DW788 Rebuild

Rick_B

Rick
Corporate Member
OK - my current approach is to start over so I have a couple of questions.
1. In watching the Bob Brokaw 2019 update video they show the bellows not attached to the button on the rocker arm. On my machine the rocker arm button was inserted into the narrow end of the bellows. I'm not sure what is the right way? (Photos below)
2. I've got side to side play on all of the connecting points - I'm not sure if that is right or not

Rick
Bellows Assembled.JPG
Bellows Button.JPG
 

Charlie

Charlie
Corporate Member
When I disassembled my saw, the bellows was attached to the button on the rocker arm so I reinstalled it that way.
 

Rick_B

Rick
Corporate Member
When I disassembled my saw, the bellows was attached to the button on the rocker arm so I reinstalled it that way.
Thanks Charlie - that makes sense to me. If it wasn't attached I'm not sure what would keep the bellows from sliding off the arm and not compressing

Rick
 

Rick_B

Rick
Corporate Member
I decided to put it all back together and start fresh, Below isa video of the noise


Rick
 

Rick_B

Rick
Corporate Member
After doing some internet researching and reviewing a document sent to me by a fellow member - It seems the most predominant cause of noise is in the tension adjustment. More specifically banging of the tension adjustment arm against the top cover for the bellows. Some pictures - first is the tension adjustment rod - it has a 90 degree bend and the long section goes back to a wedge. As the rod is pulled forward or pushed back (by a cam surface in the adjustment lever assembly) thew wedge raised or lowers the arm. The wedge has a threaded hole which the rod goes in. The primary adjustment is to turn the rod into or out of the wedge.
Tension Adjustment Rod.JPG
Tension Adjustment Rod.JPG (51.28 KiB) Viewed 3 times
The next two pictures are of the bellows cap which the adjustment rod rides in There are numerous recommendations to remove material from the top groove and/or the bottom "hump"
Bellows Cover Top.JPG
Bellows Cover Top.JPG (65.38 KiB) Viewed 3 times
Bellows Cover Bottom.JPG
Bellows Cover Bottom.JPG (60.73 KiB) Viewed 3 times
I decided to blue both of those areas to identify where a rub might be. No luck - after running with the bluing all seemed to be undisturbed.

Then I removed the covers and ran the machine 0 it sounded like the noise was coming from the main connecting link in the rear of the machine.
Covers Off - Lower Arm Rear.JPG
Covers Off - Lower Arm Rear.JPG (74.25 KiB) Viewed 3 times
If I push on that link the noise pretty much disappears - see the video below


The left side motor shaft bearing is the only sealed bearing in the machine and "seems" to be OK. The right side bearing is a needle roller bearing with a sleeve - I can move the connecting link slightly front to back. 'm not sure what is going on yet.

Rick
 

Rwe2156

DrBob
Senior User
I have the same issue with mine.

You got your answer.

Brokaw said that the eccentric is the one that goes bad the most.

Thanks for posting the videos!
 

Rick_B

Rick
Corporate Member
I have the same issue with mine.

You got your answer.

Brokaw said that the eccentric is the one that goes bad the most.

Thanks for posting the videos!
I"m not 100% convinced that it is a bearing problem yet. I plan to disassemble and check further

Rick
 

Hmerkle

Board of Directors, Development Director
Hank
Corporate Member
I"m not 100% convinced that it is a bearing problem yet. I plan to disassemble and check further

Rick
Rick,
In your video it appears you put "side-load" on the eccentric? (is that right?)

WARNING! non-married marriage counselor advice coming... :cool:

I am not familiar with this eccentric assembly, but could it simply be that you can tighten that nut or shim the assembly to take the play out of it?
Or is it originating from slop in the bearing / shaft and you are "masking" the effect by putting pressure on the arm?
 

Rick_B

Rick
Corporate Member
Hank - the nut (that is on the motor shaft) is tight! I am putting side load on the connecting link to eliminate the noise but youb are correct in that I'm not sure why yet. My gut sys it is side play in the smaller bearing on the right.

Rick
 

Hmerkle

Board of Directors, Development Director
Hank
Corporate Member
Hank - the nut (that is on the motor shaft) is tight! I am putting side load on the connecting link to eliminate the noise but youb are correct in that I'm not sure why yet. My gut sys it is side play in the smaller bearing on the right.

Rick
I think I would pull the socket head cap screw out of the eccentric to the vertical arm to see if it is loose side to side or "radially" (bad bearing) or (GOD forbid) warn motor shaft! (as I understand it a worn motor shaft = a new motor and WOAH are those expensive!!!)
 

Charlie

Charlie
Corporate Member
Rick,
Check the needle bearing where the connecting rod from the motor attaches to the vertical arm. Mine had no visible sign of grease and was rusted. It would barely pivot. I think it was assembled without any grease. All other bearings had grease.
 

Rick_B

Rick
Corporate Member
Rick,
Check the needle bearing where the connecting rod from the motor attaches to the vertical arm. Mine had no visible sign of grease and was rusted. It would barely pivot. I think it was assembled without any grease. All other bearings had grease.
Hank - I did the check you recommended -the connecting rod to motor shaft seems like a very good fit - no detectable movement.

Charlie that bearing look good too - I had previously disassembled and lubed all the bearings. That connection was pivoting very well.

I disassembled the entire drive mechanism. First check was the connecting rod to motor shaft - the bearing fit was very good (in my opinion). Then I pulled the connecting rod out of the vertical rocker arm. That's when I found the self inflicted wound! I remember when I assembled this initially that it was a very tight fit between the rocker arm slot and the connecting rod sleeve. Unfortunately I went to my primary move - brute force. This caused some damage to the rocker arm and some imbedded slivers at the top of the bearing. Rocker arm damage

See 1st picture below

I cleaned up the burrs and slivers. The connecting rod bearing and sleeve seemed to be good to me. Since my initial bang it till it goes in approach I learned there is a better recommended way

See 2nd picture below

The tapered punch is used to open the slot so the connecting rod just slides in.

After reassembling it seemed to be less noisy to me - but take a listen and tell me what you think - first video is the same as upthread (noise before any work) and the second is after today's reassembly




Verical Rocker Damage.JPG
Connecting Rod Assembly.JPG
 

Hmerkle

Board of Directors, Development Director
Hank
Corporate Member
OK - after watching both videos with better audio - they sound the same to me

Rick
yup, they sound the same to me too - there is "slop" or motion somewhere since if you put your finger on it you can reduce the noise, you just have to figure out where.
Maybe heavily grease the bearing and see if it reduces and then buy a new one if it does...
Too bad you don't know the diameter the shaft is supposed to be... then you could measure it...
Did you see any wear on the motor shaft when you had it apart?
 

Rick_B

Rick
Corporate Member
So its been quite awhile since I got involved with this saw - between leaves falling faster than I could collect them, thanksgiving and a general lack of interest - it just got away from me. I went back through and cleaned/regreased all the bearings and reassembled everything. Its still noisy!!!

Here is what I have noticed:
1. At the lowest speed it is not a bit noisy but as the speed increases the noise gets worse - kinda. there are some speed settings that are not as noisy as others. For example - setting 2 or 3 - pretty noisy. Setting 5 - noise gets better. Setting 8 - very noisy. At some settings I can press down on the upper arm and the noise level reduces - not eliminated but better.
2. There is a lot of side to side play in the chuck jaw castings and some play in the arms back from/the chucks. Not sure if side to side play is a problem or not.

I'm at a loss of where to go from here and am looking for any suggestions
Thanks
Rick
 

Rwe2156

DrBob
Senior User
Have you checked the screws that go thru the bearings in the front upper and lower heads? Mine had a broken screw and made a hell of a racket.

Ultimately it may be sending it off is is what you need to do.
35D341FB-C71A-4DBE-B3EA-2C9734345670.jpeg
 

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