SOHC.co.uk Forums > CB350/400

Rear disc conversion

(1/29) > >>

allankelly1:
Hi all

As some of you know my rear drum has developed a crack that renders it either scrap or look to a possible repair.




Bike was never going to be standard / original, so now looking to see what is involved in conversion to a rear disc and thought I would do a thread about how I did the conversion unlike when I converted the front end to dual disc




First thing I needed to do was suss out a way of fitting a “disc carrier” that fits the standard hub to see what design was needed.

Spent some time yesterday modelling up a simple dummy disc carrier unit in 3d so I could then overnight print  and then dummy up the build on the bike just to see how it all fitted together and from first dry fit it looks good.

This is the 3d printed disc carrier in ABS.




And this is how it all fits together on the wheel and bike.







The final carrier itself will be machined from a solid aluminium billet and will be designed to lock the carrier in the internal bore so that it is solidly held in place to prevent sideway movement and other features such a extra bosses to lock it in place using some of the internal hub features to prevent possible rotation under braking (and also a oil seal like the sprocket side to prevent water entry to now exposed wheel bearing as the end spacer / boss you see on the dummy disc carrier will be a separate part the final disc carrier will revolve round this spacer)

But for now I am happy with the overall shape and size / distance of the disc from the swing arm and there is plenty of space to add a caliper hanger etc

The next stage will be to source a caliper and then design a caliper mount to suit my chosen unit to mount the caliper on the disc and use the original torque arm mount with a new torque arm arrangement

Again this will be modelled and printed so I can first test fit my design

Then the final stage will be how to convert my rear sets to operate a remote master cylinder

Once these three parts of the design are finalised I can then commit to the final parts in aluminium and then fit

Will update as thing go

Catch up soon

Best wishes Al


Sent from my iPhone using Tapatalk

allankelly1:
Hi Oddjob

Thanks for the compliment it means a lot

Yes there is some better discs out there but wanted to at least keep the period look and avoid modern discs at the expense of a bit of extra stopping power

It’s a  summer bike anyway and there are better pad materials these days. And can always drill the period discs to improve things without making it look too modern

But I do have a spare twin piston rear  brembo caliper in a box




So may machine off the logo and paint it black to hide its a modern unit but will need to tweak the disc size diameter to suit as its for a smaller disc

It’s early days yet and plenty of time to play around with different ideas but at least  the disc idea looks possible

Catch up soon

Best wishes Al


Sent from my iPhone using Tapatalk

allankelly1:
Hi Oddjob

The cb400n super dream disc I am planning to use is a standard 5mm thick (the one in the pics is an original CB400F front disc that I just had in a box as awaiting the cb400n disc to arrive ), so suits the Brembo unit nicely and just need to reduce the disc diameter by 20mm so the Brembo pad with of 30mm uses the whole disc face as the original cb400n disc has a pad width of 40mm. So the Brembo pad would leave a 10mm unused section on the inner most section of the disc working face


Sent from my iPhone using Tapatalk

K2-K6:
Nice work and interesting project, good to see work as it progresses.

A thought though as to design. Have you considered that the disc may need an outrigger bearing? The original brake shoes ordinarily sit equally over the existing wheel bearing (well technically the braking surface of the drum does) to distribute braking torque equally when applied.

The disc arrangement in mock up appears too far out to use that alignment and as I understand the description to centre the assembly into the existing hub which may not be "ahem" symmetric. In other words, as brake is applied it could try and "corkscrew" for want of a better word, the assembly out of the hub. Any failure there ultimately could lock the wheel. It's not a natural torque application line as I view it.

allankelly1:
Hi K2-k6

Yes there is plenty of room to add a bearing to the disc carrier and good idea

I will at some point add a bearing location as part of the seal arrangement as there is plenty of space

Also I could use an angular contact bearing rather than a normal single race ball bearing so as well as supporting axially the disc carrier it is also held in place radially too for any type of loads / forces

Food for thought

Thanks  for your input and ideas

Best wishes Al


Sent from my iPhone using Tapatalk

Navigation

[0] Message Index

[#] Next page