Re: KR> home-brew thermocouples...for cheap!
Can you send the link to the wire you used. I assume you twisted the ends and then just melted a tiny blob on the end with no rod, correct? Brian Kraut 904-536-1780 br...@eamanuacturing.com Original Message Subject: KR> home-brew thermocouples...for cheap! From: Mark Langford via KRnet Date: Thu, June 08, 2017 6:46 pm To: KRnet Cc: Mark Langford NetHeads, I finally got my Revmaster heads last week, and have installed them and have put five hours on the engine so far. With new-found compression and big-valve heads, it's back to the ~170mph top speed and nice climb rate it had after the first rebuild. But the Revmaster heads come with 12mm spark plugs, and at $35 each, I really didn't want to shell out $140 for four CHT probes, so I bought some K-type thermocouple wire for $9.50 off ebay (free shipping), 12mm-#8 ring terminals for $0.55 each from Digikey, and built all four CHT probes for $18. Having seen thermocouple welders on youtube, I used my TIG welder set on 10A (the lowest setting) and just barely struck an arc with the pedal to weld the twisted thermocouple wires together in about 1.5 seconds, crimped the thermocouple to the ring terminal, and double heat shrank the terminal unions, with some superglue added underneath the shrink tube for good measure. Now I have home-brewed custom thermocouples for cheap, that are exactly the right length for each spark plug. And the fact that some are as much as 20% longer made no measurable difference. I tested all four (plus a spare OAT sensor and a Fluke temp probe) and they match within .6 degree F of each other using a six channel Omega tester at room temperature, so I'd call them "close enough for KR work"! Something else I learned was the effect of tinning the instrument end of the thermocouple wire. My thermocouple wire is stranded, so when I plug into the little slots on the tester the strands separate and make a mess. [And yes, know there's a connector for that job.] So I wondered what the accuracy difference would be if I tinned the end of the thermocouple wires with some solder. The answer, despite what I've read over the years, was "no measurable difference at all", at least not at ambient temperature. I flew the plane today, and cylinder head temps were amazingly uniform for a change. Of course a new pair of Revmaster heads didn't hurt either. So neither length nor material compatibility at the connections make enough difference to accurately measure, and the difference may just be the way I welded them or some other tiny factor. And given the low accuracy required for CHT duty, the tiny differences in accuracy are "in the noise" anyway. So there's another thing I can quit fretting over, and so can you. See enclosed photo... -- Mark Langford m...@n56ml.com http://www.n56ml.com ___ Search the KRnet Archives at https://www.mail-archive.com/krnet@list.krnet.org/. Please see LIST RULES and KRnet info at http://www.krnet.org/info.html. see http://list.krnet.org/mailman/listinfo/krnet_list.krnet.org to change options. To UNsubscribe from KRnet, send a message to krnet-le...@list.krnet.org ___ Search the KRnet Archives at https://www.mail-archive.com/krnet@list.krnet.org/. Please see LIST RULES and KRnet info at http://www.krnet.org/info.html. see http://list.krnet.org/mailman/listinfo/krnet_list.krnet.org to change options. To UNsubscribe from KRnet, send a message to krnet-le...@list.krnet.org
Re: KR> home-brew thermocouples...for cheap!
On 6/9/2017 7:44 AM, Chris Kinnaman via KRnet wrote: Then you would be testing your oven's thermostat. Depending on elevation, boiling water will be pretty close to 100C no matter what. But you're right, factory thermocouples probably get tested maybe 1 out of 100. Yep, I understand that water is better for testing actual accuracy, but accuracy isn't nearly as important as them all reading the same value at the same temperature (in my CHT application) so I can pick out a cylinder that's higher or lower than the rest, or use the info to optimize cooling through baffling tweaks. When I tested these four at ambient, I also used a "factory" Fluke K thermocouple that came with my Fluke 52 Thermometer, and I have several others, so those would have been used in the oven as "reference" thermocouples to verify accuracy. Given that these are now hooked to my flaky iEFIS, all bets regarding accuracy are off anyway Mark Langford m...@n56ml.com http://www.n56ml.com ___ Search the KRnet Archives at https://www.mail-archive.com/krnet@list.krnet.org/. Please see LIST RULES and KRnet info at http://www.krnet.org/info.html. see http://list.krnet.org/mailman/listinfo/krnet_list.krnet.org to change options. To UNsubscribe from KRnet, send a message to krnet-le...@list.krnet.org
Re: KR> home-brew thermocouples...for cheap!
How are the Revmaster heads Cht doing I had already ordered heads before I saw your review to replace my cracked ones Sent from my iPhone > On Jun 9, 2017, at 7:46 AM, Chris Kinnaman via KRnet > wrote: > > Then you would be testing your oven's thermostat. Depending on elevation, > boiling water will be pretty close to 100C no matter what. But you're right, > factory thermocouples probably get tested maybe 1 out of 100. > >> On 6/9/2017 5:33 AM, Mark Langford via KRnet wrote: >> Chris Kinnaman wrote: >> >> >>The only thing I would have done different would be testing them in >> >>boiling water as well as ambient.<< >> >> I thought about that, but clamping them all together and putting them in a >> preheated oven and then switching if off to let oven temps stabilize would >> have been even better, but it was late, and I wanted to fly early the next >> day. Even the test I gave them is probably more than "factory" thermocouples >> get before they reach the end user, so I'm happy enough with them... >> >> Mark Langford >> m...@n56ml.com >> http://www.n56ml.com >> >> >> ___ >> Search the KRnet Archives at >> https://www.mail-archive.com/krnet@list.krnet.org/. >> Please see LIST RULES and KRnet info at http://www.krnet.org/info.html. >> see http://list.krnet.org/mailman/listinfo/krnet_list.krnet.org to change >> options. >> To UNsubscribe from KRnet, send a message to krnet-le...@list.krnet.org >> >> > > > ___ > Search the KRnet Archives at > https://www.mail-archive.com/krnet@list.krnet.org/. > Please see LIST RULES and KRnet info at http://www.krnet.org/info.html. > see http://list.krnet.org/mailman/listinfo/krnet_list.krnet.org to change > options. > To UNsubscribe from KRnet, send a message to krnet-le...@list.krnet.org ___ Search the KRnet Archives at https://www.mail-archive.com/krnet@list.krnet.org/. Please see LIST RULES and KRnet info at http://www.krnet.org/info.html. see http://list.krnet.org/mailman/listinfo/krnet_list.krnet.org to change options. To UNsubscribe from KRnet, send a message to krnet-le...@list.krnet.org
Re: KR> home-brew thermocouples...for cheap!
Then you would be testing your oven's thermostat. Depending on elevation, boiling water will be pretty close to 100C no matter what. But you're right, factory thermocouples probably get tested maybe 1 out of 100. On 6/9/2017 5:33 AM, Mark Langford via KRnet wrote: Chris Kinnaman wrote: >>The only thing I would have done different would be testing them in boiling water as well as ambient.<< I thought about that, but clamping them all together and putting them in a preheated oven and then switching if off to let oven temps stabilize would have been even better, but it was late, and I wanted to fly early the next day. Even the test I gave them is probably more than "factory" thermocouples get before they reach the end user, so I'm happy enough with them... Mark Langford m...@n56ml.com http://www.n56ml.com ___ Search the KRnet Archives at https://www.mail-archive.com/krnet@list.krnet.org/. Please see LIST RULES and KRnet info at http://www.krnet.org/info.html. see http://list.krnet.org/mailman/listinfo/krnet_list.krnet.org to change options. To UNsubscribe from KRnet, send a message to krnet-le...@list.krnet.org ___ Search the KRnet Archives at https://www.mail-archive.com/krnet@list.krnet.org/. Please see LIST RULES and KRnet info at http://www.krnet.org/info.html. see http://list.krnet.org/mailman/listinfo/krnet_list.krnet.org to change options. To UNsubscribe from KRnet, send a message to krnet-le...@list.krnet.org
Re: KR> home-brew thermocouples...for cheap!
Chris Kinnaman wrote: >>The only thing I would have done different would be testing them in boiling water as well as ambient.<< I thought about that, but clamping them all together and putting them in a preheated oven and then switching if off to let oven temps stabilize would have been even better, but it was late, and I wanted to fly early the next day. Even the test I gave them is probably more than "factory" thermocouples get before they reach the end user, so I'm happy enough with them... Mark Langford m...@n56ml.com http://www.n56ml.com ___ Search the KRnet Archives at https://www.mail-archive.com/krnet@list.krnet.org/. Please see LIST RULES and KRnet info at http://www.krnet.org/info.html. see http://list.krnet.org/mailman/listinfo/krnet_list.krnet.org to change options. To UNsubscribe from KRnet, send a message to krnet-le...@list.krnet.org
Re: KR> home-brew thermocouples...for cheap!
Thanks, Mark. Years ago I used to make thermocouple probes and fixtures similar to this for taking heat rise profiles & calibrating various pieces of composite curing equipment around the plant. The only thing I would have done different would be testing them in boiling water as well as ambient. I got similar results - nothing seemed to be critical in the manner of construction or anything else that had a major effect on accuracy. I'm sure if I was going for a finer degree of accuracy I could have found that some of my probes were worse than others. Looking for a range rather than a pinpoint helped - which is what we're doing measuring CHT. Chris K. On 6/8/2017 7:46 PM, Mark Langford via KRnet wrote: But the Revmaster heads come with 12mm spark plugs, and at $35 each, I really didn't want to shell out $140 for four CHT probes, so I bought some K-type thermocouple wire for $9.50 off ebay (free shipping), 12mm-#8 ring terminals for $0.55 each from Digikey, and built all four CHT probes for $18. ___ Search the KRnet Archives at https://www.mail-archive.com/krnet@list.krnet.org/. Please see LIST RULES and KRnet info at http://www.krnet.org/info.html. see http://list.krnet.org/mailman/listinfo/krnet_list.krnet.org to change options. To UNsubscribe from KRnet, send a message to krnet-le...@list.krnet.org
Re: KR> home-brew thermocouples...for cheap!
Awesome report and final product. I am ordering the heads for my Revmaster this week and now I have a game plan for the CHT wires. Thanks Mark Luis R ClaudioDallas, Texas KR2S still 6 months out on a running engine/airplane On Thursday, June 8, 2017 8:48 PM, Mark Langford via KRnet wrote: NetHeads, I finally got my Revmaster heads last week, and have installed them and have put five hours on the engine so far. With new-found compression and big-valve heads, it's back to the ~170mph top speed and nice climb rate it had after the first rebuild. But the Revmaster heads come with 12mm spark plugs, and at $35 each, I really didn't want to shell out $140 for four CHT probes, so I bought some K-type thermocouple wire for $9.50 off ebay (free shipping), 12mm-#8 ring terminals for $0.55 each from Digikey, and built all four CHT probes for $18. Having seen thermocouple welders on youtube, I used my TIG welder set on 10A (the lowest setting) and just barely struck an arc with the pedal to weld the twisted thermocouple wires together in about 1.5 seconds, crimped the thermocouple to the ring terminal, and double heat shrank the terminal unions, with some superglue added underneath the shrink tube for good measure. Now I have home-brewed custom thermocouples for cheap, that are exactly the right length for each spark plug. And the fact that some are as much as 20% longer made no measurable difference. I tested all four (plus a spare OAT sensor and a Fluke temp probe) and they match within .6 degree F of each other using a six channel Omega tester at room temperature, so I'd call them "close enough for KR work"! Something else I learned was the effect of tinning the instrument end of the thermocouple wire. My thermocouple wire is stranded, so when I plug into the little slots on the tester the strands separate and make a mess. [And yes, know there's a connector for that job.] So I wondered what the accuracy difference would be if I tinned the end of the thermocouple wires with some solder. The answer, despite what I've read over the years, was "no measurable difference at all", at least not at ambient temperature. I flew the plane today, and cylinder head temps were amazingly uniform for a change. Of course a new pair of Revmaster heads didn't hurt either. So neither length nor material compatibility at the connections make enough difference to accurately measure, and the difference may just be the way I welded them or some other tiny factor. And given the low accuracy required for CHT duty, the tiny differences in accuracy are "in the noise" anyway. So there's another thing I can quit fretting over, and so can you. See enclosed photo... -- Mark Langford m...@n56ml.com http://www.n56ml.com ___ Search the KRnet Archives at https://www.mail-archive.com/krnet@list.krnet.org/. Please see LIST RULES and KRnet info at http://www.krnet.org/info.html. see http://list.krnet.org/mailman/listinfo/krnet_list.krnet.org to change options. To UNsubscribe from KRnet, send a message to krnet-le...@list.krnet.org ___ Search the KRnet Archives at https://www.mail-archive.com/krnet@list.krnet.org/. Please see LIST RULES and KRnet info at http://www.krnet.org/info.html. see http://list.krnet.org/mailman/listinfo/krnet_list.krnet.org to change options. To UNsubscribe from KRnet, send a message to krnet-le...@list.krnet.org
