Disc brake actuator

[a.lo]

would there be enough material to re- peen over the original pin or would a new one have to be made?

[Storkfoot]

I very much suspect not. I wouldn’t risk it on such an important part. I filed it flat and it now needs to be very carefully drilled and tapped.

[shane BBoys]

Even though it wouldn’t look original, I guess this may niggle some! But it leaves it serviceable.
Yeah, win win.
Cheers Shane

[Warkton Tornado No.1]

I very much suspect not. I wouldn’t risk it on such an important part. I filed it flat and it now needs to be very carefully drilled and tapped.

If I were you, I'd do so on a lathe.

I do not know the size of the spigot that the retaining washer is, but if it's, say, 10 mm diameter, I would drill & tap M10 deep enough to allow fitment of a high tensile M10 socket head fastener. That would effectively remove the existing spigot. The fastener I would select would have an unthreaded shoulder portion (referred to as 'grip' length) which would be massively stronger than the OEM riveted design. To allow fitment of such a screw would require removal (counter-drilling) of the first portion of threads to allow for the grip length of the screw. The screw would undoubtedly require shortening as it may well be too long (50 mm minimum in the case of an Unbrako M10 SHCS is where grips start being incorporated)

An alternative would be to use a GPW (Gear Pin Washer) in place of the OEM retaining washer & a high tensile Socket Countersunk Screw which would still be extremely strong but much lower profile.

If all of that makes sense & is feasible but you have no access to a lathe, let me know, as I have a Myford

[Storkfoot]

I see what you are saying. That would make it even sturdier.

I was always planning on taking them to a local precision engineers who I use. I am yet to even invest in a pillar drill, although that will be remedied soon, so me taking it on was never going to happen. I know my limitations

I was planning to ask them to drill a 5mm hole to a depth of at least 20mm and tap it M6 to the full depth. I was then going to use an M6x16 or M6x20 high- tensile button-head Allen screw, which I already have, and a sturdy washer. I’d loctite the screw in.

Hopefully, I am going to do 3 at once. I’ll see how they go doing it this way but thanks for the offer. If they don’t go well, I may well ask for your help.

[Warkton Tornado No.1]

What I hope to have convinced anybody wishing to convert the actuator to an assembly capable of being disassembled, is that I see no merit in retaining the small spigot that is peened over, other than to a real anorak. In which case I have original John Bull & Varnamo tyres somewhere......

Also, maximum tensile strength of a fastener is only available @ the appropriate torque but theoretically, a screw with a portion of grip is advantageous, but really only in a 'shear scenario', which is not the case here, to be truthful.

As far as compactness, neatness & aesthetics, having slept on it, I would source a good, hard GPW, or make one, & use a Countersink Socket high tensile screw.

If I get the chance I will measure up an actuator imminently & follow this discussion up.

[Warkton Tornado No.1]

I had a quick shufty @ an actuator in a spare disc brake, & reckon an M8 would do it. I also think there might be getting on for 5 mm space beneath the 'I' cap, so room for the head of a screw, though my favourite would be to use a Countersunk high tensile screw with a GPW.

[vegansydney]

I had a quick shufty @ an actuator in a spare disc brake, & reckon an M8 would do it. I also think there might be getting on for 5 mm space beneath the 'I' cap, so room for the head of a screw, though my favourite would be to use a Countersunk high tensile screw with a GPW.

As per the photo I posted earlier on this thread, I've been running a few rebuilt actuators for over a decade, all are fitted with M6 x 20mm high tensile button heads. All are holding up fine after 10+ years of regular use (as are several others fitted in scooters belonging to friends) and there is plenty of room to fit the 'i' cap.

[Warkton Tornado No.1]

I had a quick shufty @ an actuator in a spare disc brake, & reckon an M8 would do it. I also think there might be getting on for 5 mm space beneath the 'I' cap, so room for the head of a screw, though my favourite would be to use a Countersunk high tensile screw with a GPW.

As per the photo I posted earlier on this thread, I've been running a few rebuilt actuators for over a decade, all are fitted with M6 x 20mm high tensile button heads. All are holding up fine after 10+ years of regular use (as are several others fitted in scooters belonging to friends) and there is plenty of room to fit the 'i' cap.

I'd have no misgivings about using the method you have adopted, but if I personally were to bastardise an OEM part, I'd do it the way I suggested purely as I consider it the strongest option, & better than the OEM retaining method with its rather flimsy, aged washer. That said, I'd ensure the fastener was either GKN, Holocrome or Unbrako, torqued to the correct value

[Storkfoot]

Just waiting for new 8mm ball bearings and will then be able to reassemble.

[Storkfoot]

[Warkton Tornado No.1]

There are two school's of thought about the positioning of the circlip ears, but my own take is that the circlip, being a spring, is best placed with the ears placed where they can exert pressure. In the groove, rather than fresh air. That way, it can best conform to the shape of the groove with less tendency for any voids & be as fully supportive as possible.

Do you fit clutch circlip said the same way?

[Warkton Tornado No.1]

Ooops!

That looks marvellous, BTW!

[Storkfoot]

There are two school's of thought about the positioning of the circlip ears, but my own take is that the circlip, being a spring, is best placed with the ears placed where they can exert pressure. In the groove, rather than fresh air. That way, it can best conform to the shape of the groove with less tendency for any voids & be as fully supportive as possible.

Do you fit clutch circlip said the same way?

No, I always make sure the clutch circlip ends are not exposed as, probably, most people do. So, I can see your point. Against that, I have a hydraulic inboard disc on my TS1 which is just held by the circlip, with ears in the same position as the photo. I have never had an issue with the circlip and I would think that does have a lot of pressure placed against it.

Possibly the issue of more concern is ensuring that the powder coating allows the circlip to sit deep enough.

Anyway, I am pretty pleased with how the actuator has finished although it’ll be some time before I can test it on the road

[gaz_powell]

Cracking job Paul, it's not a run of the mill job, I've never tackled stripped/rebuilding one, however having now seen it done, I would.
Good to have shared the progress.

[Storkfoot]

Cracking job Paul, it's not a run of the mill job, I've never tackled stripped/rebuilding one, however having now seen it done, I would.
Good to have shared the progress.

Many thanks to vegansydney who led the way. Cheers, Benji

[Warkton Tornado No.1]

The OEM design of the front disc brake is still a superbly aesthetic piece of Italian design that proves that if something "looks right, then it is right"

The only flaw IMHO are the plastic windows, but that is all down to personal taste.

Amongst some of the stuff that I have bought @ Parts Fairs etc are the oddball conversions that the UK seems to spawn. Amongst them are a backplate with a cast 'full' actuator area with a top hat drop in hydraulic slave & another 'cut & shut' backplate with two hydraulic pistons c/w two static pad locations.

I suppose it goes to prove that not all of us are convinced that external discs are essential & some have even tried re-engineering the basic concept. Charlie Edmonds on a full bodywork Group Four with internal disc may have been ou-braked by Guy Topper's Group Six with an external disc, but that would be similar to a Christmas Hamper versus a Selection Box!

Ha! Who would bet against the likelihood that before too long, there will be copies of the brake as fitted to the twin cylinder concept available to buy? I think the idea deserves to be manufactured & followed through to the rear if there is any point in having a rear disc brake! The principle certainly couldn't look any worse than some of the thins that I have seen.....

[Storkfoot]

Having sought a second opinion on the circlip orientation, I have moved it around so that the ends are in the groove as you suggest, WT.

Interestingly to me, I also did the same on my inboard hydraulic disc brake. This then meant that I had to adjust the static side as the brake was binding quite badly. I suspect strongly that this shows that the circlip is now more secure in the groove.

[Warkton Tornado No.1]

Anything retained by an open sided recess will be bound to tip upwards in the area of least resistance, so it makes complete sense that moving the circle gap to (ideally opposite) any other place will result in the moving pad being minutely more 'activated'

Somewhere I have technical details concerning circlips & there are alternative types to the common or garden variety we are all familiar with. Although there may not be strength/deflection advantages to the differing types, there are superior types as far as ultimate retention. If you think of a bearing that has a snap ring fitted on the outer, there is an equivalent for recesses in bores as well. There are also the type that look as though they are an external circlip, but they are not, that offer a more consistent loading of themselves within the recess by virtue of the shaped outer having several points of contact.

There may even be available in the size required a clip that is essentially made of a thinner strip of steel in the form of a helix that can be wound into a circlip groove. Imagine a flattened compression spring, slightly oversize for the groove, & you'll get the picture. As a disclaimer, I have not checked the capabilities under load, but they potentially offer a neat solution because there are no gaps as with normal circlips.

Getting further off track (for which I apologise) I am awaiting a half dozen or so conventional internal circlips to fit in place of the clutch plates assembly OEM 'circlip' as I'm sure that I am not alone in finding the OEM design replacements to be very poor. The Covid scenario has meant delays, but I think they will be worth the wait....

[vegansydney]

Many thanks to vegansydney who led the way. Cheers, Benji

Nice work! Seeing these pictures totally made my day. Happy to help you out and share what I've been taught from people more knowledgeable than myself. The difference will be immediately noticeable and hopefully this will encourage others to start rebuilding them.