Beseler 120 Negatrans Belt

[faberryman]

Does anyone know the length and diameter of the belt for the Beseler 120 Negatrans?

 

[George Nova Scotia]

I almost do. I guessed a bit too small and is too tight, it's on my to-do list. I'll look it up in the morning but maybe someone will have the dimensions. Do you have an O ring store nearby?

 

[Jim Noel]

If you have a good auto parts store nearby, they willhave a large selection of "O" rings. That is where I get all of mine.

 

[mgb74]

I use the -167 size for my 35mm negatrans (can't remember the dimensions). Not sure if it's the same size as the 120. I bought a few extra last time, PM me if you want to give one a try.

 

[faberryman]

Do you have an O ring store nearby?

McMaster Carr seems to have a good selection. If I knew the correct size, perhaps it is in their inventory.

 

[darkroommike]

The o-ring for the 120 negatrans is larger than the one for the 135. I will measure mine later.

 

[anikin]

PM me with your mailing address. A few years back I had the same issue and a bought a set of replacement belts. They were coming only is sets of dozen or more so I have several life times supply. My only worry is whether I can find them now. It has been a few years, as I said... If I find them, I'll mail you one.

 

[George Nova Scotia]

Sorry for the delay in getting back - not too well yesterday, better today.

If anikin found his supply you might be all set, if not here's the best info I have.

Unfortunately the 120 negatrans I have was completely missing the belt so I had to guess and only came close.I bought three sizes and the largest fit but just barely and is really too tight to use.
Width: 3/32" ID: 8-1/2" OD:8-11/16 McMaster-Carr dash number: 173 <- this number is part of the part number from my local supplier so it might be a standard reference.
As I said this size is too tight, I'd go up at least one or two sizes. It looks like McMaster-Carr likes to sell packs of 25. If you can find a local supplier you might be able to buy just one of different sizes. The supplier I found specializes in Hydraulic parts and repairs. The had the second floor filled with rows of shelving full of o-rings and one guy at a desk to find things.

If anyone has found the right size please let us know, if not I'll try and get a full more sizes to try..

 

[mgb74]

Sorry for the delay in getting back - not too well yesterday, better today.

If anikin found his supply you might be all set, if not here's the best info I have.

Unfortunately the 120 negatrans I have was completely missing the belt so I had to guess and only came close.I bought three sizes and the largest fit but just barely and is really too tight to use.
Width: 3/32" ID: 8-1/2" OD:8-11/16 McMaster-Carr dash number: 173 <- this number is part of the part number from my local supplier so it might be a standard reference.
As I said this size is too tight, I'd go up at least one or two sizes. It looks like McMaster-Carr likes to sell packs of 25. If you can find a local supplier you might be able to buy just one of different sizes. The supplier I found specializes in Hydraulic parts and repairs. The had the second floor filled with rows of shelving full of o-rings and one guy at a desk to find things.

If anyone has found the right size please let us know, if not I'll try and get a full more sizes to try..

The AS568-173 size oring has the dimensions you gave. So you're right about the 173 designation. A -174 will have an ID of 8 3/4 and a -175 will have an ID of 9 (both retain the 3/32" width). Chart here.

I have a partial 120 Negatrans is a box somewhere (missing glass and o-ring). I'll have to see if I can find one to fit.

The issue with buying from many o-ring suppliers is the minimum quantity. Not so bad when you know the right size, but not so good for experimenting.

 

[faberryman]

The belt length is approximately 28.5". Using the formula circumference/pi=diameter, the diameter is approximately 9" (28.5"/3.146=9.07"). The width is either 3/16" or 1/4". I'll order a package of 5 from McMaster Carr and see how it goes.

My Negatrans 120 is missing the glass, so that is the next thing to figure out. Does anyone have a photo of the inside of the Negatrans 120 showing how the glass is installed. Is it anti-Newton ring glass? Size?

 

[George Nova Scotia]

I think you might be a little high on the width. The 3/32 ring I tried grips the film nicely I just need a little longer one as the one I tried is very tight. I do have one with glass but no pictures yet. Give me day or so and I'll see what I can do.

 

[George Nova Scotia]

I found it a little sooner than I thought. Do you have the metal frame for the glass? There is an embossed arrow, push the tap and it removes. Pictures below. 2.19" wide 3.25" long .13 thick (1/8 inch) note the bevels on the ends. One of the metal clips unscrews. I don't think it's anti-newton but maybe it should be.

 

[faberryman]

No, I am missing the metal frame too. Thanks for the measurements on the glass. You are right - I mis-measured the width of the o-ring. It is 3/32" or 1/8".

 

[faberryman]

I ordered the 9" diameter belt, 3/32" width, Dash No. 175, from McMaster Carr (http://www.mcmaster.com/nav/enter.asp?partnum=9452K333). They come in a package of 2 for $4.79 plus shipping. I'll let you know if they fit.

 

[faberryman]

Belt arrived and fits. It is a little sluggish turning the knob but is improving as I work it. Probably should have shaken the belt in a bag of talc before installing so it glides easier. With shipping, a bag of 2 runs $10.71. Now I just have to find the glass and holder.

 

[George Nova Scotia]

Thanks for the update. I'll try and dig out my box of negatrans, I'm not sure if there is another 120 version. Might get lucky and find one with a frame, maybe even glass but I don't think so.

 

[mgb74]

Belt arrived and fits. It is a little sluggish turning the knob but is improving as I work it. Probably should have shaken the belt in a bag of talc before installing so it glides easier. With shipping, a bag of 2 runs $10.71. Now I just have to find the glass and holder.

The point of the belt (o-ring) is to move the negative when you turn the wheel. So friction is a "feature", not a "bug". I suspect talc might prevent that friction and also end up on your negative. When you say "sluggish" to you mean it's too hard to turn the wheel or that turning the wheel doesn't result in the o-ring moving evenly?

Did you try a 8 3/4" belt?

 

[faberryman]

Hard to turn the ring because the belt is very grippy along the path where the negatives are. It may be easier when I actually start running negatives through it.