Dualling Chonos

[DC]

In order to get a more accurate reading I have mounted my other chrono on my machine. I now have a dual chrono shooting machine. I have a Caldwell and a Chrony. If I put the Caldwell up front I get a 4-5 fps difference. The Caldwell is higher. If I put the Chrony up front they read identical but I'm having a hard time getting a good reading on the Caldwell. I keep getting 67-68 fps reading on the Caldwell but the Chrony says 204-206. Does anyone know what causes these low readings? It's about 33% of what the proper reading would be and I can't figure what's triggering it. If I knew that I may be able to figure what's causing it.

[bradsmith2010]

usually my readings like that are caused by the light source

[DC]

That may be it. I'm on hold waiting for Caldwell to answer the phone but it's been a half hour now. Maybe it's lunch time there. I'll fiddle with the lights. It's just a couple of incandescents in ice cream buckets but it's worked til now.

[Badger]

  68X3 =204!  Could it be yds per second? More commonly it will read meters per second.

[Azmdted]

I occasionally get a strange double digit reading on my Caldwell as well.  If you find out what it is let us know.  I've assumed that maybe the arrow is going across the sensors somewhat sideways and not catching the sensor at the same part of the arrow.  Just an assumption I make.

[DC]

When you get that double digit it always seems to be the same or very close to it. When my bows were in the 180's the number was in the high 50's. I added another light like brad suggested and that seems to help. I guess it could be a glitch and be meters per second. That is an option on the Caldwell. I'll try phoning them again tomorrow.
Now the bad news. Most of the time the chonos don't agree. There can be as much as 6 fps difference. I don't know whether to average or take the lowest. Not that it really matters I guess. I'm using the new bow, it's a bit slower. I don't want to wear the other one out

[Badger]

  I just remembered something. In one area of my yard I get readings like that. The only thing I can think of is that it is close to wires but not in the field of view.

[DC]

I'm 200 ft from the high tension wires.
The Chrony and the Caldwell both give funny numbers.

[Markus]

http://www.tradgang.com/tgsmf/index.php?topic=34418.msg550893#msg550893
Some info on using two speed testers set up in a tandem configuration. This is how Blackie explained it. I hope it is okay to link to this as I think it is valuable information.
Myself I use two ProCronos when speed testing.

[DC]

On my machine the bow sits horizontal and the chono's are looking up. I'm wondering if this way the arrow is bending away from the chrono and that way stays in the chono's window. Hope that's clear.

[Markus]

If testing bows with no cut out sight window a temporary plastic arrow rest can be glued on so the bow can be tested in a vertical or slanted position.
I tried to post pics of my shooting machine, but the attachments and other options won’t work.

[DC]

Is there an reason for having the bow vertical? I thought having the chrono looking so the arrow was bending away was an advantage.

[willie]

Markus,

do you mind if I quote your post at the other site? you have to be a member there to see the link.

Back in 2009 I asked Blacky the following question: When you are testing bows you say that you use two speed testers set up in a tandem configuration to ensure straight arrow flight during measurement. Does this mean that the two testers are somehow connected to each other, or are they separate testers where the average speed is calculated. If they are connected to each other,bow is this done? I find it very interesting to read about bow testing.
What he answered may be of interest to some.
Here is his answer word for word: I use two separate chronies, that are mounted in line (one behind the other). If the arrow is flying straight through the chronies, the displayed speeds don't differ more than one fps, with the further away chrony showing the slower speed.
If the arrow doesn't fly straight, because of deflection , more than normal paradox etc. the two speeds are quite a bit different.
Here's why:
If the arrow is not passing the first sensor point on, the  sensor is triggered by the shaft passing over the sensor in an angle. Since the arrow is straightening out on his flight, chances are, that the second sensor is triggered by the point or a section of the shaft, that is further up front. The speed reading will be faster, than the real speed of the arrow.
By the time, the arrow is passing the second chrony, which is further down the flight path, the arrow's flight is already more straightened out and the reading will be more  accurate. So if the two readings are quite a bit different, the arrow did not pass both chronies in a straight line.
The biggest problems occur, when I am testing non-center shot bows, or bows, that are cut a bit before center. By using a mechanical  release, there is almost no paradox. That means the arrow do not clear the bow like shooting with fingers. The arrow hits the sight window, will be deflected and will not pass the chronies in a straight line.
Hope this explains what I'm doing.
Just a little more info. There is two sensors on each chrony. Once the arrow triggers the second sensor, the chrony is calculating the speed. That means the chrony only shows the real speed, when the sensors are triggered point on.

And yes I have read many of Norbert's bow reports, but I find Blacky's easier to follow.
Markus.

[willie]

Is there an reason for having the bow vertical? I thought having the chrono looking so the arrow was bending away was an advantage.

Don, I was reading somewhere about the arrow paradoxing from side to side. A finger release would certainly get it going in that direction. There was an opinion stated that a mechanically released arrow will paradox up and down, so if your bow is horizontal, it may now be side to side if that is true.

whether the up and down happens on account of the absence of a finger flip or because in a centershot bow there is less side pressure I don't think was mentioned. Probably because not many bows with offset arrow passes are shot with a release.

Do you know the viewing angle of the sensor? Are your arrows passing over the sensors pretty low in the chrono "window"?

[DC]

My arrows go about 8-12 inches above the windows. I use a rolling block release. I can't see it paradoxing "up and down". If anything it should sort of duplicate fingers. I kind of think that Blacky's explanation depends on how far away from the bow that the chono's are. If the first chrono is very close then chances are that the arrow will be bent when it goes through which would make it shorter=higher speed seen. Due to room limitations my first chrono is one arrow length plus two inches from the bow. The second chrono is 6" past that. I'm tempted to put the chronos further away from the bow. I think I would see a more honest speed. But the dern thing is cumbersome enough as it is.