A Mini Micro 305

[racking up points]

I just acquired a Micro and I have a spare rail. I am thinking about cutting the extra rail down to about 9". I'm guessing I'd get about 305fps and a 230# draw weight. This would make for an even easier drawing bow and slightly more compact package for smaller framed hunters. Other than the arrow being longer than the stirrup, can anyone see a reason not to do this?

[Normous]

Mel and Andre (when he gets older) will surely be smiling ear to ear I'm sure. The way I see it there is no reason not too.

[strum]

a reason not to? heck no!! go for it!!!.
I think it'll be a cool rig man..

[racking up points]

Mel and Andre (when he gets older) will surely be smiling ear to ear I'm sure. The way I see it there is no reason not too.

You read my mind. I could try 9" and if that's too stout, maybe down to 8.5".

[ehntr]

I really like a lower draw weight micro but I don't think you could lose 40 lbs and only lose 30 fps in doing so. Putting a scale on the string and a tape on the rail while drawing it would give you the rail length needed at 240 lbs. Now what fps you get out of 240 lbs would be really good to know I have never put a scale on a crossbow string but I have done this many times on recurves and longbows to determine draw weights at different draw lengths.

[mainstreet]

Your Micro is packed bubble wrapped and going out tomorrow.
Cant wait till you make your creation.
Good luck.

[newbie]

heck ya go for it. I cant. wait to see the results and hopefully fondle it soon. :mrgeen:

[canoe13]

I really like that idea and would do it if I could afford another Micro right now. But it will have will wait for another day. I just did the math: 270 lb. draw weight divided by 12.75 inches (total rail length) gives you aprox. 21.2 lbs per inch. So if you shorten the rail by an inch you will be at 249 lb. draw weight. And the speed should be respectable I believe. Maybe someone else can figure out the actual F.P.S.

[strum]

I like the way the Micro riser bolts up to the rail. That could make it a challenge to cut it down. im interested to see how it works out..

[racking up points]

I really like a lower draw weight micro but I don't think you could lose 40 lbs and only lose 30 fps in doing so. Putting a scale on the string and a tape on the rail while drawing it would give you the rail length needed at 240 lbs. Now what fps you get out of 240 lbs would be really good to know I have never put a scale on a crossbow string but I have done this many times on recurves and longbows to determine draw weights at different draw lengths.

I don't know that I've ever heard of anyone measuring draw weight like that on a crossbow either, sounds dangerous! I'm was trying to use some estimation, when I came up the numbers I posted.

But at 1/2"-5/8" less power stroke, my best guess is you'd lose about 25-40lbs of draw weight and about 20-30fps. There's no real way to find out without trying it and I intend to do exactly that with my extra rail, (not my XTRA rail, that I have bigger plans for ).

[bubba]

That is very interesting!! I too would really like to know your results, if you do this please post.................

[nchunterkw]

[quote="racking up points"]I don't know that I've ever heard of anyone measuring draw weight like that on a crossbow either, sounds dangerous!/quote]

Derrick - what if you made a really long rope cocker so you could hook both handles to the same scale behind the stock. Make something to hook the stirrup on to hold it - SECURELY!! The number would be offset by the pulleys but you would be able to compare. Just thinkin' outside the box...

[nchunterkw]

I really like that idea and would do it if I could afford another Micro right now. But it will have will wait for another day. I just did the math: 270 lb. draw weight divided by 12.75 inches (total rail length) gives you aprox. 21.2 lbs per inch. So if you shorten the rail by an inch you will be at 249 lb. draw weight. And the speed should be respectable I believe. Maybe someone else can figure out the actual F.P.S.

Found this online regarding recurve draw weight vs draw length.

For a shorter draw length take draw wt @ 28"/28-brace height = how many pound per inch you lose.
Extrapolating that to a Micro...

draw wt. at 9.5" = 270
Brace ht ~~1.5"
(270)/(9.5-1.5) = 33.75"

So shortening by 1" = 236.25lbs
shortening by 0.5" = 253.125lbs

I have no idea if this is real, but all the curves I saw for recurve draw wt vs draw length showed that while the curve was not linear, it was pretty close, especially at the high end of the draw length. A linear extrapolation gives you 28.42 lbs/in. So this is all in the same ballpark.

IMO I think you will be around 255# at 9", but I think that would make a big difference in how hard it is to cock. And you shouldn't lose too much speed.

[ehntr]

If your desire is to nail down a specific draw weight the only way to do it is put it on a scale, as trying to determine a draw weight by dividing the current draw weight by the length of the rail will not give you the right answer. This division does not account for stacking or where on the rail that resistance is first encountered. Making the cut in the right place the first time is critical.....it would be nice if you could take a series of slices off............but that cannot work. It would take some thinking to rig up a scale........but if you want to nail it..........that would be the way to do it. Attach scale to a single point on the string, and pull it with a crank until 240 lbs is reached, mark this point on the rail. The difference between the point you just marked on the rail and where the trigger jaw would normally hold the string is the amount you would need to cut off. Then there is the whole thing of securing the bow and the crank.........but that is all doable. Just thinking

[racking up points]

I really like that idea and would do it if I could afford another Micro right now. But it will have will wait for another day. I just did the math: 270 lb. draw weight divided by 12.75 inches (total rail length) gives you aprox. 21.2 lbs per inch. So if you shorten the rail by an inch you will be at 249 lb. draw weight. And the speed should be respectable I believe. Maybe someone else can figure out the actual F.P.S.

Found this online regarding recurve draw weight vs draw length.

For a shorter draw length take draw wt @ 28"/28-brace height = how many pound per inch you lose.
Extrapolating that to a Micro...

draw wt. at 9.5" = 270
Brace ht ~~1.5"
(270)/(9.5-1.5) = 33.75"

So shortening by 1" = 236.25lbs
shortening by 0.5" = 253.125lbs

I have no idea if this is real, but all the curves I saw for recurve draw wt vs draw length showed that while the curve was not linear, it was pretty close, especially at the high end of the draw length. A linear extrapolation gives you 28.42 lbs/in. So this is all in the same ballpark.

IMO I think you will be around 255# at 9", but I think that would make a big difference in how hard it is to cock. And you shouldn't lose too much speed.

Thanks for the number crunching Keith. I had worked out something similar to come up with my 240# estimation. Naturally, limb deflection would play a role here so any number we come up with here is purely theoretical. I guess the only questions left are:

-when is Excalibur making a mini-micro?
-will the string, at brace height, be under the arrow retainer?

Thanks everyone for the feedback.