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Installing a Front Disc Brake on a Series ‘C’


Dave61

Well Known and Active Website User
VOC Member
Dave,

Yes, Bill has explained it. From a production point of view Vincent designed the wheels so the E80 nuts kept the wheel together as one piece. The E80 nuts snug up the bearings and the axle being tightened is just piling on, so to speak, as it is doing the same. When the racers were designed Vincent needed to make the backing plates thicker and lighter. They could make the plate the entire thickness of the old braking plate thickness plus the E80 nut. This could be done because they could use the axle being tightened in lieu of the E80 nuts.

This is the same design I am suggesting for the caliper plates. You have the the backing plate thickness and the E80 nut thickness to use for your caliper mounting plate. The fork won't notice a thing.

It may be a little over-kill, but you should use the size brakes from a modern machine that is hauling down a 500 lbs. motorcycle for a twin, or a 420 lbs modern bike for the Comet. That is the easiest way to size them.

David
Thanks for the advice David, it`s made what I was thinking clearer.
I`ve said before that the Vincent is proving a steep learning curve for me.
Cheers
Dave
 

Dave61

Well Known and Active Website User
VOC Member
Here as promised, pictures of my disc brake conversion.. a lot of work, thought and experiment... hardly a 'kit' to put together and bolt on, getting clearances etc and looking right.. oh and functioning well.. Thing is of course, like many of us I'm so busy with other projects, and making money to finance those projects... ZX10 calipers, Honda 250N discs, stock speedo drive.. all parts in stainless and dural (1430 axle) and made in my shop here.. lower mudguard support (still at powdercoat) is attached to lug on back lower corner of caliper bracket as I didn't like the support arm reaching around or over the caliper
You`ve done a very nice job there Andrew, very subtle.
Dave
 

andrew peters

Website User
VOC Member
Thanks for the advice David, it`s made what I was thinking clearer.
I`ve said before that the Vincent is proving a steep learning curve for me.
Cheers
Dave
I did experiment with mounting caliper brackets inboard of the forks, ie making the mounting brackets the thickness of the nuts, as the lightning. but decided against it for a number of reasons. 1.. mounting the caliper and speedo drive, I'd seen a caliper on one side and the speedo drive on the other (I don't doubt one caliper can be adequate for most people.. the forks don't twist, that you'd notice, really!) 2.. the caliper brackets needed milling, or bending to mount the calipers to align with discs. I find with any disc (conversion) caliper mount there needs (ideally) some amount of room for possible shims to achieve correct and proper alignment. 3.. there caliper bracket possibly may need to be of such thin material that lighter material such a aluminium or dural may be of insufficient strength, the brackets cannot have an chance of shearing around mounting bolts etc, milled thinner of bending to fit, reducing strength, is not at all good for a brake mount.
I agree with Davids 'generalized' suggestion for brake disc and caliper sizes, the Vincent twin and singles are relatively light bikes and don't need bike brakes. Also consider tyre sizes into that equation, Vincent have narrow tyres and small contact areas on the tarmac, weight distribution under heavy braking also should be considered, personally I think Normans steering head mod with 'modern' suspension absolutely essential combined with 'ultimate' braking capability. One last consideration, and not likely to be an issue with spoke wheels, floating calipers and better than opposed pistons (that are usually too wide for the spoke wheels) Floating calipers are less likely to warp fixed discs, contrary to our hopes, hydraulic pressure on all caliper pistons is not equal, due to friction and 'stiction' etc, in fact the Japanese 'built-in' for this effect with the ZX type calipers with different size pistons, I think these type of caliper work best for our needs...
Master cylinders... another big subject, I try to follow manufacturers specifications, I'd advise new or very carefully rebuilt.
Oh, and one last advantage, easy to include a front brake light switch, a hydraulic switch, either in line or on the master-cylinder banjo bolt... Be Safe Fellas
 

andrew peters

Website User
VOC Member
Edited version of my comments above...after previewing I realized my grammar and spelling made some of my writing make little sense unless you guessed my meaning... In future I'll be sure to re-read or at least not post late at night when I'm really ready for sleep or more beer... anyway, this is what I meant to say, I think...

I did experiment with mounting caliper brackets inboard of the forks, ie making the mounting brackets the thickness of the nuts, as per the Lightnings. but decided against it for a number of reasons. 1.. mounting the caliper and speedo drive, I'd seen a caliper on one side and the speedo drive on the other (I don't doubt one caliper can be adequate for most people.. the forks don't twist, that you'd notice, really!) 2.. the caliper brackets needed milling, or bending to mount the calipers to align with discs. I find with any disc (conversion) caliper mount there needs (ideally) some amount of room for possible shims to achieve correct and proper alignment. 3.. the caliper bracket possibly may need to be of such thin material that lighter material such a aluminium or dural may not be of insufficient strength, the brackets cannot have an chance of shearing around mounting bolts etc. Milled thinner of bending to fit, reducing strength, is not at all good for a brake mount.
I agree with Davids 'generalized' suggestion for brake disc and caliper sizes, the Vincent twin and singles are relatively light bikes and don't need big brakes. Also consider tyre sizes into that equation, Vincents have narrow tyres and small contact areas on the tarmac, weight distribution under heavy braking also should be considered, personally I think Normans steering head mod with 'modern' suspension absolutely essential when combined with 'ultimate' braking capability. One last consideration, and not likely to be an issue for us, with spoke wheels, floating calipers are certainly better than those with opposed pistons (that are usually too wide for the spoke wheels) Floating calipers are less likely to warp fixed discs. Contrary to our hopes, hydraulic pressure on each piston in a caliper is not equal, due to friction and 'stiction' etc, in fact the Japanese 'built-in' for this effect with the ZX type calipers with different size pistons, I think these types of caliper work best for our needs...
Master cylinders... another big subject, I try to follow manufacturers specifications, I'd advise new or very carefully rebuilt.
Oh, and one last advantage, easy to include a front brake light switch, a hydraulic switch, either in line or on the master-cylinder banjo bolt... Be Safe Fellas...
 

Dave61

Well Known and Active Website User
VOC Member
I`ve made a bit moe progress with my disc brake set up.
I had been intending to use a pair of Harrison 4 pot billet calipers as I`ve had a pair of the 6 pot ones on the shelf for around 12 years so used them for my working out but realised they`d be way over the top, but the cost was putting me off the 4 pot ones.
I`ve tried to get caliper dimensions online for different makes & have spent fruitless hours to no avail, then luckily I remembered the name Wilwood from looking at alternative brakes for a Volvo Amazon.
I found that they do a 4 pot caliper that is even narrower than the Harrison`s so good for spoke clearance & clears the mudguard stay by 2-3mm.
The good bit is that they were considerably cheaper, around £440 including import duty, though this could be affected by the weak pound.
I got my pair of calipers of eBay they were UK listed & had been bought by the seller but not fitted.
If I were to do it with brand new calipers I`d use the version of the same caliper listed for rear applications as the caliper bracket could be more "fan" shaped as the caliper mountings are symmetrical.
I`ve made mock ups of the caliper bracket in ply & plastic to check clearance & fit then made a pair of Alloy brackets but not that happy with the finish,I`m a Wood Joiner so not that good with metal.
Not doing anything anyone else hasn`t done before but it`s a really simple conversion especially if you`re happy to run an electronic speedo.
DaveIMG_20190330_115945.jpgIMG_20190330_120053.jpgIMG_20190330_120159.jpgIMG_20190330_122635.jpg20190329_150441.jpgIMG_20190330_134342.jpg
 

Cyborg

Well Known and Active Website User
VOC Member
Do you have a router? If the alloy plates are very close to size.... attach them to the pattern, and run a flush trim bit around them. Then remove the pattern and knock the edges off with a rounding over bit. High speed. thin cuts and wear a jock. The rounding over part is easy, the trimming part can be dangerous if trying to remove too much material.

Since you are a wood guy...
 

vibrac

Well Known and Active Website User
VOC Member
Just cut them from an old ice cream box to the exact shape and take them to the water cutters I just got a pair of plates done for Ben's k100 racer in 8mm alloy 4 days £20 job done edged like mirrors
 

Chris Launders

Well Known and Active Website User
VOC Member
I know clearances for some calipers is really tight and I know this sounds heinous but couldn't the forks be widened a little ? top hat fork bushes, longer spindles, a longer hollow axle and custom made bridge plate are all that would be required, no one would notice 1/8" extra each side !!!
You could probably get away without the top hat bushes, just 1/8" spacers.
 

Bill Thomas

Well Known and Active Website User
VOC Member
Once you have cut the shape, And cleaned it up with wet and dry etc, One of the best things I did was get a
Buffing wheel, About 6 or 8" across, And some Special soap, Fitted it to my wall mounted grinder,
Anything in Alloy can be made to look better than new !. Cheers Bill.
 

Dave61

Well Known and Active Website User
VOC Member
Do you have a router? If the alloy plates are very close to size.... attach them to the pattern, and run a flush trim bit around them. Then remove the pattern and knock the edges off with a rounding over bit. High speed. thin cuts and wear a jock. The rounding over part is easy, the trimming part can be dangerous if trying to remove too much material.

Since you are a wood guy...
Thanks for that,
Yes I`ve got a Router, actually got eight at the moment & that made me look on Youtube to check the possibilty of using one.
I made the first pattern out of ply then used that to make the first plastic one which I cleaned up by hand & used that to make the second one using a bearing guided cutter to follow it.
Then once I`d checked the fit I used the same setup to router the Aluminium brackets.
I used double sided tape to attach them each time but should really have put the router in a table to get better results instead of free hand like I did.
Cheers
Dave
 

Dave61

Well Known and Active Website User
VOC Member
Just cut them from an old ice cream box to the exact shape and take them to the water cutters I just got a pair of plates done for Ben's k100 racer in 8mm alloy 4 days £20 job done edged like mirrors
You`re lucky Tim,
My Wife asked a local firm about doing it & they said a minimum of £60 if they could be bothered.
Cheers
Dave
 

Dave61

Well Known and Active Website User
VOC Member
Once you have cut the shape, And cleaned it up with wet and dry etc, One of the best things I did was get a
Buffing wheel, About 6 or 8" across, And some Special soap, Fitted it to my wall mounted grinder,
Anything in Alloy can be made to look better than new !. Cheers Bill.
Got a decent polishing machine Bill, only problem I have is when it tugs what you`re polishing out of you hand & catapults it onto the floor.
Taken to putting a folded up dust sheet on the floor to soften the landing.
Cheers
Dave
 

vibrac

Well Known and Active Website User
VOC Member
You`re lucky Tim,
My Wife asked a local firm about doing it & they said a minimum of £60 if they could be bothered.
Cheers
Dave
Try H2O profiling at Kimbolton or HBH at Kettering (and thats just my area) best is to walk in and ask with the pattern in your hand
 

Dave61

Well Known and Active Website User
VOC Member
Just found th
is.
Hi Bill,
This was one of the videos I'd watched, maked me want a milling table.
I've got a decent pillar drill & thought I'd be able to muddle along if I could fit it with a milling table, there's loads of cheap Chinese ones about but they've got pretty small capacities.
Cheers
Dave
 

Sakura

Well Known and Active Website User
VOC Member
Hi Bill,
This was one of the videos I'd watched, maked me want a milling table.
I've got a decent pillar drill & thought I'd be able to muddle along if I could fit it with a milling table, there's loads of cheap Chinese ones about but they've got pretty small capacities.
Cheers
Dave
The machine shown in the video is a milling machine with a collet chuck. A drilling machine doesn't usually have a drawbar to hold the drill chuck in place. Side milling involves very different forces from vertical drilling. The side forces can cause the drill chuck to work itself out of the spindle. I definitely would not recommend it. Having said that, I've seen many jury rigged jobs work that I probably wouldn't have attempted!
 

Bill Thomas

Well Known and Active Website User
VOC Member
I agree about a normal Press Drill, But I do like different ways to do a job, I have bought one of those Magnetic Drill Machines + a Cheap XY table, So it might work for me ?.
I bought it to bore my Comet Flywheels to 560 cc, After welding some of the hole !!, That should be a Laugh !!.
After I mess it all up, They should make good Door Stops !.
Cheers Bill.
 

Dave61

Well Known and Active Website User
VOC Member
I agree about a normal Press Drill, But I do like different ways to do a job, I have bought one of those Magnetic Drill Machines + a Cheap XY table, So it might work for me ?.
I bought it to bore my Comet Flywheels to 560 cc, After welding some of the hole !!, That should be a Laugh !!.
After I mess it all up, They should make good Door Stops !.
Cheers Bill.
Bill,
Perhaps we should start a Motorbike modification company, what about Bodget & Scarper as a name.
 

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