Thread: An unusual Hercus!

Originally Posted by KBs PensNmore

Will you be making the pistons too

Yep. Here is a sample, gravity cast in an old cylinder bore:
IMG_2412.jpg

The core die:
IMG_2419.jpg


Eventually, these will be churned out by a centrifugal casting machine (which I started to document elsewhere).

The coolant pump:

IMG_2415.jpg IMG_2418.jpg

its cast iron tank:
IMG_2416.jpg


and some other random bits:
IMG_2417.jpg

Thanks for the updates Nigel.
What are the pistons for, besides an engine of course??
You must be expecting to go through a few to go to all this trouble!!!
Kryn

Originally Posted by KBs PensNmore

What are the pistons for, besides an engine of course??

Austin Sevens. The vintage engine guy isn't happy with the recent quality of J.P. pistons. (and the imported English ones aren't any better)



Instead of having to re-machine the expensive ones they would sell him, starting from scratch, with highly eutectic alloy, is the current plan.

Here is a cutaway of another gravity cast piston:
IMG_2426.jpg

IMG_2427.jpg

IMG_2422.jpg IMG_2423.jpg IMG_2425.jpg IMG_2424.jpg

IMG_2428.jpg IMG_2433.jpg IMG_2434.jpg


Struggling a bit, because we lost pre-stripdown photos. Need someone with access to the factory archives

Bed for the sliding parts now fitted:
IMG_2452.jpg


This is the old "General Electric" motor that drives the spindle and its offset(ing) cam:
IMG_2453.jpg
Note the slightly slanted rotor cores, kind of like a synchronous motor.


it hides behind the top left guard here:
HercusPistonFinisher.jpg

Originally Posted by nigelpearson

This is the old "General Electric" motor that drives the spindle and its offset(ing) cam:
IMG_2453.jpg
Note the slightly slanted rotor cores, kind of like a synchronous motor.

The reason that the rotor segments are made like that, is to reduce the cogging action and improve smooth rotation by engaging the next magnetic field slightly earlier than the whole segment.

IMG_2467.jpg IMG_2468.jpg

IMG_2469.jpg IMG_2470.jpg IMG_2471.jpg



Only thing left is the grinding wheel motor and belt, and wiring.
Note the inside of the Compton 2HP motor:
IMG_2472.jpg

Nice brazed bronze castings that form a fan to provide airflow through the "squirrel cage?"

Still need to work out a tensioner for the left (spindle rotating) motor,
so its guard isn't there yet, but assembled enough:
IMG_2502.jpg


for a quick grind test on an old piston:
IMG_2503.jpg



Still to do is some automation of the longitudinal feed. The vintage engine guy wants to attach a mill "power feed" unit, but the pinion on this bed/table is too direct – half a turn on the lever moves about 45mm – which would grind a spiral with your typical mill cranking rate.

Have to work out a reduction gearbox, and somewhere to mount it.

Why not get a three phase power feed and use a VFD?

Steve

Originally Posted by Reidy41

Why not get a three phase power feed and use a VFD?

Steve

I don't have any experience with them, but I'm not sure it would be slow enough. He is talking about very slow feed. Less than 2RPM.

Originally Posted by nigelpearson

Still to do is some automation of the longitudinal feed. The vintage engine guy wants to attach a mill "power feed" unit, but the pinion on this bed/table is too direct – half a turn on the lever moves about 45mm – which would grind a spiral with your typical mill cranking rate.
Have to work out a reduction gearbox, and somewhere to mount it.

Isn't a mill power feed unit variable speed, or is it still too fast at it's slowest rate?
Would it be possible to use a stepper motor etc to drive it, that way you would have infinite control over it?
What sort of ratio would you need, I think I've a couple of right angle drives about 60:1, if that helps?
Kryn

That has come up real nice .

Originally Posted by KBs PensNmore

Isn't a mill power feed unit variable speed, or is it still too fast at it's slowest rate?
Would it be possible to use a stepper motor etc to drive it, that way you would have infinite control over it?
What sort of ratio would you need, I think I've a couple of right angle drives about 60:1

They are variable speed, but like most AC & DC motors, power drops off a lot at lower voltages (or PWM duty cycle). He thinks still way too fast (the Hercus pinion is too direct).


A large stepper would work (or a small one geared down),
but a power feed has end stops, and a convenient direction handle.

He is thinking hundreds to 1. I suspect that would be too slow. We will have to experiment. RS has a few that might hold up to the load for a while:

https://au.rs-online.com/web/p/gearboxes/0424065

https://au.rs-online.com/web/p/gearboxes/0424027

this has machine the sort of feed rate he is after. A Repco connecting rod boring machine:

IMG_2504.jpg IMG_2505.jpg

There is a lead screw up the middle. A very fine lead screw. Maybe 50 or 60 TPI. It might take 45 seconds to bore through a 1/2" big end bearing.




This machine also has an odd/ingenious attachment for cutting a figure-8 groove in the bearing:
IMG_2506.jpg