Lo3000/ITT Creed Cheetah Printer
Verfasst: Sa 29. Jul 2023, 09:44
Having picked up another BT Cheetah 85 this week, I need to resolve a printer issue that also causes a problem for the Lo3000
The Printhead Drive belt...
Referring to this thread https://telexforum.de/viewtopic.php?p=26657#p26657 it can be seen that SEL/ITT Creed have gone their own way and developed a drive belt that is custom to the needs of the machine.
It looks like the design of the machine was done by a committee, with each side loosing an argument - the paper drive is a standard metric belt,the print head drive is an imperial belt.
The same measurements as found by Wolfgang are present on the Cheetah.
This leaves two options.
1, Find a company that will produce a timing belt that is 5/16" wide, 144 teeth, and 1/6" tooth pitch
2, Change the drive pulleys to suit a commonly available belt.
Considerable discussion was made in the previous thread, regarding the second option, there seems to be a lot of concern that the different belt pitch would cause character spacing problems - perhaps this is a problem of translation, but the belt tooth pitch does not set the character spacing - the combination of the step angle of the motor, and the diameter of the drive pulley does this - the teeth are just there to provide an indexed drive.
My thoughts currently are to change the drive pulleys to allow a standard belt, matching the diameter of the pulleys as close as is possible - this presents another problem - the printhead has a bracket that allows a simple clip to attach the head to the belt - this is also on the 1/6" pitch, but could be worked around by using a "belt clamp" that is fixed perhaps by screws.
Of course all of this requires machining of standard parts to fit to the existing system - there is room to increase to a 3/8" wide belt, with a 1/5" pitch - with a custom anchor bracket under the printhead,any new belt could be trimmed to allow the correct tension to be applied.
Before I go down this route has anyone tried to get the original belts remanufactured in rubber? I am of course aware of Johannes 3D printed part, but would prefer to be fitting a belt that is a proven reliable system.
The Printhead Drive belt...
Referring to this thread https://telexforum.de/viewtopic.php?p=26657#p26657 it can be seen that SEL/ITT Creed have gone their own way and developed a drive belt that is custom to the needs of the machine.
It looks like the design of the machine was done by a committee, with each side loosing an argument - the paper drive is a standard metric belt,the print head drive is an imperial belt.
The same measurements as found by Wolfgang are present on the Cheetah.
This leaves two options.
1, Find a company that will produce a timing belt that is 5/16" wide, 144 teeth, and 1/6" tooth pitch
2, Change the drive pulleys to suit a commonly available belt.
Considerable discussion was made in the previous thread, regarding the second option, there seems to be a lot of concern that the different belt pitch would cause character spacing problems - perhaps this is a problem of translation, but the belt tooth pitch does not set the character spacing - the combination of the step angle of the motor, and the diameter of the drive pulley does this - the teeth are just there to provide an indexed drive.
My thoughts currently are to change the drive pulleys to allow a standard belt, matching the diameter of the pulleys as close as is possible - this presents another problem - the printhead has a bracket that allows a simple clip to attach the head to the belt - this is also on the 1/6" pitch, but could be worked around by using a "belt clamp" that is fixed perhaps by screws.
Of course all of this requires machining of standard parts to fit to the existing system - there is room to increase to a 3/8" wide belt, with a 1/5" pitch - with a custom anchor bracket under the printhead,any new belt could be trimmed to allow the correct tension to be applied.
Before I go down this route has anyone tried to get the original belts remanufactured in rubber? I am of course aware of Johannes 3D printed part, but would prefer to be fitting a belt that is a proven reliable system.