Read Gum dust and Stihl HD Filters

[husq2100]

One would think so, but it would be fair to say that a 371/372 would have a similar size ratio and setup to a 385/90, or even a 395.

Increase the cubic capacity and efficiency of a 372 (throwing that ratio out of whack) and the filter performs no worse and still better against the 385/90.

im not quite understanding???? are you referring to the size of the filter in relation to cc???

if so its not the size but the media...if the media is the same for a 346 through to 395 say, then size wont help totally if the air is being sucked harder.....Im guessing that the media is designed to work at certain verlocities for a given partical size.....

This is gut feeling engineering....no science or knowledge being applied

 

[imagineero]

I took the HD2 part number into my sydney tools guy, he said $65 and can get them in a couple days. I'm just going to have a little think about that, but in the end I'll probably cave and get one for my 044 as well....

You guys with all your complaints of dust. All you need to do is file your rakes down an extra 20 file strokes or so, and you'll ahve nice big chips instead of dust :hmm3grin2orange:

And while we're on the subject, what do you clean your saws with stihlman441?????

Shaun

 

[AUSSIE1]

im not quite understanding???? are you referring to the size of the filter in relation to cc???

if so its not the size but the media...if the media is the same for a 346 through to 395 say, then size wont help totally if the air is being sucked harder.....Im guessing that the media is designed to work at certain verlocities for a given partical size.....

This is gut feeling engineering....no science or knowledge being applied

Yep.

I tend to think so regarding the media. It seems to be the only logical answer.

The woodland pro/372 filter is performing as well as the OEM.

I think I have a Woodland pro 395 filter here it would be interesting to see how it performs against the inadequate OEM 395 media.

 

[AUSSIE1]

What do you clean your saws with stihlman441?????

Shaun

A Gerni!

 

[MCW]

One would think so, but it would be fair to say that a 371/372 would have a similar size ratio and setup to a 385/90, or even a 395.

Increase the cubic capacity and efficiency of a 372 (throwing that ratio out of whack) and the filter performs no worse and still better against the 385/90.

I could be wrong Al but I think cubic capacity and rpm is all that effects the "sucking" power of a non forced induction motor - a 2 stroke motor is nothing more than a positive displacement air pump. A bigger motor at the same rpm will always pull more air. If a 390XP is 20% larger in capacity than a 372XP then the 372 needs to be turning 20% more rpm in the cut to suck the same air - I'm sure your modded 371XP is capable of that though old son. What you did to that saw is illegal in most states and territories.
I can however see your point that if the filter area is 20% less on a 372XP compared to a 390XP then there is the possibility that the same pressure differential across the filter media can be produced.

 

[MCW]

A Gerni!

More like cotton wool buds, Mr Sheen, and some car polish.

 

[Stihlman441]

I took the HD2 part number into my sydney tools guy, he said $65 and can get them in a couple days. I'm just going to have a little think about that, but in the end I'll probably cave and get one for my 044 as well....

You guys with all your complaints of dust. All you need to do is file your rakes down an extra 20 file strokes or so, and you'll ahve nice big chips instead of dust :hmm3grin2orange:

And while we're on the subject, what do you clean your saws with stihlman441?????

Shaun

Can tell ya, but if you get really close to Matts 660 you may still be able to smell it.:hmm3grin2orange:
Anyway you would not beleive me anyway.

 

[imagineero]

I think it's one of those KFC 11 secret herbs and spices things - does the guy have his own secret proprietary polish? I think you're spot on with the cotton wool buds, but I'm pretty sure that there is also some cotton tips involved, as well as tissue paper and compressed air.

Shaun

 

[MCW]

Can tell ya, but if you get really close to Matts 660 you may still be able to smell it.:hmm3grin2orange:
Anyway you would not beleive me anyway.

YOU PEED ON IT YOU DIRTY BUGGAR!!!

Cool idea though. The extra heat and salt should really shift some grease and oil. Did you put your thumb over the end for more cleaning pressure Andrew?

 

[Stihlman441]

More like cotton wool buds, Mr Sheen, and some car polish.

Your getting wormer

 

[MCW]

Your getting wormer

Well Shaun did tell me it arrived cleaner than any new in box saw he's ever bought...

 

[Stihlman441]

I think i sent the correct one.

 

[husq2100]

I could be wrong Al but I think cubic capacity and rpm is all that effects the "sucking" power of a non forced induction motor - a 2 stroke motor is nothing more than a positive displacement air pump. A bigger motor at the same rpm will always pull more air. If a 390XP is 20% larger in capacity than a 372XP then the 372 needs to be turning 20% more rpm in the cut to suck the same air - I'm sure your modded 371XP is capable of that though old son. What you did to that saw is illegal in most states and territories.
I can however see your point that if the filter area is 20% less on a 372XP compared to a 390XP then there is the possibility that the same pressure differential across the filter media can be produced.

I dont think you can just increase the filter size using the same media and expect it to work to cover greater pressure/verlocities

Ben really needs to step in and school us

 

[AUSSIE1]

I could be wrong Al but I think cubic capacity and rpm is all that effects the "sucking" power of a non forced induction motor - a 2 stroke motor is nothing more than a positive displacement air pump. A bigger motor at the same rpm will always pull more air. If a 390XP is 20% larger in capacity than a 372XP then the 372 needs to be turning 20% more rpm in the cut to suck the same air - I'm sure your modded 371XP is capable of that though old son. What you did to that saw is illegal in most states and territories.
I can however see your point that if the filter area is 20% less on a 372XP compared to a 390XP then there is the possibility that the same pressure differential across the filter media can be produced.

Yeah mate, this is what I'm saying. :msp_thumbup:

 

[AUSSIE1]

I dont think you can just increase the filter size using the same media and expect it to work to cover greater pressure/verlocities

Ben really needs to step in and school us

I would tend to agree, but I don't think Matt was suggesting an increase in area would solve the problem?

 

[Stihlman441]

Does any one know how much air is getting sucked into a saw / min or what ever,im thinking its going to be a lot.

 

[MCW]

Does any one know how much air is getting sucked into a saw / min or what ever,im thinking its going to be a lot.

I'm no mathematician but it's a simple formula of capacity (cc's) times the revolutions per minute.

Therefore your MS660, being lets say 93cc, pulling 12,000rpm in the cut, is shifting...

93 x 12,000 = 1,116,000 cc of air a minute or 1,116 litres per minute.

Maybe deduct a few litres for ring leakage

If I'm wrong can everybody shut up for a while and let me feel like Einstein for a little bit. Thats all I ask. Thanks

 

[mtngun]

Does any one know how much air is getting sucked into a saw / min or what ever,im thinking its going to be a lot.

There has been excellent data posted on this subject in the past by TW and Lakeside -- which we can't find now due to the broken search function :bang: -- but the gist of the data was that a Stihl HD filter flows way more than the saw requires.

Stihlman441, I blew up your photo to better see the dust. It's not that bad, but ...... I agree that any visible dust is unacceptable on a pro saw.

However, we haven't established where the leak is. Is the media leaking, or is the seal leaking ? People are jumping to the conclusion that the media is leaking, but how do you know ?

Stihlman, have you modded the attachment stud so that the filter can be screwed down tighter ? If you have not done so, there's nothing to lose by trying it.

I notice you are using the hard inner baffle. I recommend chucking the hard baffle, because the filter can bottom out on the baffle before a good seal is formed. Either use the foam inner baffle, or else run without any baffle. All the inner baffle does is deflect spitback when the saw is idling. It adds no value in the cut.

I notice you have stuck foam on the filter cover to help push the filter tight. The foam should help, but if you mod the attachment stud and chuck the hard plastic baffle, then the foam will not be necessary.

As I have stated in other threads, it may be that the HD2 filter is taller than the HD1, which would solve the seal problem without modding the stud or chucking the hard baffle. That's how I would solve the problem if I were Stihl's design engineer.

 

[MCW]

I dont think you can just increase the filter size using the same media and expect it to work to cover greater pressure/verlocities

Ben really needs to step in and school us

I'm sure I could do with some filter schooling but I believe a larger filter will indeed lower the pressure differential on the same saw. If a saw is sucking let's say 1000 litres per minute that means there is a given volume of air crossing every square centimetre of filter material per time unit. By increasing the filter area less air is being pulled through every square centimetre in the same time unit so both pressure and air velocity should be decreased.

Once again, could be wrong

 

[MCW]

However, we haven't established where the leak is. Is the media leaking, or is the seal leaking ? People are jumping to the conclusion that the media is leaking, but how do you know ?

No disrespect mtn but the issue of finer particulates going straight through the filter media is even widely accepted by Stihl Australia. I'm not saying you're 100% wrong in 100% of cases (or even this case) but it's funny how a simple squirt of filter oil with no other modifications has fixed every dust ingression issue I've come across, and that's been on a number of saw brands. This is also a simple fix recommended by saw dealers and widely used in the drier areas of Australia. Many other Aussie members have also chosen to simply oil their filters with 100% success.