

Yep some washers would sort it, a quick easy bodge.

As it sounds like its catching only by a tiny amount maybe a better solution is to take off a bit of the edge of the drum.

Careful use of a sanding block with coarse grit paper should be enough to take a uniform amount off around the edge if you don't have access to machining.
Chris Madge

If what Trevor says is correct, and we have no reason to doubt that, it would be interesting to swap the drums over side to side and see if the problem follows the drum-
It could be that one drum is slightly wider than the other
Machining the edge of the drum would fix it rather than washers but if you wanted to retain std drums, maybe manufacture yourself a full circle tin plate spacer for between the flange and the drum rather than dodgey washers
William Revit

could also be that one backplate has gone slightly saucer-shaped. Application of a BFH interposed with a block of wood at several places around the periphery of the backplate is an alternative bodge!
David Smith

William - I did say using washers was a bodge!
And regarding the drum, Bill said in his first message that he had tried swapping the drum to the other side, where it turns freely.
Bill- are you sure it's the backplate that is catching? Not the edge of the brake shoe, or the handbrake mechanism!
GuyW

Been out all day but just had another half hour with it. The drum is definitely contacting the backplate. I did try using the hub extractor to draw the hub a little against the halfshaft but, although it initially seemed to move up, when I bolted the drum back to the studs it was still binding. When I say "binding" I mean you can hardly move it.

But now another problem with the V70 - ABS light. I have diagnostics for it so will find out which wheel is playing up. Probably a rear tone ring - it's had the two front ones plus sensors already. Together with other commitments the Sprite will have to wait, probably till Monday. I think I'll extract the hub and rebuild it, taking measurements as I do. Annoying, as I'd tightened up the hub nut, fitted the brake shoes and bent up the washer. I hate having to re-do things but I guess it's a story as old as time......
Bill Bretherton

Bill, I had exactly the same result when I did the same with my wife's Frog. I tried grinding the drum but due to lack of time (I was rushing before going to Le Mans) I resorted to washers between drum and flange.
I tried bashing be-jesus out of the backplate on both sides but they are tough old things and didn't improve anything.
Interestingly, it was worse on one side compared with the other. I can't recall which side now, it was for 2014 Le Mans, so a long time ago.
Currently, I still have washers on one side but ground the drum edge sufficiently to stop it rubbing on the other side. I had to file a flat on each washer, can't remember why though!!
Rob
MG Moneypit

Interesting Rob. From what Trevor Jessie says and other comments I've found on other forums (!) I'm now thinking it is maybe an issue with later backplates sitting further out on Frogeye axle flanges. I have a later axle I can pull out so I'll have to do some measuring. The strange thing is that later mk2 Sprites/ mk1 midgets still had quarter elliptic axles but later backplates and double acting slave cylinders so they must have aligned properly. Unless the axle flanges were modified of course. Horler anyone?
Bill Bretherton

Bill, Terry Horler will be at our monthly meet this Wednesday. 7:30 at the Wishing well Codrington.

You would be welcome to come along, and could ask Terry.
Chris Madge

Thanks Chris. I'm afaid I have another commitment this week which I can't change. Maybe March!
Bill Bretherton

Guy--Duly noted, no offence intended and I had missed that the drums had been tried on the other sides-----------------cheers

Bill
When you have another play with it, could it be possible that the main nut on that side has been loose some time in the past and the bearing has worn into the end of the step on the tube, Actually if there is enough thread on the tube a spacer ring between the step and the bearing would move the whole assy out and away from the backing plate--a bit more acceptable than washers I'd think
You could experiment with washer thicknesses first to get an idea of thickness required for a spacer ring, maybe an old locking tab might be thick enough--?
William Revit

Willy, I had an hour on it today. The big nuts are more or less in the same place on the thread and I measured each side from the half shaft flange to the backplate - almost identical. So I wondered if the outer part of the backplate was bowed in a little. I hammered at it via a cold chisel but no joy. So it's still a work in progress. I may try grinding the brake drum next but don't want to make a mess of it.
Bill Bretherton

Should these bearings be face adjusted like the notorious FWBs?
If the inner race were recessed relative to the inner surface of the outer race, wouldn't the hub pull further onto the axle casing?
GuyW

Isn't that only for tapered bearings Guy? I don't think the rear bearings are tapered and should only locate in one place unless the step has been worn slightly as Willy suggests.
Bill Bretherton

Guy,

See my comment 5/02/2020 at 23:17. IIRC it's a bog standard 6207 deep groove ball bearing, you can get fancy by going for shielded or sealed options but the original axles used a standard lip seal running on the axle case to keep the oil in the axle. Shielded has the advantage of allowing some change of lubricant while keeping out larger damaging debris which might be in the axle casing, sealed could help keeping oil in the axle if the lip seal faces are worn and in need of a speedisleeve.
David Billington

Bill
The drums are as soft as butter
If you know someone with a lathe they could spin the edge off quite easily
OR
If your local brake shop has a disc/drum lathe they could spin them off in 2 mins flat
William Revit

Willy, I do know someone with a lathe so may ask him, although he's moved further away but comes my way now and then. I didn't know drums were soft but it makes sense.

Since I've got an ABS problem to fix (diagnosed) and now some fencing due to high winds here plus other commitments I've plenty to do!
Bill Bretherton

Bill,

Drums are cast iron and so easy to machine but you want to keep the swarf off the lathe ways as it's abrasive due to the iron carbide content. If you're lucky enough to have minifin alloy drums they'll be cast iron lined.
David Billington

Just to conclude the thread, I did a test grinding using the grindstone and it did improve the situation, as expected. I'll try to get the drum finished off on a lathe as it will be a much better job, but that may be a while yet. I prefer this solution to using spacers.

Thanks everyone for your suggestions, it is much appreciated.
Bill Bretherton

Bill,

I'm down in Clevedon if you want to machine them back a bit you are welcome to pop down and do it on my lathe (its used to cast iron !)
As I understand it, its only the depth you are reducing ?


R.
richard b

Richard, that's a very kind offer! Yes, it's the depth only. But do you have a means of securing the drum in the lathe?
Bill Bretherton

Good point Bill !

Various options internal jaws of 3 jaw or 4 jaw chuck, or bolt to faceplate if necessary - that's why I asked about machining only the depth as on the faceplate it can be set by eye - and not need the 'dti; set up for concentricity.
With a 4 jaw it may be possible to grip the outside dia but it is slightly tapered.

The cutting speed of cast iron will require a very low machine speed for an approx 8 inch dia - say 30-39 rpm so not likely to go awal at any speed ! and using light cuts.



richard b

Internal 3 jaw chuck option.




richard b

Ah, I see Richard. Long time since I used a lathe! Please contact me at:

brethertonwilliam(at)yahoo(dot)co(dot)uk
Bill Bretherton

Richard,

What lathe is that? My main lathe is a Harrison M300, I had a double take when I went to check it before buying it when I saw the 18" face plate, it's a gap bed version. I kept my old worn Kerry 1140 as it's good for dirty job like grinding or maybe CI that I wouldn't want to do on the Harrison.
David Billington

Hi David,

Itís a Denford Viceroy a later metric model, bought it off a mates dad who was selling up - had little use and well tooled up. Iíve fitted an inverter drive which is amazing - any speed with no loss of torque - need to be a bit sensible with duration when using very low motor speeds as in theory it could overheat due to lack of air cooling the motor.
I tend to use a swarf tray when possible and on my Cowells I have fitted an EPDM sheet tray attached to the saddle. Then I blast the bed with WD40 to wash it clean etc.

I have lathe envy - Harrison M300 - I donít have suitable accommodation for one that big - I once lusted after their M250 but couldnít afford it.
richard b

Out of the two options there I'd go the bolted to the faceplate-
3 jaws are ok but it 'could' walk around unless it's a decent sized chuck

Here's a pic of a brake lathe
Brake lathes usually just have a largish threaded shaft (app. 30mm) and the drum slides over against a backplate, then a cone slides on the shaft to centre the drum and hold it against the plate, all secured by a large winged nut on the shaft

Bolted to a faceplate will be fine for what you're doing---going by the pics of them drums there's quite a bit of material hanging out past where the shoes run so no problem taking a decent cut for clearance, be greedy and take heaps, you don't want to have to go back and do it again---I'd be tempted to go about half way between where the lining has been touching and the edge of the drum----

willy



William Revit

Progress report,

Skimming back depth completed to drums and tea drunk !

Can't seem to get the pic to stay up the right way !

R.


richard b

Yes, thanks to Richard the drum now clears the backplate! Also cleaned up the other drum a little to ensure clearance. A lathe is another invaluable tool. I presume we all want one!
Bill Bretherton

You know, I was just beginning to wonder if all later Spridgets use the same backplate. All the way through this thread I have had a vague Deja vu feeling about having the same problem on one side when I rebuilt my 1275 bitsa car, years ago.

I resolved that by taking a bit off the edge of the drum. I used an angle grinder with the drum mounted back to front on the car rear hub and then running it in gear at tick-over to try and avoid creating an imbalance. It worked ok, though wasn't perhaps the safest of methods, so I daren't advise anyone else does this.
GuyW

Richard,

The Viceroy lathe looks like a decent unit from lathe.co.uk page and the same 5.5" centre height as the Kerry I think. I hadn't intended to buy a 40" between centres lathe when I got the Kerry but it has proved useful on many occasions so when I bought the Harrison it had to be the 40" version. What sort of things do you do on the Cowells, me I'd have thrown it back as being too small ;) .

Bill,

You can see that Richard has 2, I actually have 3 if you include the Denford ORAC CNC lathe. I don't plan to get any more.
David Billington

David,
The viceroy is a very late model a TDS1GB - some likeness to the Synchro I think - so gearbox and auto feeds etc.
In the picture did you see the loose EPDM membrane catching the iron swarf ?

The Cowells is a brilliant little machine (90mm) swing with a gap bed for wheels etc and backgears etc. It is much more capable than many first think and is pretty heavily constructed for a small unit. Now very sought after.
I use it for smaller things and where other machines are just to powerful. It and its other varients are also used for clock making, but I tend to stick with steam engines or just making repair bits for all sorts !

I also have a Cowells miller again for small parts.

R.
richard b

David, Three!! I'd have one myself but simply lack the space and I suppose it is very rarely I've needed one. I still like the idea though!
Bill Bretherton

Richard,

The EPDM membrane was not obvious initially but I guess that is masking the ways and keeping them clean. I often use cling film or aluminium foil for temporary protection but may get some EPDM, I think my neighbour has some spare from his fishpond. He also has machine tools as do a few others in the neighbourhood.

Bill,

Not all tools are expensive, a mate got his Raglan Little John lathe for bugger all when he was looking to buy a house in the Sussex area and one he looked at but didn't buy had to have a lathe removed as the owner was downsizing and he made a cheap offer and got the lathe but didn't buy the house. A mate offered me a Hayes Diemaster mill from the estate of a friends widow and I didn't need it so offered it to my mate and he made a decent offer to the widow and it now has a new home . I've heard of many stories like that but most people pay a good price.
David Billington

This thread was discussed between 21/01/2020 and 25/02/2020

MG Midget and Sprite Technical index

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