Removing a shaft

[Erfolg]

I am replacing a shaft in a Hyperion motor.

I have removed the rotor carrying the magnets, from the static component, along with the shaft. I have also removed the grubscrews which grip the shaft.

On removing the grub screws it was evident that loc-tite or similar fluid had been used on both the grub screws and the shaft, to secure them.

Mounting and supporting the shaft and rotor on a block of wood, with a hole to allow the shaft to pass through, the shaft has been struck with some authority. The shaft will not drift through, or move.

It is apparent that the loc-tite is holding the shaft in location very positively. I need o degrade the effectiveness of the loc-tite, But how?

[ken anderson.]

hello erfolg....i've never had a prob like yours..normally a knockometer..does the trick.......have a go at applying some heat to the shaft via...... your soldering iron...keep it in contact with the shaft for a few min's and then...give it a belt.......

ken anderson...ne..1 give it a belt dept...

[Anthony Billings]

Hi,

I too have used the heat method for releasing loctite and it works well.

Tony

[Tim Mackey]

Yup, localised heat.

[Rob Sten]

or use a bigger hammer!

they can be a really tight fit, just hit it straight on...or you'll bend it!

Rob

[Erfolg]

Heat to date has not done the trick.

I will retry, with heat and I need to locate a better drift, than the one I am using.

I have used a lot of force so far, the most difficult I have encountered so far, by a wide margin.

[Biggles' Elder Brother - Moderator]

Erfolg - can you try a homebrew version of a press? Make up a block of wood with a central hole, place block and motor in a large bench vice and....carefully squeeze! Even if you only get a little bit of movement it will break the grip of the threadlock.

BEB

[Erfolg]

BEB I have broken the grip as it were, I have driven the shaft the wrong way (in that I would have to drive the whole of the shaft through), driving the shaft in the right direction, it resolutely refuses to go move past the original position.

The shaft appears to be more of an interference fit than a transition fit.

I have heated the housing up. then gripped the shaft in a vice, then usi a gloved hand twisted the magnet housing. It will move a little, but on cooling seizes.

It is a bit of a beggar.

[Martyn K]

Hi Erfolg

Had a similar problem today. The way I shifted mine was to place the junction end on a ceramic hot plate until it was too hot to hold. Don't overheat or you will demagnetise the magnets. I then placed the rotor on 2 blocks of wood and then hit the shaft with a copper mallet -in effect knocking it through the long way - it only took a couple of firm taps to start it moving. Once I got it mainly through. I simply clamped the protruding shaft in a vice and twisted the rotor off using my hands. Nothing damaged and nothing bent. Last night I couldn't budge it.

Good luck

Martyn

[Simon Chaddock]

I would also preach caution with heat not only for the magnets themselves but also their adhesive.

I appreciate you have to work with what you have available but pressing a shaft out is a safer option. The shock of a hammer blow may also loosen the magnets.

Indeed as wood 'gives' a bit it actually requires a harder blow to break the joint than if the rotor was supported on a substantial metal block.

[Erfolg]

I guess all engineers think alike. In my case i certainly borrow ideas and perhaps strangely never feel any way guilty.

Whilst on a train going to London I did think back as to when i was an engineer, or at least thought I was, when i did reflect on how tradesmen would use pullers, heat, and a hammer. I then drifted how fly presses were used on assembly and dismantling tasks, by women on the assembly lines. How so called drill presses were from time to time, pressed into similar tasks. Finally i though of how engineers vices were also used.

Yes i thought, that is what I will do.

This evening when looking at the E-Mails, i see that BEB has had the same thought.

The long and short of it is, I placed the the wooden block in the vice (with the previously drilled hole), a 2BA screw (with end filed flat, from a dome) was then placed on the end of the shaft. The whole lot juggled into the vice. My high wattage wattage soldering gun set on the bearing housing.

Rather surprisingly, with very little force from the vice, the shaft was pressed out.

I did half heartly attempted to reinsert the shaft, no way will it go in. I suspect the hole is a very tight fit.

I have a new shaft on order.

Whilst on the train, my mind did briefly dwell on would the manufactures select a shaft based tolerance system of hole based? which had me thinking, once the manufacturing capacity sinks to a certain level, the ease of obtaining reamers and to some extent drills, for shaft based systems becomes more of an issue, As people say, thankfully the nightmare internal debate cease on the arrival in at Euston. I have however resolved to save some money and cease my institute and CEng contributions in the new year.

[Biggles' Elder Brother - Moderator]

Glad you got the shaft out in the end Erfolg. A little gentle, well directed, force - opps, I mean persuasion! - usually does the trick!

Don't give up you CEng - very useful for bullying - opps again, I mean persuading - companies you are in dispute with to take your complaint seriously!

BEB (CEng)

[Barrie Dav 2]

I use a block of wood with a hole drilled through to accept the pushed-through shaft and put the assembly in a carpenters screw 'G' clamp. This provides sufficient pressure to force the shaft through. Similar to the above 'vice' methods but it's portable.

[Erfolg]

Barrie, as they say, "there is more than one way to skin a cat". I applauded your ingenuity.

BEB, there was a time when I looked forward to the arrival of the IMechE magazine. Now I find that it is often either trivial, or used by vested interests to push a position, such as some nuclear power stratagem, as news. It has been for the magazine that I remained a CEng.

I have been considering the most effective means of reassembly. At the moment my thoughts are along the lines of freezing the shaft (maybe a pair of pliers to,) to -20 C in the freezer part of the fridge, whilst warming the housing bulge with the solder gun. Then quickly uniting the two parts. The engineers vice could be pre-set, with a wooden housing support block (to thermally insulate) to permit the quick application of pressure, to reassemble.

Normally I would not go these lengths, as the fit is normally a transition, rather than an interference fit.

[Barrie Dav 2]

Thank you Erfolg but I expect others have used this method too. I keep some short steel rods of various gauges to use as drifters when I need to remove a shaft completely. I should also mention that it's wise to use a thin buffer taped to the moving face of the cramp to protect the back-end of the shaft being removed/installed.

[Erfolg]

To be honest Barrie, I just miked up the shaft, then went into my BA screw hoard, selecting one slightly smaller diameter, happened to be brass.

I rarely change a shaft, so a dedicated set of drifts, would be a luxury, shear luxury.

Of course your approach is better practise and organised.