Turning a "B" Section Vee Belt Groove

Added: 2026-05-31

[00:00:01][music] [music] [music] [music] >> Hey, welcome back to Engineer's Workshop. This is my first real video in a long time.

[00:00:30]So, I've been busy building a house, little cottage type house for my in-laws. And that's consumed basically most of the last year.

[00:00:41]Uh they're living with us currently, and we're working on getting them into their own little home that is on our property.

[00:00:48]But, since then uh a couple projects have stacked up here in the shop.

[00:00:52]And the one I want to work on today is um for my son's 1947 Jeep. And he wants to convert that to 12 V.

[00:01:03]So, he's got an alternator for it. And we need to make a a change to the V-belt shiv to accommodate uh it's a B section belt. The shiv is currently sized for like an A belt. So, there's enough meat in the width we can take the groove out to the correct dimensions for a B section belt. But, speaking of shivs, have a look at this.

[00:01:25]This [snorts] is a shiv.

[00:01:28]A little bit bigger than the one on the alternator.

[00:01:30]And this is a 10 V.

[00:01:34]I believe these are D size V grooves. These are inch and a quarter wide at the top. 1 2 3 4 5 6 7 8 9 10.

[00:01:44]And this bad boy weighs in at just under 1,500 lb. I don't know if you can see the crane scale up there.

[00:01:54]Yeah, there we go. Just under 1,500 lbs.

[00:01:59]And I put out a just a very brief short video on this asking myself, "What am I going to do with this?" And I said, "I don't know."

[00:02:06]Well, I do know what I'm going to do with it.

[00:02:09]Uh this is ultimately going to be set up in the small barn as a uh an energy storage device to balance out the uh the crankshaft pulses of my Ruston Hornsby single cylinder horizontal diesel.

[00:02:26]Uh and then this will ultimately drive a generator for the for the farm.

[00:02:31]So, this is going to be set up with hydrostatic bearings uh supporting the weight of the flywheel.

[00:02:40]Jack shaft and belting to spin this up to about 250 to 300 RPM and then taking a belt off of this to drive the generator at 1,800 RPM.

[00:02:54]And the mass and the inertia of this flywheel virtually eliminate all of the pulsations from the four-stroke single cylinder horizontal diesel, which uh only operates at 370 RPM.

[00:03:07]And so, its pulsations are pretty strong.

[00:03:10]And uh you want to take that out uh of the um the output so that you have a smoother you know, AC without any ripple. So, got this into the building and have to do significant amount of cleanup on it and then fit a shaft to it. I think it's about a 4 and 1/2 in. It's either a 4 or 4 and 1/2 in shaft. I can't recall.

[00:03:30]But uh really neat little piece. So, let's go over and I'll show you what I'm going to do with this smaller V-belt shiv for the Jeep.

[00:03:38]So, here's the son's Jeep project. He's got a 12-V regulator to go in place of the 6-V regulator.

[00:03:45]And he's got the GM style alternator over there.

[00:03:49]Uh I got to find where he put the pulley. But let's talk about the um V-belt groove that matches a B-size belt, which is what's on the Jeep. Okay, you got your basic V groove.

[00:04:02]And for an A belt, that width is 494 to 504.

[00:04:08]And for a B, it's 637 to 650.

[00:04:16]And the chart actually has >> [clears throat] >> an inflection point.

[00:04:20]Basically, it says for pulleys over 7 in, you're at 650.

[00:04:24]And for pulleys 4.6 to 7 in, you're at 637.

[00:04:29]And the other interesting thing is that this angle, so we'll just continue this on down here.

[00:04:36]This is 38° for pulleys over 7 in, and it's for pulleys over, or excuse me, under 7 in.

[00:04:49]Now, why is that?

[00:04:51]Well, when you take a V-belt and you look at its cross-section, let's draw one in here.

[00:05:01]Here's your V-belt.

[00:05:03]There's tension members.

[00:05:06]And those are usually near the top of the B-belt V-belt. There's cords in there.

[00:05:11]When you wrap a V-belt from flat down, these tension members essentially don't change length. But, because you're pulling this thing into a tighter and tighter radius, this bottom part of the V-belt actually squashes out. So, the V-belt starts out maybe looking like this.

[00:05:32]But, then as you pull it into a around a pulley, this bottom part bulges out, and then it effectively makes the angle shallower as this bottom goes out like this.

[00:05:46]Now, obviously, it doesn't magically just change at 7 in.

[00:05:51]The tighter and tighter you you uh wrap this, you know, progressively more uh with the increases along the along the bottom. So, I actually worked up a formula that determines, you know, based on the uh radius of the wrap, what should this angle be within this range?

[00:06:11]And that formula works out to be the angle of the shiv is equal to 38°.

[00:06:21]minus 25 over diametrical pitch of your shiv.

[00:06:29]And for the small shiv we're working with, which is actually, you know, below the minimum recommendation for a V uh a B-size belt.

[00:06:38]So, he's going to have to run a belt with a cog uh on the on the ID to let it flex a little tighter.

[00:06:46]Let's work this up here.

[00:06:48]So, for a 3-in shiv, that angle actually gets tightened down to about a 30° angle.

[00:06:55]So, that's what we're going to machine the groove to.

[00:06:59]637 30° angle, 15° on either side of vertical, and center it up on the existing pulley.

[00:07:09]There's a little projecting hub on the backside. It's not real tall, maybe an 8 in or so, but it gives me enough grip.

[00:07:16]And uh with that to the bore, there's a runout of about 3,000. I would say that's good enough.

[00:07:26]So, um the V-belt groove to the bore is going to have, you know, 3,000 runout. That's best I can do without swapping out, setting up the four-jaw chuck. Ron and Sid don't worry about it, so I'm not going to worry about it.

[00:07:43]So, we're starting off with a groove width Let's see if we can measure this accurately. 389 390 and we have 733.

[00:07:58]So, we've got to take 0.670 - 0.390. We got to go 140,000 in both directions. So, from just touching this face and then 140,000 uh progressive cuts probably 10,000 apiece.

[00:08:20]And we got to set up the compound at a 15° angle.

[00:08:25]So, use the combination square to sight this in parallel to the cross slide and set that at a 3° angle.

[00:08:35]And I had to buy this real narrow 15° cutter.

[00:08:40]That's going to be able to reach in here and cut down it to that face of that pulley.

[00:08:52]First couple of passes the groove is barely wide enough for me to get to the bottom.

[00:08:58]I keep track of my carriage movements.

[00:09:00]I've got an indicator attached to the ways and I can dial in about 10,000 cuts at a time.

[00:09:13]And I'll just have to write them down cuz I got to go 140, so that'd be 14 passes on each side of this groove in order to take it up to the correct width. So, I guess I'll just make a chart and count them up. Let's give this a try.

[00:09:28]And I will take a couple of light passes here until I know I'm touching and then I'll zero the indicator.

[00:09:45]>> We'll call that first contact.

[00:09:55]Let me get something to write down my progress.

[00:10:49]So that's been 50,000.

[00:10:57]That's 60 and you can definitely see the one flange getting thinner.

[00:11:06]Kind of works out good on the indicator because one full uh circle of travel is 30.

[00:11:14]So every 30 I just reset the uh I just wind it in back to zero.

[00:11:23]So now this is 70.

[00:11:59]>> That's a 100,000. I'm going to switch it over to the other side and take a 100 off that one to try to keep things centered and see where we're at on the groove width.

[00:12:11]That's my cleanup pass on this side.

[00:12:41]That's 60. I'm going to have to increase the clearance on my insert. I'm scuffing on the side there.

[00:13:29]>> Watch the water.

[00:13:32]>> Right at 600,000th now.

[00:13:36]And we got to go to 637.

[00:13:40]So, need about two more passes per side.

[00:14:02]I think that is pretty much right where it needs to be.

[00:14:06]See if I can get a little very little bit of uh easing edge on that uh pulley without hitting my chuck jaws.

[00:14:14]That's going to be a challenge.

[00:14:17]Now, there's a finished item.

[00:14:19]Let's you fish the belt out of there and let's see how it lays in there.

[00:14:26]Now, that's coming out.

[00:14:34]Pretty good.

[00:14:40]What do you think?

[00:14:42]>> Looks snug.

[00:14:46]I think I'm going to need a new belt.

[00:14:48]>> Yeah, I'd say that one's uh ready to be replaced.

[00:14:52]Probably older than we are.

[00:15:00]Is it press fit? What about all these spacers?

[00:15:02]>> Uh it is just friction from the nut.

[00:15:05]>> Ooh, boy.

[00:15:08]>> I had to grind off the nose of that shaft, too, cuz it wanted to clip my fan.

[00:15:36]>> Suddenly it's a lot closer to the new coolant fan.

[00:15:41]>> Oh, yeah?

[00:15:54]Happy?

[00:15:56]>> [snorts] >> Yeah, now I hope it doesn't scrub the face of that fan.

[00:16:00]>> Well, as long as you align it with the other pulley, it shouldn't >> [sighs] >> I mean the the belt drops into the groove a little bit, so it's got a 16th clearance. Clearance is clearance.

[00:16:11]>> Lot of lot of tight clearances with this.

[00:16:13]>> Yeah.

[00:16:14]>> [sighs] >> I'll send you the bill.

[00:16:19]So, the idea is you just put a 12-V battery in and run everything off 12-V.

[00:16:26]6-V starter just spins harder.

[00:16:29]Spark is hotter. And you said you got to play with the fuel sender.

[00:16:35]>> coil.

[00:16:36]And you need a resistor or something to put across the fuel sender to get that to work on 12-V.

[00:16:43]>> Okay.

[00:16:47]>> And I specifically got an externally regulated alternator for this with an analog regulator.

[00:16:56]Cuz I've got this uh this little thing from the '70s, looks like.

[00:17:03]It's a 110-V power supply you can put inside the Jeep somewhere.

[00:17:11]It'll uh it'll give you DC power that'll run tools like grinders and drills.

[00:17:21]And you can even do little stick welds with it.

[00:17:27]But you can't plug anything that actually needs 60 hertz AC into it.

[00:17:32]>> Got you.

[00:17:34]It It generates 110 volts DC.

[00:17:38]>> Yes. Well, I think you're supposed to rev it up until it hits 80 volts on the gauge.

[00:17:47]>> Okay.

[00:17:47]>> So it's like uh good enough to run your tools, I guess.

[00:17:53]>> Got you.

[00:17:54]>> As far as I know, all it does is just kind of cuts out the regulator, so as you spin it up faster, it makes more voltage.

[00:18:01]>> And is that a 12-volt starter contactor?

[00:18:07]>> I don't remember.

[00:18:08]>> Looks new.

[00:18:10]>> Hopefully. It We started it once with it.

[00:18:14]>> On 12 volts?

[00:18:15]>> Yeah.

[00:18:17]>> Good deal. Looking forward to seeing it run.

[00:18:22]>> And then next up is some wiring.

[00:18:24]>> Yep.

[00:18:28]Okay.

[00:18:30]Engineers Workshop out. I hope you enjoyed that. It was kind of a small project, but it needed to get done.

[00:18:36]Rainy day, so we can't really do work on the on the cottage today.

[00:18:40]So we decided to spend a little bit of time in the shop knocking out a couple of small projects. So that's it for for today for Engineers Workshop. Hope to be doing more videos for you on a somewhat more regular basis, but they're not going to get really regular until we get this cottage all built and get my in-laws moved into it. So that's it for today. Um hope you enjoyed. Stay subscribed. Subscribe if you haven't already, and look for new content in the in the future. And till always as I say from Engineers Workshop stay safe.

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