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Hammond chassis mounting question
#1
Hi all,



For mounting a usual Hammond chassis in a wooden enclosure MArshall-style, I use angled brackets mounted on the chassis using blind rivets where the whole construction is then fastened using bolts and screws, but I've always wanted to have a system that uses cage nuts instead...




How would you mount it? What hardware would you use?






P.S. Couldn't find a more relevant subdir, hope its is ok to post here. Wink
Cheers,
Klearchos
Formyx Amplifiers
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#2
Hi Guys

Cage nuts might be a little difficult for hobbyist to use since most such nuts (cage nuts not hobbyists) require a square hole.The return on the chassis may not be wide enough to provide much support the nut mount. Hammond's chassis in general can be a bit flexible when they are asked to support as much transformer weight as a medium-size tube amp is.

An alternative to the cage nut is the J-clip. In cross-section, a J-clip looks like a 'J' made out of a folded over strip of metal with a clear hole on one side and formed "half nut thread" on the other. Slip the J-nut over a round hole drilled in the chassis return. The J-clip spreads the load over a small amount of the return and again may not be the best means of securing a heavily loaded chassis.

With either the cage nut or J-clip, if one were to go beyond the traditional and intuitive four mounting points then either would be quite viable on stock Hammond chassis. Best to consult with the hardware catalogues to make sue the chassis return is deep enough to accommodate the prospective mount.

An alternative is to do what Traynor did with most of their tube amp chassis. They drilled pairs of holes lined up in the return and the top of the chassis, both near the fold for the side apron. A long bolt is passed through the amp sleeve and both of these holes, atop which a washer and nut can be tightened n. The washer should be larger than the nut so the compression forces will be spread out more. Traynor often used nuts with integral toothed washer to lock the nut in place, in addition to the flat washer suggested above.

Large diameter washers are often called "fender washers" - they won't clean your Fender amp or guitar, but are so named because of their use for automotive body repair and/or assembly. Some general hardware stores carry these as do specialty stores that carry extended varieties of mechanical hardware.

Have fun
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#3
Another thing you could do is install threaded rivets. It's fairly easy since you just drill a hole in the material and the use the rivet tool to install them. Habor Freight has a cheap one that works fairly well. You could some angle iron or joining hardware pieces used for roofing and attach those to the sides of the chassis with the threaded rivets installed on those.
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#4
Thanks for the input, guys!

@Kevin
Using cage nuts would require lots of filing after drilling since I don't own a square hole drill.
I have encountered J-clips on some cheap Marshall combos, but their construction did not strike me as reliable.

The Traynor way would be something to consider, though. In high gain amps it would also allow for aluminium sheets to not get in the way of contacting the chassis, so this is a consideration. This is something I have met in Fender combos where the bolt-nut holds the chassis up in its place.

@makinrose
Threaded rivets is a quite nice solution, actually. So using the aforementioned angles attached to the chassis with blind rivets, one can just vertically mount them so that they align and get tightened by a bolt from the underside of the wooden enclosure!
Cheers,
Klearchos
Formyx Amplifiers
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#5
Glad to help!
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