This is topic Eumig 807D Question in forum 8mm Forum at 8mm Forum.
To visit this topic, use this URL:
https://8mmforum.film-tech.com/cgi-bin/ubb/ultimatebb.cgi?ubb=get_topic;f=1;t=010227
Posted by Steve Carter (Member # 4821) on September 30, 2015, 04:24 AM:
Can any-one tell me if the first load sprocket should be tight on the drive shaft as mine is slipping, there appears to be a small allen grub screw in the side of the sprocket but I can't be sure.I think this is causing the film to stutter in the gate, as the sprocket drive slips on the shaft. I just got this projector as I wanted a standard 8 sound projector.
Posted by Lee Mannering (Member # 728) on September 30, 2015, 07:14 AM:
Hi Steve. Captain Eumig to the rescue! ![[Eek!]](eek.gif)
A few things to check out.
1/ With the mains disconnected remove the black back cover and check the toothed drive wheel attached to its shaft behind the front drive is not loose. If so just re tighten it.
2/ From the front release the super 8 top drive attachment and check the little black mount has not cracked. Over the years I have repaired or replaced a few of these as with age/heat they do split sometimes due to the little allen bolt having been over tightened. If it is that and you cant get a spare I have glued them back together and left clamped over night to stick firm. Glue it back on the metal shaft and gently tighten the bolt.
Hope this is of help.
Posted by Steve Carter (Member # 4821) on September 30, 2015, 07:17 AM:
Yes Lee the plastic is broken, what size allen key is it to remove the cog?...
Posted by Lee Mannering (Member # 728) on September 30, 2015, 07:23 AM:
I'll just check my file back in 5.
Back. History book says 0.050... Very small.
Take it out and use good quality super glue to stick the black parts together.
Tomorrow stick it back in carefully with Bostik and gently tighten the allen bolt.
Posted by Steve Carter (Member # 4821) on September 30, 2015, 08:20 AM:
Thanks Lee, I've used an abs glue not sure it will be any use. When you say bostick do you mean actually glue the plastic to the drive shaft as well as using the grub screw? I was thinking of glueing the tiny nut to the plastic in the slot with epoxy then it would not rely on the plastic slot for purchase and give it more strength what do you think?.
Posted by Lee Mannering (Member # 728) on September 30, 2015, 09:22 AM:
Yes its what I have done in the past quite a few times. The smaller top sprocket does not have to deal with a great deal of torque but its worth putting a bit of Bostik between the metal and thin plastic mount. If you over tighten that little bolt it will split again.
One thing with the Eumig 800 range they are easy to get around.
Posted by Steve Carter (Member # 4821) on September 30, 2015, 09:48 AM:
Lee is gorilla super glue any good for this sort of plastic...
Posted by Steve Carter (Member # 4821) on September 30, 2015, 09:49 AM:
Lee is gorilla super glue any good for this sort of plastic...
Posted by Paul Adsett (Member # 25) on September 30, 2015, 09:54 AM:
My Eumig 810 kept on losing it's top loop during projection, and it puzzled me for a long time until I discovered the crack in the plastic sprocket holder emanating from the tapped hole at the tiny set screw- just as Lee describes. I used a two part epoxy to glue the plastic back together, but when I tightened the set screw the plastic holder still opened up and I had to resort to gluing the black plastic part of the sprocket holder directly to the drive shaft, which has worked fine.
Another example of Eumig overstressing their plastic components.
Posted by Steve Carter (Member # 4821) on September 30, 2015, 10:22 AM:
What sort of glue did you use to fix to the drive shaft Paul...
Posted by Paul Adsett (Member # 25) on September 30, 2015, 10:36 AM:
The stuff I used is called JB KWIKWELD. It is a 2-part epoxy, one part black and the hardener is white.
Equally good would be Scotchweld 2216 adhesive, again a 2 part epoxy.
Posted by Steve Carter (Member # 4821) on September 30, 2015, 11:55 AM:
Thanks Paul...
Posted by Lee Mannering (Member # 728) on October 01, 2015, 04:07 AM:
Not familiar with Gorilla but it is a good brand so should be OK, I see Screwfix stock it.
If ever you see one of the old 800 range models sold for spares Steve its work keeping one to hand as we are now turning the clock back over 40 years since the 807 was introduced. You'll all know the 800 range got a makeover with a slightly different sprocket change method, improvement to some internal components and these upgraded machines can be spotted by a larger black lamphouse front.
Posted by Steve Carter (Member # 4821) on October 01, 2015, 05:00 AM:
Well I didn't pay much for it Lee, so if I can get it fixed it's a bonus, as I have some standard 8 sound films and I needed it for those. Plus my love of silent films which mostly come in standard 8. Some standard 8 prints are really good and sharp, have you noticed this?...
Posted by James Wilson (Member # 4620) on October 01, 2015, 06:19 AM:
Hi Steve,
I do a lot of film transfers and I`ve noticed that Standard 8 most of the time knocks the socks of of super 8.
Posted by Edwin van Eck (Member # 4690) on October 01, 2015, 08:04 AM:
Indead! We notice the same. In many cases regular8 films have more bright colors then the modern super8 films! We also do a lot of film transfers.
Posted by Steve Carter (Member # 4821) on October 01, 2015, 08:06 AM:
Yes James & Edwin I've noticed a lot of my standard 8's are really sharp and of good contrast, excepting the smaller frame size so smaller projected picture I prefer some of my Standard 8 prints, maybe more care was taken back in the day who knows?, which only goes to prove size ain't everything, now where have I heard that before...
Edwin are you going to make a 3d print of this part in the future, as it seems to be a weak point on the Eumig 800 series...
Posted by Paul Adsett (Member # 25) on October 01, 2015, 09:34 AM:
quote:
which only goes to prove size ain't everything
Try telling that to a nine-fiver! ![[Wink]](wink.gif)
But there are many people who think that super 8 was unnecessary as standard 8mm had the huge advantage of roll film and precision metal camera gates, instead of that horrible Kodak cartridge. My standard 8mm home movies have a crispness and contrast which I think is superior to my S8 home movies.
No reason that standard 8mm would not have progressed to stereo sound tracks, and all the other innovations that were applied to super 8mm cameras and projectors.
Posted by Andrew Woodcock (Member # 3260) on October 01, 2015, 09:39 AM:
Super 8 did give us a considerably larger frame size though Paul.
Posted by Lee Mannering (Member # 728) on October 01, 2015, 09:48 AM:
Um... We've been transferring film here for a few decades now and so seen a bit, probably to much. Standard 8 colour home movies are oft mistaken for being better than Super 8 which I put down to the old Kodak stock rather than Std vs Super 8mm frame size. Certainly the 60's footage I have seen over the years looks smashing.
The prospect of Std 8 optical sound was sorry to say short lived but was a goer for a very short period.
9.5 now you are talking Paul! ![[Big Grin]](biggrin.gif)
Posted by Andrew Woodcock (Member # 3260) on October 01, 2015, 10:19 AM:
So you think the old Kodak Standard 8mm camera stock is better than the later K40 Super 8mm stock? Is that what you're saying here Lee or have I misunderstood what you're saying Lee?
Posted by Paul Adsett (Member # 25) on October 01, 2015, 12:33 PM:
quote:
Super 8 did give us a considerably larger frame size though Paul.
Absolutely true Andrew, and all things being equal Super 8mm should be about 50% better in all respects than standard 8mm. I think super 8mm could have been awesome if Kodak had stuck with the tried and proved concept of double 8mm roll film, that is by selling super 8mm as double super 8mm roll film and not in a plastic cartridge. At about the same time that super 8mm arrived, zoom lenses were taking over from prime lenses. and as convenient as these zoom lenses are, they cannot equal the sharpness and contrast of the best prime lenses such as the Kern Switar lenses on Bolex 8mm cameras. I see this every time I use my Ektar f1.0 prime lens for projection.
One place where the larger frame area of super 8mm really shines is in projector screen brightness, where it pays off handsomely, and of course the faster linear speed of super 8mm has to give better mag and optical sound quality,
Posted by Dominique De Bast (Member # 3798) on October 01, 2015, 01:55 PM:
Paul, the difference of the picture size between standard 8 and super 8 is far from the difference between 9.5 :-)
Posted by John Hermes (Member # 1367) on October 01, 2015, 02:14 PM:
I have been doing transfers for about thirty years and shot home movies from about 1970. One thing I've noticed is a difference between the original Kodachrome (up to 1961) and Kodachrome II. Although the latter version was sharper with less contrast, it is alone prone to varying black levels at times. Especially the early-to-mid-1960s stuff had a tendency to have too high of a black level in bright sunlight with halations around white objects such as someone's shirt. The original Kodachome never had this issue. When everything is right with KII, regular 8 can look excellent, comparable to super 8. Under the right lighting conditions, the original Kodachrome can look awesome, where its high contrast is to its benefit. I've had some 1950s 16mm Kodachrome that is just fantastic, with a "look" that KII just didn't have. I still lament that Kodachrome (in all its versions) is gone as it was one of the greatest developments ever in photography.
Posted by Lee Mannering (Member # 728) on October 02, 2015, 06:15 AM:
The old chaps always used to mute at our Cine Society it was a backward step going to K40 Andrew. Yes I've seen some astounding images over the years for Std 8 Kodak more recently a guy who filmed a 1 hour Scope holiday, it was interesting getting that on Blu-Ray for them.
Lets get back to the wonderful Eumig 807D. ![[Smile]](smile.gif)
Posted by Steve Carter (Member # 4821) on October 02, 2015, 06:58 AM:
Well I've glued it with 'industrial' strength super glue, I glued the little nut in place hoping it won't put so much strain on the glued plastic. I'm letting this cure for 24 hours, I'm going to glue it to the shaft with this glue and let it cure for a further 24 hours, the grub screw will only be lightly tightened as I'm hoping the glue will do the job of securing this in place. Question Lee will gluing this to the shaft have any effect on the running of the projector, does there have to be any play in this part, or is firm fixing what it needs to keep the top loop formed.
Posted by Steve Carter (Member # 4821) on October 03, 2015, 04:34 AM:
Lee, when I try to put the plastic piece on the drive shaft, the shaft moves back into the projector chassis,is this correct, is it the actual plastic sprocket that holds the shaft in place once the grub screw is tightened, this is asking a lot, no wonder this is a weak part as it must take a lot of strain on the plastic...
Posted by Paul Adsett (Member # 25) on October 03, 2015, 01:05 PM:
Steve, the cracking problem is solely associated with the stress induced by the tightening of the grub screw. In use, the only running stress on the plastic hub is the tension induced by the roll off of film from the supply reel, which is negligible. The tapping of the grub screw thread in the plastic hub results in a stress concentration around the tapped hole, which produces a crack when the screw is tightened, which gradually gets larger until the whole part fails (sounds like the Dehavilland Comet disaster doesn't it, and its the same kind of thing, resulting from what was probably zero stress analysis by the Eumig engineers). A lot of the small plastic parts on Eumig's seem prone to cracking, which leaves you wondering that some people in their design team thought that designing parts in plastic was no different than designing the same part in metal.
so, if this part were to be remade in plastic it should include helicoil inserts in the plastic thread to help distribute the stress in that area, plus a filled type of plastic such as Delrin AF might be more suitable material. Bottom line though, the part should probably have been metal.
Posted by Andrew Woodcock (Member # 3260) on October 03, 2015, 05:30 PM:
Nice to read what an Engineer makes of all this.
Posted by frank arnstein (Member # 330) on October 05, 2015, 07:02 AM:
Hi Paul....
Thanks for your interesting analysis of this vexing plastic sprocket-hub design by Eumig but it raises a few further questions about its operation.
a. Can you tell us exactly what the purpose is of the small nut found inside the plastic hub. ?
b. Consider the amount of sudden stress that's exerted on the hub when you turn a Eumig 800 projector from forward project to reverse project. Especially if the rewind clutch has been over tightened by some one wanting a fast slip free rewind.
I think the sudden force would be more than merely negligible. If it doesn't break the film or some sprocket holes it may be enough to cause the hub to move around on the shaft or even crack the hub after a number of applications. Just as we have found them cracked so mysteriously.
What are yours and others thoughts on the above scenario?
dogtor frankarnstein
Posted by Steve Carter (Member # 4821) on October 05, 2015, 07:29 AM:
The small nut as I see it is because the plastic hub is not threaded and also isn't a self tapping screw, the nut is the thread and it then forces it's self to the top of the plastic hub, there by making the 'weak' point stress on the thin plastic part. I have glued my nut to the bottom on the hub where it then goes directly through the hole to the drive shaft, and doesn't put the stress on the top weak plastic moulding, I have also glued it to the drive shaft. The stutters I found was that the standard 8 gate was adjusted too wide and the film was 'sloppy' as it passed through, I loosened the two tiny screws and moved it over slightly, now up till the last running it was OK, even with a poor print I had.
Posted by Paul Adsett (Member # 25) on October 05, 2015, 09:42 AM:
I had forgotten about the nut! So I took the sprocket off my 824D to get some picks, and low and behold the plastic is cracked on this one too! So this failure must be very common.
Anyway, Steve's observation is quite correct, the plastic itself is not threaded, and when you tighten the set screw it pulls outward on the nut plate as you tighten the screw against the shaft, This puts a very high tensile stress right at the outer corner of the rectangular slot in the plastic hub, where there is already a stress concentration by virtue of that sharp corner. You can see from the photo exactly how the crack would propagate outward from the corner.
To Frank's point about the load induced upon reverse projection. Yes this would obviously be much greater than during forward running when the feed spool is not being driven. But this load would be a torque load on the sprocket which would not put anywhere near the load on the plastic hub compared with the load induced by tightening the set screw. Remember that threads have huge mechanical advantage. I think the failure mode of the radial crack propagating from the slot pretty well nails the root cause.
If Eumig had rounded the corners i.e. like an oval with a full radius at each end of the slot, then the stress concentration would have been much less, and then maybe the part would not have cracked. (This is sounding more like the Comet disaster every day- rememeber that the square windows on the original Comet resulted in a very high stress concentration in the fuselage and ultimate cracking and explosive decompression)
Posted by frank arnstein (Member # 330) on October 07, 2015, 06:32 AM:
Thanks for the informative response Paul and sounds like we both agree with Steves previous explanation about the purpose and operation of the threaded nut.
It is a little tricky to figure out the forces involved without careful inspection of it.
Steve,...with regards to your question about the shaft moving into the projector when refitting the sprocket..
The sprocket shaft should have a small locating groove on it, This is where the tightened grub screw is designed to locate the sprocket correctly on the shaft and prevent excess end float.
If you are still going to glue the sprocket hub back on the shaft, first make sure the grub screw is located directly over the locating groove in the shaft.
If the shaft has slipped in, then you will need to push it back out from the inside, and block it there while you attach the sprocket hub in the right spot. You may not get a second chance to reglue in the right spot so get this right 1st time.
Good luck if gluing...
dogtor frankarnstein
[ October 11, 2015, 02:09 AM: Message edited by: frank arnstein ]
Visit www.film-tech.com for free equipment manual downloads. Copyright 2003-2019 Film-Tech Cinema Systems LLC
UBB.classicTM
6.3.1.2