Revell Visible V8 Engine Rebuild/Upgrade

[dr_gn]

This is another model I built a very long time ago (probably Christmas ‘78 or ‘79). It was quite complicated for an 8 year old, and I never finished it. I managed to assemble the crankshaft, pistons and cylinder heads, but the main issue was the camshaft was badly warped, and I couldn’t straighten it. Looking back, it never really had a chance of fitting, never mind working. Despite this, I was fascinated by the model, and I never threw it out. I re-discovered it the other day during a major clear out. I found another partially built one on EBay, which I got for £12.80 (unbuilt kits go for £70+). The newer versions go for much less, but aren’t motorised and don’t have the spark plug lights. This is what remains of mine:



The plan is to make one good one out of the two, using my original parts wherever I can. I’m also going to make some refinements to make it look better and run more smoothly.

[dr_gn]

Still waiting for the EBay one to arrive, so I stripped mine and washed all the lubricant off the moving parts. Luckily, after 40 years the glue has gone brittle, meaning that it was easy to disassemble without much damage. Some of the transparent parts are ok, but the majority are scrap, so I’m really hoping the new one is sound:



I’m going to need a very small dc geared motor - By some miracle the kit gearbox components survived, but assembling them into the casing and spinning by hand results in a terrible noise. I assumed from YouTube clips it was the mechanics of the engine itself, but it’s actually the drive gearbox.

I’m wondering if something from Lego might work.

[Turn7]

In for updates....

fully expecting a full ally block n pistons......

[dr_gn]

Turn7 said:

In for updates....

fully expecting a full ally block n pistons......

No, I’ll leave anything major for my steam engine build! I want to keep this one in the spirit of what it is - a fairly rough and ready working model rather than an exercise is precision. It would be nice to refine some parts though to make it operate more smoothly.

[CanAm]

dr_gn said:

.........I want to keep this one in the spirit of what it is - a fairly rough and ready working model rather than an exercise is precision..........

Hands up anyone who believes this!

[Turn7]

[dr_gn]

CanAm said:

dr_gn said:

.........I want to keep this one in the spirit of what it is - a fairly rough and ready working model rather than an exercise is precision..........

Hands up anyone who believes this!

No I want to keep it looking pretty much standard. I think I might fill and sand the joints in the red and black parts, and then spray them satin red and satin black. All the parts do look very plasticy.

I’ll replace the plastic rocker shafts with steel - easy.

Might replace the cam followers with machined Teflon, and make them a decent fit in their guides - easy.

I could also make Teflon inserts for the valve guides - easy depending on how thin the walls would need to be.

I thought about applying aluminium bare metal foil to the main bearing surfaces - easy.

Finally, replace the fragile distributor drive bevel gears with metal - could be easy, could be a disaster.

[tr7v8]

dr_gn said:

I’m going to need a very small dc geared motor - By some miracle the kit gearbox components survived, but assembling them into the casing and spinning by hand results in a terrible noise. I assumed from YouTube clips it was the mechanics of the engine itself, but it’s actually the drive gearbox.

I’m wondering if something from Lego might work.

Best bet would be either MFA or one of the model suppliers like component shop or Robobirds

[dr_gn]

tr7v8 said:

dr_gn said:

I’m going to need a very small dc geared motor - By some miracle the kit gearbox components survived, but assembling them into the casing and spinning by hand results in a terrible noise. I assumed from YouTube clips it was the mechanics of the engine itself, but it’s actually the drive gearbox.

I’m wondering if something from Lego might work.

Best bet would be either MFA or one of the model suppliers like component shop or Robobirds

Thanks, yes I’ll take a look. I might end up going to 12v and use a mains transformer.

[dr_gn]

EBay engine arrived:



It got a bit mashed in the post, but all the missing bits on mine are there, apart from one distributor rivet:





The camshaft is there - not warped, but the end with the gear was snapped where the previous owner tried to glue it after a breakage:



Looks like they got about as far as I did with mine, then had an issue with the camshaft and gave up (like me!). I don’t think it’s ever been run.

The original cam bevel is hopeless, but a Lego one might work:



The clear plastic is brittle, but I think I can make one good block out of the best bits from both kits:



Also nice to have the original instructions:



The original 8 bulbs work too:



Now to clean up the clear bits...

[dr_gn]

Cleaned up the best bits from both blocks and re-assembled. This time I used canopy glue because

a) It dries clear

And

b) If it all goes wrong I can dunk it in some warm water and it’ll revert to kit form with no further damage:

[dr_gn]

M2 fasteners arrived today from EBay:

[dr_gn]

Bit more progress on the block:

[dr_gn]

I decided to split the con-rod bearings using a razor saw:



As well as looking a bit more realistic, it means I can assemble the crankshaft into the block and get it running smoothly without the pistons.

The standard kit has you assembling the crankshaft webs and pins with the eight one-piece con-rods, and eight pistons, and then building the cylinder block parts around it (there isn’t enough clearance for any other way). It means aligning and glueing many different parts simultaneously, which isn’t easy.



The other advantage is that although the bearing hole is not circular anymore due to the saw cut, it actually makes it a better fit on the crank pins - as moulded, they are a very sloppy fit.

[dr_gn]

So after realising I couldn’t get to hold the nuts when the pistons are in place, I tried again. This time I tapped the upper part of the rod, and left the bearing shells with clearance holes. I 3D printed a simple jig to speed up the whole process:

[dr_gn]

anonymous said:

[redacted]

Yes, I built a few real engines in my time, and I did want to replicate the 'real' method. Unfortunately, I'd have to remove a significant amount of plastic to allow a standard nut to turn freely on the bottom of the bearing housing.

I could give it a go with a spare rod and see how it looks. I would definitely have to glue the bolts into the rod because there's not enough access on top to hold it easily.

[dr_gn]

So in the end I filed the bearing housings to within a whisker if their lives and Araldited the bolts in place. I also flatted and sprayed the crowns Grey to get rid of the prominent joint lines:

[dr_gn]

Machined some new cam followers out of PVC to get rid of the slop from the originals, and to stop them snapping over the cam and making a knocking noise. Also machined the first two aluminium pushrods. I’m going to put threaded adjusters in the rockers so that I can take any free-play out of the system and hopefully make everything smoother:

[Turbobird1988]

I ran into the same problem with the cam. My solution was to boil it in water until it was pliable enough to tweak back into shape. The result while not perfect seems like it will work.

[dr_gn]

I got bored with this one I'm afraid - there is a lot of noise from the cam/cam follower interaction due to slop between the followers and guides. The followers really need to be metal, and run in tubular guides. I was going to turn some up, and press them into the existing plastic mouldings, but I got into model engineering a steam engine, and that took up a lot of time. This should be no issue, but its a matter of time...