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Balance Procedure
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drgert1
Hi Joe,
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It's best to have a slight imbalance so that any (small) gear backlash is always pushed out. I prefer the mount always to 'pull' a bit. Clear Skies, Gert --- In ap-gto@..., "Joseph Zeglinski" <J.Zeglinski@...> wrote:
... as one can. |
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Joe Zeglinski
Thanks Jeff,
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I had forgotten about the large initial worm stress, with no OTA. I suppose if it can (and must) survive that, then the normal imbalance is no issue at all, in comparison. I had some concerns about operating the mount, and not rebalancing on meridian changes, if something of the size of say a large SBIG camera were hanging out there. Shifting weights so often, to protect the worm drive, would be a hassle. I'm also relieved, that the servo motors have a safety trip point protection circuit against this as well. I see from your comparison of the 600GTO and 1200GTO mounts, that I made a very good decision in purchasing the AP900, in this regard. Thanks for the added reassurance. The AP900/1200 are one heck of a nearly bullet-proof mount. Joe ----- Original Message -----
From: "Jeff Young" <jey@...> To: <ap-gto@...> Sent: Wednesday, April 25, 2007 11:10 AM Subject: RE: [ap-gto] Balance Procedure Joe -- |
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Joe Zeglinski
Hi Roland,
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Not knowing the centre of gravity of your (160/F7.5) OTA, but assuming it is at mid point (23.6 inches), that would be approximately a moment of 189 inch-lbs. O.K. that is a useful working example to know, to judge our own OTA conditions. I am a bit surprised that AP uses "weight" instead of "moment (torque)" when talking about imbalance. I found the same terminology used on page 23 of the AP900 user manual: Troubleshooting - (additional explanation) - "It typically takes about 4 lb. of unbalance to trip the overload circuit ... etc." This is a "weight", not a "moment arm" reference, which really depends on which OTA you are using on the mount. A long OTA with 4 lbs is different from a short SCT with the same 4 lbs. of unbalance. As for not being concerned about "damaging the worm gear teeth", once again, the user manual page 15 - RA & DEC Clutch Knobs: "3: How tight can they be...etc." warns: "You should not attempt to push your scope by hand against this locked up resistance, or undue stress will be placed on the worm wheel/worm an bearings". My concern arose from reading that section in the mount set-up manual. In using the mount for astrophotography, it is "recommended" to tighten the clutches a bit more (1/8 turn by wrench). An overly "unbalanced OTA" may introduce the same stress situation as "pushing the mount by hand", as described in the manual. No "guideline" is given about how many "inch-lbs of torque", potentially from OTA imbalance, are considered crossing the line on too much stress on the worm gear. Of course, the safest bet is to minimize any imbalance, as best as one can. Joe ----- Original Message -----
From: <chris1011@...> To: <ap-gto@...> Sent: Wednesday, April 25, 2007 10:47 AM Subject: Re: [ap-gto] Balance Procedure In a message dated 4/25/2007 9:21:36 AM Central Daylight Time, |
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Jeff Young <jey@...>
Joe --
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I accidentally balanced my 600E GTO once without diagonal or eyepiece. When a 2" diagonal, 2" Barlow and T4 Nagler was added, it produced intermittent stalls when slewing (but not when tracking). I'd guess it was about 40 in-lbs out of balance. I never re-balance my 1200 GTO with equipment changes. I might go from no eyepieces in either SCT or refractor to a heavy T5 Nagler in each with a Barlow in one. These weights are much farther out on the moment arm, so I'd guess we'd be looking at more than 100 in-lbs of inbalance. I've never had this mount stall. Lastly, when I load up my scopes on the 1200, I load the c-weights first. This leaves the mount temporarily some 2,500 in-lbs out of balance. Cheers, -- Jeff ________________________________ From: ap-gto@... [mailto:ap-gto@...] On Behalf Of Joseph Zeglinski Sent: Wednesday, April 25, 2007 3:22 PM To: ap-gto@... Subject: Re: [ap-gto] Balance Procedure Hi Roland, This is good news - I was becoming concerned about "meticulously" rebalancing the counterweights, every time I crossed the meridian. Indeed, the AP900 is a superb design, and even more so, from what you say about the rebalance issue. One question: You use the phrase "8 lbs out of balance", do you mean 8 inch-lbs? Being "out of balance" with an 8 lb camera overhand at 6 inches is different from the same weight overhanging 2 feet away. Could you be more specific about the "moment arm" on the OTA imbalance you are describing? Actually, it would be interesting, if someone there could do a bit of testing in this regard, on various "moment-arm measurements", before you would consider the AP900 or AP1200 seriously out of balance, for the expected performance. For that matter, before you would consider possible damage to the worm gear. That might provide a good rule of thumb which could be applied to any OTA overload situation, to specific AP mounts. I suppose one might say that the imbalance on any mount has reached a maximum, if the clutches won't hold, but some might torque down the clutches too tightly, even with a wrench, in order to avoid having to shift the weights. Thanks for any further info, Joe ----- Original Message -----
From: <chris1011@... <mailto:chris1011%40aol.com> > To: <ap-gto@... <mailto:ap-gto%40yahoogroups.com> > Sent: Monday, April 23, 2007 1:04 PM Subject: Re: [ap-gto] Balance Procedure > In a message dated 4/21/2007 8:52:34 AM Central Daylight Time, > drichey@... <mailto:drichey%40sandia.net> writes: > > >> What's the procedure for rebalancing. If I have very good polar alignment >> and a good >> pointing accuracy, but need to loosen the clutces and reblance the load due >> to adding >> equipment, how do I maintain my pointing model. >> > > Your pointing model is not affected if you loosen the clutches to rebalance. > On the other hand, why do you need to do this? I image all the time without > ever rebalancing. It is not really necessary. I have been as much as 8lb out > of > balance on both 900/1200 mounts, and recently ran 6lb out of balance on my > little bitty Mach1 mount. The tracking/guiding was spot on perfect. > > Roland Christen > > > ************************************** > See what's free at > http://www.aol.com. <http://www.aol.com.> > > > > > > > To UNSUBSCRIBE, or for general information on the ap-gto list > see http://groups.yahoo.com/group/ap-gto <http://groups.yahoo.com/group/ap-gto> > Yahoo! Groups Links > > > > |
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Joe Zeglinski
Hi Roland,
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This is good news - I was becoming concerned about "meticulously" rebalancing the counterweights, every time I crossed the meridian. Indeed, the AP900 is a superb design, and even more so, from what you say about the rebalance issue. One question: You use the phrase "8 lbs out of balance", do you mean 8 inch-lbs? Being "out of balance" with an 8 lb camera overhand at 6 inches is different from the same weight overhanging 2 feet away. Could you be more specific about the "moment arm" on the OTA imbalance you are describing? Actually, it would be interesting, if someone there could do a bit of testing in this regard, on various "moment-arm measurements", before you would consider the AP900 or AP1200 seriously out of balance, for the expected performance. For that matter, before you would consider possible damage to the worm gear. That might provide a good rule of thumb which could be applied to any OTA overload situation, to specific AP mounts. I suppose one might say that the imbalance on any mount has reached a maximum, if the clutches won't hold, but some might torque down the clutches too tightly, even with a wrench, in order to avoid having to shift the weights. Thanks for any further info, Joe ----- Original Message -----
From: <chris1011@...> To: <ap-gto@...> Sent: Monday, April 23, 2007 1:04 PM Subject: Re: [ap-gto] Balance Procedure In a message dated 4/21/2007 8:52:34 AM Central Daylight Time, |
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Roland Christen
In a message dated 4/25/2007 9:21:36 AM Central Daylight Time,
J.Zeglinski@... writes: You use the phrase "8 lbs out of balance", do you mean 8 inch-lbs?I have had an imbalance of 8 lb at the end of a 160F7.5 refractor. You will know when the imbalance is too large because the motors will have a problem slewing in one direction, but it will take more than 8 lb except maybe when it is bitterly cold outside. Also, if the clutches won't hold, it is probably too much imbalance. I doubt very much that you could ever damage the worm gear teeth. These are quite large and rugged. Rolando ************************************** See what's free at http://www.aol.com. |
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Roland Christen
In a message dated 4/21/2007 8:52:34 AM Central Daylight Time,
drichey@... writes: What's the procedure for rebalancing. If I have very good polar alignmentYour pointing model is not affected if you loosen the clutches to rebalance. On the other hand, why do you need to do this? I image all the time without ever rebalancing. It is not really necessary. I have been as much as 8lb out of balance on both 900/1200 mounts, and recently ran 6lb out of balance on my little bitty Mach1 mount. The tracking/guiding was spot on perfect. Roland Christen ************************************** See what's free at http://www.aol.com. |
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Dick Steinberg <steinberg@...>
I have successfully used the following:
1. Slew the mount to the park 1 position (with locked clutches). 2. Precisely note the positions of the setting circles. 3. For each axis, loosen the clutches and balance without disturbing the positions of the setting circles. 4. After each axis is balanced, use its setting circle to return it manually to its prior position and lock the clutches. 5. Voila! Regards, Dick Steinberg --- In ap-gto@..., "spcrichey" <drichey@...> wrote: alignment and a good pointing accuracy, but need to loosen the clutces and reblance theload due to adding equipment, how do I maintain my pointing model. |
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Edd Weninger
My AP900 is very tolerant of imbalance, so I don't bother even when
changing from a 1 1/4" eyepiece to a binoviewer with 2 Radians on my AP155. Don't know what equipment you're changing, but try it without re- balancing. --- In ap-gto@..., "spcrichey" <drichey@...> wrote: alignment and a good pointing accuracy, but need to loosen the clutces and reblance theload due to adding equipment, how do I maintain my pointing model. |
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spcrichey <drichey@...>
What's the procedure for rebalancing. If I have very good polar alignment and a good
pointing accuracy, but need to loosen the clutces and reblance the load due to adding equipment, how do I maintain my pointing model. |
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