Primitive Archer
Main Discussion Area => Bows => Topic started by: DC on July 21, 2020, 12:22:30 pm
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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.
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usually my readings like that are caused by the light source
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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.
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68X3 =204! Could it be yds per second? More commonly it will read meters per second.
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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.
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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 ;D
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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.
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I'm 200 ft from the high tension wires.
The Chrony and the Caldwell both give funny numbers.
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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.
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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.
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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.
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Is there an reason for having the bow vertical? I thought having the chrono looking so the arrow was bending away was an advantage.
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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.
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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"?
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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.
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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.
you may well have addressed the concerns mentioned by Blacky in his conversation with Markus.
It is my understanding an arrow paradoxing is buckling under acceleration. bucking is hard to predict as it occurs suddenly and small factors can start it going and once it starts off in a particular direction.
finger flip is the biggie and your rolling block to a smaller degree when considering the release.
sideloads on the arrow as it is accelerating comes into play also.
your carbons are most likely much more consistent than a wood arrow, but discrepancies in stiffness as far as which way is the "soft" side and off center loadings, ie nocks out of alignment may be factors also.
which factor causes what when is hard to figure, but most likely once an arrow begins to buckle, that will be which way it paradoxes.
hope you don't think I am trying to doubt your accomplishment, just thinking out loud to help get both machines reading the best they can.
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Hello again :) You say the second speed tester is 6 inches past the first one??
Blackie and the late Norbert Mullaney had the first sensor of the closest chrono 3 feet downrange from the back of the handle and the next Chrono about three-four feet after that. After finding that out I do the same. Sometimes I have the first one 4 feet downrange.
One advantage of having the bow vertical is that it is not that space consuming.
I bought indoor lights for my two ProCronos. In the instructions they say if testing outdoors do not test in sunlight, but on an overcast day. Do not stand under a tree or roof, the sensors need a clear view of the sky.
Do you have a picture of your shooting machine and chronos. I tried to post a pic of mine, but the attachments function do not work.
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http://www.primitivearcher.com/smf/index.php/topic,68490.0.html
The second chrono sits just behind this one. I'm too cheap to buy something I can make so my lights are 3 led bulbs, 6.5 watts I think, with ice cream buckets for diffusers. Spreading the chonos out to 4' would mean making another new light string.
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Interesting shooting machine. I understand now why you can’t move it outside. :)
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are those bulbs true older style incandescents or the newer led look a likes?
bulb output varies on ac. the older filament bulbs much less than the florescent or leds that actually can switch off and on 60 times a second, too fast to see with the human eye for most folks.
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I was concerned about that so I tested the same bow before and after changing to the LED's and the speed was about the same. I think I trust the incandescents more. I'll test it again once I can get a little more consistency. I'm busier than a one armed paper hanger with hives and I'm losing track of what I'm doing. ;)
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I just tested the two different light and the results are the same. No discernable difference between them.
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My simple shooting machine
(https://i1289.photobucket.com/albums/b506/timian46/CE4D769F-A144-4EF2-A6ED-483516F5B0B6_zpsohwdx59b.jpeg) (https://s1289.photobucket.com/user/timian46/media/CE4D769F-A144-4EF2-A6ED-483516F5B0B6_zpsohwdx59b.jpeg.html)
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(https://i1289.photobucket.com/albums/b506/timian46/831AC0EC-8197-41FF-A76E-8C59C40380FC_zpsjzjpemfx.jpeg) (https://s1289.photobucket.com/user/timian46/media/831AC0EC-8197-41FF-A76E-8C59C40380FC_zpsjzjpemfx.jpeg.html)
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What do you have for a triggering mechanism? Picture please :D
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https://www.wish.com/product/591d18662771af27807ddbb2?from_ad=goog_shopping&_display_country_code=NO&_force_currency_code=NOK&pid=googleadwords_int&c=%7BcampaignId%7D&ad_cid=591d18662771af27807ddbb2&ad_cc=NO&ad_lang=EN&ad_curr=NOK&ad_price=229.00&campaign_id=9527731173&gclid=CjwKCAjwx9_4BRAHEiwApAt0zvEPR8v0LItt4WMwcosx7kQmrtrGOX66GBdeGN_X4HHRpmaIig6CfxoCAVMQAvD_BwE&hide_login_modal=true&share=mobileweb
I use a releaser, used by the compound guys.
I fasten the bow with a bicycle inner tire.
The 2x4 with the small boat winch is just fastened to the stand with a couple of solid screws so it is easy to take apart and do not take up any space when not in use.
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https://www.wish.com/product/591d18662771af27807ddbb2?from_ad=goog_shopping&_display_country_code=NO&_force_currency_code=NOK&pid=googleadwords_int&c=%7BcampaignId%7D&ad_cid=591d18662771af27807ddbb2&ad_cc=NO&ad_lang=EN&ad_curr=NOK&ad_price=229.00&campaign_id=9527731173&gclid=CjwKCAjwx9_4BRAHEiwApAt0zvEPR8v0LItt4WMwcosx7kQmrtrGOX66GBdeGN_X4HHRpmaIig6CfxoCAVMQAvD_BwE&hide_login_modal=true&share=mobileweb
I use a releaser, used by the compound guys.
I fasten the bow with a bicycle inner tire.
The 2x4 with the small boat winch is just fastened to the stand with a couple of solid screws so it is easy to take apart and do not take up any space when not in use.
Markus, have you had any trouble breaking arrows with thet solid target? Does that release work well with non centershot bows?
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No broken arrows, that straw target is more than 10 years old so it is not so hard.
That release works well on all bows, I place the jaws just below arrow nock.
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Thanks, I think I'll work on my release mech today.
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From the shoooting machine "how to"
I'm very pleased with the trigger mech but I have some reservations about the saddle that the bow sits in. I found it hard to make a saddle that would hold the bow securely but also fit different handles. If you can come up with a really slick saddle I'd love to hear about it.
just rereading about your trigger and bow mount and had a question....
The release seems to be hard mounted to the rail and the bow is clamped down also.
How do you prevent the bow from torquing in the mount when you tighten the clamp, and if it were, wouldnt the release be putting a side pressure on the arrow and string at release maybe similar to flipping off the fingers?
you arrow breakage issues got me thinking somethings going on, maybe there
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I'm not sure I'm following you but the clamp is lined with foam and it has a little wiggle room. Are you thinking I should have a roundish pin or something?
I'm thinking that if anything my arrows are stiff. They are leaving a mark on the bow and they are hitting about 4-6" high at 10 ft. I'm going to try to stop the rolling block from rolling flat(it spins free as is) so as to purposely give the arrow a little flip much like fingers would. When we spine arrows we put the heavy side to the bow so that when the arrow bends under acceleration it bends to the weak side(away from the bow). Carbons don't really have a weak side so what makes the arrow decide which way to bend? Maybe they need a little push. I'll let you know.
Oh, the release mech slides back and forth but I think you knew that.
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Are you thinking I should have a roundish pin or something?
not necessarily.
just thinking the clamp might be wanting to torque the bow grip somehow. when the bow is clamped in, does the string want to just barely touch the release or do you have to push it down or lift it to get it into the release fingers?
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It's strange you mentioned it because two of the bows I just played with just wouldn't sit right and the nock point wouldn't stay in place on the rolling block. The shape of the handle is the thing. Some handles are fine, some ain't. I'm modifying it now. I've been fighting this all morning. Moving the chronos hither and yon. And the lights. The best results are where I had it in the first place. Knowing that the 120volt LEDs don't work well should eliminate some problems. When I shot the air rifle through them they were within a couple of fps but arrows seem to be right a 6 fps difference. That seems to depend on the order the chronos are but the jury is still out on that. Get the saddle working better first. :D
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You mention you would like to stop the rolling block from spinning freely. In medieval times the crossbows had the hole in the block and riser drilled slightly offset so the block(nut) stopped spinning on release. The nut usually had sinew threds through the holes to secure it in its socket
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I just put in another step for the trigger to catch on. It releases when the trigger is pulled but stops again after some rotation. I may put a spring in it to return it to the original spot. If I put a heavy return spring it may act even more like "fingers".
It occurred to me that I have fluorescent light in the shop. I'll try turning them off. It seems to be working now but I have to try a few different bows in it
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It all seems to work now. I tried three bows from my best down to my grandsons. Chronos were within 1fps of each other. I got rid of the 120v LEDs, I smoothed out the release fingers and stopped them from rolling free. I lowered the lights about six inches. Now i have to go scout out some spare incandescent bulbs. They are not easy to find any more. Now I can get back to making bows.
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I’m glad you worked it out. I feel a little guilty for all this, I think I was the one who started it by asking if you used a shooting machine and two speedtesters.
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Guilty as charged ;D ;D. When I feel like it there is still a question. When I put it the way it is now, Chrony first and Caldwell second I get virtually the same result from each. If I reverse them there is about a 6fps difference. Now the way I look at it unless there is a 3fps difference in the calibration of the chronos and coincidentally a 3fps difference in the actually arrow speed between the chronos this can't happen. That's too much of a coincidence for me. I tried more distance between them and it didn't help. But having them both pop up the same number is much more impressive and convincing so I'll leave it like this for a while. It's a PITA to get them unbolted and repositioned. ;D Thanks for all the help.