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Author Topic: HELP!: Removing Century Main Drive Gear Jim Cassedy Phenomenal Film Handler Posts: 1661 From: San Francisco, CA Registered: Dec 2006 posted 05-22-2008 03:15 AM                     I've got a Century SAW with the main horizontal drive gear stripped. I'm not sure yet excactly what happened, as the bearings or no other part of the projector are seized. This is the only assembly I've never worked on in a Century, and I'm having a problem removing the drive shaft and gear. No matter what I do, I can't get it out. The manual sez: (in part) "Remove the two set screws in the main drive formica gear. Pull the main drive shaft straight out which will also free the main drive gear from the mechanism" So, here's the gear (with the set-screws removed) and no matter what I do, I can't seem to remove the drive shaft & gear. ANY IDEAS OR TRICKS I SHOULD KNOW? Can the shaft be "poked" out from the operating side by sticking a dowel or metal shaft into the hole in what I assume is the bearing cover, or will that damge something? Does the screw my (very dirty) finger is pointing to need to be removed? I think the screw is for holding in a ball bearing sleeve. AND MY FINAL QUESTION> I have newer century HH that is not being used. Does anybody know if the main horizonal drive gear assembly in the HH can be pulled out and used in the SAW? or are they different? Thanks  |  IP: Logged Pete Naples Phenomenal Film Handler Posts: 1565 From: Dunfermline, Scotland Registered: Feb 2001 posted 05-22-2008 04:50 AM                     Usually I removed the two screws visible in the first photo, that will allow the gear side bearing to come out. Also I remove the chromed bearing cap in the second photo, from there you can drive the shaft out towards the gear side. You won't pull it out by hand, that's for certain. Use a wooden dowel or similar to avoid damage when drifting it out. Refit is as they say, the reverse of removal, make SURE there are no shards of gear left in there. It is usually a good plan to replace the steel gear on the bottom of the vertical shaft at the same time, I've found that often the steel gear has wear on it which quickly causes failure in the new fibre gear. It goes without saying, be gentle and use soft drifts when driving the bearing, shaft etc back in, and if it sticks, don't force it, take it out again and find out why it's sticking.  |  IP: Logged Louis Bornwasser Film God Posts: 4441 From: prospect ky usa Registered: Mar 2005 posted 05-22-2008 06:07 AM                        As far as the drive train is concerned the SA. DA. and HH are the same. The main drives will swap. Peter is right, but there is another screw, not just the two he mentioned. Louis  |  IP: Logged Mark Gulbrandsen Resident Trollmaster Posts: 16657 From: Music City Registered: Jun 99 posted 05-22-2008 06:07 AM                     Its also best to replace BOTH mating gears... especially on the main drive. If you remove the metal gear at the bottom of the vertical shaft and carefully examine the driving faces of the gear you will more than likely find that they are covered with what looks like lines er should I call em tiny teeth. These "tiny teeth" can cause excessive premature wear on the new fibre gear. ALso, ONLY USE LAVEZZI GEARS! Wolk's gears are still of questionable quality and they don't seem to have the good wearability as compared to the hard fibre that LaVezzi is currently using. Switch to using Superlube if you are currently not. The entire gear train will last far far longer because of the teflon ptfe particles that are suspended in the grease. Mark  |  IP: Logged Pete Naples Phenomenal Film Handler Posts: 1565 From: Dunfermline, Scotland Registered: Feb 2001 posted 05-22-2008 06:13 AM                     You're 100% right there Louis! My bad.  |  IP: Logged Richard Fowler Film God Posts: 2392 From: Ft. Lauderdale, FL, USA Registered: Jun 2001 posted 05-22-2008 07:33 AM                     Take care not to be too rough on removal....I have seen many Century projectors with a cracked outer bearing support. Many Westrex styled Century machines made a sub-assembly for repair but the classic Century design is not.  |  IP: Logged Sean McKinnon Phenomenal Film Handler Posts: 1712 From: Peabody Massachusetts Registered: Sep 2000 posted 05-22-2008 09:27 AM                        Loosen the screw and remove the cap from the operator side casting. Remove the pulley assy from shaft on the geat train side. Looson BOTH set screws that hold the actual main drive gear onto the main drive shaft. Remove the three screws from around the main drive bearing tap the main drive shaft and bearing out of the casting and out of the main drive gear gear, the main drive gear will stay inside the projector. Make sure to remove both bearings. Once the shaft and bearing have been removed from the casting simply lift out the main drive gear. When you reassemble gently tap the two new bearings into the casting, you may need to lightly run an emery cloth over the bearing to smooth out any rough spots if they have trouble being tapped in, then place the main drive gear inside of the projector. The shaft and gear come as a matched set. You may have to use an emery cloth to lightly sand down any rough spots on the shaft. then tap the shaftthrough the bearing on the non-operator side once the end is in the bearing position the main drive gear with your other hand so that it is level with the openening of the bearing and continue to tap the shaft through the bearing and the main drive gear, and intot he bearing on the other side. Once the shaft is properly in tighten BOTH set screws on the main drive gear, tightn the three screws on the outside of the bearing on the non-op side, and replace the cap and tighten the screw that holds the cap in on the operator side. Re assemble the pulley on the non-opertaor side of the shaft. Make sure that you do not just fire up the machine after doing this!!! You WILL strip another gear! You must loosen the four screws on the vertical shaft and adjust the gear "Lashing" You want to make sure that none of the gears are mating too tightly or too loosely, turn the machine by hand when checking this out DO NOT RUN THE MOTOR! A good rule of thumb is running a peice of paper in between mating gears. The paper should not rip but the gears should be close enough to move the paper through.  |  IP: Logged Steve Guttag We forgot the crackers Gromit!!! Posts: 12814 From: Annapolis, MD Registered: Dec 1999 posted 05-22-2008 12:22 PM                     On gear compatibility...watch out. From your photos, you have the later style (current) main drive shaft (ST-2154). Your HH is likely to have the older style ST-744 shaft. The ST-744 has the pulley mount as part of the shaft rather than having the pulley mount as a subassembly. The standard drive gear for the ST-744 type shaft is the GR-8. The Standard drive gear for the ST-2154 is the GR-302. The bore diameters are NOT the same. Additionally, your HH may been a direct drive (I've seen it) in which case the gears are completely incompatible (wrong teeth). As to the gear brands...Mark's opinion differs from mine here. I have had much better wear characteristics from the Wolk plastic gears than from the LaVezzi fiber. I've seen this from both the main drive and the shutter drive. I too am in the camp that more often than not, you NEED to change the steel gear on the main drive or you will be doing it again sooner than you would think. The finish on the LaVezzi steel gear (GR-4 for standard drive) looks better to me. I also think it is a good time to check the other critical gears when you are going to have to pull the vertical shaft...that is, check the shutter drive and the intermittent drive gears (and keys)...if they are sloppy and/or worn...change em whilst it is in your hands. You then won't find yourself going back into that machine in a few months to change a part that you could have changed with about 5 extra minutes. Steve  |  IP: Logged Mark Gulbrandsen Resident Trollmaster Posts: 16657 From: Music City Registered: Jun 99 posted 05-23-2008 10:04 AM                     quote: Steve Guttag As to the gear brands...Mark's opinion differs from mine here. I have had much better wear characteristics from the Wolk plastic gears than from the LaVezzi fiber. I've seen this from both the main drive and the shutter drive. While you may see better wear characteristics for a while once the steel mating gear becomes worn as they typically do it has a tendency to make mince meat out of the plastic and a mess in the machine, plastic particles being much harder than fibre and if not clenaed up could spread through to other nearby gear pairs speeding up the wear process at other points. There also exists with the plastic gears a much more serious problem than the particles and this is true of all "pressed hub" type of plastic gears and that is one of the gear itself cracking and splitting apart just like we saw on the white plastic gears that Century once tried. I have already seen the Wolk Intermediate X-L drive gear do this as well as had one with a loose hub right out of the box! We've seen the pressed brown plastic intermediate drive gear from Strong go Wrong many many times. Thinking back through the myriad of plastic gears that others have tried to sell over the years we decided to quit testing the Wolk gears after that one was found loose. The problem is that the bore diameter of the plastic gear if not extremely precise vs. the O.D. of the knurl its pressed onto will lead to either excessive strainn on the plastic and cause it to split or to be too loose as I once found. There is a very precise point that the gear will work properly on it's hub and we see a normal service life while fibre is at least somewhat resilient unlike plastic and we don't see this sort of problem. Wolk and others have put forth a very good many tries over the years with plastic gearing but they have never suceeded like LaVezzi to keep tolerances highly accurate and the gears on the hub. The Wolk gears are less expensive but in the end you get what you pay for. Now... if these gears were molded in place on specially made hubs for a "moulded in place system" like the Christie plastic projector pulleys are made then they'd have a pretty darn reliable gear, that however costs money and the result would probably cost more than those old reliable fibre gears from LaVezzi or as Al LaVezzi once remarked to me "if plastic were better we'd be using it, fibre costs more but yields better machining consistancy". Mark  |  IP: Logged Steve Guttag We forgot the crackers Gromit!!! Posts: 12814 From: Annapolis, MD Registered: Dec 1999 posted 05-23-2008 08:43 PM                     Again, your findings do not mimick mine. I've had the Wolk gray gears go in at the same time as LaVezzi fiber and the Wolks have out lasted/out worn the fiber. The Wolk plastic gears also showed they they WERE more resilient..they have some give and will return to original shape..fiber generally just cracks or chips away. The biggest problem I have found from Wolk gears in the past has been the out-of-roundness to them. This was back when Norm was still with Wolk. Don Marcus seems to have made improvements in quality and the gears seem to be more consistantly good. I generally go with what works the best...remember, I'm a Kinoton guy...I would rather have a more expensive superior device than a cheaper inferior one so my preference for the Wolk gear is not out of mere cost savings. Not all plastics are alike and the gears Wolk has been making seem to wear like steel but provide a soft gear characteristic. This is one of the very rare situations where I prefer a Wolk part to a LaVezzi part. I agree, LaVezzi's machining tends to be top notch and rather consistant. One thing is for sure, any gear will fail in short order if the steel gear has striations on it (ridges). Steve  |  IP: Logged Louis Bornwasser Film God Posts: 4441 From: prospect ky usa Registered: Mar 2005 posted 05-24-2008 06:11 AM                        We inspect steel gears and replace as necessary. We use a stereo microscope/viewer. Over the years we have had good and bad results from all three gear sources. Lately we buy in quantity, test, and return defectives. This is made more complicated since LaVezzi "loses" returns; "nope, never got 'em." Usually we try the others first and then order LaVezzi "short" until we determine if they are good enough. This is time-consuming and expensive. Truly all three should be ashamed in this era of modern production techniques (automation) and miracle materials. Louis  |  IP: Logged Randy Bowden Expert Film Handler Posts: 146 From: Portland, OR, USA Registered: Aug 2000 posted 05-25-2008 04:29 AM                     I'll just be perfectly honest here. If the Main drive gear goes out that is all I replace, and I always use Lavezzi, I never bother to replace the vertical steel gear unless I'm doing a complete projector rebuild. Why would I when theatre staff will continue to neglect maintaining the proper lubrication on the gear anyway, and that will contribute to failure far quicker than anything. If you don't feel comfortable changing out a vertical steel gear, then don't. Just make sure you keep the main drive lubed!!!! You have the current version 3/4 bore that reguires a GR-302 gear. Keep in mind that the main drive bearing on the gear side is a press fit, while the bearing on the operator side is a slip fit.  |  IP: Logged Sean McKinnon Phenomenal Film Handler Posts: 1712 From: Peabody Massachusetts Registered: Sep 2000 posted 05-25-2008 10:13 AM                        I agree with inspecting all of the gears on the vertical shaft/main drive shaft and replacing what is needed whenever you replace any gear. It not only saves you time in the future but it prevents more dark time on the screen. I think the measure of a good technician is how much down time have they prevented by doing thorough PM routines, and catching wear and impending failure before it happens. Of course you cannot predict the future and there are still a lot of things that can fail with no warning.  |  IP: Logged Steve Guttag We forgot the crackers Gromit!!! Posts: 12814 From: Annapolis, MD Registered: Dec 1999 posted 05-25-2008 10:39 AM                     Randy...I think you will find that many of us that service a great many theatres over a great distance do not want to revisit a problem anytime in the near future. It is worse for the customer (down time and the expense of yet another service call). The additional time it takes to change out the additional gear versus a return trip isn't even in the same price category. I'm NOT advocating changing out perfectly working parts so I DON'T always change out the steel gear BUT I DO give that steel gear a very good looking over to see if IT was the casuse of the fiber gear failure. I have seen fiber gears (LaVezzi) fail in less than a year's time by due to the steel gear knawing at the fiber gear because it has ridges. While the lack of lubrication will certainly also prematurely wear a gear (fiber or steel), so will the abbrasive surface, even if well lubricated. I don't know about the rest of you, but, in the field, I can generally change out all of the wearable fibre gears in a Century and be back running in about 1.5 hours with all of the gear meshes set, worn bearings changed...etc. It isn't as good a doing it in the shop where you can really get things clean and start in on the various gibbs...etc but functionally...it will be a good performer. So, in my mind, if I see a worn steel gear, it is always going to be cheaper to change it than to come back and do the job again in the near future. If the job has me pulling parts out of the machine, I always check them before putting them back in...it just makes sense (and cents). Projector gears and shafts are just not that expensive, regardless of your favorites...extra service call are expensive. Just something to consider. Steve  |  IP: Logged Mark Gulbrandsen Resident Trollmaster Posts: 16657 From: Music City Registered: Jun 99 posted 05-25-2008 11:33 PM                     I have been more or less following Steve's reasoning since I've been in this buisness. I travel way way too far sometimes over 500 miles each way to take chances. Repairing a Century on site is far too quick and easy a repair not to do things 100%!! Mark  |  IP: Logged

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