Durst RCP20

Giorgio_23 · Sep 6, 2010

Hello, I found a Durst RCP 20 processor and i would like to use it for 8x10 color paper processing... The problem is that this Durst works with a long time of developing and bleaching-fixing... about 2,20 minutes. I'm using the Tetenal Kit 5l that is for 35° developing, 45 seconds for each bath. I'm trying it with drum at 30° for 1,20 minutes, and it seems to work fine! If I try to work at 20° the processing time should be about 2,20 minutes... So, according to you can I use Durst RCP20 with chemicals at 20° and 2,20 minutes for each bath?

Or, do you know if is possible to modify Durst rcp20 time processing (for 45'' or 1,2 minutes processing?)

p.s.
last question: can you suggest me a good color processor machine up to 20x24''? I'm using a 3063 jobo drum, but I would like to process all formats of paper in the same machine.

thank you!

Andrew K · Sep 6, 2010

yes you can modify the RCP 20 to speed up the process, but sorry I can't remember how it was done..

A friend of mine used to use one for color and black and white processing - he had a switch on it which changed the motor speed.

If you are only going to use 1 processing time then I would replace 1 of the gears on the drive unit - changing the size of it will change the running speed of the machine..

You do not have to get exactly 45 seconds in each bath - 40 or 55 seconds will work just as well - as long as it is the SAME time every time

Cheers

fotch · Sep 7, 2010

if is possible to modify Durst rcp20 time processing (for 45'' or 1,2 minutes processing?

If you Google for info, you will find you can change two gears to get the proper speed for RA 4. I have a RCP20 and loved using it with the old EP-2 process. One of theses days, I may convert mine, meanwhile, I will use my Jobo.

fotch · Sep 7, 2010

I found the link for the info
http://www.vogelstimmen-wehr.de/rcp20.htm

Giorgio_23 · Sep 7, 2010

For a 20° processing any experiences?
However thanks for your help

mtjade2007 · Sep 8, 2010

I have modified my RCP-20 back and forth many times. It is not difficult to do. There are a set of plastic gears that you need to deal with. One is on the driving shaft from the motor and the other is on the long driving shaft for the rack rollers. The gears can be taken off without much difficulty. I got a couple of gears found from an electronics surplus store for a few dollars. I was able to match them to speed up the driving shaft for the rack rollers to about 1 minute for the developer and blix bath. This is still still slower then 45 second desired. But The RCP-20 temperature can be lowered to maybe around 80 degrees for this 1 minute development time.

I also modified it again to change the gear ratio so that the time becomes 3 min and 30 seconds. I thought to use it as a C-41 processor. I can use C-41 RA chemicals as it needs less than 3 minutes to bleach the film and I can run the fix and final rinse cycle on separate tanks. Well, I never get to use it yet though. I may reverse it back to the gear set for 1 minute process time for RA-4 again.

RCP-20 uses a toothed belt for linking the gears. So the gears do not contact each other. The gears are industry standard gears and so is the belt. You can find different sizes of them for the conversion. The motor mount is adjustable so you can move the motor either closer or farther between the gears. Just adjust it so that the belt is tightly wrapped on the gears.

thedancefloor · Nov 29, 2015

I've re-geared my RCP20 for RA4 also. I 3d printed some XL pitch gears that work with the original belt. The motor has 36 teeth and the other one has 11. Prints take about 40 seconds in each bath.

I'd really like to use the machine for proofing 4x5 negatives in the studio. How do I figure the gear ratio to make the machine run at 3:30 for C41?

Here's what I'm using so far:
RA4 - 36 teeth on Motor gear : 11 teeth on Racks gear = 3.27:1 = 40 sec
B&W - 20 teeth on Motor gear : 25 teeth on Racks gear = = 0.8:1 = 140 sec - original gear set

I'm going to try this next:
C41 - 14 teeth on Motor gear : 25 teeth on Racks gear = 0.56:1 = 200 sec
Do these numbers look right?

fotch · Nov 30, 2015

Wow, 3d printed.. Keep us posted. Good luck.

raymondvanmil · Dec 12, 2015

Hi. Could you please post the 3d files, or point me to them. At at the point of buying a machine like that and I do have a 3d printer! Would just be great not to have to look or design those gears myself.

fotch · Dec 12, 2015

raymondvanmil said:
Hi. Could you please post the 3d files, or point me to them. At at the point of buying a machine like that and I do have a 3d printer! Would just be great not to have to look or design those gears myself.

You can buy the gears off the shelf. I use to have the info somewhere, its just a matter of getting the right gearing.

thedancefloor · Dec 28, 2015

https://drive.google.com/folderview?id=0ByPRo2_iUslnT0UxZ0MtNzJ6aVE&usp=sharing
Here are the .stl files I exported from Autocad.

But my Autocad/Windows is crashed right now so I don't know which file is which.
One of these files: (1.stl,2.stl,3.stl) is an 11 tooth gear for the rotating shaft that turns the rollers. The bore needs to be filed out a bit to fit the shaft. The other two files are my first attempts at making the 36 tooth gear.

And these files are my second attempt at the 36 tooth gear. Has an outer ridge to keep the belt from sliding off (which will be slightly larger on the next version). These are the same file with slightly different center bore diameters. One of these files: (RCP_1a.stl,RCP_2b.stl,RCP_2b.stl) fits nicely onto the motor shaft without filing.

I've printed them with PLA, but when the machine gets hot, the 36 toothed gear melts off the motor shaft! So I'm planning to preheat the chemicals and just run the machine intermittently to keep things at 38c. If that doesn't work, I'm going to have the 36 tooth motor gear printed in ABS. If that doesn't work, I'll order a metal one.

Let me know what you come up with!

raymondvanmil · Jan 26, 2016

fotch said:
You can buy the gears off the shelf. I use to have the info somewhere, its just a matter of getting the right gearing.

could you please give me some more info or point me in the right direction, can't fin dit anywhere, already got the machine in the house...

AgX · Jan 26, 2016

I assume fotch was referring to a standardisation of gears (similar like threads). Once you got to know characteristics like their "module" you can buy substitute gears off the shelf.

Just as an example:
http://qtcgears.com/products/gears/spur_plastic_kps.php

peoplemerge · Jun 20, 2021

So I'd like to resuscitate this thread because I had some trouble sourcing one of the parts in 2019 and had a convo with @V A. For posterity, here's where I left off:

The site https://www.vogelstimmen-wehr.de/rcp20.htm is excellent to start. It quotes [line numbers added]:

Parts list:
[1] A large gear wheel with 30 teeth and a diameter of 54 mm. Catalog part number: 226041-44; Price: 11,95 €.
[2] A small gear wheel with 10 teeth and a diameter of 24 mm. Catalog part number: 226106-44; Price: 6,95 €.
[3] A toothed belt with 65 teeth and an effect length of 330 mm (ZAHNRIEMEN 65 Z), if the drive operates so far with a drive belt. Catalog part number: 226076-44; Price: 2,75 €.

Close equivalents:
1. https://www.mcmaster.com/1277N54/

For Maximum Belt Width 3/8"
OD 2.125"
Number of Teeth 30
Teeth Shape Trapezoidal
Pitch 0.200"
For Shaft Diameter 1/4"

2. https://www.mcmaster.com/1277N41/

For Maximum Belt Width 3/8"
OD 0.875"
Number of Teeth 10
Teeth Shape Trapezoidal
Pitch 0.200"
For Shaft Diameter 3/16"

3. https://www.mcmaster.com/6484K223/

Belt Trade Number 130XL037
Width 3/8"
Outer Circle 13"
Number of Teeth 65

IIRC it's item 2, the small gear that doesn't fit. Anyone tried this recently?

mshchem · Jun 26, 2021

peoplemerge said:
So I'd like to resuscitate this thread because I had some trouble sourcing one of the parts in 2019 and had a convo with @V A. For posterity, here's where I left off:

The site https://www.vogelstimmen-wehr.de/rcp20.htm is excellent to start. It quotes [line numbers added]:

Parts list:
[1] A large gear wheel with 30 teeth and a diameter of 54 mm. Catalog part number: 226041-44; Price: 11,95 €.
[2] A small gear wheel with 10 teeth and a diameter of 24 mm. Catalog part number: 226106-44; Price: 6,95 €.
[3] A toothed belt with 65 teeth and an effect length of 330 mm (ZAHNRIEMEN 65 Z), if the drive operates so far with a drive belt. Catalog part number: 226076-44; Price: 2,75 €.

Close equivalents:
1. https://www.mcmaster.com/1277N54/

For Maximum Belt Width 3/8"
OD 2.125"
Number of Teeth 30
Teeth Shape Trapezoidal
Pitch 0.200"
For Shaft Diameter 1/4"
2. https://www.mcmaster.com/1277N41/

For Maximum Belt Width 3/8"
OD 0.875"
Number of Teeth 10
Teeth Shape Trapezoidal
Pitch 0.200"
For Shaft Diameter 3/16"
3. https://www.mcmaster.com/6484K223/

Belt Trade Number 130XL037
Width 3/8"
Outer Circle 13"
Number of Teeth 65

IIRC it's item 2, the small gear that doesn't fit. Anyone tried this recently?

I got 30 tooth and 10 tooth Pulleys from https://www.automationdirect.com/adc/home/home
They sell belts too. I've got a 2min 40 second throughput, but you can feed in another 8x10 every 45 seconds or so. I'm going to make ring around prints of a couple nice negatives.

pwadoc · Jul 13, 2021

Super helpful stuff in this thread! I'm on the hunt for one of these processors, and this info will definitely come in handy when I locate one.

Lacman · Feb 4, 2023

mtjade2007 said:
I have modified my RCP-20 back and forth many times. It is not difficult to do. There are a set of plastic gears that you need to deal with. One is on the driving shaft from the motor and the other is on the long driving shaft for the rack rollers. The gears can be taken off without much difficulty. I got a couple of gears found from an electronics surplus store for a few dollars. I was able to match them to speed up the driving shaft for the rack rollers to about 1 minute for the developer and blix bath. This is still still slower then 45 second desired. But The RCP-20 temperature can be lowered to maybe around 80 degrees for this 1 minute development time.

I also modified it again to change the gear ratio so that the time becomes 3 min and 30 seconds. I thought to use it as a C-41 processor. I can use C-41 RA chemicals as it needs less than 3 minutes to bleach the film and I can run the fix and final rinse cycle on separate tanks. Well, I never get to use it yet though. I may reverse it back to the gear set for 1 minute process time for RA-4 again.

RCP-20 uses a toothed belt for linking the gears. So the gears do not contact each other. The gears are industry standard gears and so is the belt. You can find different sizes of them for the conversion. The motor mount is adjustable so you can move the motor either closer or farther between the gears. Just adjust it so that the belt is tightly wrapped on the gears.

Could tou help me with removing the plastic gears? How did you do it? Dis you use any specific tool?

pwadoc · Feb 4, 2023

Lacman said:
Could tou help me with removing the plastic gears? How did you do it? Dis you use any specific tool?

I used a very large set of bent needle nose pliers. Basically you get the open ends under the gears and apply some leverage.

koraks · Feb 5, 2023

Lacman said:
Could tou help me with removing the plastic gears? How did you do it? Dis you use any specific tool?

Ideally you use a bearing puller for this. Since it's OK if the gears die in the process, you could also use any kind of tool that allows you to exert sufficient force on them. Be creative.

Durst RCP20

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