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Thread: Grinding machine for drum brakes.

  1. #1
    [email protected] tonyfoale's Avatar
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    Grinding machine for drum brakes.

    Drum brakes are a thing of the past aren’t they? So why would I want to make a grinder for motorcycle drum brakes when disc brakes are so much better? Well, I race motorcycles in classic races. That means old farts wobbling about on old motorcycles. Classic racing organisations have eligibility rules constraining the bikes to use features from way back. Each organisation has its own rules, but the ones that I race with ban disc brakes in the categories that interest me. So instead of using nice efficient disc brakes I have to try and squeeze the maximum performance from drum brakes.
    With use drums become distorted and also the rubbing surface can become very hard and shiny. This is not good for optimum braking and it requires a lot of cutting force if you try to machine it with a single point lathe tool. Hence it is better to grind which can dramatically reduce the cutting forces and strain on the tool used.

    Grinding machine for drum brakes.-how-works.jpg Grinding machine for drum brakes.-ready2go-02.jpg
    Here are a couple of pix. of the device that I made. Although I always grind drums using a complete wheel these photos are without a rim. It is only necessary to move the drive motor closer to enable the belt to fit onto the rim rather than the hub.

    Spoking a rim onto a drum brake hub causes addition distortion to the surface of the drum and so any truing of the drum should be done with the wheel complete and not just the hub.
    Many hubs are difficult shapes to mount in a lathe accuratelyeven if you have one large enough for the whole wheel, and in any case to ensure accuracy it is better to rotate the wheel about it own bearings to ensure true concentricity of the drum.
    I have a lathe just large enough for a wheel and an internal tool post grinder, however I decided that it would be better to build a tool dedicated to just grinding drums.
    Here are a couple of pix. of the device that I made. Although I always grind drums using a complete wheel these photos are without a rim. It is only necessary to move the drive motor closer to enable the belt to fit onto the rim rather than the hub.

    Grinding machine for drum brakes.-glue.jpg Grinding machine for drum brakes.-machining-01.jpg
    I made a frame out of materials from the scrap box. I used a stick welder to glue the frame together and machined the assembly in a milling machine to ensure good alignment of all surfaces.

    Grinding machine for drum brakes.-basemtg.jpg Grinding machine for drum brakes.-fence.jpg
    I also added some “fences” machined at right angles to ensure good alignment.

    Grinding machine for drum brakes.-frame.jpg Grinding machine for drum brakes.-base.jpg
    I have a cross slide that I kept from an old very worn lathe that I scrapped which was ideal for the traversing axis of the grinding head. I machined on shoulder on the bottom of the cross slide base which aligns on one of my fences. The other two mounting faces are for aluminium clamps to hold the wheel axles.
    Here are shown the finished frame and the base of the cross slide with the machined alignment surface which locates against the fence on the frame.

    Grinding machine for drum brakes.-alignment01.jpg Grinding machine for drum brakes.-alignment02.jpg
    These two photos show a ground steel bar being used to check alignment of the wheel axle mountings.

    Grinding machine for drum brakes.-startassembly.jpg Grinding machine for drum brakes.-getting-closer.jpg
    These pix. show the old cross slide mounted which is the first stage of the assembly. The other shows the cross slide and QD tool post temporarily borrowed from my working lathe. Also shown is the wheel mounting method.

    Grinding machine for drum brakes.-detail_01.jpg
    Detail of the wheel mounting. The wheel rotates about its own bearings and there are two of these tapered nose shafts which locate the bearings. The piece of “All-Thread” holds these shaft tight against the bearings. The shafts are 25mm. and so are suitable to cater for 15, 17 and 20mm bearings which are all that interest me.

    Grinding machine for drum brakes.-assembled_01.jpg Grinding machine for drum brakes.-assembled_02.jpg
    The grinding is done with mounted points driven by a high speed (30,000rpm) turbine style die grinder. That is mounted in a fixture for the QD tool post. I made the bracket to enable internal grinding on the lathe.

    Click image for larger version. 

Name:	Ready2Go 02.jpg 
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ID:	15661 Grinding machine for drum brakes.-wow.jpg
    Here we see the finished tool set up ready to grind. The lower slide does the in and out traversing of the grinding head whilst the upper one at rt. angles adjust the depth of cut.

    In practice the tool works really well and I can now set up drum brakes better than I have ever managed in the past. For those interested in optimising motorcycle drum brakes I developed some simple software to help design the important placement of the friction material on the shoes. This is important to get the right balance between a brake that grabs too fiercely and one that doesn’t brake well enough. That software can be downloaded FOC from the Freeware section of my web site.

    A tool like this can also be configured to do car drums as well as motorcycle ones. It is just a matter of making a shaft with a fixing plate for the drum and spinning the shaft between centres or adding bearings. Without too much modification it could also be used for discs.

  2. The Following 8 Users Say Thank You to tonyfoale For This Useful Post:

    bigtrev8xl (12-23-2016), Frank S (12-22-2016), olderdan (12-24-2016), Paul Jones (12-24-2016), Seedtick (12-24-2016), sossol (01-14-2018), Toolmaker51 (12-26-2016), Vyacheslav.Nevolya (01-01-2017)

  3. #2
    Frank S's Avatar
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    Tony I like it. When single point turning on a lathe it is often hard to get under the Bilby layer ithout having to machine out more than you actually want.Your grinding method makes perfect sense
    Never try to tell me it can't be done
    When I have to paint I use http://kbs.justoldtrucks.com/

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    Paul Jones (12-30-2016), tonyfoale (12-23-2016), Toolmaker51 (12-26-2016)

  5. #3
    [email protected] tonyfoale's Avatar
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    Quote Originally Posted by Frank S View Post
    Tony I like it. When single point turning on a lathe it is often hard to get under the Bilby layer ithout having to machine out more than you actually want.Your grinding method makes perfect sense
    "Bilby" layer, I think that should be Beilby but no matter. Until now I had never come across that term, it is nice to start the day with some new knowledge, thanks for that. My problem will be remembering it.

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  7. #4
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    Thanks tonyfoale! We've added your Drum Brake Grinder to our Motorcycle category,
    as well as to your builder page: tonyfoale's Homemade Tools. Your receipt:




  8. #5
    Frank S's Avatar
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    Quote Originally Posted by tonyfoale View Post
    "Bilby" layer, I think that should be Beilby but no matter. Until now I had never come across that term, it is nice to start the day with some new knowledge, thanks for that. My problem will be remembering it.
    Yes, I sometimes drop letters or even manage to arrange them it totally useless sequences.
    The keyboard on my laptop also jumps and will start off trying to complete sentences wherever it wants at times.
    The Beilby layer is sometimes formed by air or work hardening due to heat, friction or percussion. The use of a sharp prick punch on the surface of a sample can also be used as a way to determine fatigue areas even where no apparent cracks are yet visible on the surface, where constant flexing has occurred over a long period of time.
    Never try to tell me it can't be done
    When I have to paint I use http://kbs.justoldtrucks.com/

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    Paul Jones (12-30-2016), PJs (01-02-2017), Toolmaker51 (12-26-2016)

  10. #6
    [email protected] tonyfoale's Avatar
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    Quote Originally Posted by Frank S View Post
    The Beilby layer is sometimes formed by air or work hardening due to heat, friction or percussion. The use of a sharp prick punch on the surface of a sample can also be used as a way to determine fatigue areas even where no apparent cracks are yet visible on the surface, where constant flexing has occurred over a long period of time.
    Yes. I am well familiar with the concept, it was the name that I didn't know until today, thanks again.

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    crazypj's Avatar
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    Nice tool,
    Last edited by crazypj; 12-24-2016 at 01:00 AM.

  12. #8
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    Nice tool, been thinking about making 'something' for a while as I've built a load of wheel last few years and bought a cheap Chinese multi axis 'milling' vice which I never ended up using
    What is the outer diameter of that drum though? I'm assuming your using 18" or 19" wheels so it must be huge as there doesn't seem to be enough clearance if it's 180mm drum (maybe just camera angle?)
    Oh, found picture, it was the red Suzuki with FFE (funny front end )

  13. #9
    [email protected] tonyfoale's Avatar
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    Quote Originally Posted by crazypj View Post
    Nice tool, been thinking about making 'something' for a while as I've built a load of wheel last few years and bought a cheap Chinese multi axis 'milling' vice which I never ended up using
    What is the outer diameter of that drum though? I'm assuming your using 18" or 19" wheels so it must be huge as there doesn't seem to be enough clearance if it's 180mm drum (maybe just camera angle?)
    The frame was made to take up to 19" wheels although I don't anticipate anything other than 18". The hub in the photos is from a Kettle. Dual sided 200mm diam.

    Quote Originally Posted by crazypj View Post
    Oh, found picture, it was the red Suzuki with FFE (funny front end )
    That one was made as a project bike for SuperBike magazine. It is in private hands now but is still being used by its owner for track days, sprints and road use. Not bad for a 30 year low production machine. In fact I built around 7 or 8 of them and I know of 5 or 6 that are still in use or being restored. Here are a couple more pix. It had a key-less controls, Ignition, lights etc. controlled from the number pad protected by a PIN number. That was back in the 80s.

    Grinding machine for drum brakes.-bodies.jpg Grinding machine for drum brakes.-q2_01.jpg
    Last edited by tonyfoale; 12-24-2016 at 04:22 AM. Reason: Forgot to include drum size

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    Great machine and a solution to a common problem, it certainly beats my method of gluing diamond cloth on sacrificial brake shoes and riding round the block a few times.
    Great web site by the way, I will register soon out of interest.

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