What wiring for Trevor Gore style side bender?

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mChavez
Gidgee
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What wiring for Trevor Gore style side bender?

Post by mChavez » Sun Jul 14, 2019 3:43 am

Hi All,

I would be grateful for some advice on what wiring to use in the double-size Fox style side bender, as described in Trevor Gore's book.

I have just tried test-running the heat box that I have built using heat resistant oven wiring (soldered inside the box, insulated with high-temp glass fibre tape) and the test has failed miserably.

Wiring was rated up to 200C (as is any heat-resistant wiring that is easily accessible to me). Solder melting point is 180C. Glass fibre tapes should be able to withstand 300+C prolonged exposure.

I dropped a barbecue thermometer inside the box to have an idea of how hot it gets and added extra insulation in case any of the components failed (at the end of the day, the inside of the box is covered with aluminium foil!). My main concern was the solder.

First 15 minutes went well - the open box has heated up to 120C. I then covered the box with a steel sheet, simulating a closed side bender.
at about 23 minutes (thermo showing 170ish ) the tape has melted rapidly (the glass fibre was OK, the stuff that was holding it together has turned liquid), the soldering appears to have started to melt and heat-resistant wiring started smouldering.

I can upgrade the tape to polyimide perhaps (Rated at 260C @ 30 min exposure) and I can drill a few extra holes and minimise the amount of wiring inside the box with no solder, but what about the wiring itself?
Assuming that polyimide stands up to the heat, I can add a few layers of it as safety insulation - has anyone used it?

Thanks and stay safe!

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kiwigeo
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Re: What wiring for Trevor Gore style side bender?

Post by kiwigeo » Sun Jul 14, 2019 10:35 am

Welcome to the forum.

For bending sides you're going to need temps generally in the range 176 to 204degF. If you're having issues at 200degC then your bender isn't going to work.

The two main (practical) ways of supplying heat for a Fox style side bender are either incandescent light bulbs or silicon heating blankets. I started off using light bulbs (3 x 200 watt wired in parallel) screwed into porcelain fittings and with all wiring external to the box but bulbs are hard to find these days so I now use a silicone heat blanket. For bending with the blanket I use a sandwich consisting from bottom up of stainless steel/wood/spring steel. Power to the blanket runs through a router speed controller. I don't have any sort of temperature controller or a cut out timer but I'd strongly advise to use both just for safety's sake.

Al the above aside...I do most of my bending the old fashioned way on an iron....not sure why, think I just enjoy being more in touch with the wood as it bends.
Martin

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kiwigeo
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Re: What wiring for Trevor Gore style side bender?

Post by kiwigeo » Sun Jul 14, 2019 10:44 am

Light bulb powered fox style benders discussed here. Do a search and you should come up with discussions on using heat blankets.

viewtopic.php?t=768
Martin

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Trevor Gore
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Re: What wiring for Trevor Gore style side bender?

Post by Trevor Gore » Sun Jul 14, 2019 2:55 pm

When I built my side bender it was really hard to find ceramic globe holders for a decent price. What I ended up doing was buying 3 sets of security lights (with photo/movements sensors etc.) which had ceramic globe holders for PAR 38 globes (rated at 250w, iirc). This (crazily) was a lot cheaper option than buying 6 plain ceramics fittings. I scavenged enough cabling out of the the security lights to wire up the bender and then add a standard mains lead on the end of that in a switch unit on the outside of the frame.

It's been running without maintenance for about 20 years now. And incandescent PAR 38s are still available.

The electric heating pipe made out of aluminium yacht mast section uses a 500w linear globe scavenge from a cheap flood light from which I also used the ceramic globe holders and associated wiring. That has also been running for 20 years and I've changed the globe once. It gets a lot hotter than the side bender.

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kiwigeo
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Re: What wiring for Trevor Gore style side bender?

Post by kiwigeo » Sun Jul 14, 2019 3:56 pm

Reptile equipment supply shops are a good source for ceramic light sockets.....it's where I got mine:

https://www.ebay.com.au/p/Leviton%2DMfg ... 6303&rt=nc
Martin

mChavez
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Re: What wiring for Trevor Gore style side bender?

Post by mChavez » Sun Jul 14, 2019 6:48 pm

Thank you very much for the replies.

I have the sockets already and they should stand up to heat. Tried heat blankets in the past and didn't like them, so the bulb idea sounds better.

I did the soldering inside the box, assembled the box and then realised that it was not very smart, as solder melts at 180C. Decided to try it out anyway to see it fail. What I id not expect was to see the rest of the components go. I guess that the temperature ratings declared for various components do not necessarily reflect their long exposure limits.

I will re-wire the box to take the wiring outside as soon as it exits the bulb sockets, add some more shielding and upgrade to ptfe wires - hopefully, that will sort out the issues.

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kiwigeo
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Re: What wiring for Trevor Gore style side bender?

Post by kiwigeo » Sun Jul 14, 2019 9:19 pm

mChavez wrote:
Sun Jul 14, 2019 6:48 pm
Thank you very much for the replies.

I have the sockets already and they should stand up to heat. Tried heat blankets in the past and didn't like them, so the bulb idea sounds better.

I will re-wire the box to take the wiring outside as soon as it exits the bulb sockets, add some more shielding and upgrade to ptfe wires - hopefully, that will sort out the issues.
Make sure the sockets are ceramic...nothing else will do.
Take the wiring to and between the lights out the bottom of the ceramic sockets and then straight out the bottom of the box....you shouldn't have any wiring inside the box. Also make sure you run the bender on a timer.....people have burned down workshops leaving benders turned on.
Martin

MattW
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Re: What wiring for Trevor Gore style side bender?

Post by MattW » Mon Jul 15, 2019 9:16 pm

RS components has ceramic terminal blocks to replace solder or other joints in the hot zone

https://au.rs-online.com/web/p/non-fuse ... s/7033846/
Cheers

Matt

mChavez
Gidgee
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Re: What wiring for Trevor Gore style side bender?

Post by mChavez » Mon Oct 28, 2019 4:33 am

Thanks everyone - I've upgraded the wiring and took it straight out of the box. Double bender works like a dream (like every other idea I have tried from the book)! Tested 4 sets of b&s, moulded linings, bindings.

One thing I've noticed is that the moisture seems to condense on the steel sheets, then run down the wooden blanks, leading to discolouration on some woods, as the natural colours start to run (mahogany was particularly bad). Easy enough to fix with a bit of scraping, but it did get me wondering if I am doing something wrong.
The process so far was to sprinkle some water, then heat up and tighten.
The temperature seems to go up to about 160-170 C by the time I close the box and I then give it another 5 minutes, keeping the temp within 165-175 C range. At this point there's a bit of hissing coming from the wood (as the moisture starts to boil?).
Tried the above without sprinkling some water, and the result was marginally better, but the actual bending was a lot harder.

Thank you for all the advice.

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