Help - broken dimple ring -could it be caused by new spring?

[newmark]

Hi guys,

I've never had a dimple ring/position ring break before, but have had 2 break in 2 days.

The only thing they have in common is with both, I have recently replaced the centre spring, as the springs we lacking tension. I didnt really pay much attention, but have noticed that where the original springs are "flat" at the top and bottom, the new replacements are not.

Could this put additional pressure on the ring, causing it to crack?

It could be coincidence, but it seems odd for 2 to break so close together. I even checked if the spray of PTFE I used could have caused the plastic to go brittle, but I've checked everywhere and can't see any mention of this.

The most worrying thing is, both of these broke when the machine was not even being used - they were stored waiting to go out, so the dimple ring broke by itself!

Any thoughts would be much appreciated, as if it could be caused by the new springs, I will need to get them out ASAP!

Thanks in advance, Mark.

[Siting Services]

Hello Mark

We have never come across a broken indexing ring. Being made of nylon these are extremely durable, and do not have a particularly overwhelming workload to perform! What maybe causing the indexing ring to break seems rather a mystery. As for the spring, technically speaking it should be correctly finished with a formed flat top and bottom to produce even pressure on the entire indexing ring, being cut off and unformed would mean that there would be a higher point of pressure where the spring contacts the indexing ring which would potentially make the indexing process slightly less efficient, but whether this would cause the indexing ring to break seems unlikely. Therefore the question is why is the indexing ring breaking to which having though it through Peter cannot proffer a potential cause.

He suggests you try modifying another 10 towers and see how you get on. We regularly solved the problem of reduced spring pressure with resultant weak indexing by putting the springs in a vice and extending their length by stretching. This simple solution cured weak indexing issues although over a period of time the process would need to be repeated as the spring lost its “memory”.

Regards,

Barbara

[newmark]

Many thanks Barbara, I have modified about 10 towers, so I will see what happens to the other 8. Luckily they are not on site at the moment, which is good as changing the ring on site would be a pain.

As you say, the rings seem very durable, so I'm surprised they broke. It seems they broke in 2 places, as with both the ring ended up in 2 parts.

On closer inspection, although the "new" springs are different, they still sit flat so I don't think that is the problem.

The only other thing, I don't usually use any lubricant but on a few I used a quick spray of PTFE dry silicon lube, which does not say it causes a problem with plastic, so I'm wondering if that would have caused any problems (however I have "googled" this extensively, and cant see anywhere suggesting it would not be suitable).

I am planning to spend some time tonight turning the segments a few times on each remaining tower and seeing if the problem reoccurs and will report back.

If anyone can think of anything that might cause this in the meantime, please let me know as it seems very odd! Oh, and I guess it goes without saying, but I checked the rings were good before I put them on, so they were definitely not cracked before they were installed.

I would hate for this to happen straight away on a new site, as it might be enough to get the machine kicked out straight away.

Thanks again,

Mark

[Siting Services]

Hi Mark

I have had a quick word with Pete and he says there is no need to lubricate the nylon indexing wheel as nylon is self lubricating and some products can undermine the molecular structure, although he doubts that the dry silicon lube you sprayed on it would have had that drastic effect.

Barbara

[newmark]

Hi Barbara,

Thanks for checking and speaking to Peter - to be honest I'm not usually a fan of lubricating anything (from my history with pinball machines, I know that lubrication can often do more harm than good, attracting dirt and dust and making a sticky residue). I only used the PTFE as I thought being "dry" it would be better, but I think tonight I will remove the rings and wash them off and replace, in case that that is causing any problems.

Thanks again,

Mark

[newmark]

Hi guys, I thought I'd report back on the broken dimple ring situation....

I've spent the last couple of hours dismantling and rebuilding the 10 towers I serviced recently, and of the 10 I found 5 in total had the cracked dimple rings - so it is positive that I discovered the problem before the machines went onto a site.

I am still very confused about the cause of them cracking though - there are two possibilities as far as I can see. All of the dimple rings were bought as used parts, so it is possible that they were already cracked and I didn't notice (it is only when you bend them that the cracks open up), although this seems unlikely as I would imagine the parts are checked before they are sent.

The other possibility is that the PTFE spray I used on these caused the crack. For the 5 that didn't crack, I washed them in warm soapy water and dried them before putting them back to try and ensure they do not crack, if it was caused by the spray. Again, this seems unlikely though as apart from the single crack, when I try and break them by bending them, they are still strong - you would imagine that if the spray made them brittle, they would snap easily - but they didn't!

The last thing it could be is the new spring (they all had new springs), although as Barbara said, they are made of tough stuff so the pressure of the spring should not be enough to cause a break.

My plan is to rotate them all several times at home each day before they are sited, and see if it happens again!

The moral of the story I suppose is that in future I will double check any used parts before I install them, and I wont use PTFE lube just in case!

If anyone has any ideas or thoughts on this let me know!

Cheers, Mark

[Central2vend]

Sounds like these were cracked when you installed the. Secondhand parts are often not checked and sent out faulty. Try to always buy new. Ptfe spray wouldn't have caused the problem as I have used this for over a year and had no problems whatsoever.

[newmark]

Thanks Central2Vend, that is certainly a possibility! I will definitely check all parts more carefully in future in case that was the case.

I'm just glad I discovered these before they went on site!

Cheers, Mark.

[newmark]

Hi all, quick update........

I have been to check the machines again since I replaced the cracked rings and washed the good ones, and can confirm that they are all fine since I've done this. So, this looks like the spring was not to blame (as they would have probably broken again).

So, still a bit of a mystery, but I'm slightly happier now as at least I'm more confident that that they will be ok on site :)

On another note, does anyone know where to buy new dimple rings, as I can only seem to find used rings for sale?

Many thanks,

Mark