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Help damping vibration from DC?

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Forum topic by JohnMcClure posted 05-10-2018 04:23 PM 900 views 0 times favorited 12 replies Add to Favorites Watch
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JohnMcClure

634 posts in 1063 days


05-10-2018 04:23 PM

Topic tags/keywords: dust collection blower motor vibration vibration mitigation damping dampening sound

Can you recommend a way to dampen vibration from my DC? It’s vibrating the whole house.
Details:
I’m building a ducted dust collection system using the 2HP HF blower motor, atop a cyclone separator, atop a trash can, blowing the exhaust through a dryer vent to the outside.

Have not yet installed the ducting because the vibration is so severe, I think I need to mount the motor differently. Once the motor is where it needs to be, I can put up the duct work and finish this. In the photo, I simply put on some flex hose to get a feel for how good the suction is – and to investigate the vibration intensity.

The system is located in a closet of the garage. The wall on the right is between the system and the garage workspace; the wall on the left is between the system and the master bedroom. Both walls (1/2” drywall over 2×4 frame, of course) I covered with 3/4” plywood, screwed through to the studs, before starting this project. I had hoped the extra mass would reduce sound transmission out of the closet.
A 2×4 frame (like a ladder actually) is screwed to the plywood wall liner on the right.
A 3/4 plywood piece is screwed to the frame, and the blower/motor is bolted to the plywood piece.

While audible noise is not really a problem, it seems vibration from the motor is transferred directly through the mounting screws to the plywood plate to the “ladder” frame, into the wall, into the ceiling joists, and into the opposite wall and master bedroom, where LOML will be sleeping when I want to use this thing, of course.

QUESTION: How can I mitigate this? and, of the options I can think of, which are most sensible to you?

I have put enough work into this that I don’t really want to undo it all and rebuild. Only if absolutely necessary. And the hole for the dryer vent has already been made.

Thought 1: Insert rubber between the motor and the plywood mounting plate. Objection: I fear the mounting bolts will still transmit all the vibration into the plate… I could be wrong.

Thought 2: rubber between the plywood mounting plate and the 2×4 “ladder” frame. downside: the screws may transfer vibration, just like the previous thought.

Thought 3: Detatch the 2×4 “ladder” frame from the wall, and make it standalone on the floor.
Upside: No path for vibration to be transmitted into the wall. Downsides: there are 2. One: “walking” along the floor. The system is going to be built with rigid duct so it cannot be allowed to move. Two: how? The frame is not wide enough for me to put feet on it that wouldn’t hit the trash can… I think… or maybe I can work around that. I could make some small triangular braces to attach a plywood “floorboard” that would fit underneath the trash can, barely.

Still I think it needs to be stabilized… maybe a thick layer of foam between the frame and the wall, with one screw securing the top of the frame to the wall?

Thanks anyone for your input.

-- I'd rather be a hammer than a nail


12 replies so far

View pintodeluxe's profile

pintodeluxe

5955 posts in 3236 days


#1 posted 05-10-2018 04:30 PM

You’ll need to mount the blower to the wall via thick rubber pads to isolate the vibration. My local hardware store sells dense rubber matting in bulk. You would just need a few small squares of it. Most of the material is 1/4” to 3/8” thick. It won’t compress much as you tighten the bolts.

As far as sound dampening, you may need some acoustic tiles on the wall and in the corners.

Good luck.

-- Willie, Washington "If You Choose Not To Decide, You Still Have Made a Choice" - Rush

View RobHannon's profile

RobHannon

278 posts in 953 days


#2 posted 05-10-2018 04:32 PM

2 things I can think of to try.
Put some rubber between the motor and the plywood to take up some of the vibration. You can find ones for HVAC equipment that will probably fit well.

Pull the impeller off and see if it is well balanced. If it is off, you are not going to mask the vibration without fixing the balance and your motor bearings will probably fail earlier than expected.

View LittleShaver's profile

LittleShaver

555 posts in 1042 days


#3 posted 05-10-2018 04:38 PM

In addition to the rubber pad, I’d make some rubber washers to go between a metal washer and the nut or bolt head on the mount and another set to go between the other end of the bolt and the motor frame. Back in my submarine days, our motors were all sound isolation mounted to prevent transmitting sound to the hull. There was as much rubber isolating the bolt as there was isolating the motor frame.

I would also rubber mount the fan to help minimize vibration transfer.

I understand the sleeping wife syndrome. My shop is in a detached garage about 150’ from the house. All the windows are double pane. The house is ICF construction up to the eaves, which means the walls are about 14” of drywall, Styrofoam, concrete, and stucco. Even with all the doors closed on the house and the shop, the planner will wake the wife. Never a good thing.

-- Sawdust Maker

View JohnMcClure's profile

JohnMcClure

634 posts in 1063 days


#4 posted 05-10-2018 08:05 PM

Thanks for the tips all.
LittleShaver, that must be one heck of a planer – or a light sleeper – considering that construction.

I’ll round up all the rubber matting I can find and try to incorporate your suggestions. First, rubber at the motor mount and inside both washers on each bolt. Then another layer between the motor plywood mounting panel and the 2×4 frame.
Also I’ll unscrew the frame from the wall, put a thin sheet of rubber behind it, then secure it to the wall in as well-damped a way as I can that will still hold it stable, but minimize vibe transfer. I’ll let you know!

-- I'd rather be a hammer than a nail

View bilyo's profile

bilyo

746 posts in 1525 days


#5 posted 05-10-2018 11:15 PM

Many automobiles use tough rubber donuts to suspend their exhaust system and isolate it from the body. Maybe you could get some replacement donuts from an auto parts store and use these to suspend the motor and blower from a frame above rather than mounting it to the wall.

I also wonder why there is so much vibration. Is the motor and/or fan badly balanced?

View eflanders's profile

eflanders

326 posts in 2273 days


#6 posted 05-10-2018 11:21 PM

The rubber mounts as others have suggested really help but I also added some carpet scraps to absorb the sounds not sent via vibration. I simply stapled them around the framing that supports my DC. I think catches the air movement sounds as it travels through the system.

View Redoak49's profile

Redoak49

4052 posts in 2411 days


#7 posted 05-10-2018 11:31 PM

Yes, you can find all kinds of vibration absorbing mounts. But, they are not a solution. If it is vibrating that badly, something is wrong. I would check things out to figure out why it happens. My larger dust collector has almost no vibration. Are the bearings bad or impeller off balance? With that amount if vibration, it is going to destroy the bearings.

View fivecodys's profile

fivecodys

1437 posts in 2059 days


#8 posted 05-10-2018 11:44 PM

Hi John,
My set up is very similar to yours but instead of boxing out the panel that the blower mounts to, I just bolted the panel right to the wall and into the studs. (no ladder)

The box (and ladder) may be creating a resonance chamber and magnifying the vibrations of the blower.
You might try loosening one or more of your bolts (one at a time) to see if you determine if one is carrying the vibration to the house.
It’s a challenge for sure.

Good luck!

Chem

-- When you leave your shop for the night, make sure you can always count to 10.

View JohnMcClure's profile

JohnMcClure

634 posts in 1063 days


#9 posted 05-10-2018 11:46 PM

Redoak, you may be right. But I bought the blower from HF months ago as part of their kit. I had planned on the way I’m doing it now, but some unplanned delays came up… I got rid of the rest of the kit and thus can’t take the motor back if it’s off.
I’m hoping the vibration I saw is more of a resonance thing with the house framing… it wasn’t even bad in the garage, much worse in the bedroom. So I’ll try dampeners, then if that doesn’t work or when my bearings work out, I’ll buy a better blower.

-- I'd rather be a hammer than a nail

View JohnMcClure's profile

JohnMcClure

634 posts in 1063 days


#10 posted 05-10-2018 11:48 PM

Now I’m embarrassed – your setup looks so much more elegant than mine! But if you’re having no vibration issues, I think that narrows it down – either resonance, or off balance. I didn’t know HF had a white blower – what brand is yours?


Hi John,
My set up is very similar to yours but instead of boxing out the panel that the blower mounts to, I just bolted the panel right to the wall and into the studs. (no ladder)

The box (and ladder) may be creating a resonance chamber and magnifying the vibrations of the blower.
You might try loosening one or more of your bolts (one at a time) to see if you determine if one is carrying the vibration to the house.
It s a challenge for sure.

Good luck!

Chem

- fivecodys


-- I'd rather be a hammer than a nail

View Fred Hargis's profile

Fred Hargis

5595 posts in 2916 days


#11 posted 05-11-2018 10:47 AM

Redoak is correct, there’s something wrong with the blower. But what about suspending it from chains to remove it from the structure completely? You’d have to put an anti twist brace on it, but it should stop the shudder in the house.

-- Our village hasn't lost it's idiot, he was elected to congress.

View fivecodys's profile

fivecodys

1437 posts in 2059 days


#12 posted 05-11-2018 07:48 PM


Now I m embarrassed – your setup looks so much more elegant than mine! But if you re having no vibration issues, I think that narrows it down – either resonance, or off balance. I didn t know HF had a white blower – what brand is yours?

Hi John,
My set up is very similar to yours but instead of boxing out the panel that the blower mounts to, I just bolted the panel right to the wall and into the studs. (no ladder)

The box (and ladder) may be creating a resonance chamber and magnifying the vibrations of the blower.
You might try loosening one or more of your bolts (one at a time) to see if you determine if one is carrying the vibration to the house.
It s a challenge for sure.

Good luck!

Chem

- fivecodys

- JohnMcClure


Now I m embarrassed – your setup looks so much more elegant than mine! But if you re having no vibration issues, I think that narrows it down – either resonance, or off balance. I didn t know HF had a white blower – what brand is yours?

Hi John,
My set up is very similar to yours but instead of boxing out the panel that the blower mounts to, I just bolted the panel right to the wall and into the studs. (no ladder)

The box (and ladder) may be creating a resonance chamber and magnifying the vibrations of the blower.
You might try loosening one or more of your bolts (one at a time) to see if you determine if one is carrying the vibration to the house.
It s a challenge for sure.

Good luck!

Chem

- fivecodys

- JohnMcClure

Thank you for the compliment John.
This was in the planning stage for about 3 years.

My blower is not an HF it’s from a JET DC1100 that I modified.

My run is very short and I used duct-work and fittings from Oneida (with the exception of the exhaust. that’s just HVAC duct from Lowes running to a 6” dryer exhaust port.)

I hope you find the cause of your vibration and that it is an easy fix.

-- When you leave your shop for the night, make sure you can always count to 10.

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