The new engine

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Posts: 108
Joined: 19 Jun 2019, 04:09

The new engine

Post by bluejets » 13 Jul 2020, 00:57

Started on this particular design some 4 years ago but as is sometimes the case, things get put on hold.
Photos below show the timber patterns both for the external sand castings and for the cores.

Friend of mine, George Punter, has been doing aluminium casting for many years and his expertice comes in handy against my limited (I might add successful) attempts. George is last years Duke of Edinburgh Award winner in the UK in model engineering.

Engine will be V8 water cooled somewhere around the 50cc mark, spark ignition petrol fuel, four stroke, centre top cam with pushrods and rockers to overhead valves, sump with oil pump. At this stage, hall effect sensor for either cdi or kettering ignition and possibly some temperature monitor.

Most of the design will follow the already tried and proven 25cc four cylinder I built a few years back. As with this, the V8 will eventaully get to live and work in a scale model boat, type yet to be decided on,however it would be a shame to conceal the engine down in the hull so this will be a consideration.

Patterns yet to receive a final coat of paint after a trip to see George and a couple of minor modifications.
Lower left is the sump cover which is a pattern for both the sump and the core of the same.
Top left and centre are the core boxes for the internal waterways and the crankcase inner core. 2 of each of these are used within the casting.
Finally the patterns for the crankcase itself.
Eventually will get around to the rocker covers.

George loaned me a set of aluminium patterns for the piston cores which makes for far less machining as it is then used as it comes from the casting process. Outer pattern for the piston is timber as shown in the last photo.
The four cylinder I built used 20 x 20mm pistons turned from solid whereas with George's piston molds, I can select anywhere between the same and around 22mm diameter, hence the previous "around 50cc".
Also in the last photo is the outer pattern and core for the lower crankcase.

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Joined: 16 Feb 2018, 14:11
Location: Warwickshire

Re: The new engine

Post by Martin » 13 Jul 2020, 13:19

Impressive stuff! Are you planning to use a cross-plane crank, like the American V8s, or a flat-plane crank like a Ferrari?

I prefer the sound from the cross-plane ones, but I suppose at model size, and RPM, it might not be possible to tell the difference. Probably depends a lot on whatever sort of exhaust headers (if any) you intend to fit.

Posts: 108
Joined: 19 Jun 2019, 04:09

Re: The new engine

Post by bluejets » 14 Jul 2020, 03:39

Yes actually there is a difference in the sound.
I really like the Challenger V8 flathead sound and it has a lot to do with the crank and also apparently the exhaust system
Plan is to use a flat crank, same as I used in the four cylinder (as below pic of a Challenger crank) there are 2 conrods per big end, one has to keep in mind the timing of the cylinders.

Short video of a Challenger running below.
Cheers Jorgo

And this is my little 25cc screamer.......
Challenger V8Crank.jpg

Posts: 108
Joined: 19 Jun 2019, 04:09

Re: The new engine

Post by bluejets » 05 Aug 2020, 10:44

Had a call from George to drop my patterns up to his place to make sure it "all fits his sand boxes".
Thought that a bit strange as he has quite a range.

Anyhow, busy with day job and getting his temperature and tacho gauges finalised so dropped them off on my way to work.

Get home that afternoon, email waiting, check your mail box.
Never had a parcel like that before, still warm too.
Photo below of casting up and done.

Guess the favours work both ways.

Small defect in the centre valley but neither here nor there as a quick repair with some metal epoxy should seal it up.
Didn't break through anywhere so all good.
2Kg of alloy there....machining will remove a large portion but as it is for a boat, no real drama.

Now, where did I leave his Oleds for the guages....????...... :D :D

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