# Proposed Improvement to Log Loader #751



## Lairbear (Aug 20, 2012)

Changing the subject, I will be designing a variable AC output device (triac) that connects to the 18 Vac solenoid coil which lifts the log into the carrier of AF#751 log loader.
Hopefully, smooth up and down movements of the lifter will occur without burning up the coil, instead of the current up and down movements of the lifter. Coil is intermittent duty, just like the coil in the log unloader car #914 which is 1 ohm @ 18 amps momentary to dump 3 large logs!


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## Lairbear (Aug 20, 2012)

Changing the subject, I’ll be designing an AC circuit (triac?) to vary the voltage to the solenoid coil of the log loader #751 which timed correctly, should eliminate the jerky up/down movements of the current lifter scheme. Voltage increase’s to max within 2 sec’s and then decreases slowly to zero within 2 sec’s.
Me design will attach to the underside of the bakelite base with velcro ® which will allow removal of same to restore to original wiring.

Perhaps a varistor or something in line would do the trick...Once power is applied, the resistance of the device in series with the coil winding will decrease allowing the lift to move up slowly within 2 sec’s, but remember, the button must be released after 4 sec’s to prevent burning up of the coil. 
I think a device that starts out with high resistance for a second or so, then decreases resistance to a minimum for about .5 sec’s, then back to a high resistance would nice to purchase. Just a thought, two devices in series, one with high resistance to start and decreases with current, a second in series that starts out with low resistance then increases to a max resistance.
Any feedback would be appreciated.


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## Lairbear (Aug 20, 2012)

Sorry for repeating parts of the subject. 
I'm still getting the vBulletin Message screen after I login, checked "remember me" to respond to posts.
I no idea why the link dosen't proceed to the original page with the post so I can respond to the same page?


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## gunrunnerjohn (Nov 10, 2010)

Lairbear said:


> Sorry for repeating parts of the subject.
> I'm still getting the vBulletin Message screen after I login, checked "remember me" to respond to posts.
> I no idea why the link dosen't proceed to the original page with the post so I can respond to the same page?


Try specifically logging out and then come back and log in. That will remove the cookies for the site. If that fails, next step is to clear all your IE cookies and then come back and login.

Note, I've moved your new topic to it's own thread to keep the confusion down.


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## Nuttin But Flyer (Dec 19, 2011)

I like the concept you are proposing. It would certainly provide more realistic operation if you succeed. I am anxiously awaiting the details and video when it is working.


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## Lairbear (Aug 20, 2012)

With a push of the button, the prototype circuit is working. It varies the 18 volt AC for about 2-sec's up and 1 sec pause, then 2 sec's down. I’ve used a 12 volt turn signal lamp as a load, so far the brightness varies correctly. I'm waiting for the log loader to arrive to test this system.

I must remember, the solenoid coil is intermittent duty, one cannot apply continuous power, which will burn up the coil. I'm surprised Gilbert didn't design coils that were continuous duty in case a push button got stuck. Probably has to do with costs. A burnt up coil is a repair item which means revenue for the shop.

I'm thinking about incorporating some type of thermo device that would help limit current to the coil and triac after a certain period of time. The thermo device should have a ?-amp rating initially, and then resistance increases. 

I just realized, the thermo device scheme is an excellent idea for the log unloader car. If button gets stuck, current drops off, protects coil from burning up! I think I just gave away a “secret.”

I'm aware of such devices, but I don't remember the correct name for it or where to purchase these devices.

Before I forget, how do I upload videos? Do I have to have an account with YouTube?
Do you or someone have pictures/video showing the modification to the log loader that did away with the solenoid coil lifting the log into the carrier?


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## gunrunnerjohn (Nov 10, 2010)

The "thermal device" you refer to is a TDR (Time Delay Resistor) I can't seem to find any right now, but they used to be popular in CRT TV degaussing circuits. Here's one that was for TV use: http://hwalon.en.alibaba.com/produc..._for_color_Television_TV_degaussing_18RM.html


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## Lairbear (Aug 20, 2012)

Here's the link readers, unless you are an engineer, you probably know all about these items and their applications in which the sky the limit.

http://www.littelfuse.com/products/...ct Brochures/Content/EC327-E_Polyfuse_PTC.pdf


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## Lairbear (Aug 20, 2012)

Why didn't Lionel, MTH, Atlas, etc, utilize these devices years ago when they first came out to protect their coils in the switches, etc? Aristocraft ues them with their G scale switch frogs.
With my electronics background, I should have realized this concept in my teens, instead of overheating the AC/DC switch coils during testing.
One's never too old to learn even if they suffer from "oldage."


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## Lairbear (Aug 20, 2012)

The current limiting device is a "NTC."
Web link: http://www.ametherm.com/feedback.html
With the use of this device, the triac heat sink may be reduced in size.
I'll keep the readers posted as project continues.


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## gunrunnerjohn (Nov 10, 2010)

The PTC isn't quite the same as the TDR, however since I can't seem to find the TDR, perhaps they'd do the same function. I've never thought of them to protect a coil, but it's an interesting concept.


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