Glow Plug Use

[HAR]

Tomorrow, I may get a chance to 'test' my glow plugs! Forecast is
Tonight low around -7F. Saturday high near 3F. Saturday Night a low around -6F

 

[HAR]

So. It was -5F earlier this morning, and about 2F when I finally got out to try the cold start. While not definitive, it took at least 20 seconds for plugs to be hot enough for the cold start this morning. I cracked the throttle about 1/4 and I tried 10 seconds, then 15, and after the 20 seconds, I got a good start. As tomorrow will be another cold one, I will try once more, and go with 20+ for the first try.

Once started, I wanted the engine to warm up some and I got a chance to answer a long term question. And that has to do with the HOBBS meter. They are calibrated in 1/10 of an hour units or each tenth is 6 minutes. I had mentioned once before that I questioned how the meter worked as I was pretty sure that when the engine was running at low RPM, the meter was not clocking true hours.

Member newbury had said: "Just make sure how the hour meter on the equipment runs.
For example some tractors only count hours at full PTO speed."

Supposedly, my engine is at full power at 2900 RPM. While the engine was running, set at about 2000 RPM, I got my cell phone out and set it to a stop watch and waited for the HOBBS to turn 1/10th. When it did, I started the stop watch. When it turned again, to the next 1/10th, I stopped it. If my HOBBS only works correctly at full RPM, by simple math, at 2000 RPM, the HOBBS should have changed at about 8.7 minutes. As I am not sure the exact RPM, I was somewhat pleased when the meter turned at 8min 2seconds. Working that backwards, I estimate my engine was probably running about 2175 RPM. Ahhh...the things I do when I have way tooooo much time on my hands! Isn't retirement fun!

 

[mjonesnh]

Believe my New Holland counts actual time tractor is running. Idling vs full PTO speed seems to count at same rate.

 

[Mtsoxfan]

So. It was -5F earlier this morning, and about 2F when I finally got out to try the cold start. While not definitive, it took at least 20 seconds for plugs to be hot enough for the cold start this morning. I cracked the throttle about 1/4 and I tried 10 seconds, then 15, and after the 20 seconds, I got a good start. As tomorrow will be another cold one, I will try once more, and go with 20+ for the first try.

Once started, I wanted the engine to warm up some and I got a chance to answer a long term question. And that has to do with the HOBBS meter. They are calibrated in 1/10 of an hour units or each tenth is 6 minutes. I had mentioned once before that I questioned how the meter worked as I was pretty sure that when the engine was running at low RPM, the meter was not clocking true hours.

Member newbury had said: "Just make sure how the hour meter on the equipment runs.
For example some tractors only count hours at full PTO speed."

Supposedly, my engine is at full power at 2900 RPM. While the engine was running, set at about 2000 RPM, I got my cell phone out and set it to a stop watch and waited for the HOBBS to turn 1/10th. When it did, I started the stop watch. When it turned again, to the next 1/10th, I stopped it. If my HOBBS only works correctly at full RPM, by simple math, at 2000 RPM, the HOBBS should have changed at about 8.7 minutes. As I am not sure the exact RPM, I was somewhat pleased when the meter turned at 8min 2seconds. Working that backwards, I estimate my engine was probably running about 2175 RPM. Ahhh...the things I do when I have way tooooo much time on my hands! Isn't retirement fun!

Where in VT are you. Just got in and we are still at -8. Better than -18 at 3 am. At least the wind stopped.

 

[HAR]

Where in VT are you. Just got in and we are still at -8. Better than -18 at 3 am. At least the wind stopped.

Addison County, near Middlebury...hmmm...as for actual coldest overnight temp....I was tucked snuggly in my bed at 3AM! We are on top of a 400FT hill which makes a difference, and the sky has been clear and sun bright since sunup. Currently 7F in the shade.

 

[Mtsoxfan]

We're as bit further north. Currently -7 in shade. We're at about 1600' but on an east ridge, so wind is plentiful all year round. Damn snow drifts. I was only up at 3 because catalyst on woodstove plugged and issues arose. About to bundle up and see how far I want to snowshoe. Wind picked up, so may be short lived. Hope the weather guessers are off on their amounts of snow tomorrow evening.

 

[HAR]

We're as bit further north. Currently -7 in shade. We're at about 1600' but on an east ridge, so wind is plentiful all year round. Damn snow drifts. I was only up at 3 because catalyst on woodstove plugged and issues arose. About to bundle up and see how far I want to snowshoe. Wind picked up, so may be short lived. Hope the weather guessers are off on their amounts of snow tomorrow evening.

Well, your 1600ft level explains part of it. From my days as a 'student' pilot, I remember that there was approximately a 3°C drop (or 5.4°F) for every 1,000 feet gained in elevation under dry conditions, up to a certain altitude. If it's snowing or raining, the decrease is about 1.8°C (or 3.3°F) for every 1,000 feet. That is why, if you happen to be flying in a passenger airline at 35-40MASL, and the little screen on the seat back in front of you shows some bizarre outside temp of say -40F, you now know why.

While you are correct about the 'weather guessers', it appears we in VT will be in the white by later Monday! Let's hope the tractor starts and no problem arise with the snowblower!

 

[Mtsoxfan]

Never made it out of negative numbers. -6 was the "high".

 

[grsthegreat]

Last year my tractor struggled to start since fall. I wasn’t able to get around to changing the plugs until this spring. Major difference. Today was 12°f, tractor fired up without any issues. Acted like brand new. 10 second auto timed glow cycle, fired off beautifully.

 

[ponytug]

So. It was -5F earlier this morning, and about 2F when I finally got out to try the cold start. While not definitive, it took at least 20 seconds for plugs to be hot enough for the cold start this morning. I cracked the throttle about 1/4 and I tried 10 seconds, then 15, and after the 20 seconds, I got a good start. As tomorrow will be another cold one, I will try once more, and go with 20+ for the first try.

Once started, I wanted the engine to warm up some and I got a chance to answer a long term question. And that has to do with the HOBBS meter. They are calibrated in 1/10 of an hour units or each tenth is 6 minutes. I had mentioned once before that I questioned how the meter worked as I was pretty sure that when the engine was running at low RPM, the meter was not clocking true hours.

Member newbury had said: "Just make sure how the hour meter on the equipment runs.
For example some tractors only count hours at full PTO speed."

Supposedly, my engine is at full power at 2900 RPM. While the engine was running, set at about 2000 RPM, I got my cell phone out and set it to a stop watch and waited for the HOBBS to turn 1/10th. When it did, I started the stop watch. When it turned again, to the next 1/10th, I stopped it. If my HOBBS only works correctly at full RPM, by simple math, at 2000 RPM, the HOBBS should have changed at about 8.7 minutes. As I am not sure the exact RPM, I was somewhat pleased when the meter turned at 8min 2seconds. Working that backwards, I estimate my engine was probably running about 2175 RPM. Ahhh...the things I do when I have way tooooo much time on my hands! Isn't retirement fun!

I'm glad that you've got a starting plan sorted out.

I have several Hobbs units on various engines, and they all run true power on hours, but mine are all voltage driven, rather than a mechanically driven Hobbs.

Thanks for the general rule on altitude driven temperature drops.

All the best, Peter

 

[dkmc]

They’re not training manuals. Kinda like engineering plans for building the infrastructure on a subdivision. It’s not a plan for a carpenter or a mechanic. Certain amounts of knowledge or knowledge, experience and correlation are in order.

Didn't say it was a 'training manual'. Don't need training, need correct info on repairing the machine.
It says right on the front....Repair Manual. I expect it to offer step by step instructions on how to repair the machine. Kinda like a good repair manual works, not lacking steps because the authors cut corners and basically didn't do the research needed to include meaningful content. Your comment makes no sense, but some people will eagerly express their counter opinion just to be able to disagree.

 

[aircommuter]

Well, your 1600ft level explains part of it. From my days as a 'student' pilot, I remember that there was approximately a 3°C drop (or 5.4°F) for every 1,000 feet gained in elevation under dry conditions, up to a certain altitude. If it's snowing or raining, the decrease is about 1.8°C (or 3.3°F) for every 1,000 feet. That is why, if you happen to be flying in a passenger airline at 35-40MASL, and the little screen on the seat back in front of you shows some bizarre outside temp of say -40F, you now know why.

While you are correct about the 'weather guessers', it appears we in VT will be in the white by later Monday! Let's hope the tractor starts and no problem arise with the snowblower!

You need to go back on your student pilot days and study. 3.3f is per thousand feet and no commercial aircraft can fly at that altitude you referenced. I am not student pilot but a licensed pilot.

 

[aircommuter]

I'm glad that you've got a starting plan sorted out.

I have several Hobbs units on various engines, and they all run true power on hours, but mine are all voltage driven, rather than a mechanically driven Hobbs.

Thanks for the general rule on altitude driven temperature drops.

All the best, Peter

Hobbs hours are actual hours the meters are activated typically by oil pressure. Mechanical tachometer hours are average hours based on revolutions. Usually about 60% of actual.

 

[ponytug]

Hobbs hours are actual hours the meters are activated typically by oil pressure. Mechanical tachometer hours are average hours based on revolutions. Usually about 60% of actual.

Perhaps, and I do not work on aircraft, but I've never come across a Hobbs meter connected to oil pressure. As I understand it, oil pressure connections are an aviation use case, but again, not an expert here.

Hobbs meter - Wikipedia

en.wikipedia.org

All the best, Peter

 

[aircommuter]

Perhaps, and I do not work on aircraft, but I've never come across a Hobbs meter connected to oil pressure. As I understand it, oil pressure connections are an aviation use case, but again, not an expert here.

Hobbs meter - Wikipedia

en.wikipedia.org

All the best, Peter

I agree with part of your statement.