Fan belt troubles

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Model T Ford Forum: Forum 2010: Fan belt troubles
Top of pagePrevious messageNext messageBottom of page Link to this message  By Gary Gilmore on Monday, December 27, 2010 - 06:25 pm:

Need help! Just put the engine in but cannot keep the fan belt on. The fan assemblage is tipped downward causing the belt to ride toward the radiator. The casting holding the entire fan to the block is solid cast so I do not see bending it upward is possible. All the bolts are tightened up and the fan is not sloppy on the shaft. I took the water pump off. The bottom pulley was relined with braze and turned on a lathe to make it a snug fit on the crankshaft. (it was wobbley)Any suggestions?


photo of fan belt


Top of pagePrevious messageNext messageBottom of page Link to this message  By Norman T. Kling on Monday, December 27, 2010 - 06:53 pm:

That looks like a pretty old belt and could be stretched. The adjustment should not be too tight. Just tight enough that the weight of your hand on the fan blade will not cause it to slip, but if you push down on the blade it should slip. If too tight you risk stretching the belt and premature wear on the bushings. If a new belt doesn't fix the problem, then look very carefully at the alignment of the two pullies. The lower pulley should be crowned in the center which will keep the belt centered on it. It could be possible that the top pulley is back of the crankshaft pulley. If so, a washer between the pulley and bracket could align it better.

I have put these things in the order I would do, and if the first one fixes it. That's where I would stop.


Top of pagePrevious messageNext messageBottom of page Link to this message  By John Gelfer on Monday, December 27, 2010 - 06:55 pm:

Is it possible that it was not bored perpendicular to the pulley face? The 09-19 3.25" pulleys are $52.75, and the 20-27 3.75" ones are $59.95 at Snyders. They have adjustable centers to deal with the wobble. They also have ears on them to keep the belts from walking off. This might be an easier solution to the problem.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Mike Saltsgaver on Monday, December 27, 2010 - 08:18 pm:

If that's the same belt you were running with a floppy bottom pulley, it is probably stretched out of proportion. Order a new belt. While you're waiting for it to arrive, make sure there's no extra slop in the bushing for the fan shaft which would let it droop. Make sure the fan pulley still has a little crown to it & that the crank pulley is "straight" (no crown).

As was mentioned,don't over tighten the new belt.
Lots-o-luck
Mike Sa


Top of pagePrevious messageNext messageBottom of page Link to this message  By John Gelfer on Monday, December 27, 2010 - 09:07 pm:

I thought the crank pulley needed to be crowned. Mine sure is.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Jim Thode on Monday, December 27, 2010 - 09:14 pm:

An idea would be to reverse the belt and see if it runs off the side toward the engine. If it does, you know the belt is at fault.
Jim


Top of pagePrevious messageNext messageBottom of page Link to this message  By Norman T. Kling on Monday, December 27, 2010 - 10:07 pm:

Both pulleys should be crowned.
Norm


Top of pagePrevious messageNext messageBottom of page Link to this message  By CharlieB-Toms River N.J. on Monday, December 27, 2010 - 10:54 pm:

The belt guide worked for me on the '27. Had a water pump on it. But that belt does look a little tired.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Gary Gilmore on Monday, December 27, 2010 - 11:05 pm:

OK, thanks for the ideas. I made the belt which has become stretched on the one side as it was pulled around the edge of the fan pulley. I'll reverse it tomorrow and try again. The pulleys are in good shape with no slop. There is a slight crown on both pulleys. Stay tuned!
Gary


Top of pagePrevious messageNext messageBottom of page Link to this message  By John F. Regan on Tuesday, December 28, 2010 - 02:10 am:

Gary:

You mentioned in your very first posting that the fan assembly was tilted down. If that is true - no amount of crowning or new belts nor pulleys with guides on the sides will keep the belt from doing this again. You need to address the alignment and tilt of the pulleys. Did someone grind the front of the head at the water outlet at a crooked angle or is there something not square or parallel with the fan shaft and that back mounting surface at the water outlet on the head? I think you will fight this for a very long time if you don't find out what is going on and fix it correctly. Just my $.02


Top of pagePrevious messageNext messageBottom of page Link to this message  By Allan Bennett on Tuesday, December 28, 2010 - 07:22 am:

I'm with you John. The fan shaft must be parallel to the crankshaft. To compensate for the nose down attitude on the fan, it might be easiest to face the top water outlet where it mates with the head.
I have re-surfaced outlets using a 4" wide linishing belt on my bench grinder. It fits nicely on the surfacing plate, and with care, one can angle the outlet to take more material where it is needed. Go carefully and be patient!
Allan from down under.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Jim Patrick - (2) '26's - Bartow, FL on Tuesday, December 28, 2010 - 08:35 am:

With the fan adjustment tab at the top, It looks like the cammed fan pulley is as loose as it will go. If you loosen the nut and tap the top tab toward the passenger side (which will give you more room between the belt and the timer), it will tighten that pulley. Also, it looks like there is an inordinate amount of space between the fan pulley and the housing. You need to make sure the shaft centering discs that sandwich the housing through which the shaft passes are fully seated up to their shoulders and that the fan shaft nut is plenty tight. On mine the end of the shaft on the engine side can be clearly seen, while on yours the end is hidden inside the nut which indicates to me something is not right. The end of that shaft is flattened on each side so you can hold it with a wrench while you tighten the nut, but if everything is not seated and that shaft does not extend far enough for you to hold it in place, you will be unable to properly tighten the shaft nut. Take it apart again and make sure everything is seated and that shaft goes in far enough for you to be able to get a wrench on it so it can be properly tightened. Jim Patrick


Top of pagePrevious messageNext messageBottom of page Link to this message  By Kenneth W DeLong on Tuesday, December 28, 2010 - 11:13 am:

Simple,Get the belt off and use a straght edge to aling the pullys! You can't get to where you want to be if you don't know where you are when you start?? Bud.


Top of pagePrevious messageNext messageBottom of page Link to this message  By John Fenton on Tuesday, December 28, 2010 - 12:20 pm:

Something to keep in mind, is that a flat belt like the T has will climb to the high side of the pulley. If the pulley is crowned, the belt climbs to the middle.Possibly your fan shaft is bent up, not down.


Top of pagePrevious messageNext messageBottom of page Link to this message  By David Stroud on Tuesday, December 28, 2010 - 05:44 pm:

John, I respectfully disagree with you. I used to work flat belt conveyors a lot in the past. When the pulleys are not square with one another, the belt will work to the short side, at least that was my experience. Dave


Top of pagePrevious messageNext messageBottom of page Link to this message  By Garnet on Tuesday, December 28, 2010 - 06:08 pm:

What's the shiny bolt head in between the pulley and casting? Never had anything like that on mine. Make sure the main through-bolt isn't bent.

Regards,
Garnet


Top of pagePrevious messageNext messageBottom of page Link to this message  By Hal Davis - Lyons, GA on Tuesday, December 28, 2010 - 07:08 pm:

I've always heard that same thing about belts climbing to the tight side, but I don't believe it. That is certainly not how the belt on my belt sander works. It tracks toward the loose side. Same goes for lining up machinery to a hit and miss engine or flat belt PTO on a tractor. I wonder if the reason 'crown' helps a belt to track is because the belt gets stretched somewhat in the center and the tight edges would rather stay low?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ron Patterson on Tuesday, December 28, 2010 - 07:42 pm:

Gary
I agree with Garnet. It appears the upper pulley eccentric assembly is not correctly installed on the water inlet casting and is causing the misalignment.
Ron the Coilman


Top of pagePrevious messageNext messageBottom of page Link to this message  By Gary Gilmore on Tuesday, December 28, 2010 - 10:13 pm:

Here is the latest update. The fan belt now stays on. One side was stretched when it rode over the fan pulley. I reversed the belt and it works. BUT, in reading the replies, I still think something is wrong. The pictures show how the fan is assembled on the bracket. The large washer with two holes goes in front of the water inlet bracket. One hole is 1/2" in diameter for the fan bolt while I have no idea what the 5/16" hole is for. However, it lines up with a similar size hole in the piece that turns inside the bracket. I tapped this hole for a short bolt to hold the disc in place when the fan bolt was lossened. (Garnet, that is the nut you noticed and commented on) The fan bolt does not have any flats on the end to hold it while the nut is tightened. This may be a bolt from another style fan but it is what came with the "barn fresh" engine. The black stuff is not bitumen, but roofing tar. This makes a great belt dressing and was necessary to get the water pump to spin. (Water pump has since been removed) I took this hub apart, took the pictures and put it back on with an extra washer between the fan hub and the large disc. Fan belt tracks well and problem seems solve, but still wonder about how the correct way to assemble this setup.
PS, The fan hub was not tilted down. It just needed moved ahead 1/8" and a belt with even tension.
Thanks for all your help. I love this forum!bracket1bracket 2view 3


Top of pagePrevious messageNext messageBottom of page Link to this message  By Dave Dufault on Tuesday, December 28, 2010 - 10:22 pm:

Gary,
Good for you - in many respects...you got one up on Hugh Jass!

Happy New Year!


Top of pagePrevious messageNext messageBottom of page Link to this message  By Jim Thode on Tuesday, December 28, 2010 - 11:58 pm:

Gary,

The smaller hole in the plate between the pulley and eccentric is supposed to match a pin in the eccentric. Your pin was apparently missing. I'm not sure what holds the pin in place but I assume it is just a friction fit. On yours now you should be able to thread (tight with locktite) a bolt into the hole you taped and cut the bolt off. The pin extends out about 3/8" from the eccentric.

You should also be able to grind flats on the main bolt/shaft so you can hold it to tighten the nut.

Jim


Top of pagePrevious messageNext messageBottom of page Link to this message  By Gary Gilmore on Wednesday, December 29, 2010 - 09:15 am:

JIm, as they say, a picture is worth ..... Thank you for the picture and thankyou to everyone else who chimed to help.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Jim Patrick - (2) '26's - Bartow, FL on Wednesday, December 29, 2010 - 09:51 am:

Your pulley appears to be properly crowned in the center, but if all that buildup of tar or belt dressing is causing the pulley to be uneven it may be causing the belt to want to move off center to the false crown created at the front edge by the build up of tar. I would take some lacquer thinner and remove that buildup from the pulley. It should not be necessary unless your old belt is so hard and slick that it will not turn on its' own. In that case, you need a new fan belt. The belt on mine is called an "Endless Belt" It has no seam, is impervious to oil, is very flexible and gets great traction on the pulleys so that no belt dressing is needed. Jim Patrick


Top of pagePrevious messageNext messageBottom of page Link to this message  By Jim Patrick - (2) '26's - Bartow, FL on Wednesday, December 29, 2010 - 10:03 am:

One more thing. You should take a Dremel tool with a disc grinder and flatten both sides of the shaft end (see Jim Thode's photo), so you can get a wrench on it so as to hold the shaft in place while you tighten that nut. Before you do this, screw the nut on the shaft so that after you flatten the sides, you can unscrew the nut, which will chase the threads open that were distorted by the Dremel tool.

Also, that flat washer between the front disc and the fan bearing, is not needed. All it does is lessen the amount of shaft length on the engine side, that is needed in order to tighten that nut. Jim Patrick


Top of pagePrevious messageNext messageBottom of page Link to this message  By joncrane on Wednesday, December 29, 2010 - 10:35 am:

I never understood the physics behind the mystery of a flat belt. I have seen many at tractor shows etc and everybody including the Model T crowd tell me that they run to the crown and that is the key. However, my brief understanding of physics is that things go to the least resistance, things fall down, and things don't fall up...So why does the belt want to travel to the center of the crown? The crown is up, the crown is the greatest resistance, and the crown is the largest diameter to travel. Just does not seem right..


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ron Patterson on Wednesday, December 29, 2010 - 10:57 am:

Gary
While you have the fan assembly apart check closely for this common Model T fan blade cracks. Lang's Old Car Parts sell a nice new powder coated fan blade.
1
Ron the Coilman


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ron Patterson on Wednesday, December 29, 2010 - 11:17 am:

Here is a photo of the early 1926 fan eccentric.
2
The nut at the bottom has threads which rotate the round piece that fits into the casting. There is a nut in the end of the bolt to tighten it after the correct fan pulley position is found.
This fan mount was discontinued early in 1926 because if you tightened the nut too tightly the casting ears that held the eccentric would break off.
Ron the Coilman


Top of pagePrevious messageNext messageBottom of page Link to this message  By Steve Tomaso - Milton,WA on Wednesday, December 29, 2010 - 11:17 am:

You have a fan shaft from an earlier model - too short and as Jim stated above - this type of fan adjustment arrangement needs the flats on both sides of the shaft to properly adjust the tension.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Jim Patrick - (2) '26's - Bartow, FL on Wednesday, December 29, 2010 - 11:28 am:

The belt adjustment on my belt sander is made so that the front pulley can be angled in or out so that you can adjust the belt to the center of the pulley. When you want the belt to go toward the edge, you adjust the pulley so that the outer edge of the pulley is angled further out than the inner edge and if you want the belt to go in, the outer edge of the pulley is angled further in than the inner edge, so that the belt always climbs toward the tighter side. I suppose this is because if the looser side of the pulley is not touching anything, or has less traction than the tighter side, the tighter side, which has more grab, naturally pulls more than the loose side. The fact that the belt seeks the high point is the reason for the crowned pulley. Since the center has more traction than the edges, the belt automatically centers itself on top of the crown. The only way it can move off high center is if the shaft is bent up or down causing there to be a point on the pulley higher than the crowned center, or if the belt is stretched on one side, causing the tight side to seek a new high point. Jim Patrick


Top of pagePrevious messageNext messageBottom of page Link to this message  By George...Cherry Hill, NJ on Wednesday, December 29, 2010 - 11:54 am:

JonCrane,

The use of flat belts is a mental paradox as you say. The mind thinks it should always track to the minimum tapered end of any mechanism. In the case where both shafts are not exactly parallel this sure seems obvious, eh?

Flat belts are NOT to be pulled up tight like a banjo string and therein lies the trick to why crowns work! On passing the DRIVEN pulley, surface friction will cause the belt to be FLAT on that pulley..it just does. So as the belt is returned from the pulley, it wants to return at an angle of the DRIVEN pulley plane. Say the front of the fan pulley sags down for example. On leaving the fan pulley, it WANTS, by natural reaction to go over the crank pulley CLOSER to the engine, even if that pulley is also tapered towards the radiator.

Now revisit the idea, the same thing happens as the belt goes around the crank pulley, it now leaves and WANTS the belt to naturally go towards the water fitting direction.

With two tapered cones facing in the same directions, it has its own paradox and ultimately crawls to the radiator side, but the forces in the belt are going crazy while it does. The belt quickly takes and hourglass shape because it can't fight physics.

The crown of one (or two) pulleys is NOT a way to use tension to 'find center'. Think of our example. The belt WANTS to 'return' to the high side, but physics keeps it from happening.

So make OPPOSING tapers and bada-bing and the belt just feels more comfortable finding its own 'center of travel' which just happens to coincidentally be the high points of the 'tapers' plus/minus on the 'desire' to travel line!

Hope that makes sense....in this example we set the tension to be just enough to provide natural friction on the pulley surface. Now, make the mistake and torque it up tighter than a banjo string? It still wants to do as I said, it just can't. The force vector becomes too significant for 'natural order' to prevail.

Just enough tension, and the above is why it works. :-)


Top of pagePrevious messageNext messageBottom of page Link to this message  By Norman T. Kling on Wednesday, December 29, 2010 - 12:41 pm:

My grandfather had a furniture factory. Many of the machines had flat belts. Large flat belts. I never saw one of those belts fly off. That was the type of belt commonly used when the Model T was first manufactured and the Model A was the first Ford which came from the factory with the V belt.
Norm


Top of pagePrevious messageNext messageBottom of page Link to this message  By Larry Smith on Wednesday, December 29, 2010 - 03:34 pm:

I noticed you have the felt (leather)? washer in the wrong position. It should be inside the cupped retainer. It rubs against the rear bushing. Also, I don't see how that water outlet could be bent. It is a casting, and they don't bend easily without breaking. Another thing. Old leather belts don't stay on very well. The only leather belts I've seen that work on a T are the ones that Don Lang sells that are made by an old 100+ year old belting company.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Jim Patrick - (2) '26's - Bartow, FL on Wednesday, December 29, 2010 - 03:47 pm:

Larry, I believe that is a rusted steel flatwasher.

Gary, I see some oil running down (up) your fan blade which indicates to me that you need a new gasket between the fan and oil reservoir so it will hold oil with which to lubricate the shaft. Jim Patrick


Top of pagePrevious messageNext messageBottom of page Link to this message  By Kenneth W DeLong on Wednesday, December 29, 2010 - 05:18 pm:

I never liked the stiched leather belt but i have not tryed one since the water pump left.As long as it is still long enough it could be cut square and laced with Clipper laceing. Bud.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Hal Davis - Lyons, GA on Wednesday, December 29, 2010 - 09:54 pm:

I don't mean to perpetuate an arguement here, but I just went out to the shop for the sole purpose of experimenting around with my belt sander. Both drums or pulleys are crowned and the belt most definitely tracks to the loose side.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Kenneth W DeLong on Wednesday, December 29, 2010 - 10:53 pm:

Hal,Long ago i used to do the belts on large conveyers 2 3 4 5' wide belts and tracking depends on where the take-up's are in relation to the drives.No crown on the big ones,but to run true they must be cut and laced square.What has any of this to do with fan belts?? A straght edge will tell all! Bud.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Paul Mikeska, Denver CO on Thursday, December 30, 2010 - 12:16 am:

I have one of the Lang's stiched leather belts on the 26 Coupe. It has been on the car for 4 or 5 years and I only had to tighten it once, fairly soon after it was installed. It is a quality product but is more expensive than the endless or rubberized fabric belts sold by the vendors. Over the years I have had 2 of the rubberized fabric belts fail.

Paul


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