Machining a disk that wont explode on it's 1st run ;)

[Dan-27]

I've begun to machine my tool steel disk and I've got a question. Do you think I should run it on 25id or 30id needle roller bearings?

At the moment the shaft is 29.95mm dia

I think the plan is to have the needle bearings in an Ali sleeve. I know TS2 ran the needle bearing directly in the nylon and he said the bearings got mangled.

Any suggestions welcome.

To clarify:

White = Blade and shaft
Purple = Bearing
Silver = Ali sleeve
Dotted line = where the bulk heads will run to

Teeth are 15mm but I may make them 10mm. Looking to run it around 6,000 rpm.

[Eventorizon]

Use deep groove bearings rather than needle as they can take larger vertical loads, but better are tapered roller bearings as they take bother vertical and lateral loads. Dave would be best to ask on all this but the disc design looks fine if its cut from a single piece of D2 tool steel. Make the teeth bigger if you can. to get better bite, 18mm would be good if you can manage it. 10mm is a little small IMO

[typhoon_driver]

Tapered require a pair facing opposite ways to work effectively plus you should preload them if using them properly which causes a few issues. Go for some regular ball bearings are you will be fine.

At 6000rpm 10mm teeth will be fine as you won't get that much of a bite anyway

Edit - Actually if you are CADing it up then I would design it with a single tooth to begin with and you can ensure the weight is equally balanced by machining out pockets on the tooth side of the disc

[Dan-27]

I'd rather go for ball bearing but because of the increase diameter I think the benefit of their additional strength would be outweighed by the extra material I would have to remove from the bulkhead.

A fairly standard 25mm deep roller bearing has an OD of 47mm rather than the needles 33, this would reduce the front end of the bulk head form 13.5 to 6.5. It's give and take, I could stack up 4 or 5 of these narrow section bearings but they're quite pricey.

http://simplybearings.co.uk/shop/p15...duct_info.html

TS3 and I think Drumroll run on needles and do fine.

[typhoon_driver]

http://www.ebay.co.uk/itm/6800-Serie...item336b9d085c

Some thin ball bearings. Why are you looking at a 25mm thick shaft? 20mm should more than suffice.

Boner has needle rollers but I would prefer it had ball bearings

[Mouldy]

Quick rule of thumb is make the shaft 10% the diameter of the disc e.i 200mm disc = 20mm shaft... 300mm disc = 30mm shaft etc...

I'd never use needle rollers in a disc... They are high load on paper but don't seem to take impacts well... And ts3 doesn't run well on needle rollers... He's nakard a fair few now after the few fights he's had.

[maddox10]

For RW I prefer bronze bushings. Seems to work for me.

[limpet]

We had plain bearings (no roller just flat surface against flat surface) on 13Black, made from a material called ToughMet which we got from a mining company.
We originally tried van wheel bearings but they kept breaking.

[Dan-27]

I went with the thin ball bearings Gary found. I'll be using 2 aside, at a push I could fit 3 a side but we'll see how we get on with 2.

I turned that timing belt pulley to take a 25mm wide belt, but I might settle for 16mm. Would people advise against using the smallest 10 tooth T5 pulley for the motor? From what I can tell the drums are using somewhere around an 18 tooth on the motor, is this just to keep the material on the drum?

Hopefully the CNC work will be done by the end of the week, then I can start sweet talking metal hardening companies!

[PJ-27]

You'll want a decent amount of teeth in the mesh to transfer all that start up torque, plus too small-a pulley and you'll have a violent turn in the belt.