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Clutches – How to calculate Torque Capacity


Clutches – How to calculate Torque Capacity

After an awesome comment about prison (getting sucked off, or something) I thought this would be a good time to roll out the numbers and take a look at the TORQUE CAPACITY (not capability! Its was fucking hot and once I get a word stuck in my head….)



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Genius, Innovator, Voice Actor, The Original Imposter, Cat Stroker. I like to step on crunchy leaves.



  1. Robert Small

    June 3, 2018 at 11:42 pm


  2. Ian Skeggs

    June 3, 2018 at 11:46 pm

    Cork, second

  3. Ian Skeggs

    June 3, 2018 at 11:47 pm

    Many more plates in a wet clutch

  4. Ian Skeggs

    June 3, 2018 at 11:49 pm

    A dry clutch has just surfaces to get the grip

  5. Ian Skeggs

    June 3, 2018 at 11:49 pm


  6. Average Joe

    June 4, 2018 at 12:00 am

    Radius?, Diameter?, It's late- I'm only half awake.

  7. MadxJim

    June 4, 2018 at 12:15 am

    I thought that the plates and discs never really separated when the clutch is disengaged, just the pressure is taken off so they can slip, but are still in contact, so would make that Robomika gaming's point a moot one

  8. Kbat

    June 4, 2018 at 12:25 am

    when the heck did they start making friction plates with highly polished surfaces😏..either way, slippy grippy is only good for one thing

  9. David Mccarron

    June 4, 2018 at 12:26 am

  10. nickos

    June 4, 2018 at 12:30 am

    I prefer to lick the “cat” before I put a suction cap on it

  11. Beach&BoardFan

    June 4, 2018 at 1:09 am

    Did you do a vid on the different types of clutches (like slippers not wet vs dry)?

  12. Henrik Yngvesson

    June 4, 2018 at 1:17 am

    The clutch on one of my bikes got glaced after a high rev slip. At that time I had never heard of it but had my suspicions something like that had happened so took it out and wet sanded it with a fine grit paper and it was like new.

  13. Craig Matthews

    June 4, 2018 at 1:58 am

    You actualy want the clutch to be a little slippery in order to get smooth action. dry clutches are a b#$%th to start off when hot.

  14. John Sawyer

    June 4, 2018 at 2:42 am

    An episode dedicated to Dean Harrison 😉

  15. AuMechanic

    June 4, 2018 at 3:13 am

    Mean effective radius

  16. buckaroobonsi555

    June 4, 2018 at 3:52 am

    Motorcyle wet clutches look almost identical to the friction and steels in a car's conventional automatic. Most automotive frictions if you get water on them they dissolve and fall away from the material they are bonded too. I rebuilt an automatic transmission for a project for a family member and learned a lot. I knicked a lip seal twice and had to tear the transmission down and replace that seal twices.

  17. Bruce Sabatoni

    June 4, 2018 at 3:57 am

    Thanks for this! It was very enlightening!

  18. Reality Check 123

    June 4, 2018 at 4:10 am

    I like the math videos.
    Calculations for resonace frequcy of headers and intakes would be great.

  19. Roark Gill

    June 4, 2018 at 6:07 am

    As usual, an excellent video. Thanks.

  20. 21zetec

    June 4, 2018 at 7:37 am

    Is the spring pressure at 1mm or at its installed hight ? as there is normally some preload on them when installed

  21. Lime

    June 4, 2018 at 7:45 am

    I like it when you write stuff down because literally when you just say stuff, its hard to understand. This can also apply to automotive automatic transaxles/transmissions, Differential clutches too?

    Also how do i find the CoF of some clutches and the other measurements or specs?

  22. Mick Jones

    June 4, 2018 at 8:43 am

    my cats not happy with you Mate I've been chasing her round the house for the last half hour trying to stick my sat nav sucker to her 🙂 🙂 🙂

  23. varaprasad sb

    June 4, 2018 at 10:38 am

    Churning loss…

  24. Steve Elliott

    June 4, 2018 at 11:50 am

    You drew r1 r2 and measured d1 d2? deliberate mistake?

  25. Take Flite

    June 4, 2018 at 1:24 pm

    Great video again Matt learnt a lot


  26. nicholas merwarth

    June 4, 2018 at 2:55 pm

    cant work out were to msg you … but take a listen to this fucking clown lol logic is just non existent

  27. LesNewell

    June 4, 2018 at 3:10 pm

    There is something wrong with your figures. First of all R1 and R2 are radius and you used diameter. If you use the radius your calculated torque limit becomes 50NM. Even worse your engine torque is at the crank. Primary reduction is around 1.8:1 so torque at the clutch should be around 170NM.

  28. DerKrawallkeks

    June 4, 2018 at 3:12 pm

    I have a question. On many bikes I've seen, the clutch is not mounted on the crankshaft, and the torque coming from the engine is already multiplied by a small gear on the crankshaft and a big gear on the clutch basket.

    You calculated the torque capacity, but then threw in the engine torque numbers of the SV. How does that make sense, is the clutch mounted on the crankshaft?
    Thanks for your help!:)

  29. Håkan Björkman

    June 4, 2018 at 3:26 pm

    There must be something wrong in your inputs in the equation. The clutch on the SV must handle way more than 100 Nm due to the gearing ratio between the crank and clutch basket. Could it be switching "size" to area? The radius plays in for sure but wouldn't the area be as important?

  30. Tomas T

    June 4, 2018 at 4:11 pm

    to make it complete clutches are checked also for heatup from friction. 🙂

  31. Biker Jack123456

    June 4, 2018 at 4:32 pm

    I don’t understand the “rm” part of your calculation. If you use (r2+r1)/2 then it would suggest that if you had plates that were 16cm od and 12cm id, it’d only be able to transmit the same amount of torque as if it was 15 and 13 although you have twice the friction material.

  32. Pete Campbell

    June 4, 2018 at 4:40 pm

    What the fuck!!!! Unless you are like me and understand all that stuff how the fuck is that helpful
    to the average biker who don't what the fuck your on about fix there slipping clutch (No disrespect
    to biker's as I am one) or are you hoping for a higher class of viewer like NASSA. We all know you know
    your stuff, but fuck me………..

  33. onhawaii

    June 4, 2018 at 5:30 pm

    Matt I am about to toss you a bloody tampon over… You took the diameter for the calculation not the radius! And I don't think that the calculation is right… I would take Pi x (R2²-R1²)

  34. onhawaii

    June 4, 2018 at 6:51 pm

    I notice that a dry crotch does have more friction and are hard to split open. But as wetter the crotch gets as easier it is to split it open. (I found that out when I was younger and exploring the female crotch)

  35. rockintigger

    June 4, 2018 at 6:53 pm

    I hope you explained this to Delboy, co's he's still lickin his plates before fitting. 🙂 🙂

  36. Thomas Philyaw

    June 4, 2018 at 10:29 pm

    💣💥MIND BLOWN!!! I swear the guys at my work are going to think I've divorced my wife and married an engineer once I throw this at them in a casual conversation. Thank you for your brain power

  37. Mike Skidmore

    June 5, 2018 at 12:29 am

    Hey @The Workshop I am still trying to figure out where Cristini is manufactured . I think they use a lot of high quality components .. I will be bummed if they are built in China I wondered why they didn't cost much more than a Yamaha WR-450 ect

    When I put a Yamaha GYT Kit in a Yamaha GT-80 the Clutch sure did not hold well I added washers to the springs to make more holding pressure .. Crower Glide clutches for pulling trucks and pulling Tractors use centrifugal force to increase the clamping pressure as engine RPM increases .. would not work well in a manual transmission that you want to shift on the go ..

  38. Mike Skidmore

    June 5, 2018 at 12:31 am

    The only advantage of a dry clutch is no parasitic losses from slinging oil around .. ATF automatic Transmission fluid has additives to help wet clutches .. Super Slippery synthetic oils can make wet clutches slip .. gas savings synthetic oil that is

  39. Detailverliebt

    June 5, 2018 at 11:47 am

    Obviously, we all know that a Ducati has no weakness what so ever, BUT whenever I drive the R1 from a friend I get the impression that a wet clutch is actually a nice thing to have. 😉

  40. onhawaii

    June 5, 2018 at 5:31 pm

    I just noticed mr. dislike is missing??? WTF? I am not taking his job for every video. So who is leaving the dislike this time?

  41. Vašek Krčmář

    June 6, 2018 at 12:59 pm

    Two notes to your video.

    You are measuring a diameter of clutch plates, yet you should calculate with radius (if the equation and picture on the board are correct).

    SV is not good example to do the calculations for. It has so called "back torque limiter", which works as a anti-hop clutch as well as it increases the force Fa under engine load by using internal slope mechanism (you will see that). This means the torque capacity gradually increase with engine load, as more force is applied to clutch pack.

  42. William Robbins

    June 6, 2018 at 5:37 pm

    Good one Matt! Always appreciate the deep dives into the numbers. Watch out for the Ninja zip tie attacks! 😉

  43. UsedPhore skin

    June 6, 2018 at 6:34 pm

    Man gotta love a good video about cool shit,

  44. Naushad Kharas

    June 10, 2018 at 12:03 pm

    Interesting video. The basic formula seems correct but…
    A: with 10 plates you would get 18 surfaces not 20.
    B: since the coefficient of fiction is between two surfaces i.e. two plates, shouldn't N=9 as there are 9 areas of contact between the 18 surfaces?
    C: Your formula for calculating rm is definitely wrong (Besides the fact that you used diameters instead of radii). As per your formula the bigger the inner diameter the more torque can be transmitted which seems fundamentally wrong.

    Follow up video coming soon?

  45. Jonesy

    June 12, 2018 at 6:39 pm

    Is it a problem if you pull a clutch apart and find some blue patches on the steel discs? I have seen this and presumed it was caused by heat, but wasn't sure if it was actually a problem or not. They were not warped.

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