I took my 1927 Roadster out for a ride today, I turned on the head lights and saw a negative draw on the amp meter of 10 amps. I have tail lights with a brake light so I guess it is time to turn the generator up. Is this a simple procedure ? Is anything simple on a model T ?
Randy Glowacki, Parsippany, NJ
Maybe, how is the charge rate when the lights are off? Since most people drive during day light hours you may tend to over charge with an increase in the 3rd brush setting. There is no regulator, unless you added one. You can move the 3rd brush a little to increase the charge rate, but consider your normal driving. You could over charge the battery and overheat the generator. If your generator is in good shape the setting of the 3rd brush is a compromise.
Driving in daylight the amp meter is at 0 , no charge or discharge . I have some night time driving comming up so I am thinking I have to turn it up to charge when the lights are on.
I agree with Mike. Most folks who have a cutout set their charge rate at about 4-5 amps with the lights off and that is OK for most daytime driving. If you drive at night only on rare occasions then leave it at 4-5 and put the charger on the battery if you stay out late one night. Since the typical T battery is about an 80 Amp-Hour battery, you would have to drive all night (at a net 5 amps discharge with lights on) and park all next day and drive all night again before you would significantly drain the battery. I would strongly recommend that you do not retain the use of a mechanical cutout if you are using one. Mechanical cutouts stick open and closed and can bag both your battery and your generator if you don't notice they are not working right. Diode cutouts are cheap and will not fail open which can spell doom to your generator. Diodes fail shorted and can cause a discharge of your battery if you don't notice it on your ammeter but diodes do not fail open so your generator is protected.
Thank you so much for your insight. I will turn up the generator only a little bit as I will only drive at night occasionally I have a battery tender so I will put it on after driving at night.
Check your battery tender device to make sure it does not draw any current from your battery when the battery tender is unplugged. Some of them do draw current and can actually ruin a good battery if there is a power failure while it is attached to your battery long term.
I looked into those battery tenders, but I couldn't see the point...I just disconnect the battery when I'm done driving.
The point of the so called "battery tender" is to offset the self discharge and resultant plate sulphation that occurs when the car is not in use. Left long enough, the battery is ruined.
If the car is used often enough, then it is not required.
Unfortunately the terms "Battery Tender", "Battery Maintainer", "Trickle Charger", and even "Battery Charger" are used as generic terms without absolute technical description or standards. In general they seem to imply things we want or understand but there is probably more misinformation about batteries and chargers than there is factual information. The Battery charger industry has made it as complicated as they can to thus sell a fancy charger with lots of "bells and whistles" and the battery makers really have no vested interest in wanting people to know how to really maintain their batteries for longest life.
What I find troubling is that many of the above devices have not been designed to deal with a simple power failure and they can drain a good battery if someone accidentally unplugs the charger or plugs it into an outlet that is controlled by a wall switch or the like. UL approval only deals with the safety of the device itself and its interface with the power outlet and not the functionality of the battery interface. Many claims of battery charger manufacturers are simply untrue and you don't find that out until well after you bought it unless you have an electrical engineering background and that makes me kinda ticked off at the industry as a whole. Sorry for the rant but it irks me when one of my friends spends a fair amount of money on a charger that is of no real use to them.
I hit the post button too soon. I wanted to say that I agreed with JohnH but wanted to clarify the terms a bit if I could.
Those original head light bulbs were 21 candle power and the new ones are 50 candle power.
That difference equates to the battery needing to produce a lot more current, which is above the 10 amp generator capacity.
I have found that a good battery will last about 2 or more hours at night when the ammeter shows about 6 amps discharge.
My 1927 Touring came with a generator equipped with a diode cutout (stud mount rectifier). The diode did in fact fail and ultimately resulted in an OPEN circuit (did not conduct current in either direction) so diode cutouts can result in an open circuit. Interestingly, the generator did not appear to sustain any damage in time I operated the car in that condition. Not suggesting damage will not result with the generator output open, just a data point.
I Reset the 3rd brush per information on the forum. Ron Patterson's method is very useful and effective (Thanks Ron!). Typical current readings per dash ammeter reading with Lights OFF:
0 to 1A at idle (~400 - 500RPM)
5A driving (~1000RPM)
10A to 15A higher RPM (~2000 -2200RPM)
With Lights on (head&tail/brake:
9A/8A discharge at idle (~400 - 500 RPM)
3A/0A discharge driving (~1000 - 1500 RPM)
Checked the accuracy of the analog dash ammeter using a digital Fluke ammeter and found it to be reasonably accurate. Digital meters can be influenced by EMI from the ignition system but the readings appeared stable and consistent.
Randy, I don't think anyone has spoken to your second post that the reading is 0 neither charge nor discharge driving in daytime with lights off. With that reading, your generator is not charging. Either you have an open cutout or the generator is bad. Try rotating the 3rd brush toward the engine block and then check the output. It should be from 2 - 5 amps for normal driving. 2 amps is fine if you do all your driving in daylight hours. 5 amps if you drive some daytime and some nighttime. With a 5 amp setting you will still show a small discharge when driving with lights on, but for an hour or two with a good battery, no problem unless you use a starter often during the nighttime drive.
If properly constructed a diode cutout will never fail "OPEN". I stand by that. A diode can fail shorted and then be BLOWN open by excessive current and heat but the failure mode was a short to start with. If the component is mounted properly and the device geometry large enough to handle the design current then that device will not open up when it fails. I have seen pictured on this forum recently a diode modified cutout with a stud rectifier in which the wire came unsoldered and thus the cutout was open but that is not the issue of the diode but of the cutout construction.
Stand or sit, I received my 1927 Touring with a diode cutout that was OPEN. Don't know how long it was in that state but the generator was not charging and drove the car for several weeks before taking apart the cut out and finding it was mounted to a copper heat sink and all connections looked electrically sound. Here is a photo of it after removing it from the copper heat sink.
I do not dispute the diode likely failed short circuit (Anode to Cathode) but ultimately resulted in an OPEN circuit (high impedance), isolating the generator output from ground or the battery. I had fully expected the generator field winding was toast based on what I have read on the forum but that was not the case. It did not appear to sustain any damage at all and in fact continues to work very well since I replaced the diode and reset the generator charge current. I would be interested to know why permanent catastrophic generator damage did not occur after a few weeks (at least) of operation with the generator output open. It supposedly should have burned out in short order. Any ideas?
Is there any way to determine what the charge current 3rd brush setting was before the cutout failed? I am confused on one issue and that is that you decided to set the "lead" current per Ron Patterson's instructions. I don't think that is any bad idea but what prompted you to do that? Was the charge rate excessive when you repaired the cutout? Normally the lead adjustment is a one time setting that doesn't need to be redone for the life of the rebuilt generator if done right. Its setting only comes into question when the charge rate cannot be reduced to low amounts using the third brush adjustment. It isn't a bad idea to have double checked that adjustment but it prevents us now from knowing what the generator charge rate was set at since the final charge rate setting is a function of both adjustments.
The diode as pictured does not appear to be the more typical stud mount diode and appears to be a press fit type of diode possibly pulled from an old alternator? I confess I don't recognize it in the form its in from your picture. Those type most certainly have the wire out the one end and then it would appear it got a flexible extension hooked on by the cutout fabricator. Was the other end pressed into that "housing" and then was that housing clamped up or something? Any picture of the whole thing before it was taken apart?
There are some notes and procedures that show how to modify a cutout to install a diode in place of the coil and contacts and I think one of them uses a "press fit" type of alternator diode as this appears to be. The problem is that those type during the "olden days" had a pretty large forward voltage drop and if the previous owner of your car had set the charge rate up high the diode would have overheated. If anything gets hot inside the cutout there really isn't a good place to get rid of the heat. One cutout maker uses a large heat sink but still has problems since that heat sink can only conduct the heat to the base of the thing or the trapped air inside the cutout. Since the cutout sits on the generator then once everything gets going it is more likely that engine heat is heating up the generator and thus the cutout. At the same time the cutout heat sink is trying to conduct its heat to the generator via the base of the cutout. So what is heating and what is cooling?? The trick is to not let anything inside the cutout get hot in the first place.
Once the "lead" adjustment was corrected the original charging rate would change hopefully down into the normal range for the 3rd brush to then be used as the regular means of adjusting the charge rate.
I would advise you to not park your '27 unattended once you stated your ammeter was accurate since that meter might disappear. An accurate 26/27 meter is a sought after item
Thanks for the reply. The diode sure is in a odd looking package. Looks like a stud mount rectifier pressed into another housing that itself was pressed into a copper clamp/heatsink.
I could not get the generator current adjusted properly after replacing the diode so concluded the adjustments were in some unknown state. So I figured I would start from a known calibration by following Ron's instructions. All worked well from there. I agree that the cutout is a tiny oven and rather hostel environment considering a properly operating diode will dissipate a fair amount of power (3.5W) for a small enclosure with the recommended 5A charge current and 0.7V drop across the diode.
The detail I would like to know more about is how the generator was not damaged after operating the car with the output open due to the failed cutout. I fully expected the field winding would be burned out or damaged but was not. Is the danger to the field winding a function of the 3rd brush setting? Not something I would want to experiment with to find out the hard way. Further details would be of interest.
Mike, how "open" was the diode? Perhaps it had low enough resistance to dissipate some of the energy. Of course if that were the case, it also would have dissipated the energy in the battery when not running.
Tom, The diode resistance is off scale measured on a Fluke 73III multi-meter and not conducting current in either direction. I wonder why no damage was done to the generator field winding from what I read about an open generator output.
Well since not many generators survive being run open, I can't really give you a scientific answer but in general yes the higher the 3rd brush setting then the higher the initial output that starts the runaway. I think the diode you have is not a stud rectifier but somebody has pressed that "button" end of the diode into what appears to be a BRASS (Schrader?) Valve cap off a T wheel since they are rounded like that and also have a bit of a knurl at the exact spot I can see some in your picture. The only reason I can think they did that was that they had something that would accommodate the larger and longer brass housing. T guys are very very clever and resourceful. I suspect the guy had no way to fasten any electrical lead to the button end of the diode. Take a looksee at an old alternator diode and you will see that it has grooves to allow one end to be pressed into a plate with other diodes as part of the diode bank. It would not be possible to solder a wire onto that grooved end. What was the brass wheel valve cover thingee clamped or hooked to? I can't be sure of that being a valve cap but for sake of this post lets call it that so we both know what is being referred to.
If you have not actually witnessed a generator go up in smoke I don't think you would enjoy it much and not at all if it was your generator. The output of the T generator gets started by a small amount of residual magnetism in it that generates enough current to get a small amount of output from the armature. The 3rd brush connects to one end of one field winding and the other field is in series with the end of that second field going to ground. Thus what happens is that a small amount of output allows the 3rd brush to pick up a small amount of field current. The amount it picks up is indeed a function of where the third brush is at physically. Since a small amount of field current is more than it started with, the added field current then increases the armature current output. The larger armature current output causes even MORE FIELD CURRENT which in turn causes EVEN MORE ARMATURE CURRENT and the whole process becomes a runaway unless there is a load on the generator to drag away the armature current and prevent the runaway. Now clearly the higher the 3rd brush setting then the faster this all happens with the end result usually being the field winding is burned open if it is the only load. Sometimes if there is some load at the armature but not enough to hold back the runaway then the armature fails first since it is spinning and producing way too much power so solder gets tossed off the armature and that also ends the day for the generator.
There might be several reasons you got lucky. One I must suggest is that your diode was in fact shorted and then opened up much later. The the lead adjustment was way off then perhaps the generator was not only set very low but had the lead adjustment making the current even lower if it was on the wrong side of neutral. On that last supposition I must defer to those who work on generators since that condition may not be possible. Usually the runaway can happen so fast that there isn't time to see what happened. I am betting that the diode was shorted initially and saved things since if anything was open and your generator had continuity through the various circuits the thing would have had to overheat at least. Was there any evidence of oil on the armature since the brushes will typically ride up on top of the oil and this often causes even a good generator to stop charging? A new seal at the front of the generator and a thorough cleaning will fix that. I am starting to guess and in this case YOUR GUESS is as good as mine. I wouldn't worry too much about your good fortune since clearly you dodged a bullet if you survived a bout with the generator spinning with no load. Armatures can be rewound and field coils are being made so a generator can be rebuilt even if damaged this way.
Thanks for the additional information and insight. I suspected no damage occurred because the 3rd brush adjustment and/or neutral adjustment was way off but was just a guess. I sure don't plan to see what happens if I disconnect the generator now that the brush plate and 3rd brush are properly adjusted!
I inadvertently referred to the diode as "stud mount", they usually have an end formed as a nut with a threaded stud on them. I meant press fit like used on alternators as you described. I popped it out and confirmed your suspicion is in fact the type of package. Plan to replace the diode cutout with a VR.
I have heard a lot of bad things about those VR's here on this forum the last few days. Are you sure you want to get one
There was an actual stud mount type pictured the other day here on the forum. It also was a home made cutout but the wire to its terminal end was no longer soldered since the solder had "walked off" the connection from repeated overheating. In old TV sets that sort of thing happened often on large high power resistors. They would simply be connected mechanically but the solder was gone from the heat of the power resistor. This was in the days of tube TV when point to point wiring was used and power resistors were typically wired to terminal strips, wrapped, and then soldered. I still dabble with antique radios and stuff.
I have heard a lot of good things about the VR too so worth a try.
I did see the photo of the depleted solder joint on the diode cutout. Know what you mean about the power resistors in older TVs but don't dabble with them much anymore. I do have a nice 5 tube battery set with 201As and Cathedral radio I dust off and power up every so often.
Thanks for the info on the generator.
My AK 20 compact uses 201A's. What I find interesting is that they control the output volume by adjusting the filament voltage on the output amplifier literally altering the conductance of the tube to control volume. Simple and elegant.