Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: fossilshark on March 15, 2023, 08:51:45 pm
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Im back, trying to cram this transformer in a 1U rackmount chassis. There is just barely enough clearance to fit it inside the chassis without the mounting hardware, and the bolt for the mounting hardware (that would be outside the chassis) is simply way too big.
Im thinking im gunna have to have someone weld part of the bolt right to the chassis and use a smaller mounting plate.
Anyone do a rackmount preamp like this before? Any suggestions?
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I mounted a toroidal inside a Fender chassis, same height as a 1U rack.
I basically filled the doughnut hole with epoxy, filling in around a threaded insert in the center. It is then secured by a bolt from the bottom.
The epoxy is inset from the top of the transformer, so no clearance issues.
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I was looking at that picture from the last thread I posted trying to figure out how you did it. Is that threaded insert welded to the chassis?
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Doug has theaded inserts you can use
The thikness of a threaded insert that will be on the outer side of the rack will be 1mm or 1.5mm max
Insert your bolt from the inner side (not like in the photo, the purpose Is different)
There are other way, like to use clinching nuts (installed on the inner side of the chassis) but threaded rivets is the simpler
Franco
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Franco has a good variation on the theme.
If you fill in the center of the transformer with epoxy, leaving a hole through the center (use a tube of some sort for the proper size hole), then you can bolt from the top of the toroid down into the "riv-nut" which is installed from the outside bottom of the chassis.
I thought I had a second insert to take a pic of but seems that I don't. The one I used was plastic, was internally threaded & had a flange on one end which helps anchor it in the epoxy.
FYI, I started with JB Weld epoxy but had some West System on-hand which was more pour-able & used that to fill it up the rest of the way.
The one I use looked something like the pic below.
In my application the threads are mounted in the transformer, & you use just a bolt from the bottom.
As Franco points out, the Riv-nut idea would be lower profile with very little protrusion on the bottom.
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Once you get the hang of Riv-Nuts, you never go back . . .
McMaster has a great selection of this type of fastener on this page: https://www.mcmaster.com/products/nuts/ (https://www.mcmaster.com/products/nuts/)
You can buy riv-nuts on eBay as well -- sometimes with good quality, other times not so much.
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Clinching nuts will give no protrusion out of the rack but is more difficult to arrange
To me a threaded rivet on the rack and only some rubber concentric tubes on the hole of the transformer
when you tighten the bolt, the rubber expands and blocks the transformer
a threaded part will not be necessary on the transformer, may be a washer to hold together the concentric tubes
I'll not use epoxy, this also don't cancel the transformer warranty
Franco
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Clinching nuts will give no protrusion out of the rack but is more difficult to arrange
To me a threaded rivet on the rack and only some rubber concentric tubes on the hole of the transformer
when you tighten the bolt, the rubber expands and blocks the transformer
a threaded part will not be necessary on the transformer, may be a washer to hold together the concentric tubes
I'll not use epoxy, this also don't cancel the transformer warranty
Franco
I am guessing you are talking about an rubber expansion plug.
I like the concept of holding the transformer in place that way, but I would be wary of the uneven force exerted on the coil as none of the toriodal transformers I have bought have very round center holes, in fact they are more oblong.
Lightly tightened, the plug would keep it in place. But if it starts to shift the transformer windings to get it snug, you might need the warranty.
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i have mounted the antek successfully in a few 1U racks. What you need to do is create an indentation in the bottom (using a long bolt, nut and large socket). You can then mount it the regular way. You will need to shorten the bolt that comes with the PT.
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Wow I didn't think I would get this many good suggestions haha. I like all of these methods as they all do exactly what I want.
I am in a toss up between joesatch method (the easiest and simplest and also has no protrusions out the top wich is important for a rackmount unit) and rivnuts witch seems more "professional" and I watched this video making them seem super easy to get the hang of
The only deciding factor I think is going to be if I actually end up ordering the rivnuts and putting in an afternoon to get used to using them :laugh:
there is absolutely no way the top part of the transformer hardware will fit in my 1u chassis, how joesatch managed to do that I am baffled, So I am probably going to use some silicon (instead of epoxy) and just the rubber part of the mounting hardware.
Thank you so much guys always solving my problems for me!
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Pay attention, You must not obtain a coil mounting the transformer
the bolt can touch the rack only at one extremity otherwise your transformer will heat and burn
Franco
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So I am probably going to use some silicon (instead of epoxy) and just the rubber part of the mounting hardware.
One other hybrid idea would be to find a tall rubber foot that is just slightly smaller than the transformer hole, bolt that into the chassis (riv-nut or dimple/bolt) & then goop the transformer to the rubber foot.
On a tangental note, I have been using "Shoe-Goo (https://eclecticproducts.com/product/shoe-goo/)" to secure parts to boards, etc.
I used it the first time as it was on hand with no other options, but I find it works better than silicone;
it has more initial tack, it doesn't harden in the tip of the tube like caulk so there is less waste/easier to use & it is fairly removable, as it rubs off the component/board once the bulk of it is removed.