V-Belt Retainer

Here’s a little piece on a simple V-Belt retainer that’s easy to make and does a good job.


Use 3/16" 6061 T6 aluminum.


Several ways you can do this:

Cut it out with a hole saw.
Drill the 1/4" pilot hole out to 5/16" or 3/8".
Make up a mandrel - headless bolt in the size required, saw off the hex portion and grind or file smooth, couple of flat washers and a couple of regular nuts will do it.
Bolt the aluminum disc to the mandrel, chuck it in a drill press, finish the edge with a file.
Be sure and break the sharp right angle so you don’t end up with a spinning pizza cutter.
Drill to size required to match the alternator stud.

Another way is to center punch the aluminum and use a divider or pencil compass to lay out a circle.
Use a band or handsaw to trim close to the finish size.
Grind the aluminum to the finish size with a belt sander.
Drill the center punched center with a mandrel size drill.
Finish the edge in the drill press as above.
Then drill to match the alternator stud.

Got a lathe?
Or access to one?
You’ll know what to do, but the way I knock these out is to either hole saw them or do the cut close to the line bit with a band saw and then cut it to round on the lathe.

A nice brushed finish can be brought up with a 3M medium grit abrasive pad.
The maroon one.
You can go to fine grit - which is gray I think - but the medium does a nice job.
That’s usually where I quit, but you can go past that and buff to a shiny finish if you wish.

The alternator shown in the photo is a Pinto.
Far as I know, all the 65 amp Ford alternators are the same.
Nice part about using the Pinto alternator is the stud sticks out far enough that the flat disc bolts on with no problems.

The flat flange V-Belt retainer is an old trick originally used to combat belt tossing when you build an engine that can spin up some serious revs and you’re still running the small alternator pulley.
Serious being six grand and up in my book, but once you get into the rev ranges the SBC can hit, V-Belt tossing takes on a whole new look.

There are larger factory pulleys available for some alternators as well as oversized steel and billet alternator pulleys for most of today’s popular hot rod engines, but you don’t want to run them on a gennie street driven hot rod.
In most cases they don’t spin the alternator fast enough at slow speeds - traffic etc. - and won’t keep the battery up like they should.
Things are tough enough running a built engine on the street.
Adding a low battery to the mix is a major pain in the backside.

Some alternators have the alternator retainer stud/nut combo sitting down in the pulley.
A couple ways out here.
One is gonna require use of a lathe.
As well as a chunk of billet.
Machine up the piece so the flange clears the outer pulley edge by .010 - .015 or so.
You want the stud to pull the retainer down to the pulley hub, but you don’t want to bend or pull the pulley flange down with the retainer when you bolt it on.

The other way is to make a separate center piece that’s held on by the alternator stud/nut.
Make it thick enough so the separate flat 3/16" flange clears the outer edge of the pulley.
Then you’re gonna have to do a bit of drilling and tapping so the center piece and flange can be bolted together.
If - big if - you can get the center piece cut square you’re in business.
Getting the 3-6 allen bolts used to bolt the retainer flange to the center piece and have it all well centered isn’t too difficult without a lathe, but it is easier with one.
If you don’t get the center piece cut square you’re gonna have to chuck it up in a lathe and cut it square.
If you don’t have a square center piece, the flange will wobble and how cool will that be?

These simple V-Belt retainers do a good job and in my experience they stop the tossed V-Belt problem.
Almost always the V-Belt comes off of the alternator pulley due to the sharp turn and longer run of the belt.

Only other caveat is to make the V-Belt retainer/flange size big enough to do the job and small enough to roll the V-Belt over it when installing the V-Belt with the alternator adjusting mechanism bottomed out all the way.
If backing the alternator all the way off doesn’t do the trick, you can get the V-Belt on the alternator first and then install it on the crank or water pump or whatever last.

As stated above, an easy project that answers a need and to my way of thinking adds a little bit of good looks to the engine compartment.

 

I enjoy all your little tricks, a well thought out bracket can make all the difference.

Will you share your trick for spacing the holes around the perimeter, inquiring minds want to know.
TZ

 

I am going to have to try that.
Thanks, C9

 

thanks for the tip,

last time I threw a belt I had to put it back on the hot motor with no tools!

and I was wondering where to use some billit

Paul

 

[ QUOTE ]
Will you share your trick for spacing the holes around the perimeter, inquiring minds want to know.
TZ


[/ QUOTE ]


I cheat.
I have a dividing head and a rotary table.

There are other ways to do it as well.
It depends on how accurate you want to be.

If you have access to a lathe, you can use the bull gear to divide with.
Most times these are drilled with 40 holes and the lathe has a stop.
Get the lathe spinning and score a very light line on the workpiece.
With the lathe stopped - and the amount of holes divisible by 40 you want to use decided upon - run the carriage up, lock it and with the compound set longitudinally parallel to the lathe ways, run a cutting bit in with the compound until it contacts the workpiece and then use the cross-slide to scribe a light line across the circular line.
Back off on the compound and cross-slide.
Repeat, setting the lathe at each new hole location prior to scribing.
Remove, centerpunch and drill.

You can also use a drill press to scribe your circular line, but you'll have to drill a mandrel hole first.
Do that after you've laid out your 90 degree lines as described below.
Once the workpiece is spinning on the mandrel, lower the workpiece until it lightly contacts a cutting bit, sharp edge, whatever that's clamped in the drill press vise.

Emanating from the center punch hole - do this in the layout stage and prior to drilling if you can - lay out four lines 90 degrees apart and intersecting the circular line.
Centerpunch these.
Set your dividers up to match the hole distances and verify they are the same distance apart.
(A pencil compass will work, but a divider is considerably more accurate. Dividers aren't too expensive either. Under $20. for a quality tool most times.)
Decide how many holes you want.
These will have to be divisible by 4 to make life easy.
Use an engraved steel ruler to set the divider at the distance needed for the succeeding holes.
Use one of the 90 degree centerpunched marks to set one leg of the divider in.
As an example, say you want a total of eight holes.
Scribe a line across the circular line with the divider.
Go to an adjacent 90 degree hole and double check with dividers to see if the distance is the same.
If so, centerpunch and go from there.

Hole amounts other than eight should be easy to figure out by extrapolation of the data above.
Just double check from both sides with the divider.

An automatic centerpunch is of great aid in a project like this, but a small manual centerpunch used carefully works just about as well.

Starratt has a centerpunch assortment, about six sizes I think and they're not too expensive.
I have one and the small punches are used for accurate work.

Semantics aside, the small ones are called prick punches and the idea is to just prick a small hole.
(And I know I left an opening there wide enough to drive a truck through, but cool it anyway....)

Once the small centerpunch mark is decided to be accurate, it is enlarged with the bigger centerpunch so the drill can be accurately located.

A small hint on drilling accurate holes in aluminum ... after you hit the aluminum with the larger centerpunch, use a file or sanding belt to knock the raised area back to flat.
Then use a small drill for the first pilot hole
If you leave the raised edges on the aluminum the drill tends to fall off and accuracy is compromised.

Everyone should have a pair of dividers.
You would be amazed at the highly accurate things you can turn out at home once you learn a few tricks with them.