BillFitzmaurice.info

I was thinking a little about those threaded inserts last night after seeing this: http://www.diymobileaudio.com/forum/558253-post27.html Pretty impressive.

You guys may think I am nuts but I've added to my science experiment... I went out and bought 1/4" dowel which fits perfectly into the existing hole with some light hammering and some 2 part 5 min epoxy.

I now have the following in my test bed:

1) Glue
2) Glue + Sawdust
3) Glue + Dowel
4) 5 Min Epoxy
5) Dowel + Epoxy
6) 5 Min Epoxy (Control)

Tomorrow after everything is dry I'm going to see how the screw holds with these different scenarios. I'll report back and if nothing more this can help future builders. If all of these fail I'll just get an L-bracket and be done with it.

myn wrote: 3) Glue + Dowel

I think that would work well, but using PL instead of glue.

I do like those McMaster Carr EZ Loc inserts though. First time I've seen them, hmmm.

I have some on hand to evaluate. I'll give them a go in the shop tomorrow. I would agree with the link that in mdf they probably are superior. Mostly because mdf really sucks. For anything.

I predict The epoxy/dowel will work best. Somehow you sill have to drill a pilot hole for that screw, so it may be best to drill the dowel first before epoxying it in. 5min epoxy still has a 24 HOUR full cure time at 77 deg F. For every 10 degrees above or below that figure, cure time is halved or doubled. Take this into account.

The EZ Locks are great, but the knife-thread with slotted drive inserts mcmaster has are bulletproof, but no nice hex drive. If you are going to use a threadlocker like loctite, use steel and not brass inserts, and steel screws, not stainless.

JSS

The results are in..


1) Glue (Have not tested yet as it's still not dry)
2) Glue + Sawdust (Couldn't hold a screw very well)
3) Glue + Dowel (Held the screw just like native Arucoply)
4) 5 Min Epoxy (Very brittel and tough but after unscrewing/re-screwing a few times it lost its grab. Similar to screwing into plastic)
5) Dowel + Epoxy (Held the screw just like native Arucoply)
6) 5 Min Epoxy (Control) (Very brittel and tough but after unscrewing/re-screwing a few times it lost its grab. Similar to screwing into plastic)

So the Dowel + Glue or Epoxy wins.

With that said I plugged the hole with glue and dowel as the glue was easier to apply. A very nice tight fit. Prior to plugging the hole I scrapped off the excess Gorilla glue from the underside around the hole.

If I head down the screw route I am going to have to get a longer one if I plan on using another piece of wood behind the baffle. That nice socket cap screw I was going to use only barely goes through the 1/2" ArucoPly (see pic below) The Dayton DVC's gasket is pretty thick.

Bill: Is there a downside of me adding an additional small piece of 1/2" ply section directly below the now filled hole so the screw can have some extra grab? Will this affect the horn's performance as an added obstruction at the very beginning of the horn mouth is now present?

If I go the L-Bracket route is it high enough to support the height of the DVC's gasket/flange which is 3/4 of an inch? I am trying to steer clear of this situation:



Looks like I'm going to need a longer screw. Gasket + Flange is 3/4"




Will adding a piece of 1/2" ply underneigh the hole at the very beginning of the horn cause any performance issues?

Did you not drill a pilot hole in the dowel before gluing it in?? I know these types of screws are often sold as 'self-tapping', but a pilot hole reduces the amount of wood-splitting you have to deal with. If you have a way to drill a pilot in the driver chamber confines, ignore that question.

I'm pretty sure Bill will say that little piece of wood in the horn will be negligible, especially considering keeping the driver in place is probably more important...

Also, considering the speaker gasket will compress, you should be OK with the screws you have. Just don't make it the first one you tighten down....

Looks like you solved the problem well...

JSS

Glue down the appropriate sized block for the L bracket.
It should be thick enough so the bolt is plumb, and the bracket is level.

I use 5/16" bolts for this, and the large T-nuts.
This could be painful if trying to retrofit inside a finished chamber.

Bill: Is there a downside of me adding an additional small piece of 1/2" ply section directly below the now filled hole so the screw can have some extra grab? Will this affect the horn's performance as an added obstruction at the very beginning of the horn mouth is now present?

Or should I ditch that idea and just get an L-Bracket and secure it that way?

Thanks.

myn wrote:Bill: Is there a downside of me adding an additional small piece of 1/2" ply section directly below the now filled hole so the screw can have some extra grab?

No.

Bill Fitzmaurice wrote:

myn wrote:Bill: Is there a downside of me adding an additional small piece of 1/2" ply section directly below the now filled hole so the screw can have some extra grab?

No.

Short and sweet. I kinda figured that's what you'd say.

Excellent So I will skip the L-Bracket clamp and go with the screw solution adding some additional stock 1/2" ply underneath the baffle where the bum hole is.

While I was at Home Depot last night I bought some of these 2" round head slotted wood screws. I think these will give me the extra length to grab into the double stacked 1/2" ply (1" total). On the downside they aren't as user friendly as my other shorter socket cap screws. These being a slotted head.

myn wrote:Excellent So I will skip the L-Bracket clamp and go with the screw solution adding some additional stock 1/2" ply underneath the baffle where the bum hole is.

While I was at Home Depot last night I bought some of these 2" round head slotted wood screws. I think these will give me the extra length to grab into the double stacked 1/2" ply (1" total). On the downside they aren't as user friendly as my other shorter socket cap screws. These being a slotted head.

Be REALLY REALLY careful if you use these. It's all too easy to be applying torque to a screw one minute and then be pulling a flathead screwdriver out of a speaker cone and cussing at yourself the next. Trust me on this one. Be REALLY careful.

WiSounds wrote:Oh and washers of some variety preferably lock washers as well, I have had to tighten the driver mounting screws in mine, until I placed lock washers.

Good call.

I forgot I had purchased some Internal lock washers. Where in the chain did you apply the lock washers?

I was thinking the following:

Screw head --> lock washer --> flat washer --> top of speaker flange --> wood

Should the lock and flat washer be switched around in the opposite order?

Wi beat me to it....do not use those slotted screws (I don't use slotted screws for ANYTHING anymore, square, hex or torx drive for me, philips in a pinch). Your 1" hex sheet metal screws will work well. Just be sure to install all the threaded screws first, and do the sheet metal screw last, so the gasket will already be somewhat compressed. Also, be sure the lock washers have teeth on the inside, not the outside of the washer.

Considering this was your first build, the mistakes you made were all easily fixable, and soon you'll be firing that bitch up to see what it can really do...I would definitely like to hear what you think about the THT vs the LLT...

JSS

EDIT - Just saw these - Transformers 2 spectral waterfalls....looks like it will be right in the THTs wheelhouse:

http://img196.imageshack.us/img196/9571/021147.jpg
http://img12.imageshack.us/img12/7359/004005h.jpg
http://img18.imageshack.us/img18/6764/003018.jpg

Not sure how to do thumbnails....

maxmercy wrote:Wi beat me to it....do not use those slotted screws (I don't use slotted screws for ANYTHING anymore, square, hex or torx drive for me, philips in a pinch). Your 1" hex sheet metal screws will work well. Just be sure to install all the threaded screws first, and do the sheet metal screw last, so the gasket will already be somewhat compressed. Also, be sure the lock washers have teeth on the inside, not the outside of the washer.

Considering this was your first build, the mistakes you made were all easily fixable, and soon you'll be firing that bitch up to see what it can really do...I would definitely like to hear what you think about the THT vs the LLT...

JSS

EDIT - Just saw these - Transformers 2 spectral waterfalls....looks like it will be right in the THTs wheelhouse:

http://img196.imageshack.us/img196/9571/021147.jpg
http://img12.imageshack.us/img12/7359/004005h.jpg
http://img18.imageshack.us/img18/6764/003018.jpg

Not sure how to do thumbnails....

I really would love to use the nice 1 1/8" socket cap screws I have but I am fearful they won't be long enough to take advantage of the 2nd piece of plywood below the baffle. The cork gasket on the driver flexible but it is pretty thin so I don't see too much gain even with compression. Maybe I am missing something?