Early coffin brake master seal replacement?

[Mr Gazza]

Jeff, the first thing I checked was all the folds in my jeans, and the tongues and laces of my boots. The favourite place for things to settle is just under the Monster's tyre, probably the case this time too?

I ultra-sound cleaned all the master and calliper bodies last night, so everything is ready to go back together today. I will try out my idea of slitting down the 22mm pipe for a drift and let you know... Cheers for the offer of the drift. Hopefully getting the ring back in will turn out to be as simple as hoiking it out turned out to be.

Lovin' the ultra-sound cleaner.... What a nice toy..

I try fitted the Commando heads in last night, and it looks like I can do it in two goes both ways up, without the lid. Not sure if it will completely substitute vapour blasting, but it could be a good way to jiggle all the media out afterwards?... And thanks..

[Mr Gazza]

Job jobbed at last.
The new seals went into the masters with no bother at all. I made a drift out of a short length of 22mm copper pipe, with 6mm cut out of it length ways. Pythagoras told me that the circumference is 6.284 less for a 20mm pipe and he was right.
Simply held together with a jubilee clip and carefully de-burred, it worked a treat. It pushed the slippy assembly down nice and square and then just a light doink with a hammer and everything was nice and firm.
Covers and levers polished and Titanium banjo bolts in for show.
After cleaning, the tired anodising was a sort of bluey/grey colour, but I rejuvenated the masters and caliper with grate polish (formerly known as Zebrite). Paint is no good for these items in my opinion, due to the proximity of brake fluid and also the heat of the caliper. The paste has an aggressive black dye and consists mostly of graphite which is very heat resistant. It polishes up a treat to a nice.. er.. Graphite colour, with a slight sparkle in it. Very pleasing and hopefully very easy to touch up later on.
Seals yet to go in the caliper and so only bolted up for show.. you get the idea.
Lucky Commando.

[utopia]

Lucky Commando indeed.
Notice folks, there's a hydraulic clutch lever there too, not just the brake.

Lucky former owner too (that's me).
An acquaintance of mine seized the motor in the mid 70s and I bought the remains.
Its been in boxes most of the time since then.
Now I get to watch Gazza rebuilding it to a super standard.
Apparently I'll even get to ride it when its done.
Happy days.

[Darkness]

I like the Zebrite idea. Temperature shouldn’t be an issue if our log burner is anything to go by.
You wouldn’t want it anywhere near the pads though as graphite is a good lubricant too!

[Darren69]

Yea, they'll look nice on a Commando and it should be able to stop ok too.

[Mr Gazza]

Definitely not a good idea to get graphite on the friction material but I think it might be good where the pads touch the calliper, as you say Darkness it's a good lubricant and this paste does polish off so that none could drop off and cause trouble.

The aim IS to make it stop Darren. I acquired a very nice 12" disc from RGM (The standard is a solid cast iron 10" jobbie) It has a fully floating cast iron rotor on an ally carrier that replicates the shape of the original disc quite faithfully.
I made a new bracket from 18mm billet after a few MDF patterns. The billet was all machined using woodwork tools. Rebated to get the offset on a radial pull saw, outline cut with a bandsaw and holes drilled with a chuck in my bench mortiser. The very fine tuning of the offset to get the calliper sitting perfectly on the disc, was done with a hand held router.
A little bit of a buff and some Titanium bolts to finish it off..

Hubs are now polished ready for new rims and spokes.. Will post some pics when they are done..

[Darkness]

Very nice and the large holes in the disk carrier are redolent of the 60s bacon slicers.

[Mr Gazza]

Yes, I see what you mean about the bacon slicer look. I think they did a good job of making a much better disc whilst keeping a traditional look, unlike the Norvil ones which are just like modern Brembos with bright anodised carriers.

I am toying with the idea of nickel plating the rotor to keep the unswept areas and holes bright. Hopefully the plating would quickly wear off the swept area.

[350TSS]

Looking good -
if you are after new spoked rims might be worth contacting this crew
https://www.pirinimoto.it/CERCHI-E-R...NIO-19-POLLICI

[Darren69]

That is nice. It is how they say up your way a 'proper job'. You'll be glad you didn't fit period brakes for originality sake, trust me. As I found with my Mirage project you can have powerful brakes eg freshly rebuily P-08's and period masters with iron disks but there is just not enough feedback and you can if you're not careful flex the forks so they tap the header pipes (maybe not such a problem for a light weight bike not 300KG of 1200 Laverda) or make the front wheel just squeal for a foot or 2 as I found out trying to do a stoppie one time. You just don't know.

[Mr Gazza]

Cheers Richard, I've had the rims and spokes on order for a while. They should be here any time come to think of it.
Doing the disc and calliper conversion will allow me to put the rim on the centreline between the forks, as I have gained clearance from the spokes. The standard Norton disc wheel is built about 5mm off centre, so the spokes can clear the calliper, believe it or not...The wheels don't follow one another!!

I was going to PM you at some point to ask you about your Nickel plating kit.

Darren, even the people that sell Norton parts say that the original brake (or at least the calliper) is now regarded as obsolete. A lot of folks go for Lockheed or Grimeca conversions, but they are still rather weighty and a little dated. The convertor brackets are large and clumsy looking too, and then there are complications with the lower mudguard stay, which I think I will get away with on mine. Not to mention being able to get the wheel central.

To brake hard properly... First step, compress the forks with moderate lever pressure. When the fork pressure balances tyre pressure, the contact patch will increase in size with increasing moderate lever pressure. Once the contact patch is fully extended, lever pressure can be increased further until the rear wheel lifts. The rear wheel should remain rotating (so no back brake) to take advantage of the gyroscopic stability this affords. There should be no wheel locking or skidding if done properly and the ABS will not be activated. This will work in the wet too if the lever pressure is sensitively built up.
The limit to how much power can go into the front brake ultimately is governed by the fact that the rear wheel will go over the front and dump the rider in front of the bike.

It's not hard to perform a "stoppie" as detailed above, with only the right hand on the bars, by gripping the tank with the knees. Only two fingers are used on the lever at any time. (great fun practicing this on the runway at Coltishal under professional supervision.)

Actually not expecting the Commando to do stoppies, but as short an arrest as possible would be nice.

[Darren69]

Yea, my mate with a Commando has a Lockheed master on his and not sure what caliper he had but it may have been one of the early Brembo ones I can't remember.

Sounds easy in theory and I don't know what I was thinking trying to pull a stoppie on the Mirage, maybe just to prove a point to myself? The standard brakes are poweful but lack any real feedback on what the front's doing. First I knew I heard the front tyre squealing!

Iit must be an age thing and probably can't help with the calipers out front on the forks which was all the rage back in the day but I can't help wondering if there would be some improvement by reversing the fork legs so that the calipers are behind as the factory eventually did along with most other bike manufacturers as well and still do.

[Mr Gazza]

It's all about getting the contact patch nice and big and plenty of weight transferred to it before really throwing the anchors out.
Use too much power too soon and there could be more friction on the disc than on the tyre = skid.
Organic pads give much more feel and progressive braking than sintered, which have "good initial bite". (counter productive imo!)
Squeeze the lever in progressively harder and you will feel the front end firm up and then stop compressing, at which point you can squeeze a bit more. Keep the lever pressure rising all the time to prevent any rebound in the forks or the tyre.

Here's a picture of Tom demonstrating a one handed stoppie to another class.
I recommend the Machine handling course by i2i Motorcycle Academy (run by Tom) https://www.i2imca.com/About.asp



Callipers behind or in front of the forks makes no difference...How can it?
The only difference is that the bracketry is in compression when mounted behind and in tension when in front. I would prefer the former to the latter as it stresses the mountings less. There are other arguments about airborne debris/water contamination and so forth, but I still think behind is better.
There was a recent debate about whether behind or ahead was better on a Commando, on the noc forum.
They were saying that the bike will pull to the right with the disc on the right side (behind) and slightly the other way when on the left (ahead). What they were choosing to ignore, or were just ignorant of, is that the Commando disc wheel is built all on the p1ss so that the spokes will clear the huge calliper, so all they are doing is switching the wheel to one side or other of the centre line!!

[Darkness]

Pulling left or right also depends on your fork brace: how much the forks flex with a single disk.

Callipers in front or behind the fork leg change the polar moment of inertia about the steering axis, so affects the castor shimmy of the forks.

[Mr Gazza]

I used to watch the forks bend backwards on my Ajay after converting to a hydraulic twin leader with Mini shoes instead of the 7/8" single leader. But I was still a single sided drum with the torque anchor on one fork only and there was no twist or pulling to any side. So the brake was essentially only anchored to one fork leg like a single disc.... I've never seen forks twist under braking.

If you're serious about this statement.. "Callipers in front or behind the fork leg change the polar moment of inertia about the steering axis, so affects the castor shimmy of the forks." I will happily listen to your explanation..