are all motorized variable capacitors built ridiculous? - Page 1
Forum section: electronics / rf-microwave

author: coppercone2
author_rank: Super Contributor
timestamp: October 30, 2023, 06:25:41 am
content: I was trying to service the collins variable capacitor I have and I managed to snap the lever arm. A bunch of like... plastic? washers totally melted and fused to porcelain.But I noticed the most ridiculous thing, the capacitor itself (the type with the baffle), has like a.. thin metal rod/rope in the middle, connected to a cross bar.I mean this mechanism is totally ridiculous. I thought it was a spring loaded piston in the middle, but it turns out its a dangling rope for like an attic door. So its naturally retracted instead of extended. There is a dodgy fiberglass arm that grips the rope to pull down on the capacitor baffle.It does not inspire confidence.Do they have variable caps that have a beefy piston on the bottom, not a rope? I mean this is how you used to flush an archeic toilet.This one is jennings brand.DO they have anything better?I don't even want to try to make a mechanism for this because it looks so rupe goldberg and dodgy. this looks like a mechanism for lora croft to play with, not one that belongs in a HV setup.that thing literary wobbles like a guitar string if you pluck it. It kinda seems like a joke. I also definitely don't trust the corroded little whipy rod at all. I figured there would be a massive shaft. Its like alot of force too. You can't pull on it with your hand. that copper baffle is a strong spring. this looks like some BS a convict made in prison to practice pull ups. I guess I should expect it, because the internals of airplanes usually look like bootleg ass exercise equipment. but god damn. when I see stuff like this I think to myself that we are not really that advanced yet.i guess all those missing airplanes or whatever are not that much of a surprise when this is the cream of the crop technology for old transmitters lollol like a potentiometer shaft that transfers no force is like 1/4 inch thick. this thing you can't pull with one arm is like a piece of thin spagehtto

author: jpanhalt
author_rank: Super Contributor
timestamp: October 30, 2023, 08:13:39 am
content: Quote from: coppercone2 on October 30, 2023, 06:25:41 amCollins made top quality avionics in its day. There have been subsequent mergers and acquisitions. In the many years since that radio was probably manufactured, it has been serviced multiple times. You seem to have accomplished breaking something no one else was able to do.QuoteA picture would help. Wire cable for many controls was typical in older aircraft and is still used today. Nothing wrong with it.QuoteSaid by someone who was able to break something carelessly that no one else could break.QuoteAfter reading this whole diatribe, my advice is to sleep on it and when sober, try to make sense of your question.

author: coppercone2
author_rank: Super Contributor
timestamp: October 30, 2023, 11:51:34 am
content: that rod that yanks on the capacitor is a total joke. with how much force that part has on it, compared to the normal forces you find on electronics parts vs their thickness, and the fact that its also connected to a thin fiberglass arm, you could say every other electronic part is overrated by a factor of 10000its ridiculously thin for what it does.and yeah you are gonna tell me what 50 year old seized and brittle plastic resin piece of shit is gonna break buddy

author: coppercone2
author_rank: Super Contributor
timestamp: October 30, 2023, 10:08:09 pm
content: it turns out there is a screw thread on the bottom of it, that little t-handle screws out. That means you can install a fiberglass rod or whatever in there so you can connect it to a linear actuator.

author: p.larner
author_rank: Frequent Contributor
timestamp: October 30, 2023, 10:51:21 pm
content: so is that just a handle to remove a blanking plug then?.

author: coppercone2
author_rank: Super Contributor
timestamp: October 31, 2023, 12:04:04 am
content: no it makes it extend that was the main thing it was pulling on. they had this like fiberglass claw built kinda like a old oil rig pump. like the movie chinatown

author: johnk0gcj@gmail.com
author_rank: Contributor
timestamp: October 31, 2023, 02:28:17 pm
content: Whole situation seems a bit hokey to me. That's not how any Jennings vacuumvariables I've seen are operated. An operating mechanism should be threadedinto that round piece(what I would call an arbor). What's missing? If therewasn't anything there, than someone somewhere along the line has made amodification.John

author: coppercone2
author_rank: Super Contributor
timestamp: October 31, 2023, 11:58:58 pm
content: well they made some pretty fuckin good quality fiber glass parts to pull on that little thing. That round piece is all smooth at the top, no threads. Thats what I thought at first, to thread it.I mean theoretically that little metal rod can support some force, but its just super anemic compared to the usual stuff you see.I have a feeling no one is gonna make a fiberglass 'claw' mold. It does kind of look like a non metal version of something you might see in some sort of car engine or whatever.. perhaps its possible someone used a modified car/engine/airplane part to make a mold with. Oh or maybe a spanner could be used for a base. I am thinking about it I think almost certainly in one of my tool boxes I have some sort of metal implement that looks kind of like that, along with some bizarre machinists tool accessories. It might be some kind of spanner for holding a shaft that has a pin installed in it.But honestly, my coffee milk stirrer (mechanized) has a thicker stainless steel shaft then the cap and all it does is stir a cup of coffee.I just wonder if it has some kind of special purpose, like a fuse. Maybe its from a storm chaser or something bizarre like that? Incase the antenna gets hit by lightning. Then that rod would vaporize... but it seems infinitely more plausible to put some kind of fuse else where in the circuit the inside of the hollow portion of a variable capacitor. The navy does have some strange planes that fly into bad weather on purpose.