3.0 QV or 3.2 Cam Pulley Lock Tool

I'm working on a timing belt/tensioner change on my 1984 Euro 308 GTS QV, it's been 6 years already since they were last done. At that time I did the full 30K major, and since I was taking the cams completely out to change seals and valve shims I didn't need to make any sort of locking tool for the cam pulleys at that time.

This time it's just the belts and tensioners, so I'll need to lock the cam pulleys from moving. I've seen the blocks of wood drilled for a bolt, but as I've been getting to learn a 3D printer for a while, I decided I should do some basic CAD work and make up a 3D printed equivalent of the scrap wood cam pulley tool!

TL;DR version - here's the file on Thingiverse: https://www.thingiverse.com/thing:4649593. You can download and print it yourself if you have a 3D printer. I used Taulman Bridge Nylon, but any rigid material should work. The only additional item is a 1/4"x3" bolt, nut, and a few washers. I know it's not metric, but it's the only bolt long enough that I had around the workshop. A single 11mm wrench fits just fine and is all that's needed to operate this tool! I wanted to share this with everyone here - I hope some of you will give this a try and find it useful.

NOTE - I'm pretty sure the cam pulley size and spacing on the 3.2 is the same as on the 3.0 QV engine and this tool should work on the 3.2; I know it's not the same on the 2V engines, so this particular iteration won't work on those.

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I'm just getting back in to drafting and design (old school mechanical engineering degree from 40 years ago), so I used the kiddie CAD program, TinkerCAD (www.tinkercad.com ) - really easy to pick up, and surprisingly capable with basic shapes.

(Side story) For practice, I designed my own Iron Ring (a Canadian Engineering tradition for nearly 100 years) in TinkerCAD, an Iron Ring is supposed to look like this:
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Every Canadian Engineer wears one on their dominant hand's pinky finger - you can read a bit about it on the Wikipedia page for Iron Ring: https://en.wikipedia.org/wiki/Iron_Ring

The design needed this assembly of objects to create the required facets on the ring:
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Merged together, and it comes out like this:
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I did print the ring in a few different materials, but I won't bother showing those, as the resolution of a home 3D printer isn't great for small objects that should have smooth finishes!

Practice CAD out of the way, the Cam Pulley lock tool started like this:
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Merge those objects to create the wedge with the appropriate curved sides, add a hole down the middle, replicate, then add a hex space at the top of one wedge, gives this print design:
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Print two sets so you can do both banks at the same time:
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I had to add a few extra washers under the bottom nut, because the unthreaded length of the 3" bolt was a bit too long to tighten the lock wedges. It works!
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Placing the cam pulley lock tool in place - no wrench needed on the top side, just a single 11mm wrench needed on the bottom. They don't need to be tightened too hard to hold the cams stationary.

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I hope that's of some use to you guys who have a 3D printer at home.

Cheers,
Gordon

 

Hi Wayne, I remember looking at a puck for this 7 years ago, and thinking that it wouldn't fit on a QV - I think the cam spacing is quite a big larger on the 2V engines. On the QV there isn't, or is just barely, room to squeeze a half puck under the top belt span between the pulleys.

Thanks Dave! From my rough notes when measuring, the gap between the closest points of the cam pulleys on the QV is ~10mm. If someone measured the gap between the 2V cam pulleys (closest points, ie tops of the teeth), then I could ungroup the objects, widen the centre block by the added distance between the pulleys, then re-group the objects to make a 2V version.

Cheers,
Gordon

 

Thanks for your comments, Verell, and I admit that even though I've gone through your offerings catalogue multiple times I've missed that item listing - otherwise I would have bought it from you!

Cheers,
Gordon

 

Verell, yes, it's a Lulzbot TAZ 6 FDM printer, using 2.85mm filament.

I appreciate all the feedback, I've revised the design an re-printed it in polypropylene, which has enough 'give' in this shape to grip the cam pulleys nicely. I changed the sizes a bit, and embedded the text 'UPPER' and 'LOWER' in them to keep track. I had to give up the hex insert for the bolt head, the material isn't rigid enough to hold the bolt head from turning.

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Compared to the nylon version:
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Now in place on the cam pulleys:
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I would have finished my timing belt and tensioner pulley change a couple of days ago if I'd just grabbed a couple of blocks of scrap wood and my jigsaw instead of messing around with these!

Gordon