The Trico-Folberth and other air-pressure wiper motor thread
As some of you may know, many older large trucks with air brakes use a form of wiper motor that works on air pressure.
Many of them are Trico-Folberth brand, some are Sprague, and there may even be others.
This thread is a place we can all discuss these air-pressure powered wiper motors in detail, and at long last, there is a simgle place on FTE to discuss these wiper motors that covers all the years they were installed.
I have some documentation from Trico on these wiper motors, and I know a few of you have tinkered with them over the years.
There are some tips and some tricks associated with thesm, and if anyone has any questions, I've done extensive work on most of the Trico motors available.
From the original "F" series, to the FP, FPS, FPSC, FPHC, etc series, to the FDC series, and beyond.
The first tip/trick for helping an old and tired Trico Folberth motor:
The muffler on the output side of the wiper motor can be one of two types. Just a muffler with a piece of cotton in it, or a muffler with a REGULATOR built into it.
If it's a short muffler, about 1/2 inch long, it's most likely a regular muffler.
However, if it's 3/4" or even longer, chances are it has a regulator built into it. There is a 3/32" allen-head set screw inside that adjusts a ball-and-spring type regulator built into the muffler.
If your muffler is plumbed to the outside, unscrew the hose barb from the muffler, and you should find the set-screw. If it's just cotton padding in the muffler, remove that and see if you have the set-screw.
Now, there are two things going on at once.
The regulator both slows down the speed of the wiper motor, AND increases the torque.
Most (all) Trico-Folberth motors come with a control that has a needle-valve in it.
To adjust the speed of your wiper motor, and the torque associated with it, the following procedure should work well.
What you want to do first is open up the regulator in the muffler all the way. AFTER cleaning it - over the years oil and varnish will build up inside and cause it to flow a lot less than designed to.
Find the needle valve on the control valve, open the control itself to MAX, and open (or close) the needle valve until you reach the TOP speed you are looking for.
Close down the set screw (clockwise) in the muffler until the speed starts to slow down. Keep tightening another turn or so, and then back off on the needle valve on the control again until you reach the TOP speed you want.
Now, of course, based on how big the wiper blade is, and whether or not the windshield is wet or dry, will affect your wiper's speed.
The more you open the needle valve in the control, and the more you close down on the regulator in the muffler, the more TORQUE you will get from the motor, and the LESS the speed will change based on wiper blade resistance.
However, going too far, you can over-work the wiper motor and wear out the seals all that much quicker.
So there is a fine line where you want as much torque as possible to keep the speed stable, but not too much as to wear out the motor prematurely.
Question: I have a 53 Mack with a trico Folberth air motor. there are no numbers on this unit other than name and patent numbers that I can find. Where are the numbers located? NOS are available but are very expensive. Are there rebuild kits available?
I appreciate any information or help you can give me. Thanks
Nice topic.... I'm restore'n a 1966 C-750 former NASCAR car hauler ( with factory sleeper cab ).
I've got the air wipers that are working ok for now. Also have a pair of electric wiper motors in storage incase the urge hits me to change over. I know on my 65 Rambler Wagon I've got vac wipers and they are so cool/temermental that I'd decided to keep the wagon original and will probably go the same way with the C-750.
Keep the info flowing... I'll take a look at the wipers next spring and see if they can be tuned up.
The interesting thing about the air-pressure wipers is that they can be run VERY slowly and still have lots of torque for big wipers/arms.
If you crank down on the regulator screw in the muffler, and up the pressure, you can produce gobs of torque at low speeds. Conversely, loosening the regulator speeds up the arms, but as soon as they meet any resistance they slow down a lot.
Just be careful. If the motors are getting old, you can wear them out that much faster by upping the regulator pressure.
Hi everyone.We just brought a 1978 Hino bus and it has these wipers and motor your talking about.We are in Australia,..Does anyone know where we can get assembly spares for the the whole assembly for this.ETC wiper arms and basically the whole mechanism?.Thanks if anyone can help this lady LOL
I have a Trico FP/FPS that I am attempting to use for another purpose . At the moment I have a shaft through the tapered bore holding an arm I am using for reciprocating motion (robotics if you will) . I really don't want to go to the bother of machining a proper tapered shaft if the part or parts are available . Given a proper shaft I'm sure I can adapt something that will suit my needs . I'm just having a time of it trying to find an illustrated parts breakdown/list . I acquired more than a few in a scrap deal and most work . Fascinating piece of equipment really .
On another note I wonder if http://www.mcmaster.com might have most O-rings needed for repair and rebuild . Also several of the major motorcycle manufacturers have seals listed by progressive dimensions for cross reference .
The seals used in the Trico-Folberth wiper motors are very unique, and designed in a way that allows them to use the air pressure to seal against the cylinder bore. This way, as the seal or bore wears, the seal continues to expand as pressure is applied to it.
An o-ring just isn't going to last very long before it looses it's seal.
If any of the motors you acquired have shafts, you could always machine the end to accept whatever you need to attach to it. On the other hand, if the existing shafts aren't long enough, a good welder could probably make up something.
Just be careful - the metal of the gear segment is "pot metal" - easily melted.
Can you answer why when I have air to wiper motor the regulator leaks no matter where I have the setting on allen head or needle on control valve? At first motor leaked on ends so I resealed them and now it leaks at regulator. I assume that could be those internal seals you mentioned having a problem but I don't know. TIA
That "regulator" or "muffler" is the exhaust port, it should almost always vent some air.
Does the motor go back and forth and is it strong?
I don't know if I can answer that right as there is no blade on it. I tried grabbing shaft though and it continued to turn so yes I would say they function fine I just can't believe they leak out air nonstop (either in Park or Run) as it's annoying (to someone with good hearing). If you say its normal I shall leave it alone. I was just asking guy today who's semi I'm working on if you can ever get rid of all air leaks so you get back in truck an hour later and pressure gauge doesn't read zero. He said ones with copper lines are about as close as you get but not this plastic stuff. I should add not with these wiper motors either. Thank you.
The wiper control should, when it's on "off" not leak any air. If they do, then they need to be changed or rebuilt. If the control goes to "Park" and stays there, again, there's something wrong with it.
Even when you turn the control to "Park" (and hold it there) the wiper should not leak any air, and if it does, only a small amount.
Sounds like the cylinder seals are shot. It'll work, but it'll make a lot of noise. Although, if the cylinder seals are shot, the motor will leak air out the vent hole on the shaft/gear cover, NOT at the valve-end.
Well I will check on Monday. As I may be confused on a little bit of your explanation. I will put it together and run it then tell you exactly what's happening. I also have two of them and have only been trying the one as it was the one giving me problems. Haven't compared it to the other and maybe it leaked too so I shut control supply valve air but I can't remember. Thank you.