Need Help!- Medium speed brushless spindle..Opinions needed!

[tskguy]

Hi all,

Well I just started the process of building a spindle very close to the one in this link.
http://www.metallmodellbau.de/Eigenb...salspindel.php

I plan on using a RC brushless motor and controller combined with some AC super precision bearings. I have pretty much figured out everything except for the actual housing. I cant decide between stainless 304 tube OD 1.5" id 1.0" or 1117 steel rod that I would machine to accommodate the collet holder and bearings.
Pretty much just like the guy on the link did. With the stainless I would just machine down the id to except the 32mm OD bearings.

I guess my question is what material would be best suited? The 1117 steel is easy to machine but would it be hard enough? Or is the stainless to thin of a wall after I machine the ID to 32mm? I really cant decide!! Of coarse the steel is much cheaper.

Any help would be greatly appreciated!!!

Eric

[Herbertkabi]

Tube OD 1.5" id 1.0" ... 3 mm wall ... not at least for me - bit too thin. Although I have some elder spindles made by famed makers wheres this wall even thinner.
Perhaps for some kind of hobby, then even aluminum is OK and no needs to spend money for ACSP bearings, but for serious job - I do not. Experience says you will tear your hair when detected that your neatly made piece is not rigid and goes easily to resonance, this is especially ailing because spent some AC super precision bearings.
This is just my opinion.
Sure enough there you can see very different opinions and understandings about:
http://www.cnczone.com/forums/showthread.php?t=90495
http://www.cnczone.com/forums/showthread.php?t=12184
http://www.cnczone.com/forums/showthread.php?t=10695
http://www.cnczone.com/forums/showthread.php?t=106904
http://www.cnczone.com/forums/showthread.php?t=103610
...

And dont select wrong motor!

Regards,
Herbert

[tskguy]

Herbertkabi,

I have actually read most of your posts and I have also studied most of your drawings as well.

I now understand that the wall will be to thin with that stainless. Do you think 1117 steel work with a 1.75" OD with me machining the ID to fit the collet holder and bearings? I would rather use stainless but I am having trouble finding stainless with a thick enough wall. I suppose I could use solid stainless 304 rod but I am a little scared to try and machine it!!
As for the motor I fly rc helis and I am very familiar with quality motors. I am actually considering a neu brand 1907H/1.5Y 915KV at 30v and a 2 to 1 reduction. The bearings are NTN Super Precision 7201CDB/GNP5 for the collet end and a single double row AC for the other end. I already have the ER16 spindle and it looks like it will work well. I have plenty of brass and delrin to use for spacers and such. So I should be good there.
Please let me know what you think…

Eric

[Herbertkabi]

Common steel inclines to rust, thats because stainless mostly used. At that for most of people when no grinding equipments, there is easier to machine exact dimensions fits with bearing. I do use both - steel and stainless. Steel, when all is perfectly finished, I do oxidize, using my own method I have described somewhere in this forum.
1117 is carbon steel, Cold Roll Steel ... why not, I would do it -> machining, then hardening, then grinding exact dimensions and then oxidize what by my methot means
annealing as well.
Im sure you are very familiar with quality RC motors, and NEU is good, but NEU like the Plettenberg HP370 innerrunners have very hard cogging - I would rebuild it (when no expierences about then better not to try ;-) When you surely decided belt drive then Plett HP 300/20 (/25.../30) - well balanced, built in cooling and there cogging is bit more discreet. Or ... very smooth and well balanced Plettenberg Orbit outerrunners are perfect for belt spindles. You need to protect any motor from dust and chips, thats because I do only built in direct drive spindles.
But OK, NEU is very good motor as well and at that - you Boss!

Cheers,
Herbert

[tskguy]

Wow dude those Plettenberg motors are very pricey!!!
I have to try and keep the price as low as possible or I would have just purchased an already made spindle! DIY is fun but for me 50% of the reason I do this is to keep the cost low. You mentioned aluminum as well do you think an aluminum case would work as well?

I am keeping an eye out for some motors on ebay. Hopefully I can get one for a good price.

I have a question for you regarding a piece of your design. I noticed that you have a rear bearing cup that slides in to the stainless housing. Why didn't you just machine the ID the housing to fit the bearing? Is that a clear question?


Eric

[tskguy]

Well I pulled the trigger on a solid piece of 303 stainless. I figured it would perform the best.

I have been reading as much as possible on how to machine this stuff. I hope it turns out well. I worry the most about grinding ID for the AC super precision bearings. I have also read extensively on that subject as well but haven't figure out the best grinding wheel for the job. Should I go for a diamond bit?
Any one have any good ideas?


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