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Roller Derby Forum Discussions about banked-track and flat-track roller derby events, teams, skaters, and training methods.

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Old August 4th, 2011, 12:42 PM   #1
Nick V
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Question 688 micro bearing usage.

Would there be any tangible advantage to using 688-type bearings as wheel bearings on derby skates?

According to the information I've found, 688s are much lighter than the 608, and also contain 10 to 11 balls apiece. It seems to me that this would enable loads to be spread over a greater ball area.

However, the dimensions of a 688 are 8mm inner diameter x 16mm outer diameter x 5mm width.
Fitment to conventional skate wheels would require a machined or moulded adaptor in aluminium or hard plastic 7mm wide, comprising a thrust end 2mm thick with inner 'thrust end' diameter of approx. 12mm to 14mm, outer diameter of 22mm and inner diameter of 16mm.
It would also limit usage of these bearings to 8mm axles (and with that, flip axles go out the window).
Along with the need for a spacer, this would negate a large part of the mass advantage.

Are adaptors to fit 688s to conventional skate wheels commercially available? If so, from whom?

Who here has successfully used 688s in quad skates? What sort of feedback can you give on them?
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Old August 4th, 2011, 01:31 PM   #2
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Armadillo's your man here Nick. He uses nothing but in his Twister wheels outdoors.
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Old August 4th, 2011, 02:39 PM   #3
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I have a set of Velocity Race, which uses the same mini-bearings as the RD Twisters. I think the main thing is they weigh less, so adding a metal spacer might cancel that out. In all honesty, I wish they took standard bearings, It is tough to find replacements for them.
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Old August 4th, 2011, 02:55 PM   #4
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My R.O.C.K. skates originally came with a set of Speed Freaks wheels that use the 688 bearings. The original ones seemed to get crunchy right away in spite of indoor use only.
I bought a better set online, but they sucked also. It seemed like they wouldn't stay clean. There was always a noisey one or two.

They didn't roll especially well, and they seemed to allow the wheel to be even sloppier on the 8mm axle than conventional size bearings.

I gave up on them and replaced them with "normal" wheels.
That's the extent of my experience with them.
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Old August 4th, 2011, 04:16 PM   #5
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Default Micro selection

The microbearings are smaller and lighter, and they roll like crazy. Scary fast. The big problem is that there aren't that many wheels that take them directly, and none that I'm aware of that are in current production. Roll Line makes microbearings that come in a machined adapter to fit regular 22mm bearing races, and that's about as close as you'll get.
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Old August 4th, 2011, 05:51 PM   #6
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Quote:
Originally Posted by Nick V View Post
Would there be any tangible advantage to using 688-type bearings as wheel bearings on derby skates? According to the information I've found, 688s are much lighter than the 608,

Less weigh and friction. The weight I can measure and the sure do sk8 fast as all get out..

and also contain 10 to 11 balls apiece. It seems to me that this would enable loads to be spread over a greater ball area.

It would seam so but remember the balls are much smaller..

However, the dimensions of a 688 are 8mm inner diameter x 16mm outer diameter x 5mm width.

Sure are..

Fitment to conventional skate wheels would require a machined or moulded adaptor in aluminium or hard plastic 7mm wide, comprising a thrust end 2mm thick with inner 'thrust end' diameter of approx. 12mm to 14mm, outer diameter of 22mm and inner diameter of 16mm.

Forget the plastic, alloy is the way to go..

It would also limit usage of these bearings to 8mm axles (and with that, flip axles go out the window).

Unless you buy some of the Roll Line Micros.. Already have the adapter and are 7mm ID

Along with the need for a spacer, this would negate a large part of the mass advantage.

Let's see 37KD Fafnir weighs 12.7grams. The Roll Line Micro weighs 8.8 a delta of 31.2 grams per sk8.

Are adaptors to fit 688s to conventional skate wheels commercially available? If so, from whom?

Not as common as they used to be..

Who here has successfully used 688s in quad skates?

I have...

What sort of feedback can you give on them?
I think they are dandy.... I just wish someone would make wheels that use 16 or 17mm diameter bearings...
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Old August 4th, 2011, 08:53 PM   #7
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I just finished setting up my first set of the 688 micro bearings, installing them into Roll Line Helium 64mm x 33mm outdoor wheels.
The end result was 10 grams per wheel weight savings.

These are 688 MICRO bearing (8mmx16mm), not 607/698 MINI bearings (19mmx7/8mm Twister/VR size).

They came with delrin sleeves for the OD of the bearing that increase their OD from 16mm to 22mm. They were a too-large bad fit and had to be carefully sanded before I could fit them into the wheels.

They also came with aluminum 6mm x 8mm ID adapter sleeves/spacers for fitting them onto. 6mm inline axles. I decided to use these to be my axle sleeve/spacers by reaming them out to a perfect ID for my 7mm (19/32-32 actual thread size) titanium axles, using a lathe with a collet holder for good centering.

The result fits the axles super nicely with none of the typical wiggling.
However, the wall thickness of the stub that goes inside the the bearing ID has now been reduced to 1/2 mm (~.020") which is very thin, and I am not sure how long these will last.

The central spacer portion of the aluminum axle adapters is wider than a normal spacer because the delrin OD adapters wrap around the corners of the bearings toward inside of wheel, adding about .075" of delrin between the bearing and the shoulder inside the wheels' ID. This displaces the inside edges of the bearings outward further than normal. With the Roll line wheels being metric, the space between the two bearing shoulders inside the wheels was not a match with the aluminum axle spacer/adapter. So, I had to add several bearing spacer washers inside the wheel behind the delrin OD adapters to widen them out so that the bearings would not slip back and forth inside the delrin with every stroke. This slipping was a considerable amount ~.050+".
*** WARNING, if your axles are not very wide, these MICRO bearings may not allow the axle nuts to go far enough onto the axle to get a grip, since the delrin adapter does WIDEN the bearing spacing.

Once i got all the components positioned correctly relative to each other, I must say the result, in terms of smooth and free rolling, plus absolute rigid, no-wiggle wheels was outstanding. Howerve, since I borke my wrist right after I did these, I have not been able to rack up any miles on them.

More to follow, including PICs.

Was it worth all the cost and effort to just save 40grams per foot? Not sure -- verdict is still not in on this one. Yes the weight reduction was pretty good, but durabality is still unproven.

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Old August 5th, 2011, 06:07 AM   #8
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The result fits the axles super nicely with none of the typical wiggling. However, the wall thickness of the stub that goes inside the the bearing ID has now been reduced to 1/2 mm (~.020") which is very thin, and I am not sure how long these will last.

They fit even better and last longer if they are threaded.. But they are to be considered consumable.

The central spacer portion of the aluminum axle adapters is wider than a normal spacer because the delrin OD adapters wrap around the corners of the bearings toward inside of wheel, adding about .075" of delrin between the bearing and the shoulder inside the wheels' ID. This displaces the inside edges of the bearings outward further than normal.

With the Roll line wheels being metric, the space between the two bearing shoulders inside the wheels was not a match with the aluminum axle spacer/adapter.

Metric?? What ever you call it, roll line bearing spacing is .363, about half way between standard quads at .3 - .31 and .4 - .41 of standard inline wheels.. No big mystery here.. Jeez you make things that there are known answers for so complicated...

So, I had to add several bearing spacer washers inside the wheel behind the delrin OD adapters to widen them out so that the bearings would not slip back and forth inside the delrin with every stroke. This slipping was a considerable amount ~.050+".

So .363 to plus your 0.05 slide = .413... Why didn't you machine the shoulder on the spacer to get the proper clearance?? I did.
There ya go dillo I fixed the typo.... .363+ .05 = .413...

*** WARNING, if your axles are not very wide, these MICRO bearings may not allow the axle nuts to go far enough onto the axle to get a grip, since the delrin adapter does WIDEN the bearing spacing.

I would not recommend this on anything but threaded axles.. with threaded adapters.. The threads will chew right through the insides of the alloy sleeves.. Been there done that, could write a book..

Once i got all the components positioned correctly relative to each other, I must say the result, in terms of smooth and free rolling, plus absolute rigid, no-wiggle wheels was outstanding. Howerve, since I borke my wrist right after I did these, I have not been able to rack up any miles on them.

Sorry to hear that... How did that happen??

More to follow, including PICs.

Oh , like this??



Yep 688s on a SG Ti 7mm axle using a modified inline spacer.. We discussed this before, remember??

Was it worth all the cost and effort to just save 40grams per foot?

You need to be asking that question when you have to screw the plates on the boots that you hope will be raced at Nationals next year...


Not sure -- verdict is still not in on this one. Yes the weight reduction was pretty good, but durabality is still unproven.

Well let me help you... Based on your descriptions of how you sk8, I would keep a few sets handy to replace the ones you break.. Cause you will. Especially rolling outside.. I quit making them for that very reason..

-Armadillo
Now...after all this, you were not answering the question ("Who here has successfully used 688s in quad skates? What sort of feedback can you give on them?" ) Instead you were bragging on what you are going to do. Typical Dillo thread jack....

While interesting, you are covering old ground and once again acting like something you read on the forum is an original idea...
Quote:
I decided to use these to be my axle sleeve/spacers by reaming them out to a perfect ID for my 7mm (19/32-32 actual thread size) titanium axles, using a lathe with a collet holder for good centering.
The inner spacers are an idea I developed before you ever heard of micro bearings.. Let me emphasize that..... My idea and probably not original then.. I showed you the pic above before.. and the large spacers were from one of our friends down under... Be nice to give credit where it is due...
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Last edited by Doc Sk8; August 5th, 2011 at 07:00 PM.
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Old August 5th, 2011, 08:06 AM   #9
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Now...after all this, you were not answering the question ("Who here has successfully used 688s in quad skates? What sort of feedback can you give on them?" ) Instead you were bragging on what you are going to do. Typical Dillo thread jack....

While interesting, you are covering old ground and once again acting like something you read on the forum is an original idea...
The inner spacers are an idea I developed before you ever heard of micro bearings.. Let me emphasize that..... My idea and probably not original then.. I showed you the pic above before.. and the large spacers were from one of our friends down under... Be nice to give credit where it is due...
Gee do I smell the start of another pissing contest here? Am I the one starting it?

Working backwards Doc, I already have given credit to the one down under for the bearing spacers idea, in the other thread on flip axles, where I first saw them.

You seem a bit confused on the numbers Doc. The amount of lateral bearing slipping inside the delrin cups was ~0.050" not .50", which required using a set of 3 washers on either side of the wheel.

You have way too much time to burn if you suggest machining the shoulder(s) of the axle spacers. Too many surfaces needing precise machining. Washers are not that expensive. Leaving spacer longer means it can work with a variety of different wheels. I don't want to dedicate a whole set of the axle sleeves to to every set of wheels I test them in, at least not until I have tried these in several other sets of wheels. Changing up the washers for differences in the bearing shoulder spread inside various wheels is no big chore.

If you are moving the micro bearings between wheels and skates, then threading the ID makes sense ONLY if ALL your axles are fully threaded. Many of mine are NOT fully threaded. This is why I stuck with the .277" reamed smooth bore.

Broke wrist skating the Chicago Inline 1/2 marathon in a rain storm. 1st time ever skating in the rain. Hit deep puddle going fast onto a slight downhill turn, and did not expect the level of braking that the water would produce. As I fought to avoid falling forward, the wheels then came clear of the water and shot forward right out from under me. Reaching back to brace for the fall on my butt had my left wrist guard hit pavement awkwardly and I broke a piece off bottom end of radius bone just above wrist. Got up fast and finished the last 8 miles just breaking 60 minutes by 6 seconds. 1st quad finisher and made my goal of breaking 60 min. Beat better, faster skaters than me mainly because of my better outdoor optimized skates/wheels and my better endurance.

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Old August 5th, 2011, 07:37 PM   #10
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Gee do I smell the start of another pissing contest here? Am I the one starting it?

You showed up... right?? And didn't answer the question, right??

Working backwards Doc, I already have given credit to the one down under for the bearing spacers idea, in the other thread on flip axles, where I first saw them.

You seem a bit confused on the numbers Doc. The amount of lateral bearing slipping inside the delrin cups was ~0.050" not .50", which required using a set of 3 washers on either side of the wheel.

OK Mr. intuitive engineer... I fixed the typo if you had bothered to check my answer you would have seen that was correct for .050 I f I had used 1/2 inch I would have had .863. I can see you sure don't do much math in your posting..

You have way too much time to burn if you suggest machining the shoulder(s) of the axle spacers. Too many surfaces needing precise machining.

Sorry, I must have over estimated your machining knowledge.. I used to both in 1 set up.... dead nuts square and true every time.. Wish I had a collet chuck however.. Indicating in a 4 jaw is what takes the time...

Washers are not that expensive. Leaving spacer longer means it can work with a variety of different wheels. I don't want to dedicate a whole set of the axle sleeves to to every set of wheels I test them in, at least not until I have tried these in several other sets of wheels. Changing up the washers for differences in the bearing shoulder spread inside various wheels is no big chore.

Well mine were machined thin enough that they did not interfere with the bearing spacing so no adjustment necessary..

If you are moving the micro bearings between wheels and skates, then threading the ID makes sense ONLY if ALL your axles are fully threaded. Many of mine are NOT fully threaded. This is why I stuck with the .277" reamed smooth bore.

Have fun.. I will just about guarantee you will break them all.. I only used threaded adapters on threaded axes after the smooth bore ones started snapping off on both axles.. ..

Broke wrist skating the Chicago Inline 1/2 marathon in a rain storm. 1st time ever skating in the rain. Hit deep puddle going fast onto a slight downhill turn, and did not expect the level of braking that the water would produce. As I fought to avoid falling forward, the wheels then came clear of the water and shot forward right out from under me. Reaching back to brace for the fall on my butt had my left wrist guard hit pavement awkwardly and I broke a piece off bottom end of radius bone just above wrist. Got up fast and finished the last 8 miles just breaking 60 minutes by 6 seconds. 1st quad finisher and made my goal of breaking 60 min. Beat better, faster skaters than me mainly because of my better outdoor optimized skates/wheels and my better endurance.

-Armadillo
Sorry you got hurt... That sucks.... I pulled up the results... Much improved over last year.. You really are a speed sk8r... Congrats..
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Old August 6th, 2011, 04:25 AM   #11
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Sorry you got hurt... That sucks.... I pulled up the results... Much improved over last year.. You really are a speed sk8r... Congrats..
I knew it was a typo and I was not really implying your dimensional analysis was off the mark. Your approach makes perfect sense if a full set of axle sleeves are being permanently dedicated to a specific pair of plates with fully threaded axles. Once I reach that stage I WILL abandon the steel washers between the delrin sleeves and the heel hub shoulder, and then do the same kind of machining you did on the aluminum axle adapters.

Thanks for the acknowledgement. I never expected that my outdoor skating speed would improve so much by doing indoor rink speed workouts.

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Old August 6th, 2011, 04:31 AM   #12
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Thumbs up THE "ONLY PERSON" who should be using a mini bearing IS!

A ART Skater on Roll line plate on a roll line wheel. This is there DESIGNED purpose. ART & Freestyle.

Anywhere is is a excerise in futility.
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Old August 6th, 2011, 05:22 AM   #13
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A ART Skater on Roll line plate on a roll line wheel. This is there DESIGNED purpose. ART & Freestyle.

Anywhere is is a excerise in futility.
okie

Thanks for that bit of Bones Propaganda.. The only exercise in futility is expecting you to say anything besides Bones Ceramics...


There are a lot of us that have rolled the heck out those and have been quite pleased.. maybe the problem is you just don't know how to sk8..
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Old August 6th, 2011, 05:29 AM   #14
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Thanks for the acknowledgement. I never expected that my outdoor skating speed would improve so much by doing indoor rink speed workouts.

-Armadillo
Props where due Richard.. You cannot argue independently verified results..
Now when are ya going to get some indoor meet time?? That is a whole 'nuther ball game..
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Old May 20th, 2014, 11:55 PM   #15
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A ART Skater on Roll line plate on a roll line wheel. This is there DESIGNED purpose. ART & Freestyle.

Anywhere is is a excerise in futility.
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