Thanks: 0
Needs Pictures: 0
Picture(s) thanks: 0
Results 1 to 13 of 13
-
21st August 2014, 10:12 PM #1Intermediate Member
- Join Date
- Feb 2010
- Location
- Beaconsfield Upper
- Posts
- 31
Suggestions for making 3 concentric axles
Greetings.
I want to build a large orrery (mechanical display of the planets orbits, google it) and I find that I need 3 independant rotating motions on the one axis. This is usually done in orreries with precision telescoping brass tube, like from K&S from hobby shops, but what I am building is large, and heavy, a few kilos, but rotating very slowly, the fastest will be 1 rpm. The axis is vertical, most of the load is vertical but the drive will give a bit of side force. Since I have no lathe (but I do have a drill press) most of my work is with steel and I tend to weld things together a lot, just with tacks if I might want to dismantle it one day.
What I am thinking is to use the black industrial pipe available from steel suppliers 15NB, 20NB & 25NB (medium wall thickness) (OD's 21mm, 27mm, 34mm) which from the pipe tables are a reasonable fit inside each other, maybe 0.5mm clearance, and just grind off the high spots until I have tubes that all turn with no binding. Is there any reason why this won't work? Then lots of dry lube to keep it turning freely (grease attracts dust which turns to grinding paste).
-
21st August 2014 10:12 PM # ADSGoogle Adsense Advertisement
- Join Date
- Always
- Location
- Advertising world
- Posts
- Many
-
21st August 2014, 10:57 PM #2GOLD MEMBER
- Join Date
- Nov 2011
- Location
- Sutherland Shire, Sydney
- Age
- 71
- Posts
- 1,301
Assuming you only need short lengths of each pipe, try and get some offcuts of seamless pipe from a pipe fabricator who works for the oil or chemical industries or maybe hydraulic pipe people. The alternative is ERW pipe (electrically resistance welded), but this will have a bit of an internal seam which may cause you problems. Seamless pipe is used where the end user will not take the risk of a welded seam letting go (most unlikely, but I have seen it happen). Both pipes have the same general dimensions and pressure rating, but most oil refineries in Australia won't use ERW pipe in critical areas, and some won't use ERW on their site unless it is galvanised and therefore easily identified and then only for water or air reticulation.
Good luck with your project,
Alan...
-
21st August 2014, 11:04 PM #3
I made a cement mixer using pipe inside pipe for the drum pivot and rotation, many years ago. It still works perfectly. I have seen tables from steel manufactures that list various sections which fit inside others for sliding fits. What I remember was square section from memory, but I am sure the same would be available for round tube/pipe.
Dean
-
21st August 2014, 11:43 PM #4Pink 10EE owner
- Join Date
- Aug 2008
- Location
- near Rockhampton
- Posts
- 4,304
The ID of your standard pipe is not smooth, as the welded seam protrudes inside..
Light red, the colour of choice for the discerning man.
-
22nd August 2014, 12:36 AM #5Senior Member
- Join Date
- Oct 2008
- Location
- blackburn vic
- Posts
- 221
Brass Tubing
Go see George White in "Springvale"( or somewhere near there). They will have heavier brass tubing than the hobby stuff.
Roger
-
23rd August 2014, 03:28 AM #6Intermediate Member
- Join Date
- Feb 2010
- Location
- Beaconsfield Upper
- Posts
- 31
I know George White. Where I work we design industrial power supplies and the workshop guys are always popping over for some copper shim or sheet. I have bought lots of scraps from their scrap bin in the past.
However whilst having brass sleeves would be a very good solution, the project is for a rural sculpture contest where the materials should be as found on the farm. Steel pipes are believable, but brass would just look too good. Besides the rest of the creation is steel, and I don't want to be brazing as I don't have a torch.
So thanks for the idea.
TomH
-
23rd August 2014, 03:32 AM #7Intermediate Member
- Join Date
- Feb 2010
- Location
- Beaconsfield Upper
- Posts
- 31
Aha! I learnt a trick from a farm mechanic to fix this little problem. Put a length of rod in your drill chuck. Tie a bundle of rags to the end slightly larger than the pipe. Then tie some strips of very coarse emery paper (40g) to the rod so that they hang over the rags. Then run it up and down the pipe a few times. Cuts off that pesky seam.
-
23rd August 2014, 03:34 AM #8Intermediate Member
- Join Date
- Feb 2010
- Location
- Beaconsfield Upper
- Posts
- 31
-
23rd August 2014, 03:36 AM #9Intermediate Member
- Join Date
- Feb 2010
- Location
- Beaconsfield Upper
- Posts
- 31
-
23rd August 2014, 05:46 AM #10Intermediate Member
- Join Date
- Feb 2010
- Location
- Beaconsfield Upper
- Posts
- 31
-
23rd August 2014, 09:52 AM #11
No, I used a
zirksorry, grease nipple in the middle of each section. The first time I had used a grease gun in years was when I got the mixer ready to cement the lathe foundation. Grease nipples are very "rural" and the grease sitting at the ends will keep out any dust.
Dean
-
23rd August 2014, 10:56 AM #12Pink 10EE owner
- Join Date
- Aug 2008
- Location
- near Rockhampton
- Posts
- 4,304
-
24th August 2014, 07:09 PM #13Intermediate Member
- Join Date
- Feb 2010
- Location
- Beaconsfield Upper
- Posts
- 31
That is such a good idea Dean. Low tech solutions I like. Agricultural engineering used to have lots of grease nipples, when I was young I did a week helping a farm mechanic, he was so keen on his grease gun that was his nicname "greasy". Since I have concentric axles I shall make a cross hole to allow the grease to flow in to the inner axles.
I have just spent the day making the axles run nicely, I made a hone with a very powerful Sher drill (Aussia made!) with a rod with floor sanding paper wrapped round it to clean up the insides of the sleeves until they all ran true. Then it started raining.
Thanks for the help!
Similar Threads
-
Making a pizza paddle - suggestions?
By surfdabbler in forum WOODWORK - GENERALReplies: 5Last Post: 29th May 2013, 12:12 AM -
Router bit not concentric
By Tiger in forum HAND TOOLS - POWEREDReplies: 4Last Post: 29th July 2012, 12:26 AM -
Suggestions for multiple gift making
By Tiger in forum WOODTURNING - GENERALReplies: 13Last Post: 16th December 2008, 08:57 PM -
Concentric bowls and spheres
By RFNK in forum WOODTURNING - GENERALReplies: 1Last Post: 4th May 2000, 08:51 PM -
Concentric bowl systems
By RFNK in forum WOODTURNING - GENERALReplies: 0Last Post: 20th April 2000, 01:51 AM