Capacitor Discharge Units

Eaglecliff

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Is there any "point" to adding a CDU to the operation of LGB point motors?
 

Gizzy

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They are not required for LGB imo?

The power feed to the Point switch is AC which then supplies a Half wave rectified DC signal via a diode of either a negative or positive polarity, which moves the motor (not a soleniod as used on the smaller scales) a half turn, via a rack and pinion....
 

nicebutdim

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Although they are not required, I use one for all my LGB points. They ensure a good positive throw and a safety fallback should anything 'stick', i.e. if the contacts stick within the switch it will not burn out the motor.
As the output of cdu's is basically dc all that is required for operation is a dpdt switch wired for reversing. I actually use a modified Tamiya speed controller as I've rc'd everything.
 

ntpntpntp

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IMHO, CDU's are more useful for solenoid coil point motors which require a brief "kick" of high current. solenoid point motors typically have three wire connections (two coils and a common) and work with either AC or DC (without requiring any polarity change if DC)

As Gizzy has said, LGB motors, being more akin to motor drive than solenoid drive, don't work in the same way in that they use only two wires and require a reversible DC feed. They need (arguably) a slightly longer pulse to drive the motor all the way over but don't need such a high "kick" of current.

(some very old LGB motors were three-wire and maybe were solenoid driven?)
 

minimans

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LGB Point motors are SOLENOIDS they use a reversable current to throw the magnet one way or t'other the rotation of the magnet is 90deg in either direction and yes you can use a cap discharge unit in fact LGB make one only they call it a booster but it's the same thing..............
 

nicebutdim

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I think some of the problem with these lgb point drives is they have the properties of both motors and solenoids. They have the (semi) rotation and electrical properties of a motor (where polarity of the supply can reverse the operation) but also the lack of multi coils and magnets or non-constant rotation like a solenoid.
The simple answer is that you don't need a cdu to operate the drive, but can use one if you wish, as they DO work. I use the Gaugemaster type, it works fine and is powered from lgb's 18v transformer. But the choice really is yours. :D
 

Eaglecliff

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Thanks to everybody for your quick responses. I guess the answer is to try it and see! My cdu is also a Gaugemaster. Now where did I leave the soldering iron?
 

Eaglecliff

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Just a quick follow-up - I wired two crossovers via two-way switches and push-to-make button switches with power from an old Scalextric 14v transformer - presto! Enough oomph to work two points at once. So I didn't need the cdu, although I will keep it in reserve just in case. Incidentally, I've never seen any reference to Relco track cleaners for use with G scale. Anybody tried to build their own 20v version? If not, why not? They would be a lot cheaper than an LGB track cleaning loco!
 

nicebutdim

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Don't put anything with high frequency & voltage operation near G scale. The electronics in most locos (especially mts equiped) are very sensitive and a Relco will release the special smoke from within. Although I use CDUs, they are totally insulated, in every way, from track power.
 

stockers

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I have several sets of LGB points that throw in pairs together - never had any power problems.
I agree - keep relco type things away from electronics.
A relco will not replace clean track in the garden. It will probably burn the chrome plate on the wheels as well.
 

ntpntpntp

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Relcos and the like are not really track "cleaners" as such: IMO the function is more along the lines of creating an hf arc to break down the dirt/air-gap resistance and allow the traction current to flow. Useful for small layouts in the tiny scales (I use one with my Z gauge and the assistance is noticeable) but the effect diminishes once you have significant runs of wiring and rail joints. I gave up using them on my larger & more complex N gauge layouts 20+ years ago. I agree they could pose a risk to locos with DCC or other electronics.
 

dutchelm

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If you scale up the energy pushed into the track from an N gauge relco up to G scale their may be a health & safety problem!
 

Eaglecliff

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Isn't GSC wonderful for info!!!
Thanks to all concerned.