Reprex No. 2 Missing drive gear

Reprex01I recently acquired a Reprex No. 2 [No. 1] proof press.  While everything on this Reprex appears to be in excellent shape, it is in fact missing the drive gear on it’s form roller. The original manual I have specifies that there should only be one drive gear, and the part number for this gear is D48 on the Reprex parts list.

Reprex02Assuming I won’t be able to locate a replacement part off another press, it looks like I’ll need to have one made. I need to determine proper specs for the gear, since the gear rack and roller cores differ from those on the Vandercooks I have access to. Unlike many of the Vandercooks I’ve seen, the gear rack for the inking system on the Reprex appears to have the same tooth pattern as the gear racks for the entire carriage. What I know at this point is that the diameter or my roller cores are 0.5″ and the roller diameters are 2.5″. There’s an image below of the gear rack for the missing drive gear for measurement purposes.

Reprex03I’m hoping some other Reprex owners may be able to offer some insight on replacing this drive gear in whatever way possible. I’m thinking I should be able to have a new gear machined if I can supply a gear diameter and correct number of teeth to correlate with the gear rack on the press. Or perhaps the gear/rack is a standardized part that may be readily available?

I’d greatly appreciate any and all info anyone may be able to share. I need to (hopefully!) get this press up and running for a visiting artist by mid-March, so I’m trying to tackle it as soon as possible.

Many thanks!

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kpmartin
10 years ago

Josh,
Gear diameters are measured at the pitch diameter, which is about halfway down the teeth, not the tip-to-tip diameter. The pitch diameter should equal the form roller diameter (otherwise slurring will occur). For 2.5″ rollers you would want a 20-tooth gear. Although a pressure angle of 14.5 degrees is most likely the place to measure this is on the rack, not the gear. The pressure angle is half of the vee angle formed by the teeth on the rack (and also the gaps between the teeth).

Paul Moxon, Moderator
Admin
10 years ago

There are seven known No.1 in the Reprex census. I will ask these owners to provide the specs.

Paul Moxon, Moderator
Admin
10 years ago

Mike, as to model, I was going by what’s in the Reprex census. Perhaps I incorrectly recorded the info provided to me. This would be going back several years now. Given that the bed is only only 15″ wide that would indeed make it a No.2 and not a No.3.

Mike Day
10 years ago

Is it possible that Josh’s rollers are the wrong size. I am reasonably sure our Reprex is a no. 2, not a 3. I don’t have the spec sheets handy to check. Any way, if it is 2.5, the gear would be .25 larger or 2.75. The half inch core is consistent. The bed is 15″ wide allowing for a 141/2 form. Certainly not 19″ wide. All I can say is it prints well when adjusted.

I believe we had our roller made by NA Graphics and probably sent the cores and old rollers to them to match.

maysorum
10 years ago

My Reprex no. 2 has the same drive gear dimensions (3.25in) and number of teeth (24) as Mike Day’s press. The rubber rollers are 3in in diameter as well. Hope that is helpful.

Paul Moxon, Moderator
Admin
10 years ago

Reprex product sheets do not state roller specs but note that the maximum form for a No.2 is 14½ × 22½” and for a No.3 is 19 × 26″. So a 2½” diameter for the No.2 and 3″ diameter for the No.3. is comparable to a Vandercook SP15 and an SP20.

kpmartin
10 years ago

Mike, your rollers don’t seem to be the same size as the ones Josh mentioned; he says his as 2.5″ diameter but yours look like they are 3″.
Your gear has the same diametrical pitch of 8 teeth per inch of diameter, though.
Perhaps the roller height adjustment on this press has enough travel to accommodate either roller diameter?

Mike Day
10 years ago

One more photo. Paul, could you reduce the size of the first. don’t know why it is bigger. all were same size.

Mike Day
10 years ago

I am attaching three photos. I hope this is what you are calling the drive gear. The diameter is 3.25″, gear tip to gear tip. The teeth are 7/16″ tall. 24 teeth. Inside diameter of base of gears 2.8125. The hub diameter is 1.375″, forgot to measure its length. shaft for roller and hole in Hub is .625″.

The hub is locked on the shaft by two hex allen head screws .1875 diameter. The two holes are 1 quarter apart on the hub. The roller has about .125″ play side to side so the gear needs to be positioned so it does not get off the track. We had to cut some of the rubber off when we had them recovered to make a flat end for the gear. Inside (roller side) of gear is flat whiled outside is convex.

kpmartin
10 years ago

That seems to be 18 teeth in 7″ linear rack, which represents a diametrical pitch of 8 (that is, a gear that matches the rack will have 8 teeth for every inch of diameter). You want a gear whose pitch diameter is 2.5″ (to match the roller) so you need a 20-tooth gear with a 1/2″ bore. There are two common pressure angles (equal to the incline of the tooth face on a rack), 14.5 and 20 degrees, but I can’t see the teeth in the photo to tell (it is almost assuredly 14.5 degree). Boston Gear NH20B-1 looks like the right teeth but has a 1″ bore and would need a bushing for the hub so it would fit the 1/2″ shaft. Boston Gear GH20 has a larger bore but might be cheaper. Either way a hub has to be made. Both of these are 14.5 degree pressure angle.

This is of course all on the assumption that this is standard gearing, but that’s a pretty good assumption.

I did something similar for an SP15 that had an oddball roller diameter and adapting a 38-tooth gear to replace the standard 40-tooth one was cheaper than re-covering the roller (but then I made the hub myself and so did not have to pay a machinist).

Mike Day
10 years ago

I will take a photo or two of the gear on our press and post the measurements in a day or two. I am not at the college right now.

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