Making idler wheel

[Natlek]

Well , i'm working on another belt grinder so I need idler wheels . I Intend to make them from front forks fork tubes from Honda Transalp bike .They have hard chrome surface and 41mm outer dia. 6301 ball bearing will fit perfectly with little work on lathe .41mm outer diameter make them perfect for press fit of rubber , silicone or polyurethane tube with 40mm inner Dia . with 5mm wall thickness .

Now , somewhere on net I found this ......

Is there any advantage to use bearing this way ? What do you think guys ?

 

[mike-E]

Simple physics says the further apart the bearings are from eachother the less angular force they will be subjected to from belt tension. Put a bearing at each end of the wheel.

 

[Natlek]

Simple physics says the further apart the bearings are from eachother the less angular force they will be subjected to from belt tension. Put a bearing at each end of the wheel.

Mike , they claim this . .. . . .

Bearings are placed back to back. A 10 mm wide standoff (sleeve) will raise the wheel of the mounting plate. This bearing combination is the best tested solution against bearing failure as it allow for tightening the mounting bolts without causing any axial force on the bearings (ball bearings should not bear lateral load)

But in normal configuration I use steel tube between bearings , so ............... no advantage ?

 

[mike-E]

Sounds like some bullsnot they pulled out of their nose to justify laziness in machining. That wheel is made in a single set up and parted off. No spacer required and the tolerances are much easier to hold.
While you will find bearings paired together like that in things like machine spindles, there is almost always a third bearing (usually a radial thrust type) further down the line supporting them. The only place Ive seen that is on high pressure roller situations where the wheel is barely(a few millimeters)wider than the double stacked bearings and two snap rings.

 

[Natlek]

Sounds like some bullsnot they pulled out of their nose to justify laziness in machining. That wheel is made in a single set up and parted off. No spacer required and the tolerances are much easier to hold.
While you will find bearings paired together like that in things like machine spindles, there is almost always a third bearing (usually a radial thrust type) further down the line supporting them. The only place Ive seen that is on high pressure roller situations where the wheel is barely(a few millimeters)wider than the double stacked bearings and two snap rings.

That s what first I thought , too .But I decide to ask just in case . Thanks for confirmation Anyway this give me excellent idea... On outer bearing I will make deeper grove for bearing and seal completely at least that side from dust ...Maybe I will make some nice round walnut piece for cover

 

[Stacy E. Apelt - Bladesmith]

Let's look at it from an engineering standpoint.
The diagram shows a spindle (bolt in our use) of 1/4 the wheel diameter. This is a low ratio for rigidity due to the next issue .....

The wheel extends double the length of the bearing surface. This is also not good because it allows a strong side vector on the spindle.

The bearings being on both sides with a metal sleeve between the inner sleeves is a far better setup for wheels that will bear any amount of pressure ... like a belt grinder.

Another important issue missed by people making their grinders is the type of bolt for the spindle. It needs to be a precision Grade 8 hardened bolt.

The arm the wheel bolts to also needs to be thick enough to resist any minute twist. I think this is where many low budget grinders have their tracking problems ..... 1/2"/12mm thick arm for the tracking wheel and any support bracket ( flat grinding platen frame) is not excessive. Even a flex/twist of a fraction of a degree will affect tracking. Think about it .. why do you want a 5/8" to 3/4" ( 16 to 18mm) shaft on you motor/drive wheel but a wimpy bolt and arm on the next wheels ???