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[Nick W]

A fancy drawing board. The thing you have to keep going back to when stuff doesn't work.

Sometimes, it shows problems as proved by these sectional views










As it stands, the only way to create the block's water jacket is with a cored casting. Considering the amount of metal that would have to removed for the other features from a large, expensive, solid block, that would be a sensible way to proceed. Making both parts of each main bearing cap bolt in would make machining them and the block easier.


As modelled, there's no good way to get the curved ports in the head without another casting. Changing them to angled ports and throats would remove this need, although continuing the water jacket to surround the combustion chambers would put it back. The head needs to 5mm longer at each end to prevent the headbolt counterbore breaking out. This would make the nose on the cam boxes redundant and make the water jacket surround the end cylinder liner if carried into the block.


There are no crank or rod bearings, although there is space for them. Nor is there any oiling system; I'd probably use an external pump for the main and cam bearings, driven off the water pump belt. Splash oiling for the conrods and pistons. The water pump is currently empty, and needs some serious thought to make it work.


I modelled the sump using surfaces for some practice and to make it look like a stamped sheetmetal part, but if actually building this thing I would hollow it out of a block or add it to the casting list.


It's easy to say that this would be an electronically managed engine, but scale injectors are an entirely different matter. Ignition systems are available. I've a friend who built a 180cc OHV V8, and getting the carburation even working, let alone well, was the hardest part of the build.


I suspect it will need domed pistons, instead of the flat top ones shown, to get enough compression to actually work.


It has a 25mm bore on 35mm centres, and a 30mm stroke

[TheBoy]

I keep toying with those cheap nasty small CNC machines you can get, in order to convert some of my designs into something a little stronger than 3d printer plastic.

But I know I'll be disappointed with it's capabilities, so keep talking myself out of it.

But the flip side is that during the ongoing climate where I don't want to go to busy pubs and eateries, I'd probably only spend the money on RC Planes/Drones/Cars/Trucks instead...


//TB wanders off pondering again...

[Sir Tigger KC]

I keep toying with those cheap nasty small CNC machines you can get, in order to convert some of my designs into something a little stronger than 3d printer plastic.

But I know I'll be disappointed with it's capabilities, so keep talking myself out of it.

But the flip side is that during the ongoing climate where I don't want to go to busy pubs and eateries, I'd probably only spend the money on RC Planes/Drones/Cars/Trucks instead...


//TB wanders off pondering again...

I'm sure you could find something suitable on Ebay?   

[Nick W]

I keep toying with those cheap nasty small CNC machines you can get, in order to convert some of my designs into something a little stronger than 3d printer plastic.

But I know I'll be disappointed with it's capabilities, so keep talking myself out of it.

Think of them as very low power/rigidity routers. So, if most of your jobs would be small profiles machined from thin, soft, sheet materials(including aluminium) then they're a good start. But as you say the limitations are probably greater than the majority of the work you'd finish.


I have an equivalent of THIS and the engine block shown here is too big for it. Milling on the lathe is similarly restrictive. I must get around to fitting the CNC parts I have for my my mill.


 I mentioned the V8 a friend built:





Although he did the finish machining on a bigger benchtop mill, it was roughed out on the CNC machine he uses at work, to reduce the amount of time and potential mistakes. That's quite important when the billet cost over £150. And if you want to get the job done in one lifetime

[Migv6 le Frog Fan]

That is a thing of beauty. 

[Nick W]

That is a thing of beauty. 

It looks better in the 'display stand'

[Migv6 le Frog Fan]

That looks superb. 

[Nick W]

That looks superb. 

You should see what happens in between projects, when he gets bored

[Nick W]

This week, 'can you stop the wheel falling off my RC car?'


This is what's left of the rear axle:





That broken bit is a hex, and the screw should hold the wheel on. There should be one on the other end too, but it's missing.



Maxwell is six and the car was £30 from a toyshop, so spares aren't available.


The axle is 9mm diameter, hollow and I don't like the screws.


So some scrap 10mm bar and a bit of machining produced two new ends complete with M4 retaining screws:





Epoxied in place:





That ought to sort it

[Raeturbo]

Good job👍

[ronnyd]

That's good to see, a well used workmate. Axle repair ain't bad either. 
Also, what was it like drilling out the axle to fit the stubs that you turned?

[Nick W]

That's good to see, a well used workmate. Axle repair ain't bad either. 

It's one of the £15 cheapies that I've had for about twenty years. I'll have to replace the tops again soon - I have another couple of pieces of decking...

[TheBoy]

This week, 'can you stop the wheel falling off my RC car?'


This is what's left of the rear axle:





That broken bit is a hex, and the screw should hold the wheel on. There should be one on the other end too, but it's missing.



Maxwell is six and the car was £30 from a toyshop, so spares aren't available.


The axle is 9mm diameter, hollow and I don't like the screws.


So some scrap 10mm bar and a bit of machining produced two new ends complete with M4 retaining screws:





Epoxied in place:





That ought to sort it

I don't think I could do that on any of my 6S RC cars, they'd rip it to shreds

[Nick W]

I don't think I could do that on any of my 6S RC cars, they'd rip it to shreds

As they cost more than £30, I suspect that your axles don't have integral gears on 2mm thick tubes, and drive stubs that are much thinner than that. They also have bigger motors than the basic DC thing that's been used in small toys for decades.


I think you'd be surprised at what a properly used Loctite will do; it's replaced a lot of light press-fits.
 
And you're not six, although you break things as if you are...

[TheBoy]

I think you'd be surprised at what a properly used Loctite will do; it's replaced a lot of light press-fits.

Loctite's superglue only sticks rubber. And skin.

 

you're not six, although you break things as if you are...

Eternal youth, my friend, that's what I have. I am, according to Mrs TB, still 5