The internet is a wonderful, magical place (parts sourcing content)

So today I'm spending some time in front of a computer day dreaming of putting a single brake disk on the diff of my bike engine challenge build.

Diff has 10 bolts (where the ring gear used to mount) spaced evenly in a 150mm circle. I already found out that front rotors from some sportbikes will fit, but at 330mm diameter they eat a TON of my available space.

Some googling leads me to stumble across this brembo disk catalog in - italian? http://www.carpimoto.it/Images/Products/Pdf/Brembo_Disk_Bike_2018.pdf

And I scrolled through the document but later realized I could've done a Ctrl+F to search the document for "150". Turns out, there is a motorcycle manufacturer called "KYMCO" and they made a bike called the "xciting". And it uses a rear brake rotor that mounts with 5 bolts placed evenly around a 150mm circle. Well that should bolt on. And at only 240mm diameter it should hardly be any bigger than my sprocket!

"Hey Google" or "Alexa" or "Hey Siri" + "Is anyone on eBay selling a rear disk brake for a KYMCO xciting?" = "Why yes, of course, and it is only $17 with free shipping."

Looks like it will be here for test fitting to the diff late this week.

(By the way, I bought the sprocket in much the same way. It is from an aprilla 250cc 2-stroke sport bike that was not sold in the USA. But I identified it with a sprocket catalog website and bought a used one with free shipping from Germany on ebay for less than $25. Also has the 5 bolt 150mm circle pattern. WIN!)

In to see how this turns out.  

I love doing this sort of thing, however the g00gles have been more difficult lately; it appears that there are far less forum based solutions than even a year or two ago.  I don't want my results to simply be a bunch of listings for products that aren't relevant to my odd search parameters. 

Cooter said:

In to see how this turns out.  

 

I love doing this sort of thing, however the g00gles have been more difficult lately; it appears that there are far less forum based solutions than even a year or two ago.  I don't want my results to simply be a bunch of listings for products that aren't relevant to my odd search parameters. 

Yes, I agree its getting a bit more difficult. However, I will say that I think I am better because my work computer defaults me to bing (can't change it). So invariably I end up searching on bing for 5-10 minutes and finding nothing, then remembering I'm on bing and navigating manually to google and then with the bing "practice" I usually get what i need on google 1st or 2nd search.

And today, it arrived!

Mock-up

Here they both are on the ring gear to show the bolt pattern.

I'm confused. Is the differential going to be exposed/open? If so, how will those bearings be lubed? If not, how does a disc brake work in an oil bath?

Not questioning your design. Just curious what outoftheboxgeniuschallengesolution you've come up with.  Gonna have to read through your build again.

The parts availability and interchangeability and resourcefulness that the internet enables is truly amazing. Party on. 

barefootskater said:

I'm confused. Is the differential going to be exposed/open? If so, how will those bearings be lubed? If not, how does a disc brake work in an oil bath?

Not questioning your design. Just curious what outoftheboxgeniuschallengesolution you've come up with.  Gonna have to read through your build again.

The parts availability and interchangeability and resourcefulness that the internet enables is truly amazing. Party on. 

Well, the gears do need some lube, but this is a mock up diff too. Our real diff is a viscous lsd, and is basically sealed. Other option is to use grease on the spider gears and make a cover for the diff to keep it all in. The diff support bearings on the ends will also be replaced with sealed type bearings.

I was researching this and there was concern that it might have problems with an LSD diff under hard braking. Something about one wheel actually turning backwards?  Maybe it was just internet myth. 

Stampie said:

I was researching this and there was concern that it might have problems with an LSD diff under hard braking. Something about one wheel actually turning backwards?  Maybe it was just internet myth. 

An open diff with a brake could get wonky, and depending on the type of lsd I guess you could have issues too (torsen maube).

Viscous and clutch pack are speed equalizers, so they work to keep the speed of the two outputs similar. Open and torsen are torque equalizers, so they keep the torque similar to both ends. 

With an open diff, stopping the diff could result in locking only one wheel if one wheel has significantly less traction than the other. In that case I think the other wheel would spin backward. 

But again, since we are using the viscous, it should keep the speeds similar and there would never be an output spinning backward (worst case is diff is stopped and one wheel stops and the other wheel doesn't but it keeps rolling forward at whatever speed the vicious coupling can haul in down to).

Actually let me be a little more clear about the open diff:

If you had a car rolling, and a diff brake was used to slow the open diff, both wheels would slow if they had equal traction. If they didn't have equal traction, the wheel with less traction would get slowed down more, right up to the point where one wheel had no traction at all (up in the air). Then the diff would instantly come to a complete stop, and since the diff was stopped but one wheel was on the ground being driven forward, the other wheel in the air would rotate backward, but there would be no braking force going to the wheel on the ground (or the wheel in the air).

Basically the same as if you have an open diff with a wheel in the air under power. Since there is no torque applied to the wheel in the air, the diff applies no torque to the engine or the other wheel.