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View Full Version : 40 fps slow!!!



rdmwc
04-17-2011, 04:53 PM
Ok, I just got my new 70# limbs and cams and roto cups! I put the cams on the limbs and they were pretty snug. When I say snug I mean they weren't very free spinning...
I just got back from the range where I had them weigh my arrow, 441 grains had them check my draw weight, 75# and my draw length is 31". I shoot a Martin warthog. I ran the numbers on an online calculator and it said I should be at 327 fps. The shop chrono averaged me at 293 fps!! What are you guys getting for numbers from your warthog? Is there anything I could do to get this thing closer to where it should be shooting?

Ehunter
04-17-2011, 05:06 PM
First thing I'd do is check ATA, brace heigth, and make sure the strings and cables are at their correct length. 75# is a bit over what I would want with 70# limbs. If that all checks out, I'd look at the cam timing. I also think that 327fps might be a bit optomistic for that arrow weight. Also, what do you have on the string (D-loop, silencers, peep, etc.)? All of those slow down a bow. Give us all the info you can about the bow, and I'm sure others will pitch in too. As far as the limbs being tight in the roto cups, that's normal with the new style. Mine are a very tight fit.

martinbowhunter
04-17-2011, 05:25 PM
x2 on everything above poster said

rdmwc
04-17-2011, 05:33 PM
The cams weren't free turning... I would have expected them to be very free turning.
As far as measurements, my brace height is dead on, 6.25" my ATA is off though. It's at 34 5/8. I'm not sure on how to get that to where it needs to be. As for what's on my string, I have a tied on nock, tied on d loop and 2 cat whisker silences, I don't shoot with a peep. I had it chronoed before I put the silences on and after, when I had my 60# limbs on and they only cost me 1fps. As far as cam timing, I have it timed to the specs on the archerytalk.com thread on cat cam timing.

Ehunter
04-18-2011, 02:16 AM
Sorry about the misunderstanding there. The cams should be pretty easy to turn. Did they send a new set of shims with the new cams? It may be that there are too many, or too thick of shims between the cam and limb. When I upgraded my old '09 Firecat, I didn't get a new shim set with the new limbs from Martin. Ended up having to use part of my old ones, as well as come up with new ones. For the ATA, you need to untwist your cables to lengthen your ATA. Do it two twists at a time in each cable. Then recheck ATA and BH. This will also lessen the draw weight of the bow a little, and slightly change the draw length. It sounds like your cables are running a little short, so untwisting them will lengthen them, getting your ATA back to specs.

rdmwc
04-18-2011, 12:15 PM
The new cams didn't come with spaces, and they actually are quite snug in there little pocket. But it was like the hub on the bearing was rubbing in the limbs, as if the bearings weren't actually doing their job. What is the ATA supposed to be on the warthog because I have seen 34" and 35".

rdmwc
04-18-2011, 04:17 PM
Well, I just shot about 30 shots through my chrono... average, 296.3 fps. Now my question is, is there a break in period for the cams to loosen up or something, I just feel it should be at least shooting in the mid 300 teens... like 315 I would be happy.

rdmwc
04-18-2011, 04:53 PM
I just had a friend draw my bow while I watched the cams rotate. The bearing hubs are rotating with the cams, shouldn't that part be stationary as to lessen the friction from rubbing on the limbs?

gibson 787
04-18-2011, 05:06 PM
I just had a friend draw my bow while I watched the cams rotate. The bearing hubs are rotating with the cams, shouldn't that part be stationary as to lessen the friction from rubbing on the limbs?

On your specs my 09 warthog with same conversion is around 312fps. My A2A and BH are almost identical to tours. Your cams should be turning freely but without any movement on axle. I think this is your problem. I would contact Martin tech, unless you feel confident about doing a little filing and sanding yourself. There is a spacer kit containing many different size spacers that Martin sent me upon request, as I had a similar problem when upgrading an 09 Moab recently.

Spiker
04-18-2011, 08:46 PM
I just had a friend draw my bow while I watched the cams rotate. The bearing hubs are rotating with the cams, shouldn't that part be stationary as to lessen the friction from rubbing on the limbs?

If you have the new 'shouldered' bearings ( the bearing sticks out past the cam surface and acts as a spacer to prevent the cam itself from touching the limb) then yes - that is going to rotate with the cam. It is the outer bearing race and is pressed and staked into the cam so it will rotate with it. The inner bearing race stays stationary along with the axle.
If it, the cam and bearings, fit too tight in-between the limb forks then it could cause excess drag and lose of speed.
If you are saying that the inner bearing race is turning with the cam and not staying static with the axle - then you have a problem.

rdmwc
04-20-2011, 06:53 AM
Could it be my strings and cables? If so, what are the best to get? And size?

SonnyThomas
04-20-2011, 07:34 AM
Wet and cool outside so I read up here.

Seems everyone told you correctly.
For sure I'd get the draw weight down. If you don't have a press then take it a shop and have them back off the cables and strings. They can adjust timing and correct draw length in the process if need be. As for the cams, yes, they should be free and even spin. And yes, the outer bearing moves with the cam and the inner race is only needed, no spacers. My Shadowcat has no spacers. So contact Martin if not free wheeling.

Actual fps and program fps can be quite different.

I've put up the following several times. You start with factory IBO fps and add or subtract from IBO specs.
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

rdmwc
04-20-2011, 09:01 AM
What length should my strings and cables be?

SonnyThomas
04-20-2011, 09:19 AM
What length should my strings and cables be?

Look up on Martin website - they have a listing for older bows.

Here's the thing, ata does not have to be to specs. ata is a approximate. The real spec will be when max listed draw weight is achieved. so ata could be long to get draw weight down. If I remember correctly the industry standard tolerance for ata is +/- 3/8". Beings most hit max poundage at +/- 1/8" I'd say they are doing something right.

rdmwc
04-20-2011, 09:46 AM
My ATA is at 34.5 I remember seeing somewhere the ATA was 34" but now see dyes say 35..? I will look it up. My bh was dead on, but now is 3/8 long.

archerx7
04-20-2011, 12:47 PM
The string should be 57" and the cables should be 40.5". AtA should be around 35" and brace should be around 6 1/4". The brace and AtA are appox. specs only. Get the string/cables set to spec and the cams timed and go from that point.

The cams should rotate freely, if you take the string and cables off you should be able to spin them with your finger and they should make 2-3 revolutions before stopping. If they stop almost right away they are too tight and you will lose a lot of speed.

rdmwc
04-20-2011, 01:26 PM
well, i took off all my cables and string. they were all within a 1/16 of an inch! shocked me! i put some nylon shims by the cams so that the only thing touching is the axle race( paper thin nylon washers, the cams now spin very freely with no slop!) i am now timing the cams according to the cat cam timing thread on archerytalk.com

rdmwc
04-20-2011, 02:14 PM
well, thanx for the help everyone, not sure what happend, but i put it all back together and all the measurements are the same. but im now shooting 309fps. i kinda want to try to get that bh down to the 6.25 from the 6.5 its currently at, but i dont think i will gain much. and am afraid i will not get it set back to how it is now. what you think?

gibson 787
04-20-2011, 02:52 PM
well, thanx for the help everyone, not sure what happend, but i put it all back together and all the measurements are the same. but im now shooting 309fps. i kinda want to try to get that bh down to the 6.25 from the 6.5 its currently at, but i dont think i will gain much. and am afraid i will not get it set back to how it is now. what you think?

My advice would be, that if you're happy with the way it's shooting, leave it alone. If you do decide to alter things, just make a note of exactly what you did, so you can get back to square one.

rdmwc
04-21-2011, 10:49 AM
I'm averaging 301 fps. With a d loop and 6 whisker silences... thanks for the help guys!

rdmwc
04-27-2011, 09:05 AM
Update.
Well I just received my new arrows and fobs. Ran it through the chrono lastnight.....347fps average!

MLN1963
04-27-2011, 10:52 AM
You must have went a lot lighter on your arrows to gain 46 fps!!!