If you did not buy belts yet, get ones with carbon fibre or steal core. Kevlar may be ok if you can get the better one (there seem to be more variants). Avoid glass core belts. They are too stretchy. It is good to get precisely matching pulleys for your belts.
Do not bother with the original arms ending with u-joints. Get ball joints (e.g. MP-Jet is good; other people use Traxxas so maybe there are good too). Magnetic joints are too heavy and may rattle at high speeds.
Just get geared extruder from the beginning (even when you use 0.5 mm nozzle). A good ratio seems to be in the rage 1:2 - 1:3. You do not want to gear it down too much since your retrace speeds will get too slow and there will be blobs of plastic at the retrace (retrace reverse) locations.
Go directly with 24V power source. You need also 24V heat bed for it. You can get hotend for 24V power supply or just limit the duty cycle for 12V hotend somewhere to the range of 1/4 to 1/2.
If you want to print high speed you will need to stiffen the frame more than the original two vertical plywood plates.
If I would build it again I would go with 12 mm smooth rods too.
No need for springs on heat bed. Mount it firmly.
If you intend to run at low acceleration limits of about 1g and low jerk (at most few tens mm/s) and speeds up to 30 cm/s then you can assume the belt stretch just below 0.1 mm. That is if you use steel core T2.5 belts. If you use glass core GT2 belts then the maximum error is about 3 times worse (i.e. 0.3mm). Add play between the belts and their pulleys to that (this will be worse for T2.5 belts). The 8mm rod bend error will be around 0.1 mm.
Do not bother with the original arms ending with u-joints. Get ball joints (e.g. MP-Jet is good; other people use Traxxas so maybe there are good too). Magnetic joints are too heavy and may rattle at high speeds.
Just get geared extruder from the beginning (even when you use 0.5 mm nozzle). A good ratio seems to be in the rage 1:2 - 1:3. You do not want to gear it down too much since your retrace speeds will get too slow and there will be blobs of plastic at the retrace (retrace reverse) locations.
Go directly with 24V power source. You need also 24V heat bed for it. You can get hotend for 24V power supply or just limit the duty cycle for 12V hotend somewhere to the range of 1/4 to 1/2.
If you want to print high speed you will need to stiffen the frame more than the original two vertical plywood plates.
If I would build it again I would go with 12 mm smooth rods too.
No need for springs on heat bed. Mount it firmly.
If you intend to run at low acceleration limits of about 1g and low jerk (at most few tens mm/s) and speeds up to 30 cm/s then you can assume the belt stretch just below 0.1 mm. That is if you use steel core T2.5 belts. If you use glass core GT2 belts then the maximum error is about 3 times worse (i.e. 0.3mm). Add play between the belts and their pulleys to that (this will be worse for T2.5 belts). The 8mm rod bend error will be around 0.1 mm.