Marks Holt 75

[Robert Ritchie]

Now that was cool, nice work , I'm awaiting your next detailed post very interesting.

 

[cooksservices]

This is a very nice thread, very informative thank you for sharing. I will definitely be using some of your techniques.

 

[John Antliff]

Can I ask that you describe the breaking with more detail e.g. how was the ring presented to the sharp edge of the chisel?

 

[dnalot]

Can I ask that you describe the breaking with more detail e.g. how was the ring presented to the sharp edge of the chisel?

In the photo showing the rings after snapping you see the rings sitting on the top of the vice's jaws. The chisel is mounted in the chuck used for drilling. To snap the ring I placed the ring over the dimple you see under the chisel and then using the quill feeding handle I brought the chisel down on the ring with light pressure until it snapped. The dimple is optional, the ring will snap without it but will take a little more pressure.

Mark

 

[John Antliff]

Thanks Mark, I wondered if you held the ring in the vice and brought the chisel down onto it which would seem to me risky. The dimple would localise the stress and be a much more safe way of doing it.

 

[kvom]

I assume you used a ball endmill for the rounding on the big end of the rods.

 

[gbritnell]

Hi Mark,
That is the same process that I have been using for years to make piston rings. I have tried other but always go back to the Trimble method. Great documentation!
gbritnell

 

[dnalot]

I assume you used a ball endmill for the rounding on the big end of the rods

Yes, I used a ball end-mill on the big end.

Mark

 

[dnalot]

Thanks for the comments, and the likes.

Mark T

 

[dnalot]

Some simple parts here but very necessary. The pistons are made off aluminum and were turned as a group. After turning they were drilled for the small end of the connecting rod and a small flat was cut where the hole went through the piston.

After parting off the pistons were faced top and bottom. From there they went to the mill to be hollowed out.

The wrist pins are made from drill rod. I used a brass rivet to provide a soft end to the pins.

And then one by one I assembled the con rods with pistons attached to the crankshaft (No rings) and installed the cylinder. And then the crankshaft was rotated to check for binding and clearance. All was good.

At this point I will go back and give each part of the engine a final fitting and detail before assembling the parts with gaskets and sealants. This needs to be done before I can make and fit the rocker arms and push rods.

Mark T

 

[kuhncw]

I've never thought of making pistons that way. Interesting.

Great build thread.

Regards,
Chuck

 

[awake]

Nicely done! I like the ganged approach.

What are you using to hold the rivets in the wrist pin?

 

[dnalot]

What are you using to hold the rivets in the wrist pin?

680 locktite

 

[kuhncw]

Mark, I noticed how you are using the flats on the pinbore sides of the piston, along with matching pieces of metal to align the piston for milling the undercrown. I'll try to remember that trick. Thanks.

Chuck

 

[Robert Ritchie]

Some simple parts here but very necessary. The pistons are made off aluminum and were turned as a group. After turning they were drilled for the small end of the connecting rod and a small flat was cut where the hole went through the piston.

After parting off the pistons were faced top and bottom. From there they went to the mill to be hollowed out.

The wrist pins are made from drill rod. I used a brass rivet to provide a soft end to the pins.

And then one by one I assembled the con rods with pistons attached to the crankshaft (No rings) and installed the cylinder. And then the crankshaft was rotated to check for binding and clearance. All was good.

At this point I will go back and give each part of the engine a final fitting and detail before assembling the parts with gaskets and sealants. This needs to be done before I can make and fit the rocker arms and push rods.

Mark T

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Excellent work Dnalot, great detailed posting, can't wait to see her run!

 

[SPOTTER]

Great job, I ask you, why do you have to do the piston rings heat treatment?
thanks

 

[dnalot]

The rings are machined to match the size of the cylinders bore. They are then split and expanded over a mandrel. The heat treatment causes the ring to take a set at the expanded shape. Once done the rings will be larger than the bore and will be springy. When installed in the bore the rings will press against the sides of the cylinder's walls making a seal.

Mark T

 

[dnalot]

Time to assemble what we have made, starting with the camshaft. The three center bearings are slit type with a bit of copper wire holding the halves in place. Once in position a screw locks the bearings in place. The end bearings are a very light press fit and are tapped in place with a soft face mallet.

Before installing the crankshaft in the case the rods were lapped with a 400 grit compound until the rods turned smoothly on the crankshaft.

Now the risky step, installing the rings to the pistons. I stretched the bottom most ring over the well oiled piston from the bottom. I then used a cylinder to push the ring up the piston to the bottom ring groove. The top two rings were then stretched over the piston from the top one at a time. Happy to report no rings were damaged.

The pistons were then mounted to the rods. And then the pistons were installed into the cylinders. I had chamferd the bottom of the cylinder's skirt and the rings were easily compressed allowing the pistons to slide into the well oiled cylinders.

And then one by one the cylinder with piston and rod were assembled to the crankcase. And then one by one the heads were installed. I used a “Portrait Cutter” to make the gaskets. If your not using one of these your really missing out.

The joining of the case halves and installation of the crankshaft end bearings completed the main assembly. To seal the case halves I use “Honda bond 4”. Honda uses it to seal close fitting parts on their outboard motors. Brush it on as thin as you can, it is a latex like material when cured. As long as you burp any air out of the tube after use it will last a very long time.

I then installed the gear boxes and made a skid out of some Hickory wood. The wood was finished with a “wipe-on Polly”

Everything went together nicely and after giving the crank a spin with a drill motor I have compression on all cylinders. Number 3 cylinder may be a bit lower than the rest but not by much. I will need to wait until the valves are moving to give a proper compression check.

I live in Washington State, one of the first places in the US to see the Corona bug flare up. We have been in lock-down for over a month now. So my next step on this project depends on what materials I have on hand. I would like to do the rockers and push rods next but may need to move on and do the flywheels.

Thank you all for watching.

Mark T

 

[kuhncw]

Excellent work, Mark!

I really enjoy your thread.

Regards,
Chuck

 

[johnmcc69]

Wow! That looks GREAT!

John