Here is a list of all the postings William Ayerst has made in our forums. Click on a thread name to jump to the thread.
|Thread: Centec 2B - New arrival and Q&A|
Dave, You could not be further from the truth. I don't get a fee from anyone, I have no ad revenue, I have no people sending me donations, I have no sponsors or payments from anyone. I do (did?) all of this purely to document what I'm up to for the few people who care to watch me trying to learn what I can for model engineering and it takes SIGNIFICANTLY longer to video than to simply do.
I had written out a longer response but clearly it will fall on deaf ears. I am not sorry that I am making mistakes and I will continue to do so - because I have nobody to teach me, and it's been made clear to me that my questions are no longer welcome here.
Thank you again for your help and support, I don't think I'll be back.
Hello all, I wanted to post my results here but it's clear it's not welcome.
I really do thank you all for your advice, it really truly is appreciated. I am merely documenting my hobby and what I am doing on YT and I never have pretended to be anything other than a rote amateur in anything that I have done. I am not trying to give advice or instruct, simply sharing my experience with others.
Clearly, that is anathema to a certain perspective, where the only permissable content is that which is produced by experts. I truly am sorry that you see no value at all in the additional time I'm spending to create videos for the enjoyment and amusement of others. I do not feel ashamed at all in my efforts to bring what I am doing to a wider audience. If you feel like you can do it better, please step forward.
I hear a constant bemoaning that engineering is a dying hobby with an aging population - and if this is the reaction to someone who is patently not an expert, does not have an infnite budget in time or money, who is doing their best with the resources available in a medium that is contemporary to them - I can see why.
Edited By William Ayerst on 02/09/2021 13:03:36
Edited By JasonB on 02/09/2021 18:25:50
I bored out the pulley from 0.750 to 0.780 and the eccentricity is now removed. I found a sheet of 0.015" brass so used that as a sleeve, cut to π(0.750)-0.188 with a hole for the existing grub screw to fix onto the shaft and I'm pretty pleased:
It is a solid fit on the motor shaft with no play whatsoever.
I have noticed that the end caps for the motor housing seem to have integral lips to fit against the groove in open bearings, and I have ordered sealed bearings. Hopefully no dramas, but if not I'm not sure whether to send back the bearings for open ones, or shave off the lips on the inside of the caps...
Anyway, my slab cutter also arrived
Edited By William Ayerst on 12/08/2021 21:56:42
Thanks NDIY - ordered a pair of KSM (japanese?) sealed imperial bearings - figured I may as well replace both while I'm here - and components for a brace across the inside-rear face of the stand.
Ordered a pair of AX71 belts and an A35.5 for the VH just to be on the safe side, too. Based on your earlier advice I guess I'll knock up the support by 1/4" or so to reduce the tension a little?
I've got a line into a metal fabricator who I'm friends with who is prepared to make me up whatever I need for the motor supports, but it's likely to be a month or two - so I'll knock up some temporary legs for the back of the motor plate down onto the plinth to stop the wild oscillation for now, and get him to build me what I need - when I figure what that is!
Edited By William Ayerst on 11/08/2021 19:48:24
I meant to ask whether I should change both bearings, not pulleys, sorry
The bearing seems to be 3/4" ID, 2" OD, 11/16" wide. It is marked as 'Hoffman England Imperial NM M8 v2' so I assume it doesn't have a 20mm bore? With that in mind this looks like a drop-in replacement: https://simplybearings.co.uk/shop/p510033/Major-Brand-MJ3/4-Imperial-Open-Deep-Groove-Ball-Bearing-3/4x2x11/16-inch/product_info.html - but am I better off getting a sealed bearing like this? https://simplybearings.co.uk/shop/p42035/MJ3/42RS-Imperial-Rubber-Sealed-Deep-Groove-Ball-Bearing-3/4x2x11/16-inch/product_info.html or ebay: 253824082621 ?
SImply Bearings offer a C3 variant which seems to be over-size I/D clearance if I understand correctly? I guess I need to pull it before I order a replacement, eh?
I don't suppose you have any tips on which of the 7000 types of grease I should be buying as well? Learning so much today!!
On those lines I've got the spindle out of the motor and it looks in good condition. No obvious damage. The bottom of the inside of the motor housing (not sure of the terminology) seems to be smoother than the top? Not sure what that means but there's no damage per se to any of it.
Edited By William Ayerst on 11/08/2021 17:47:43
Edited By William Ayerst on 11/08/2021 19:18:36
Seems that the bearing cover on the motor comes off separately - it's grease filled from a screw-lid cup. The only noise at all is definitely coming from this bearing. However, there's no play at all in the motor spindle and though the surface is rough I can detect less than a thou overall runaround:
I removed the bolts on this side - they don't go all the way through. On the other side, the bearing cap is closed. Any ideas on how to proceed? Still worth replacing? I spoke to ABC and they suggested getting the exact spec of the bearing (I can just about read it under the grease). Like the pulleys, is it best to replace both? The other SOUNDS fine.
Edited By William Ayerst on 11/08/2021 12:00:39
Edited By JasonB on 11/08/2021 12:06:46
Just bringing this to the current page - any thoughts on the mount? I'm wondering if two wooden legs underneath the outside of the existing angle might give me be a short term solution while I'm using the mill to fix itself with proper mounting brackets, etc.
I'll get a picture of the motor shaft shortly - hopefully when I get it out of the case and have a look at the bearings.
From memory it looked a little rough but the key isn't a rattle fit by any stretch.
I don't want to question the knowledge here, but is it really possible that a 20 thou oscillation is causing all of this?
Edited By William Ayerst on 10/08/2021 12:33:00
The motor shaft diameter is 3/4" and the keyway is approx 0.080"/2mm deep and 0.200"/5mm wide. I assume with a <0.020" oscillation that I technically only need to remove about 50 thou - which would leave the keyway in situ but would require me to use sheet material bent into a sleeve rather than machining from solid, right?
What's the stator part of the case? (shame!) The motor is 1hp.
Re: balance issues - the motor was canted about 15 degrees out of parallel with the mill spindle - would that also be a factor?
Edited By William Ayerst on 09/08/2021 11:26:42
After a weekend in the (very wet) countryside camping and ruminating, I see I have three things to investigate here:
1. The Motor Mount Stability
While I'm trying to puzzle out the best way to brace the existing setup, I'm going to see if I can get new mounts fabricated from either my mate or my uncle (both of whom have fabrication facilities). If we were starting from first principles how should the motor mount look?
I sketched out Dave's idea a little - the hole/slot mounts in the top of the angle are opposing pairs for the hole/slot in the motor baseplate:
2. The Pulley Concentricity
While I'm fairly certain I could open the existing bore out to make it even more concentric with the outside of the pulley in my lathe, I don't have facilties / haven't yet ever cut a keyway, so I guess this is a non starter? If I were to proceed anyway, I would open the bore to 7/8" and chuck in some aluminium tube in there as a sleeve, and maybe use a pair of grub screws that would positively engage with the key slot on the motor spindle.
3. The Motor Bearings / Armature
For the sake of argument let's say if I'm doing all this, then I want to at least make sure the motor bearings are OK. Is there a way to determine which screws will allow me access? Further to that, what should I be cleaning and greasing them with? As mentioned, I lack a gear puller for now also...
Thank you again all for your help and support, I wouldn't be anywhere without you - hopefully you can put up with my silly questions for a little while longer!
Edited By William Ayerst on 09/08/2021 10:22:41
Right, so a brace across the full width of the inside-back, binding the corners of the stand to each other, and to the top of the outside angles? What material should I be looking at for this?
The bottom of the existing outside angle is about 2-3" from the bottom.
Edited By William Ayerst on 06/08/2021 18:08:02
I know this is going to sound stupid, but I've never taken a motor apart, nor inspected or greased a bearing before Where should I start?
Dave - The angle doesn't reach all the way to the base of the machine, but I see what you mean - a pair of right angle triangles with the hypotenuse as a support for the outside? This is what the setup looks like in diagonal form 'as is', I have added a light green line to represent the diagonal support. The outside pink L-supports are slotted, as is the motor plate to the support. The inside L-supports seem to only be acting as oversized washers to the outside supports, they don't support anything.
Is it enough to have the braces reaching down to the bottom of the existing outside angle, or should I replace the whole thing? I don't know how to weld so would probably be dealing with bolted steel angle for the brace, or asking a friend or relative to weld me up an entirely new piece.
Getting inside the base to unscrew the mounting plate bolts was hard enough with nothing else in there - I can't imagine how much of a pain it would be, with the motor inside!
Looks like the smaller belts are OK, but the longer from the motor to the spindle has a very slight set in it at one point. I could always get the second belt for the motor and replace both at the same time? The spec on the belt is "PIX X'tra AX 71 / X 13x1800 Li" - should I look to replace like for like? It seems fairly new...
This is what the motor mount looks like - bent angle and thick plate. There is more angle on the inside of the base that these are connected to - you can see the far one inside the hole:
I hooked up the motor belt while it was outboard of the stand. I appreciate there's nowhere near the same amount of torque being applied since its just its own weight holding the belt to tension, but there's not even a whisper from that end:
So, what's the best solution for this? I wonder if a cage or frame made out of angle that can bolt to the back of the mill but also rest/be bolted onto the plinth might work, rather than having it suspended in air? Potentially polyurethane bushes or something to stop vibration?
not done it yet - got myself a clarkson spanner and a 1" spanner to lock the spindle and sort the nut - much better!
I did a quick check before turning in for the night - the pulley is about 5 thou out at the bottom of the grooves and 20 thou out at the tops (and at least one end). There is about 5-10 thou slop in the fit on the motor axle which I guess is where that's coming from? I can clock up the pulley in the lathe - but maybe more straight forward to shim it opposite the grub screw?
Either way I'm not sure how 1/2mm of misalignment could cause the sounds that I was hearing tbh?
Next plan is to see if I can get the belt hooked up while the motor is off the mounts but otherwise stable, to see if that was where the 'big noise was coming from, and then to get inside to look at the bearings (what to flush/regrease with, if open?).
Right you are - it slid right off. Motor axle is straight as an arrow - less than a thou out at the tip by my dial indicator. The pulley is 3/4" bore, with two vee grooves - minor dia 1-5/16", major dia 2-5/16". It looks like it has been bored, or the factor finish wasn't great. The axle has some score marks on it near the key.
I reattached the pulley and it was wobbly again.
I guess this means the noise in the motor may be the bearing, but it's not gone enough to affect the play of the axle?
Is it safe to rest the motor on the chip tray / etc. with a belt on it to see if the knocking/tapping is reduced/removed ? That might tell me if the sound is coming from the motor mounting arrangement?
OK! One step at a time, then!
I guess a gear puller to get the pulley off? Something like these? https://www.amazon.co.uk/Puller-Bearing-Removal-Internal-External/dp/B01CIEUXQQ/ ?
An example of the original knocking/tapping sound with the mill in use is in this video - timestamp from 0:23
No cracks, got the motor out and gave it a run with and without power - there's a faint scratching as it rotates - I'm not sure if this is the same as the rhythmic sound it gives out when the belt is connected - it seems to be once per revolution and I think that'd probably come out as a shriek or whirr at normal RPM?
Either way, here's the video:
I've not the faintest on how I might go about doing anything about this, is it best left to a specialist or is there something obvious I can check?
The motor baseplate was 'skewed' on the L-brackets with relation to the axis of the motor and pulleys.
Edited By William Ayerst on 05/08/2021 16:11:13
Hmmm! What to do? Presumably take the motor off and see if anything obvious is going on there?
Is it worth putting the motor back inside the chassis? I'm not sure what the original arrangement would have been!
Edited By William Ayerst on 05/08/2021 11:34:57
Righto, I've done some troubleshooting - slowing the mill right down, the sound which was like knocking at high RPM becomes more like a laboured 'whrr' sound at one point in the revolution.
I took some video of the various configurations:
It sounds like it's coming from the motor end of the main belt. It is audible even when the main horizontal spindle is rotated by hand. Without the belt connected the motor is quiet at all speeds.
The previous owner moved the motor mount to outside the base for easier access (and in full disclosure he said that this might need looking at) - it is bolted to the sheet metal outside. While it's not going anywhere, it looks like it's subject to a fair amount of vibration and oscillation. Were that the fault I'd not expect to hear the 'same' noise when turning over by hand. Maybe there is some misalignment or something?
I'm not really sure how to troubleshoot this one!
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