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How to strengthen this knob

WotEver

By WotEver
in Boat Building & Maintenance

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cuthound Veteran II

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Posted
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11 hours ago, WotEver said:

Yeah... the sales bumph proudly proclaimed that it was 20,000 ohms per volt on DC, so it was well posh. 

B73C5052-57E1-44EC-A777-65260D0513F3.jpeg.271d0e066d10b1a560e8edc4f9e521b9.jpeg

 

Ohms per volt was an indication of how accurate the meter was. A lower ohms per volt (aka input impedance) shunted more current through the meter thus distorting accurate reading.

 

When I was learning my trade, valve voltmeters were the dogs danglies for accurate voltage measurement, along with oscilloscopes.

 

The introduction of digital voltmeters changed all that because they have a naturally high input impedance.

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WotEver Veteran II

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Oh I know all about OPV. When I was working on flight sims there were big signs all over the place that AVO 7s must not be used on any digital equipment. The 500 OPV of a 7 (a whole 1k with the x2 button pressed) wouldn’t only give misleading readings by loading it down but could actually burn out some early driver circuitry. We had a few DMMs around but they were all bulky mains jobs. 

 

So AVO 8s were the order of the day. 

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sharpness Rising Star

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On ‎01‎/‎02‎/‎2019 at 18:02, WotEver said:

Where’s the fun in that? I have several digital meters in addition to an Avo8 and a 1970’s hobby analogue thing.

https://www.stroudauctions.co.uk/0184day2-lot-1679-a-collection-of-electrical-testing-equipment-to-include-avometers-tong-test-etc?arr=0&auction_id=0&box_filter=0&cat_id=&department_id=&exclude_keyword=&export_issue=0&high_estimate=15000&image_filter=0&keyword=meter&list_type=list_view&lots_per_page=12&low_estimate=0&month=&page_no=2&paper_filter=0&search_priority[0]=upcoming&search_type=&show_day_sale=true&sort_by=lot_number&view=lot_detail&year.

 

Want some more??

 

Steve

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Momac Veteran

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14 hours ago, WotEver said:

So AVO 8s were the order of the day. 

Would an AVO model 7 have any value ?  I have  one to sell on which seems complete with probes , a leather case and instruction book. 

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WotEver Veteran II

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8 hours ago, harrybsmith said:

If you did want a new knob 3d printed (sadly not in bakelite) then I'd happily do it for you as I've got access to a couple of industrial spec machines

Thanks for the offer Harry. If I completely screw this one up (haven’t had the time to look at it yet) I’ll look into how long it would take me to try to model it in CAD. It’s actually quite a complex shape. Great offer though, thanks :)

 

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ditchcrawler Veteran II

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3 hours ago, WotEver said:

Thanks for the offer Harry. If I completely screw this one up (haven’t had the time to look at it yet) I’ll look into how long it would take me to try to model it in CAD. It’s actually quite a complex shape. Great offer though, thanks :)

 

Can you slice it through at the knob section so keeping the edge and face then graft that onto a new shaft and thin head made of something more substantial, maybe even turned aluminium

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WotEver Veteran II

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56 minutes ago, ditchcrawler said:

Can you slice it through at the knob section so keeping the edge and face then graft that onto a new shaft and thin head made of something more substantial, maybe even turned aluminium

Yeah, that’s kind of what I described in post #20, except I’ll be using a plastic shaft. 

 

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WotEver Veteran II

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6 minutes ago, croftie said:

May be worth a PM to Bod

He did end up saying " Any one interested in one for spare/repair, I can't fathom out how it works. "

That’s the one I’m attempting to fix :D

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ditchcrawler Veteran II

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5 hours ago, WotEver said:

Yeah, that’s kind of what I described in post #20, except I’ll be using a plastic shaft. 

 

I was suggesting removing not only the shaft but a thin sliver of the knob, if the new shaft was made from metal the disk on the top could be very thin to bond the remains of the knob on. A bit like a metal mushroom

 

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WotEver Veteran II

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13 minutes ago, ditchcrawler said:

I was suggesting removing not only the shaft but a thin sliver of the knob, if the new shaft was made from metal the disk on the top could be very thin to bond the remains of the knob on. A bit like a metal mushroom

Ahh, gotcha. That would require a lathe... something I don’t have. I’ll try the plastic-shaft-glued-into-a-hole first because I do have a pillar drill, and a plastic shaft, and araldite ;)

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W+T Influencer

W+T

Posted
Posted

Hi Tony

 

Could you adapt one of these, threaded already to tap into a through drilled hole.

 

https://www.ebay.co.uk/itm/M8-A2-SOLID-STAINLESS-STEEL-WOOD-METAL-DUAL-THREAD-DOWEL-SCREWS-BOLTS-STUD/362255145111?ssPageName=STRK%3AMEBIDX%3AIT&var=631465407148&_trksid=p2060353.m1438.l2649

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