Oehler 35 P Questions (Testing arrow speed)

Unlicensed Dremel · September 19, 2014, 04:49 PM

Got a used 35P.

But it came with only 2 skyscreens instead of three.

So I put one in the front of the 2 foot pole and 1 in the rear, and used the two cables in the "Start" and "Stop" jacks, but of course none in the Mid-point jack.

So, question is, can you, or can you not use this chrony with just two of the 3 skyscreens?

I thought you could - I thought that it would recognize that there was no middle cable plugged in and just "do the math" from the front to the rear one. Might not be as accurate as with three, but it would work, I thought.

Well, I'm getting readings of 455 to 474 with my arrows. This is a heavy-ish 485 gr arrow from a 60 lb compound bow - so it should be about 200 fps less than those readouts - maybe 250 to 275 fps. (Is it possible these are in some format other than feet per second? Deca-meters per minute?

)

So what gives? What can I garner from those readouts? Is there some math I can apply to those to arrive at a correct figure, or MUST I buy a third (middle) skyscreen to use chrony this at all?

Clearly it's working and taking consistent readings. They're just way off from accurate. So some math simply needs to be applied, it would seem. Just divide by two, perhaps? But that seems too low - I think these arrows are going faster than 227 to 237 but maybe not.

And I'm in bright sunlight so that's not the issue.

Thanks very much. I read the instructions but they don't address whether you can just skip having a middle screen. It sort of implies that you must have it, but not absolutely clear on that issue.

The instructions also talk about "Switches" and settings for them. I don't know what it's talking about - there are no switches of any kind on the unit. All there is, is (a) three buttons, and (b) three input jacks, (c) battery compartment, and (d) printer cable output jack. That's it.

EDIT: Note that the instructions describe the velocity measured from the first to the last screen as the "primary velocity" and the velocities measured from the 1st to the middle, and the middle to the last, as the "proof velocities, which are then measured against one another to tell you whether the primary velocity is suspect or not. But even if it cannot measure a proof velocity, can't it just measure the primary, is what I'm asking. These primaries though are obviously way too high. I mean, it appears to be actually measuring the primary velocities, but not accurately. That would make sense if one or two were that high perhaps, but not all of them.

http://stevespages.com/pdf/oehler_mo...hronograph.pdf

SECOND EDIT: Ok, now I see that the switches are inside the battery compartment. So what switch do I throw to make this work - make it disregard the middle/proof screen? Or is that possible? I adjusted the screens to make them exactly 2 feet apart, and I'm consistently getting around 467 average readings, with only 8-10 SD. Makes no sense to me.

THIRD EDIT: Nevermind; once I found the switches, all became right with the world. It was set for 3 feet between skyscreens instead of 2 feet. So, the answer is yes, it works with just two like I thought.

PS. The chrony works MUCH better in bright light than in the waning hours toward dusk, of course.

Unlicensed Dremel · September 19, 2014, 07:01 PM

Arrow Chrony Results 9/19/2014

Bow 1 - 2012 Strother Wrath SHO 60 lbs
Arrow A - total weight 485 gr; Avg vel: 238 fps
Arrow B - total weight 434 gr; Avg vel: 244 fps

Bow 2 - 2011 Hickory Creek 23 Magnum 85 lbs, w/ "Bullpup" Draw-Loc
Arrow A - total weight 445 gr; Avg vel: 284 fps

Bow 3 - 2011 Strother XS Rush 80 lbs, w/ "Regular" Draw-Loc
Arrow A (speed arrow) - total weight 363 gr; Avg vel: 330 fps
Arrow B - total weight 437 gr; Avg vel: 307 fps

That last one will git er dun.

First one is only one that's tuned right - it's super quiet. I think I'll hunt with it first. The second one is all jacked up tune-wise. Third (fast) one is quiet and smooth, but just needs a bit of tweaking the centershot with the draw-loc arm.

Been wanting to chrony this stuff for a few years now...finally got to it.

Are we practicing for the fall, gents & ladies?

Brian Pfleuger · September 20, 2014, 08:37 AM

You shoot some heavy arrows, bro.

Unlicensed Dremel · September 20, 2014, 04:49 PM

Heck yeah, man! Main reason being about 1/2 the places I hunt, never know when a feral boar might show up.

I want that penetration, too! Want that exit hole for a blood trail.

September 19, 2014, 04:49 PM	#1
Unlicensed Dremel Junior member Join Date: February 13, 2014 Location: Flathead Valley, MT Posts: 2,187	Oehler 35 P Questions (Testing arrow speed) Got a used 35P. But it came with only 2 skyscreens instead of three. So I put one in the front of the 2 foot pole and 1 in the rear, and used the two cables in the "Start" and "Stop" jacks, but of course none in the Mid-point jack. So, question is, can you, or can you not use this chrony with just two of the 3 skyscreens? I thought you could - I thought that it would recognize that there was no middle cable plugged in and just "do the math" from the front to the rear one. Might not be as accurate as with three, but it would work, I thought. Well, I'm getting readings of 455 to 474 with my arrows. This is a heavy-ish 485 gr arrow from a 60 lb compound bow - so it should be about 200 fps less than those readouts - maybe 250 to 275 fps. (Is it possible these are in some format other than feet per second? Deca-meters per minute? ) So what gives? What can I garner from those readouts? Is there some math I can apply to those to arrive at a correct figure, or MUST I buy a third (middle) skyscreen to use chrony this at all? Clearly it's working and taking consistent readings. They're just way off from accurate. So some math simply needs to be applied, it would seem. Just divide by two, perhaps? But that seems too low - I think these arrows are going faster than 227 to 237 but maybe not. And I'm in bright sunlight so that's not the issue. Thanks very much. I read the instructions but they don't address whether you can just skip having a middle screen. It sort of implies that you must have it, but not absolutely clear on that issue. The instructions also talk about "Switches" and settings for them. I don't know what it's talking about - there are no switches of any kind on the unit. All there is, is (a) three buttons, and (b) three input jacks, (c) battery compartment, and (d) printer cable output jack. That's it. EDIT: Note that the instructions describe the velocity measured from the first to the last screen as the "primary velocity" and the velocities measured from the 1st to the middle, and the middle to the last, as the "proof velocities, which are then measured against one another to tell you whether the primary velocity is suspect or not. But even if it cannot measure a proof velocity, can't it just measure the primary, is what I'm asking. These primaries though are obviously way too high. I mean, it appears to be actually measuring the primary velocities, but not accurately. That would make sense if one or two were that high perhaps, but not all of them. http://stevespages.com/pdf/oehler_mo...hronograph.pdf SECOND EDIT: Ok, now I see that the switches are inside the battery compartment. So what switch do I throw to make this work - make it disregard the middle/proof screen? Or is that possible? I adjusted the screens to make them exactly 2 feet apart, and I'm consistently getting around 467 average readings, with only 8-10 SD. Makes no sense to me. THIRD EDIT: Nevermind; once I found the switches, all became right with the world. It was set for 3 feet between skyscreens instead of 2 feet. So, the answer is yes, it works with just two like I thought. PS. The chrony works MUCH better in bright light than in the waning hours toward dusk, of course. Last edited by Unlicensed Dremel; September 20, 2014 at 04:49 PM.

September 20, 2014, 08:37 AM	#3
Brian Pfleuger Moderator Emeritus Join Date: June 25, 2008 Location: Austin, CO Posts: 19,578	You shoot some heavy arrows, bro. __________________ Nobody plans to screw up their lives... ...they just don't plan not to. -Andy Stanley

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September 19, 2014, 07:01 PM	#2
Unlicensed Dremel Junior member Join Date: February 13, 2014 Location: Flathead Valley, MT Posts: 2,187	Arrow Chrony Results 9/19/2014 Bow 1 - 2012 Strother Wrath SHO 60 lbs Arrow A - total weight 485 gr; Avg vel: 238 fps Arrow B - total weight 434 gr; Avg vel: 244 fps Bow 2 - 2011 Hickory Creek 23 Magnum 85 lbs, w/ "Bullpup" Draw-Loc Arrow A - total weight 445 gr; Avg vel: 284 fps Bow 3 - 2011 Strother XS Rush 80 lbs, w/ "Regular" Draw-Loc Arrow A (speed arrow) - total weight 363 gr; Avg vel: 330 fps Arrow B - total weight 437 gr; Avg vel: 307 fps That last one will git er dun. First one is only one that's tuned right - it's super quiet. I think I'll hunt with it first. The second one is all jacked up tune-wise. Third (fast) one is quiet and smooth, but just needs a bit of tweaking the centershot with the draw-loc arm. Been wanting to chrony this stuff for a few years now...finally got to it. Are we practicing for the fall, gents & ladies?

September 20, 2014, 04:49 PM	#4
Unlicensed Dremel Junior member Join Date: February 13, 2014 Location: Flathead Valley, MT Posts: 2,187	Heck yeah, man! Main reason being about 1/2 the places I hunt, never know when a feral boar might show up. I want that penetration, too! Want that exit hole for a blood trail.