Chrono results

[upstatenybowyer]

I guess I must have been pretty good this year cause Santa brought me a chrony.  Anyway, I've been shooting away and getting some interesting results.

The fasted bow I've tested so far is that cherry-bark-backed mulberry I posted last week, shooting an average of 175fps. That one had just a touch of natural deflex with longer, gradual static recurves at the ends.

Coming in a close second was a hackberry static with short and sharp curves. I just finished that one up and haven't posted it. It's average was 172 fps.

Both of the above are 60# at 27#.

All the other bows I've tested were between 50 and 55# and were shooting between 155 and 165 fps.

I'm assuming these are pretty normal results?

Man, I'd really like to break 180 someday.

[bjrogg]

I was wondering how long before you had everything's speed checked. Figure you know how fast the family cat was by now. How about your arrows? Are you going 10 g per lb? Or did you use the same arrows for all of them?
Bjrogg

[DC]

Nice numbers but I want to know the arrow weight too.

[upstatenybowyer]

Well BJ, the cat moves at approximately 4 fps while chasing prey 

But in all seriousness, this goes to show how clueless I am about arrows.  All I know is I used the same cedar shaft arrow for every shot. Guess I better start saving up for an arrow scale? 

[Philipp A]

Glad Santa brought you a Chrony, it is fun to measure the arrow speed of your bows. Most of my bows (none of them recurved or backed) are typically ~67" n/n with draw weights at 60-70" and they clock in within the 155 to 165 fps range as well. Also measured with a Chrony and with arrows weighing in between 490 and 510 grains. So your speeds are in line with mine. My draw length is a maximum of ~26", so someone with a longer draw length would get higher speeds from the same bows.

[Stick Bender]

Congrats on your present I really enjoy using the Chrono and trying to tweak a bow for the finale fps it's a great tool , most of my arrows are heaver then 10 gpp for 45-47 lb bow but close enough that I can take a good guess ,chronos really make you think about mass placement !

[ty_in_ND]

Grain scales aren't too terribly expensive, but if your household already has a kitchen scale (like, for weighing food), you can place your arrows on the scale and get a somewhat general idea of how much your arrows weigh.  Just make sure you're using a scale that will measure in decimals and not fractions.  I had a food scale once that only did Imperial measurements in 1/8 oz increments, so if I wanted to me more exact with my measurements, I had to weigh things in grams (oh the horror!!).  Now I have a scale that will measure oz to .01, so life is good (in addition to having a grain scale now)! 

Then, go to the good ol' Google machine when you have your weight and type in "convert x oz/grams to grains" and you'll have your weight in grains!

[Jim Davis]

Knowing that there are 437 grains in an ounce, or that there are 15.4 grains in a gram, a slide rule would be even faster than a calculator and exponentially faster than getting Google involved, IF you could find a slide rule and IF you knew how to use one. Call it primitive math;) I  have a half dozen slide rules and they are the cat's meow for multiple calculations of ratios.

[Badger]

Knowing that there are 437 grains in an ounce, a slide rule would be even faster than a calculator and exponentially faster than getting Google involved, IF you could find a slide rule and IF you knew how to use one. Call it primitive math;) I  have a half dozen slide rules and they are the cat's meow for multiple calculations of ratios.

  I need to get a slide rule and learn how to use it. I am forever doing one calculation or another. I carry a calculator in my pocket most of the time and keep a larger one in my car. I don't think I have ever really looked at a slide rule closely.

[Jim Davis]

Steve, I think the only sources for slide rules today are eBay and other second hand outlets. I'm pretty sure nobody makes them anymore. But they can be found. I like them for scaling mechanical and architectural drawings.

[ty_in_ND]

Knowing that there are 437 grains in an ounce, or that there are 15.4 grains in a gram, a slide rule would be even faster than a calculator and exponentially faster than getting Google involved, IF you could find a slide rule and IF you knew how to use one. Call it primitive math;) I  have a half dozen slide rules and they are the cat's meow for multiple calculations of ratios.

I know it's good to know the calculations, but if we can use modern tools, glues, and strings for our primitive bows, then why not break out the handy smartphone for your calculating needs! 

Between all of this, I hope upstate has a handy tool he can weigh his arrows with so we can know what his bows are clocking at.

[upstatenybowyer]

I do have a baby scale that measures in ounces and according to it the arrow I was using weighs 1.5 ounces. So perhaps it's safe to say it's a little over 500 grains?

So is the general rule of thumb to use arrows that weigh 10 grains per every pound of draw weight on your bow? i.e. a 50# bow should shoot 500 grain arrows?

I guess another question I have is how does speed play into these calculations? For example, what's a good speed for a 50#bow shooting a 500 grain arrow? And how much faster should one expect a 60# bow shooting a 600 grain arrow to be?

Sorry for all the newbie arrow questions guys   

[ty_in_ND]

I think the general formula for how efficient your bow is something like this: you take the draw weight of your bow and add 100 and this number should be the minimum of the speed in feet per second a 10 grain per pound arrow is propelled. So... If your bow pulls 60#, then it should be shooting an a 600 grain arrow 160 fps. If it's higher, then you have a very efficient bow. If lower, then you overstrained the limbs.

Take this with a grain of salt, of course.

[Jim Davis]

I do have a baby scale that measures in ounces and according to it the arrow I was using weighs 1.5 ounces. So perhaps it's safe to say it's a little over 500 grains?

So is the general rule of thumb to use arrows that weigh 10 grains per every pound of draw weight on your bow? i.e. a 50# bow should shoot 500 grain arrows?

I guess another question I have is how does speed play into these calculations? For example, what's a good speed for a 50#bow shooting a 500 grain arrow? And how much faster should one expect a 60# bow shooting a 600 grain arrow to be?

Sorry for all the newbie arrow questions guys   

If your arrow weighs an ounce and a half, that's about 650 grains. But, when weighing something that light on a scale made for up to, what, 20#, you could be off by 40 or 50 percent.

[rps3]

I bought a grain scale off the auction sight for 8 bucks. I have a chrono that is gathering dust, seemed hard for me to get consistent readings. Probably should fiddle with it some more. I think the biggest variable for me, other than lighting, was getting to the same draw length every time.