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indiana cheetah
08-28-2010, 05:31 PM
I have a 09 cheetah and a few weeks ago the bottom cam appears to have given out and martin the great company they are with no questions asked sent out all the new parts my bow shop needed to fix it. Now that being said here is my problem, before the fix i was running 437gr 270 fps with a 28 draw at 70 lbs. after the break down got propperly fitted to me , am now at 463gr 270 fps 30 in draw at 70 lbs. shot a 373gr arrow today and it only went 280 fps with same draw and poundage 10 fps gain seems very little me with a 90gr loss of arrow wieght. after the fix the bow was totally fixed and replaced except for the string and cable they said it was fine. when the cam went out it was like dry firing it at full draw could the string and cable be the reason for the little speed increase from the big wieght loss. thanks

SonnyThomas
08-28-2010, 06:06 PM
Need to sort out some things;
1 - before the fix i was running 437gr, 270 fps with a 28 draw at 70 lbs.

2 - got properly fitted to me = Bow was fitted to you.

3 - 463 gr arrow with 30 inch draw at 70 lbs. gets 270 fps. (26 gr heavier arrow and 2 inches more draw // Just say 9 fps slower with the heavier arrows (261 fps) and add 2 inches of draw (4 fps) = 265 fps.

4 - 373gr arrow today and it only went 280 fps. 90 gr loss = +30 fps or 295 fps. Differential 15 fps.

I'd say error in chronograph reading somewhere along the line.


Common accepted Speed adjustment.
2 fps / 1 # of Draw Weight
10 fps / 1" of Draw Length
1 fps / 3 grains of arrow weight
1 fps / 3 grains of weight on the string

bfisher
08-28-2010, 06:31 PM
First I'd like to welcome you to the Tech Forums. Join the party.

Now for the bow. I have a few questions. You were shooing t a 28" draw. What made you bump up to 30"? Are you on a quest for speed? If so then you picked the wrong cam system. The cam you have is meant for a smooth draw. Smooth (easy) draw and speed do not fit in the same sentence. Simple as that, no matter who makes the bow. You want more speed you gotta work harder for it.

Anyway, I have to agree with Sonny about this. I think it's an erroneous chrono reading. Jumping up 2" in draw and dropping 90 grains of arrow weight should have given you much more speed, but don't think you are going to hit the rated IBO speed. Very few bows do. In fact, the 270 fps with the heavy arrow is more a more realistic figure and very good for a hunting setup.

Also as per Sonny's figures, anything you have on the string reduces the speed also.

indiana cheetah
08-28-2010, 08:06 PM
when i purchased the bow it was set at 28" draw i am 6'3" and the bow shop i go to now said the draw was to short for me and now that is was made 30" it is much more confortable and much better accuracy. as far as a quest for speed i am not a speed freak i run a 463gr arrow by choice for the wieght but at some point in my life a 70# draw will not be easy to do and i am trying to purchase possibly my last bow so that when i need to turn the draw wieght down it will still throw a decently heavy arrow at a speed i am happy with.

Destroyer
08-29-2010, 05:11 AM
463gr 270 fps 30 in draw at 70 lbs

Not bad really. I would be happy with that.


shot a 373gr arrow today and it only went 280 fps with same draw and poundage 10 fps gain seems very little me with a 90gr loss of arrow wieght.

Comes down to efficiency. The single cams are not as efficient the lighter the arrow gets.


1 fps / 3 grains of arrow weight

1 fps per 5 grains.

indiana cheetah
08-29-2010, 05:29 AM
thanks guys and i am happy with my current setup but like i said in the long run im looking for a bow that would give me a better spectrum of arrow speed option for when i cant pull 70# back as confortably. do you think the firehawk is a better fit for what i am looking for.

Destroyer
08-29-2010, 05:47 AM
for when i cant pull 70# back as comfortably.

By the time it happens, bows will probably be faster than what is available today. Who knows what will be available. I would stick to what you have now and not worry about the future. ;)

bfisher
08-29-2010, 12:46 PM
Personally, with your draw length and stature you'd be better served with something a bit longer like the FireCat or better yet the Warthog. The main difference here is that you could shoot your present arrow at 60# and get the speed you are getting with the Cheetah. The Cat cams do draw a little harder, but with the reduced weight it would seem even easier than the Cheetah at 70#.

You haven't filled out your profile (hint-hint) so I don't know how old you are, but if you're fairly a young guy you can count on getting a newer bow by the time you need to shoot less weight.

Oh, and reading your previous post I can see why you got the draw length changed. It was probably a very good move on your part.

SonnyThomas
08-29-2010, 01:50 PM
1 fps per 5 grains.

A short few years ago I would agree with 1 fps per 5 grains, but today some bows hit in the magical realm and see 1 fps with 2 grains. After many recordings through my two chronographs I began to lean to the 1 fps per 3 grains which is recommended by many for about the last 3 years.

bfisher
08-29-2010, 05:13 PM
A short few years ago I would agree with 1 fps per 5 grains, but today some bows hit in the magical realm and see 1 fps with 2 grains. After many recordings through my two chronographs I began to lean to the 1 fps per 3 grains which is recommended by many for about the last 3 years.

I was going to say this, Sonny, but didn't want to step on too many toes. My own chrono results on my Alien Z have shown 1 fps for each 2 grains of arrow weight. I've posted such results here in some of my "Alien Z" threads.

This might be something specific to certain cams designs. I also agree that if a person doesn't have or have access to a chrono then the 3 gr rule is a good ballpark figure.

Destroyer
08-30-2010, 03:30 AM
Why I bother sometimes.

RLW
08-30-2010, 06:17 AM
.......I'd say error in chronograph reading somewhere along the line.

Common accepted Speed adjustment.
2 fps / 1 # of Draw Weight
10 fps / 1" of Draw Length
1 fps / 3 grains of arrow weight
1 fps / 3 grains of weight on the string

I'm going with chronograph error also.

fps changes I've seen on my tests done on my '09 Bengal (range seen on my other bows):
2.0 fps / 1lb draw weight (2 - 3fps)
10 fps / 1" draw length (9-11fps)
1 fps / 4.5grs arrow weight (1fps / 3.5 - 5.5 grs....each bow was different, but typically more w/heavier arrow, less w/lighter arrow)

Being so close to the Bengal, my guess on the Cheetah would have been:
1. 70lbs @ 28" draw, 437gr arrow = 265fps
2. 70lbs @ 30" draw, 463gr arrow = 280fps
3. 70lbs @ 30" draw, 373gr arrow = 298fps


FYI: Just for reference, is you drop 5lbs at some point, my '09 Bengal is currently at 65lbs @ 29" draw, 399gr arrow at 274fps (rounded off average of 12 shoots)

J758
08-30-2010, 06:24 PM
I have a bone hunter and I shoot a 28 inch draw (70lbs) and I'm getting 289fps. I have nothing on the string but a loop. I enjoy the bow a lot! First one I plan to use it for hunting. My arrows are 380 grain. Seems to be a good median for target and hunting though for me.

SonnyThomas
08-31-2010, 06:20 AM
I was going to say this, Sonny, but didn't want to step on too many toes. My own chrono results on my Alien Z have shown 1 fps for each 2 grains of arrow weight. I've posted such results here in some of my "Alien Z" threads.

This might be something specific to certain cams designs. I also agree that if a person doesn't have or have access to a chrono then the 3 gr rule is a good ballpark figure.

I work part time at a small archery shop (only archery) and get to work on quite a few bow makes and of greatly varying ages, like in ancient, some where around the B.C. era, to present day. Older bows don't gain speed like newer ones. Wheel bows seems different. Single cams respond indifferently. The newer double cam bows seems to gain speed just sitting there.
One 10 year old single cam bow tested cranked out 295 fps with a 314 grs arrow and then churned out 301 fps with a 301 gr arrow (weird, but true). This is 13 grs and 6 fps gain. This bow would make a screamer 3D bow if brought up today's new stuff.