Exhaust fan scraping upon lights on

Hello!
I have a 6 inch hyperfan, the model built into a silencer.
I recently switched from LED cobs to HPS to help warm my little tent in the winter.
When my hps comes on in the cold morning, the warm air negatively affects my exhaust fan.
For about five minutes, it makes loud scraping sounds.

Any ideas for fixes?
Ponderings on the cause?

Something lodged in there or a blown bearing if they use them. I have a similar fan, 8" Airforce 2. It doesn't make any difference if its warm or cold, it doesn't scrape. Its been running for years non stop. If the fans running all the time then maybe a crack in the housing which is expanding when warm? Weird though. Defo not something that should be happening.
I would contact the manufacturer and explain the situation, if anyone would know it would be them.

Something lodged in there seems unlikely, I've only used it with a carbon filter.
A blown bearing! Gosh that would suck. It might get worse!
A crack in the housing which is expanding when warm? Maybe - I'm thinking along those lines, heat expansion problems.
Yes I think I will write in to the manufacturer, that's a good idea

I thing of 2 x 2 variables that could cause this

heat expansion
air flow stabilization(as the fan ramps up, the air flow is not uniform)

bearing
leak/crack in housing/duct


It could be 1 of any or 1(or more) from each group(different permutations).

Eliminate the heat and take off all the ducting. (a.k.a take the fan out setup and test it when it's cooled off)

Is it a bearing?

Remember bearing problems could cause an imbalance in your blade turning(that isn't visible with the nakkid eye)... all the time OR only at low speeds. Although it may not screech all the time, it still could be a bearing starting to fail...

Just some thoughts... good luck!

Good thoughts MJCanada!

I don't think it could be "air flow stabilization" alone, it would have to be paired with heat expansion - I can play around with the speed during the day or night fine, when the temps are steady. It doesn't make any noise like this when I take it gradually from low to high or do anything.

Also! In the few minutes after lights on when it's noisy, I can play around with the speed, trying low, high, anywhere inbetween - nothing stops the scraping noise, until it dies off after a few minutes. (But I haven't done enough testing to tell if cranking it to full speed etc. shortens the scraping period.)

Do you reckon this testing eliminates the need to take off all the ducting and test it isolated?
From a testing perspective I suppose I'd be hoping to hear it scraping in some scenario isolated from the heat, but I don't think I will.

MJCanada said:

it still could be a bearing starting to fail...

Click to expand...

That would be terrible, it's only about six months old and I love it

Take a video of the issue and post a link....YouTube Facebook etc? If possible

its a rat running away from the lights.