Fan belt tracking

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Model T Ford Forum: Forum 2008: Fan belt tracking
Top of pagePrevious messageNext messageBottom of page Link to this message  By Randy Schultz-Rathbun, Brush Prairie, Wasington on Thursday, January 15, 2009 - 03:33 am:

My 1926 roadster's fan belt has started tracking toward the engine block. It's trying to work over the ridge on the back of the fan pulley, and is rubbing on the timer and lower radiator hose. I just rebuilt my water pump, and would think I might have it mis-aligned, but it was tracking the same way before the rebuild. I've tried running the belt tighter and looser, but in both cases it tracks to the engine side of the pulleys as soon as the engine starts turning.

I notice there's a fair amount of play in crankshaft pulley (well, it seems pretty sloppy) and a little in the fan pulley. Any ideas on how to make the belt run where it's supposed to?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Warren Mortensen on Thursday, January 15, 2009 - 07:23 am:

Flat belts run on crowned pulleys. If you look at the pulleys on old machinery you'll notice that the pulley is not flat but actually has a larger outside diameter along the centerline than along the edges. The belt naturally tracks to the high spot.

Fan pulleys on Model T's often have lost this crown from years of running. In many cases a crown can be recreated by mounting the pulley to a drill and filing or sanding the crown back into the surface.

The sloppy pulley on the crankshaft can also be contributing to the problem and a water pump just adds to the equation (many of us consider a water pump an unecessary addition to a properly running T - usually the radiator needs replacement).

For the belt to run properly all shafts axes have to be parallel or the belt will wander to the highest spot regardless of where that high spot is. Determining which component is causing the problem can be a real bear.

In addition, now that the belt has started climbing the flang on your fan pulley it is probably stretch on that edge. In effect it may not be a "flat" belt anymore.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Jeff Humble on Thursday, January 15, 2009 - 11:03 am:

Randy,
The loose crankshaft pulley is a problem, you need to fix it. There are many threads regarding how to do it so just search for the key word "pulley". There are expensive replacement pulleys on the market, and ways to tighten up an original pulley. I have had good results with a shim between the crankshaft and pulley and putting a small bend on the pulley pin to keep it tight too. The pin only goes in from one side and comes out the same side it went in, there is a cotter pin on one end of the pin that is very hard to reach, and you will have the best access by removing the radiater first.

I agree with the comment from Warren regarding the water pump, you should consider removing it. A lot of people mistake a correctly operating thermosyphin cooloing system as overheating due to the pissing out of coolant due to overfilling, and the bubbling/barfing sounds, but that does not mean it is overheating. Many threads regarding water pumps too.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Kenneth W DeLong on Thursday, January 15, 2009 - 12:21 pm:

Randy,All fan belts are not created equal! Sometime you can buy a new belt that was junk when it was made or laced! I think Gates made/makes the best!!! Bud.


Top of pagePrevious messageNext messageBottom of page Link to this message  By steamboat on Thursday, January 15, 2009 - 03:12 pm:

The bolts holding the water pump at the inlet are fairly sloppy. Try loosening them and shoving the pulley end up and down and retightening. Also moving the water pump pully closer to the block moves the belt to the rear. Moving it away from the block moves it forward.

Actually, I got one of the high priced crank pulleys with flanges, and now the belt stays on.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Randy Schultz-Rathbun, Brush Prairie, Wasington on Friday, January 16, 2009 - 12:28 am:

Since I had a slow night at work last night and anticipate another one tonight, I spent the day trying everyone's suggestions. I got the radiator off, and checked the crankshaft pulley. There was about .025 play between it and the crankshaft, so we shimmed it. It is now a press-fit and the pin is nice and tight as well. We then re-installed the fan and belt. When we put a new belt on, it tracked pretty well centered, so the problem seems temporarily solved.

I think I will eventually get rid of the water pump and replace the bushing in the fan pulley as well, but for now I can get the car back on the road. That is important right now, because my wife's aunt and uncle are visiting from Syracuse, and wanted a driving lesson. He's a spry 86, and we don't get to see them much, so it's now or maybe never to get them out in the car.

Thanks very much for the helpful tips. Now I will do a key word search on how to re-install the radiator. The nuts holding the shell down were a bear to get off!


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