Here is a list of all the postings gerry madden has made in our forums. Click on a thread name to jump to the thread.
|Thread: Wilding’s tower clock|
Yes go for it ! It's a well thought out design.
The only advice I would give you is to make sure you understand how it all goes together before starting and get to know what's a flexible dimension and what is not.
I'm working on this clock at the moment but before cutting metal, or even buying metal, I've decided to create a full assembly drawing so that the whole design is clear in my mind. I don't plan to spend time on matching the exact form sketched out by Wilding so my drawing allows me to see quickly how I can modify, cut corners, save some cash or time. I did see a video somewhere where the builder bought some oversize brass for the front and rear frames then proceeded to cut slices off each with a slitting saw just in order to meet some arbitrary dimension in the plans. I really don't want to make work for myself doing things like this. Life is short enough as it is !
I also plan to metricate all the components to make life easier. I don't know about you but I find it increasingly difficult to decide quickly whether 27/64ths is bigger or smaller than 10/16ths, and by how much ! There are endless conundrums like this to contend with and plenty of opportunity in my case for mental aberations.
oh yes, I'm also thinking of ditching the gears and going for timing belts instead. I know that will up set a lot of people but I like to explore crazy ideas sometimes.
|Thread: Model Turbines|
Excellent to hear Robert, I never realised this was independent of speed ! Now I can check the efficiencies of some clock gear-trains and measure my improvements
|Thread: Cookerhood sound reduction|
Neil, thanks for clarifying that It reminds me of my ex-colleagues in Denmark that used to tell me that tube was flexible and pipe was rigid !!! All we need to do is get builders supplies catalogues on side and we'll all know what we are doing
….. and yes I have a smooth pipe ! Only issue was I drilled a hole with a 150mm core drill only to find that the standard "150mm" tube wouldn't fit through it. I had to use a 150mm sleeving which brought my bore down to 146mm ! Why do these plans always go wrong in the wrong direction instead in the right one ???!!!
Hi Sandy, yes most cooker hoods are a complete disaster as far as noise goes. That why I started to build my own. With the top notch ones costing around £2000 I didn't think I could go too far wrong. But as its pointed out to me regularly " this has been going on for 3 years now. When will it be finished?".
There shouldn't be much direct vibration coming into the hood as the fan unit is now reasonably isolated on the outside wall. But the hood is a shockingly flimsy thing and it wouldn't take much to set it off, so the lumps of lead should take care of that. At the very least the lead will stop it sounding so 'cheap and narsty' when you press the buttons to switch it on, set the speed or turn the lights on.
But there is plenty of airborne white noise coming down the pipe and when that gets into the hood it will just bounce around and be focussed down to the cooker methinks. I'm hoping that the acoustic layer will take care of some of that. I probably need a to put a horizontal baffle in front of the exhaust port too, thinking about it.
This project is very much suck-it-and-see and with hindsight I should have perhaps gone for an even bigger fan but as they say, experience is all about mistakes. I could still come back to that later when I run out of things to do!
Adrians acoustic sheeting is 'said' to be suitable for engine bays so hopefully it will have sufficient temperature resistance and the aluminised coating will make it cleanable to a degree. If not, I can rip it all out and think of something else.
Thanks for your comments chaps ! I have some lead sheet so I will place some of this in the centre of each panel and will cover over with some Adrian's acoustic sheeting. Perfect !
Dave it could never be too quiet, but sucking all the heat out of the house is a possibility! Initial tests show that on full speed any room door not properly closed is pulled open by 5 inches ! Its a good job my boiler is in the attic !
I'm continuing to make improvements to my horrible 'Luxair' cooker hood. I have already moved the fan unit outside along with hopefully most of the noise and vibration. Now I want to reduce the structural vibrations of the oil-drum-of-a-hood. You can see it in the pics below:-
I was thinking of gluing some 3/16" plywood in to the insides to stiffen up the large surfaces. But I also like to try to absorb some of the higher frequencies coming through the airstream from the external fan. I suppose I could try drilling a million holes in the plywood but if I can buy some stick-on material that has a proven effectiveness I think I'd prefer to go this route to save time. (I'm already being warned that this job is taking too long )
So, does any one have any experience of a stick-on material that will stop panel vibration, acoustically absorb and is obtainable in a 'domestic' quantity please ? mmmm ...as I write I'm thinking such a thing might quickly get clogged with grease....
|Thread: Drilling depth|
I will be making a shaft around 6mm diameter and around 130mm long. To keep the weight down I'm thinking of drilling out the centre but as we all know drills can wander off line. I can attempt to minimise this with a good quality drill, a good headstock~tailstock alignment, good collets and with lots of pecks.
With say a 3 or 4mm drill, how deep do you think I could sensibly go ? I'm not worried about the strength of the shaft, a little about eccentricity but more drill breakage.
|Thread: Drilling carbon fibre|
oops, when I referred to 'extrusions' I did of course mean 'pultrusions' ! I was involved in some discussion on rubber parts just before I wrote my reply and the wrong term was clearly still stuck in my mind.
John, yes my rod is solid 8mm by 5mm, and I have been pondering the connections. I constantly wrestle with functionality versus appearance. A cnc-made elliptical hole would be the most elegant solution, with ugliest being a press-fit into an epoxy-filled circular hole. I did wonder if I could carefully drill the rod along its axis and glue something in this hole but these pultrusions split like a banana with very little encouragement when given any significant internal pressure. I might need to do a trial or two on this idea first.
I'm planning an elliptical pendulum bob too, filled scraps of tungsten, not to match the rod but to minimise drag of course. I might bond the rod directly into this then I only have one connection to worry about at the top.
I'm in no rush to decide these details just yet as there are just so many things to think about. By the time it's finished this clock will bear about as much resemblance to JW's small tower clock as I do to Donald Trump.
John, I'm pleased you asked this question ! For my project (Wildings small tower clock) I have purchased some elliptical section CF rod with the aim of maximising the Q. Sadly this elliptical rod was only available in extruded form and I know from previous experiences that extrusions don't always drill well. In extruded form the fibres are all aligned so it has great strength but not much in the other. And there is very little resin separating the fibres. So it tends to get torn where the drill cutting edges move at right angles to the grain direction.
Of course, a lot depends on what quality of hole you are looking to achieve. A sharp carbide drill running at the highest speed with minimum force might give you a good enough result. But although I haven't tried it myself yet, a diamond burr, as suggested by Versaboss, would probably be even better as a diamond burr doesn't have one big ugly cutting edge.
Epoxies work well on CF extrusions which have almost no resin on the surface, (or in the material for that matter) so the glue can get right onto the fibres. I think I would be inclined to try put some epoxy in bore and on the outside surface you intend to drill to minimise tearing.
Personally I'm considering no drillings at all in my elliptical rod. I will bond metal fitting on to it and drill these. I'm hoping that metal parts will compensate for the small negative expansion coefficient of the extruded rod but I have to admit to not having done the sums yet
|Thread: o-ring groove in plate|
Such things do exist ! Great. And now I know what they are correctly called I have been able to search more sensibly and I see even Cutwell advertise them. Thanks all for your assistance.
Howard, the plate is actually part of a small propeller hub. I'm actually building a balancer unit for it but didn't like the fact that the plate was a clearance fit on the mounting boss. This would lead to a loss of balance, not much if one does the maths, but I cant forget such things especially when it can so easily be mostly eliminated. The O-ring will allow assembly but help maintain concentricity until the bolts are tightened is probably the most elegant solution - in my mind at least .
I have an aluminium plate 4.7mm thick and it has a 25mm dia hole in it. I would like to machine an O-ring groove (around 2 x2) in the bore of the 25 hole. What I imagine I need is a boring bar with a parting off bit coming off the bar at 90 degrees to its axis.
I don't have time to make such a beast - even self isolation wont give me enough time to do all the jobs I have to do - so I'd like to buy one. Thing is, I can find on any of the popular sites anyone selling the thing that resembles what I think I need !
Would anyone be able to point me in the correct direction ?
|Thread: Lathe levelling|
Gary, I think I would agree with you. The saddle slope should be a reflection of the bed slope.
I suppose in using the saddle one could get some small 2nd order errors creeping in, but these should be negligible in my mind, and certainly no worse that putting blocks (which have their own inherent geometric errors) in slightly different positions each time one makes a measurement along the bed.
|Thread: Wilding's Small Tower Clock|
Can the moderators correct the title so as we don't confuse people for the next ten thousand years ?
Ahhh yes Michael. I was wondering how long it would take for the deliberate error to be spotted ! I think I must have been mixing things with 'John Wild', the clock man in Sheffield. ...Damn corona.. playing havoc with the brain cells...
I have embarked on the above to keep me busy while the world goes into lockdown. Right now I'm drawing it all up so I can see properly how it all fits together. I plan to make a few "upgrades" (time will be the judge of that!) but there's also a few things that I don't quite understand. For example:-
1) On the pallet arbor there is no bearing bush on the pendulum end. The shaft runs directly in the apron. If it's because there is little load on this shaft, he could have done this at the other end but he didnt. What am I missing ? (I think I might try PTFE here anyway.)…..ahhhh as I write its just occurred to me that this might be his way of being able to adjust the end-float for the shaft.
2) The crutch assembly comprises of a fulcrum block and an arm. There are beat adjusting screws on the arm which move the fulcrum block. Then on the fulcrum block there are adjustable crutch pins to take out the play. My simplistic thinking is that the two parts (arm and fulcrum) could be one, with the beat adjusting screws made to do both beat and rod clearance adjustments. Again, what might I be not seeing ?
3) Instead of wood, I thought I might use good old Tufnol for the barrel. Any negatives, apart from cost ?
|Thread: lathe spindle runout|
Martin C - ha ha, its true. I spend my day being pragmatic and cant stand others who delve in to things that really don't matter. At weekends I like to chase perfection for fun even when its stupid, which is most of the time
Nigel B - you are absolutely right. NRR or non repetitive runout is often caused by rolling element size differences or shape errors. Its non repetitive because their own rotational speed relative to the raceway surfaces, and their speed around the bearing is not synchronised with the ring rotations. so they can produce almost random-like motion in the rotating shafts. NRR used to be a big challenge on computer hard-drive spindle brgs where precision was all, but I have never heard of it being and issue in big brgs before. Good to hear about your case.
I have just rechecked my spindle face axial runout with the 'Hoppers Elephants foot' and it has really cleaned things up. Here's the set up:-
And here's the results:-
The spindle was turned by hand and the DI was pulled back to go over the bolt holes. I was careful not to touch the slides, (which I forgot to lock down anyway!)
There is an obvious underlying runout but there is also clearly a non-repeating element to the figures of around half the magnitude of the fundamental. As was suggested by Michael G, with a very fine and slow grind, one could remove another micron or two from the repetitive runout but there is no simple way of removing the non-repititve part without improving almost every other part of the machine. Its difficult to say precisely what's causing the NRR but the main contributors have to be the drive train and bearings
When I got the machine the belts (6 ribbed poly-vee) had a pronounced sets moulded in and these caused an audible bump every time they hit one of the pulleys. So I sliced the belts into two 3-ribbed pieces and staggered the moulding inconsistencies. This really reduced the noise and although I didnt think of it at the time must have helped the true running of the spindle. Perhaps there are some better belts available which wont cost an arm and a leg. Of course runouts in the pulleys themselves will cause load variation too.
As for the bearings, these are just standard precision eastern European taper roller type. There is no point in using a better quality product as I already know the housings are quite poorly machined. It makes no sense to put a good bearing in a rubbish housing because the geometric errors just get carried through to the raceways. I have actually wondered about replacing the TRs will ball bearings as a simple "upgrade". I know some people will frown at this say that its going the wrong way, but the advantage here would be that because the balls are more compliant they will absorb some of the geometric irregularities instead of passing them straight in to the spindle.
I'm certainly not going to be short of things to do when retirement arrives, that's for sure ! But for now I think I've just about done as much as I can with the spindle on this bag of old nails, short of speeding real money.
Hi Hopper, thanks for your comment.
The spindle bearings are fine. They are taper rollers and positively preloaded. With the spindle stationary, using the micron DI its easy to see the elastic deflection as one pushes and pulls the spindle axially. Rough estimate was that the deflections are about 2um/Kgf in both directions and it returns exactly to the centre position when unloaded which confirms no clearance in the assembly.
That's deflection figure is probably a bit too compliant for TRs so I suspect that a good part of that elastic deflection is deflection in the aluminium structure walls in which they are mounted.
Absolutely agree on the elephants foot. I didn't think of that ! Will give it a try later.
Thanks all for your comments. I have to admit to having a bit of a thing about precision so I would have probably given it a go anyway . I did however try to measure the actual runout first but that wasn't that particularly successful due to pretty poor surface finish on the flange. But overall it looked to be about 5um including the chatter. So I proceeded to make a very light cut starting on the bolt pcd then moving in and out to cover the whole flange. Considering the lightness of the cut I expected to see areas appearing that were not cleaned up. But there weren't any, which suggested that either the depth of my 'fine' cut was of the same order as the runout (or far bigger of course!). Anyway here was the result:-
The intermittent cut from the bolt holes wasn't detectable at all and I was careful not to touch the spigot diameter. The 0.2 rad on the tip appeared to match the existing one quite well too. I then tried to remeasure the flange runout like this:-
...and guess what.... it wasn't much better than it was before despite the significantly improved surface finish. What I could see though was that the runout was absolutely not synchronised with the rotation of the spindle. So there are literally other forces at play here - possibly variations in drive belts or drive train making the spindle do strange things.
Well no harm done and a few things leaned. A good way to finish a wet Sunday.
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