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Feb 11, 2009 22:43:18 GMT
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So I got bored and decided to make myself an adjustable cam gear. For years, I've heard over and over that the TT/Autotech/Drake/etc is pretty simple to make, and not worth the money to buy it. I set out to prove it to myself. I used a total of $5 worth of aluminum, and 4$ worth of hardware. Kinda labor intensive, but it only took me a day and a half, working in the evenings.           Then my dremel died, so I couldn't slot the upper holes  . I did everything with plain jane tools, nothing out of the ordinary. Drill press, 1" hole saw, sawzall, hand file, dremel, sharpie, hammer, and a punch. It took me a couple hours to cut and bevel the disk itself, but it's a perfect fit. I used 1/4" aluminum, and grade 12.9, M6x1.0 hardware. ...oh, if anyone else wants to try this, a CD is 1mm smaller than the inside diameter of the gear, and makes a great template  . *** I ASSUME NO RESPONSIBILITY IF ANYONE WANTS TO TRY IT THEMSELVES. IT'S COMPLETELY UNTESTED, AND ALTHOUGH IT SEEMS TO BE PROPERLY SET UP, I HAVE NO IDEA IF IT WILL REALLY WORK.*** |
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1982 VW Rabbit 4-door (apart)
1992 Passat Wagon Syncro (daily)
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Feb 11, 2009 23:38:13 GMT
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Excellent work! How are you gonna put the markings on to show the degrees? Or are you gonna do it with some kind of protractor and lock it there?
I really like this kind of homebrewed stuff - very cool!
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Well, I know that each tooth is 6*, so I'll start with a 0, 3, and 6 mark and bisect them to get 0, 1.5, 3, 4.5, and 6. I am not really shooting for 100% accuracy, since any adjustments I make will be either seat-of-the-pants based, or dyno tuned. I figure I'll just move it back and forth and see what happens, and leave it where I like it  . If it doesn't spin into pieces and leave me stranded of course ;D |
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1982 VW Rabbit 4-door (apart)
1992 Passat Wagon Syncro (daily)
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its looks llike it will be a hell of lot stronger than ones u buy. top work
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street
Posted a lot
6.2 ft/lbs of talk
Posts: 4,662
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Feb 12, 2009 12:33:10 GMT
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Great work! Always nice to see someone spending time rather than money, looks like you've done a fine job there  |
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Frankenhealey
Club Retro Rides Member
And I looked, and behold, a pale horse! And its rider's name was Death
Posts: 3,875
Club RR Member Number: 15
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Feb 12, 2009 13:03:45 GMT
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Excellent work! I know 'cos we make these at work for various people and the markup once they get to a cam or parts company is pretty stiff.   and yours will work just as good ;D ;D ;D |
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Tales of the Volcano Lair hereFrankenBug - Vulcan Power hereThe Frankenhealey here |
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Feb 12, 2009 16:19:11 GMT
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good work there.
don't want to sound negative, but the slotted holes will be pretty crucial to the whole balance of the thing, whats the plans?
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@ CRX_IN_SCOTLAND
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Feb 12, 2009 17:35:42 GMT
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The original wheels aren't balanced at all - they're made from pressed, powdered steel and are pretty crappy TBH. Hold one in your hand divorced from the cam and you'll see what I mean. The cam and fuel pump drive wheels on modern VAG TDIs often look similar as well  |
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Feb 12, 2009 18:30:53 GMT
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good work there. don't want to sound negative, but the slotted holes will be pretty crucial to the whole balance of the thing, whats the plans? It's constructive criticism, not negativity . I'm going to remove the screws around the outer ring, flip it over so I can scribe through the bolt hole onto the back of the disk, make a mark on each side of the existing hole, and dremel it out (or make small pilot holes). I'm concerned about the balance, but I've seen various types of commercial product from big companies that use offset bolt holes instead of a slide arrangment, and that puts a locking bolt way off centre, without a counterweight. Worst case scenario is that I need to find a replacement head, and my next design will be different . I'm going to take my version and strap it to the drill press and spin it around, just to see if there is any major wobble, since I don't have a lathe. This is the type with the offset bolt (sorry for the big pic):  I have to admit, that until I found this forum...I never would have thought of trying something like this. Everyone here is so 'hands on', it's a bad influence . |
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1982 VW Rabbit 4-door (apart)
1992 Passat Wagon Syncro (daily)
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Feb 12, 2009 18:35:29 GMT
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As long as it's concentric it'll be fine, which it should be if it's initially a good fit on the inside edge and around the centre. Personally I'd have made it on the mill on the rotary table just to make sure.
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Feb 12, 2009 18:46:18 GMT
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Oh and you don't need a scale on it, you time a cam in using the crank as your datum. With the cam in and chain on the wheel get it to TDC. Use a dti for this so you get it accurate. Put a protractor on the crank and turn it round to suit the cam timing angle at full lift (you should have this in the cam spec), then turn the cam so you see the no.1 valve fully open at the top of the lobe and lock it off there. I used this from www.machinerycleanery.com for my timing disc: photos.passado.com/p01/8E/63/92ed191889f04a7596f1cc955a1b5039_o.jpg |
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Feb 12, 2009 19:22:49 GMT
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As long as it's concentric it'll be fine, which it should be if it's initially a good fit on the inside edge and around the centre. Personally I'd have made it on the mill on the rotary table just to make sure. I wish I had a mill, it would have saved me about 8 hours of grinding/filing, lol. The disc itself is a very nice fit inside the gear, since I shaved it by hand bit by bit. |
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1982 VW Rabbit 4-door (apart)
1992 Passat Wagon Syncro (daily)
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Darn, version #2 in the works...messed up the slots. I might try a vernier style, like above, mainly for simplicity.
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1982 VW Rabbit 4-door (apart)
1992 Passat Wagon Syncro (daily)
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Have you got any divider calipers? It might make it a bit easier to mark it up well first. You can get Moore and Wright ones on eBay for peanuts.
The slots shouldn't matter as long as the inside and outside faces of that disc are a touch fit all the way round when it's assembled. I'd probably mark up the circle you're drilling on and make the slots by drilling a series of holes and opening them up with a needle file. Rather you than me though!
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Feb 13, 2009 11:44:20 GMT
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I don't, but I'm certainly going to pick up a set now. I am beginning to recognize some of my 'mistakes' now that I'm going over the process. Drilling bolt holes via eyeballing is #1, next time I'll scribe a circle and be sure to always drill on that line. This same line will make it easier to slot the outer holes, since the curve will be visible. Maybe I'll take a chunk of aluminum down to the machine shop and get them to cut the circle for me too, just to eliminate any doubts of it being ovaled.
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1982 VW Rabbit 4-door (apart)
1992 Passat Wagon Syncro (daily)
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Nathan
Club Retro Rides Member
Posts: 5,627
Club RR Member Number: 1
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Feb 13, 2009 17:32:40 GMT
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Am I the only one who has no idea how these work/adjusted. So someone please tell me as I have an adjustible vernier on the capri.
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Last Edit: Feb 13, 2009 17:33:06 GMT by Nathan
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Feb 13, 2009 18:40:27 GMT
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The middle bit can be turned around and locked off so the cam can be timed in more accurately. Apparently the tolerances on standard timing wheels coupled with the tolerances on the front of cams can leave your cam up to 5 degrees out. A vernier wheel lets you measure the timing on the cam and lock it off in the right place.
And if you're really keen you can dial in different angles and play with how it affects the power delivery.
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. I did everything with plain jane tools, nothing out of the ordinary. Drill press, 1" hole saw, sawzall, hand file, dremel, sharpie, hammer, and a punch. It took me a couple hours to cut and bevel the disk itself, but it's a perfect fit. I used 1/4" aluminum, and grade 12.9, M6x1.0 hardware.
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