Marks Holt 75

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The plunge cutting left a rough surface but a few hours with a Dremel fitted with a pad sander and some fine files had it ready for buffing.

Every thing assembled well and aligns with the camshaft. So I'm thinking legs next as I repair my turntable. Lot of the upcoming parts will need a turntable.

Thanks for watching, Mark T

Gearcase 3.jpg

Gearcase 2.jpg


Gearcase 1.jpg
 
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Very cool stuff can´t wait to start my build.
Keep on posting

Michael
 
Beautiful!
 
Where can information be found about these Holt plans? Google comes up with nothing, searching this site shows some builds to no info on cost or how to purchase them.
 
vandal968 said:
Where can information be found about these Holt plans? Google comes up with nothing, searching this site shows some builds to no info on cost or how to purchase them.
Click to expand...
Hi,
You should contact gbritnell he made the nice imperial plans to build the engine from scratch without castings. At the moment i am converting this into metric with inventor. Sometimes there will be a set of metric plans.
Michael
 
So tell me when you cut the outside of the gear box you said you just plunged cut, are you just using the outline you have drawn on it as your guide. If so I am very impressed as I have a similar job to tackle and was wondering how to approach it.
 
bobden72 said:
So tell me when you cut the outside of the gear box you said you just plunged cut, are you just using the outline you have drawn on it as your guide. If so I am very impressed as I have a similar job to tackle and was wondering how to approach it.
Click to expand...

Yes but I used the turntable to rotate the part for most of the cuts. Around the screw holes I just eyeballed it. I kept the zero point on the z axis just below the surface so I could see where exactly the cutter was. The cuts were very light so I used the drill feed for lowering and raising the spendel. I'm not very good at explaining things, I hope this helps.

And thanks for the comments guys.

Mark T
 
Just want to verify this. You aren't using CNC in the machining, strictly manual turning and milling right? I have the Smithy Granite 1040 my wife got for me last month ( big upgrade from the 18 year old HF 9x20 and HF mini mill ) and really want to make engines come 2020. Not wanting to go CNC and prefer doing everything manually for more pride in my projects.
 
Rickus said:
Just want to verify this. You aren't using CNC in the machining, strictly manual turning and milling right? I have the Smithy Granite 1040 my wife got for me last month ( big upgrade from the 18 year old HF 9x20 and HF mini mill ) and really want to make engines come 2020. Not wanting to go CNC and prefer doing everything manually for more pride in my projects.
Click to expand...

That's correct, no CNC, just a lot of manual work. It actually went fairly fast.

Mark T
 
Outstanding! Now that I am wrapping up my big projects, ie: finished my ultralight airplane, and about to finish home conversion of our motorcycles to trikes, I will slow down and begin following your example in earnest. Just can't find manual machining much any longer now that CNC has come down in price and people prefer that. Have you other projects I/we can look at?
 
Rickus said:
Outstanding! Now that I am wrapping up my big projects, ie: finished my ultralight airplane, and about to finish home conversion of our motorcycles to trikes, I will slow down and begin following your example in earnest. Just can't find manual machining much any longer now that CNC has come down in price and people prefer that. Have you other projects I/we can look at?
Click to expand...

Yes, see this link https://www.homemodelenginemachinist.com/threads/gatling-gun.31594/ and go to post 6

Mark T
 
bobden72 said:
Thanks for your reply Mark and yes understand completely, how long approximately to carve it out. I will give it a go on my new project.
Click to expand...

It took about 7 hours start to finish to make the gear box. About 2 hours of that was sanding and filing. Before I started I probably spent 20 hours thinking about how to go about it. Slow witted but nimble fingers.

Mark T
 
This is a minor update. Legs. Small parts but a big deal. The engine can now sit on its own legs and is stable to work on. The plans called for the feet to point outward from the block. I opted to face them inward so that I can use their mounting bolts to mount a box for the ignition system on one side and a name card on the other. I also picked up some lose ends like cutting the groves for the crankshaft o-rings and drilled and taped the hole for the pan's drain plug.

The black chunk of metal the engine is sitting on is a slab of cast iron for making the two flywheels and the cylinder heads.

Will be starting the small gearbox soon.
Holt legs.jpg

Mark T
 
Since you are using "O" rings, could you educate me on determining the groove size to fit them or "O" ring size to fit grooves?
 
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