Hello everyone,
I have two custom (TTG-KT88PP, w/o screen taps, w/4, 8, and 16 Ω) output transformers coming from Toroidy.pl. I need to purchase the mounting screw that passes through the center of the toroid. Does it matter what material that screw is? I can purchase steel or stainless steel. The chassis is aluminum.
Thanks
Ray
I have two custom (TTG-KT88PP, w/o screen taps, w/4, 8, and 16 Ω) output transformers coming from Toroidy.pl. I need to purchase the mounting screw that passes through the center of the toroid. Does it matter what material that screw is? I can purchase steel or stainless steel. The chassis is aluminum.
Thanks
Ray
I'd use nonmagnetic stainless steel.
https://www.fastenal.com/product/Fa...bolt&productFamilyId=20460&categoryId=600005#
https://www.fastenal.com/product/Fa...bolt&productFamilyId=20460&categoryId=600005#
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As long as it does not form a ring around the toroid I don't think it makes any difference.
I read here one time where a poster used M5 (maybe M6) bolts cutting into the epoxy, which is an easy option.
I read here one time where a poster used M5 (maybe M6) bolts cutting into the epoxy, which is an easy option.
It would probably stretch and loosen a bit over time, and you couldn't ship the amp for fear of damage.
Hi Steven.
It's not really the melting point that you're interested in. Remember long before that temperature is reached the stud/bolt would have stretched and any clamping force on the transformer would have been released. Then on cooling it would solidify to the new extended length. The transformer would now be loose. The heat deflection temperature is what one is interested in, with bog standard (unreinforced) Nylon 6 this can be as low as 60 Deg C (dependant on loading) Other types of Nylon or reinforced types are far better 140C to even 200C, but one has to be specific as to what is bought. It's a bit like me asking to buy "a NPN Transistor', "what type?" you ask, I say, "a NPN transistor". One could use a higher temperature rated material like Peek, or others though these may be more expensive. 1/2 inch (imperial) or 12mm (Metric) would I think be fine, as long as the temperature requirement is OK.
I'm basing this on a 300 to 600 VA transformer as I'm unsure as to the size of the one mentioned. Hope this helps.
Nylon hardware is really fragile I wouldn't trust it to hold anything. Most companies use plain steel bolts to hold toroids without any issues. The biggest no no is accidentally creating a shorted turn.
Antek, here in the USA, sells transformer covers with integral toroid mounting hardware. They are magnetic.
Antek Cases
Antek Cases
Toroids that I have purchased in the past have all come with steel mounting plates and bolts.
The two important physical factors for me when mounting any toroids are:
Mechanical properties of the fixing hardware - if the amp was dropped, would the impulse load tear the transformer from the mounting; and
Not creating a magnetic short. This can be avoided simply by not completing the magnetic circuit.
Stainless is fine, but high tensile steel is mechanically stronger and would be my choice.
The two important physical factors for me when mounting any toroids are:
Mechanical properties of the fixing hardware - if the amp was dropped, would the impulse load tear the transformer from the mounting; and
Not creating a magnetic short. This can be avoided simply by not completing the magnetic circuit.
Stainless is fine, but high tensile steel is mechanically stronger and would be my choice.
Got to the hardware store and buy yourself a standard grade 3, 1/4-20 stove bolt of the appropriate length. Problem solved. The magnetic properties of the bolt make zero difference. You just need to make sure that the bolt is strong enough to do the job. A 1/4-20 bolt is strong enough for all but the largest transformers.
Remember "better" is the enemy of "good enough".
Remember "better" is the enemy of "good enough".
Agree with Avtech and Suncalc. Ive always used standard grade steel, and as long as you don't complete the magnetic circuit they are fine.
By completing the magnetic circuit they mean a loop through the center of the toroid and around the outside making a short circuit. “It would be bad” as a old friend once said! Think melt down like Chernobyl! Just get a couple large washers, rubber pads and a decent nut and bolt combo. The rubber keeps the insulation on the toroidal from being crushed through to the conductor when you tighten it hard.
Any old bolt will do. Toroid clamping kits are available everywhere for not much dosh. All the ones I have have a standard mild steel (hardened maybe) bolt.
Stainless bolts are better for this purpose just like using isolating washers between that bolt and the metal ring/plate.
Every toroid I've ever bought has come with magnetic hardware. If it needed to be non-magnetic, they would include non-magnetic hardware.
It's strange that the transformers didn't come with the hardware.
By the looks of the datasheet for the transformer, a 1/4" bolt as mentioned before would be the closest SAE size for a bolt - otherwise go metric.
It's strange that the transformers didn't come with the hardware.
By the looks of the datasheet for the transformer, a 1/4" bolt as mentioned before would be the closest SAE size for a bolt - otherwise go metric.
"They" include what just works in 100% of cases and costs least. "We" tend to want stuff executed best way certainly when stuff to do that costs nil to nothing extra.
You could try and check what the transformer does with a steel chassis. Standard is mounted directly to the chassis with a ferro bolt and steel mounting plate. Non standard is to mount these isolated from chassis. Only a plastic washer with collar is enough for testing. You can also add the stainless steel bolt to that if you like. Tell us if you noticed/measured a difference. Repeat that with the steel upper cover on the device and without the steel cover.
Some manufacturers mold audio toroids in a kind of metal cup with resin i.e. no centered bolt.
You could try and check what the transformer does with a steel chassis. Standard is mounted directly to the chassis with a ferro bolt and steel mounting plate. Non standard is to mount these isolated from chassis. Only a plastic washer with collar is enough for testing. You can also add the stainless steel bolt to that if you like. Tell us if you noticed/measured a difference. Repeat that with the steel upper cover on the device and without the steel cover.
Some manufacturers mold audio toroids in a kind of metal cup with resin i.e. no centered bolt.
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Steel is fine. So is nylon if big enough. Use brass if it makes you happy. I prefer to mount the transformer on a compliant pad, duct tape will do, and another pad on the top plate. Then use a spring or stack of bevel washers on the bolt to deal with any thermal expansion. ( nylock nut of course) I have seen several recently without the top plate, but cast full of epoxy.