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Post by racket on Jul 30, 2022 16:49:16 GMT -5
Hi Mark
Its only the T2 minus T1 g/g now , I swapped them around so that TOT is further away and in the clear , theres 1.5 cubic metres per sec ( >3000 CFM) of air going in , its a decent sized vac , I 'll just have to wait and see.
Cheers John
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Post by racket on Aug 3, 2022 17:50:29 GMT -5
Hi Guys While waiting for the rotor to be balanced I thought I'd tackle another issue thats been perplexing me , namely my T2 minus T1 temps . In early testing they showed comp efficiency in the high 70's % , where they should be , but in more recent times that has dropped 10% to mid 60's% , something ain't right I tried adding some "protection" around the T2 sensor to prevent radiant heat from the flametube getting to the sensor , but to no success , maybe some abberant air currents , so I've added a new/additional sensor to read T2 . Its mounted inside a length of 5mm steel tubing positioned in the middle of a diffuser channel just as the air "turns the corner" , the tube has a large entry hole and a smaller exit hole in the end , this should produce stagnation temps at the sensor with a modest air flow rate over it . Hopefully this will provide some clarity to my readings Cheers John
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dieselguy86
Veteran Member
Joined: September 2014
Posts: 186
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Post by dieselguy86 on Aug 3, 2022 18:37:13 GMT -5
John, what do you use for a sensor? I have a guy who has tried using an egt and Bluetooth grill temp sensors for measuring t2. Problem we always have is delay. Just wondering if there's anything faster, auber instruments has an open element sensor I thought about trying.
-Joe
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Post by racket on Aug 3, 2022 18:55:34 GMT -5
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slittlewing
Senior Member
Joined: November 2017
Posts: 458
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Post by slittlewing on Aug 4, 2022 11:03:09 GMT -5
Hi Joe,
I would recommend a 1mm or 1.5mm probe type thermocouple, you can buy compression fittings for them so they seal gas tight.
They will stand up to the tip being in the fast airstream but also give quick response due to the small diameter
Cheers
Scott
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Post by andym on Aug 4, 2022 14:35:55 GMT -5
John, what do you use for a sensor? I have a guy who has tried using an egt and Bluetooth grill temp sensors for measuring t2. Problem we always have is delay. Just wondering if there's anything faster, auber instruments has an open element sensor I thought about trying. -Joe try these EGT ProbeHave few I have brought for new engine
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Post by racket on Aug 12, 2022 17:37:09 GMT -5
Hi Guys
Rotor has been balanced and is safely back home ..............time to get to work :-)
Cheers John
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Post by racket on Aug 13, 2022 3:20:35 GMT -5
Hi Guys
Engine back together and on the test stand , just some ancillories and A/B to fit :-)
Nice to see her back together .
Cheers John
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Post by andym on Aug 13, 2022 4:14:16 GMT -5
Hi John Looking forward to seeing it run again.... intrested how the water injection helps or not, by how much... looking forward to video All the best Andy
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Post by racket on Aug 14, 2022 0:49:29 GMT -5
Hi Andy
Yep , it'll be "interesting" :-)
Teststand back on the trailer , just need to find all the other bits, its been a while since my last test .
I also opened up the A/B nozzle to 136 mm from its previous 130 mm , ~10% more area to cope with the extra ~10% exducer flow area increase .
Cheers John
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Post by racket on Aug 15, 2022 4:37:58 GMT -5
Hi Guys
One question for the physics nerds ..............why does my trailer want to tilt down at the front under full thrust .
The thrust line of the engine is several inches above the tether/loadcell/chain .
Is there a couple/moment causing a downforce ??
Am I not reading the actual engine thrust , but only that part "horizontal" to the ground , with some portion of thrust being "hidden" as a vertical force ??
Its been too long since school :-(
Any thought appreciated .
Cheers John
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monty
Senior Member
Currently being spanked by mother nature.......
Joined: September 2018
Posts: 400
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Post by monty on Aug 15, 2022 7:53:59 GMT -5
Hi Guys One question for the physics nerds ..............why does my trailer want to tilt down at the front under full thrust . The thrust line of the engine is several inches above the tether/loadcell/chain . Is there a couple/moment causing a downforce ?? Am I not reading the actual engine thrust , but only that part "horizontal" to the ground , with some portion of thrust being "hidden" as a vertical force ?? Its been too long since school :-( Any thought appreciated . Cheers John Hi John,
Moments are funny things. The thrust vector from the engine creates a torque about the trailer axle. It is reacted out at the front of the trailer. Your scale measures the thrust vector directly, not the moment or torque. The value of the torque is thrust times the distance from the axle (at 90 degrees to the thrust line). The force on the front of the trailer times it's horizontal distance from the axle must equal this value.
Monty
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Post by racket on Aug 15, 2022 16:29:04 GMT -5
Hi Monty
Thats sorta making sense , I might just need to get out pencil and paper and draw this up so these old grey cells can visualise it , thanks for that :-)
Cheers John
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monty
Senior Member
Currently being spanked by mother nature.......
Joined: September 2018
Posts: 400
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Post by monty on Aug 15, 2022 21:48:50 GMT -5
Hi Monty Thats sorta making sense , I might just need to get out pencil and paper and draw this up so these old grey cells can visualise it , thanks for that :-) Cheers John F1
---------------> | | Y
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+--------------------------^ | | F2
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F1 * Y = F2 * X How's this? The plus sign is the center of the axle. ;-)
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Post by racket on Aug 16, 2022 0:42:16 GMT -5
Thats it :-)
But something is troubling me :-(
If a jet kart has a high mounted engine , lets say 3 feet above the axle and the wheelbase is 6 feet and we have say 100 lbs of thrust , then there'll be an extra 50 lbs of downforce on the front wheels .
That 50 lbs must come from somewhere , LOL, it must be tied up in Sine Cos and Tan somewhere , is there a "resultant??" , do we actually lose motive thrust .
I've tried looking at aircraft "thrust lines" for inspiration , but its still got me perplexed .
Cheers John
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