Bob, I agree that as a chain heats up, the metal expands, so it gets looser. But, I also grew up in the pre auto oiler days. The only time I ever saw a properly tensioned chain seize up was when we got new guys that didn't keep their thumbs pumping oil. Why would it get so tight that it seized, if it stretches? Is it because the bar rails expand too, clamping the drive teeth?
If the chain is left alone, correctly sharpened, tensioned and oiled it should not get so tight that is seizes.
When the saw is first started and used to cut the first thing that quickly gets hot is the chain which causes it to expand and become loose. The less oil delivered to the chain, the blunter the chain so the more the user hoiks on the saw the quicker the chain heats up.
The bar has more thermal inertia and so does not heat as quickly. It can take a minute or two for the chain to heat up and expand but it can takes 10+ minutes for the bar to reach its max temp.
If the chain is re-tensioned when the chain is hot but the bar is not when the bar catches up in temp the chain can be so tight that it will seem like its bound in the bar groove and it cannot be moved. The problem is even worse if the re-tensioning was snugger than usual.
The same can happen in reverse, If a hot chain is placed on a cold bar when the chain cools down it shrinks and can bind on the saw.
Unlikely I know but might be a problem in colder climates.
These problems I have only seen on bigger bars but it might happen on smaller bars if the chain is over tensioned.
I agree the most likely thing is that the saw ran out of oil or the oil pump is producing too low a flow rate.
The one thing I hate about trying to diagnose a problem from afar, is what you call a bit tight, and what I call a bit loose, are the exact same thing, and were just confusing each other. Has anyone ever made a tool or gauge that would clip on a chain to measure the proper tightness?
I have not see such a device and have thought about making something but like you I don't find tensioning the chain is a problem and it would just be another gismo taking up space in my shop
Off topic, hows the health going. I haven't been hanging out here as much as I used to, too many other projects. But I see you are posting quite a bit again and it's a cheer to see you back. To good health and old friends, Joe.
Health is OK. The doc found a strange ripple on my annual ECG so I was sent off for a heart stress test. This involves wiring you up to an ECG, putting you on a walking machine and you walk fast on a steep slope till your heart beat reaches 160 bpm for 5 minutes while they monitor the heart trace. The strange thing was that the ripple vanished while I was using the running machine. They found nothing significant. The sarcoidosis is still present but there are hints it is on its way down - I don't feel anything associated with this.
The major stress and time consumer for me in these last couple of months has been moving our 90 year old demented mum into an aged care facility that specialises in dementia patients. Mum has been living in an apartment in a sister's new very luxurious house but unfortunately slowly driving my sister nuts. I have 9 siblings, 6 that live locally, so we all pitched in to give carer sister breaks but that was not enough and what mum really needed was specialised care. Mum is physically fit, climbed up and down the stars at my sisters place 20 times a day, and spent up to 8 hours a day outside (often in 100 F heat) in my sisters garden. Amongst many paranoids mum developed, mum became paranoid about her (my sister's) plants not getting enough water, and getting too much sun so she was covering as many of the plants as possible with old rags. It was common to go around to my sisters place and find 3 hoses running with mum inside having a nap. The garden was actually often water logged and mum was running up many $$ in water costs for my sister (Perth gets most of its water from natural gas powered desal). Mum was also was constantly injuring herself in the garden and getting bitten by insects and bugs, including a poisonous white tailed spider, which left two fingers on her left hand partially closed. The other paranoia was that her children were all stealing her "stuff" including my sisters plants. Mum could no longer handle numbers or remember what she ate at her previous meal or even if she had eaten that meal, and would also forget to drink so was always getting ill from this.
Back in Jan my sisters and I visited a number of facilities and signed mum up for 4 of the better ones. We were told to expect a 6 to 12 month wait which we thought would give us enough time to get mum psyched up for the move. However a place came up two weeks ago at a facility that we rated equal best of the 4 we had selected and we had to snap it up while it was going. Of course mum didn't not want to go as she thinks she is perfectly fine. After much avoidance, ranting and raving mainly at my sisters, mum calmed down enough so we were able to take her in two days ago. So far she seems to be OK. This is huge relief to all of us although we recognise there is more to come.
