Author Topic: Holt 75 from Germany  (Read 3636 times)

Offline michelko

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Holt 75 from Germany
« on: December 22, 2020, 03:04:45 PM »
Hi guys,
just started an new project as the title says, it is an Holt 75. It is  kind of an chimera. While i am using some castings it is alos based on plans and some is my own design.

The initial plan was building the engine from George Brittnels plan from bar stock. I purchased his set of plans but redid them in metric using a 3d CAD Program.
Some time ago i came in contact with a  fellow HMEM forum member called foketry. He was so kind to give his left over casting parts and some cores for the heads and Zylinder jackets.

So i tried to use the castings but keep the design metric.
Now i am nearly ready with the crankcase. I still have to line bore the main bearings of the crank and the middle bearing of the cam.
For this i will use a Straight bar of drill rod and mount a HSS bit in it. I just bored the Bearings at the end plates so i can use them as  guide.
Here are some pics an a short video.

Milling out the lower part of the crank case

Offline michelko

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Re: Holt 75 from Germany
« Reply #1 on: December 22, 2020, 03:06:18 PM »
boring tje cylinder holes and taping some threads

Offline michelko

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Re: Holt 75 from Germany
« Reply #2 on: December 22, 2020, 03:06:55 PM »
milling the end plates/bearing holders

Offline michelko

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Re: Holt 75 from Germany
« Reply #3 on: December 22, 2020, 03:09:30 PM »
and here is my setup for boring the bearing holders and the hole for the camshaft
for that i used my beloved wohlhaupter, a realy awesome tool

Offline michelko

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Re: Holt 75 from Germany
« Reply #4 on: December 22, 2020, 03:11:15 PM »
and here is the short video from the boring job



Offline Roger B

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Re: Holt 75 from Germany
« Reply #5 on: December 22, 2020, 05:57:42 PM »
You're off to a good start there  :ThumbsUp:  :ThumbsUp: One to follow along with  :wine1:
Best regards

Roger

Offline fumopuc

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Re: Holt 75 from Germany
« Reply #6 on: December 23, 2020, 06:23:20 AM »
Hi Michael, I will following along too.
The bar stock plans of George Britnell and parts of the engine are available as a CAD model on my computer already.
So may be some time I will follow your route, because in my eyes also it is a remarkable engine.
« Last Edit: December 23, 2020, 08:24:51 AM by fumopuc »
Kind Regards
Achim

Offline michelko

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Re: Holt 75 from Germany
« Reply #7 on: December 27, 2020, 02:55:54 PM »
Hi guys,
worked a little on the crankcase/sump. Unfortunately i did┤t notice some irregularities on the castings and so i made a hole into the sump wall.

I think i will patch this with a smal piece aluminium jb welded in place.
I have a ac tig machine but i am a little scared because of my low to nothing experience in welding aluminium.
So i think the jb weld woill e the way.

Offline michelko

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Re: Holt 75 from Germany
« Reply #8 on: January 03, 2021, 03:41:17 PM »
Hi Guys,
here is some update on the Holt.
I am ready with the sump. Because of the massive casting i decided to make mill out the material also from the underside.
This recomended an cover to close the sump again. I also drilled a hole from the side to connect the chambers. Here i also made a cover plate.
Next step was the main bairing halves. I left aprox 1 mm in the hole for lineboring.

Offline michelko

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Re: Holt 75 from Germany
« Reply #9 on: January 03, 2021, 03:43:16 PM »
and some more pics

Offline michelko

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Re: Holt 75 from Germany
« Reply #10 on: January 05, 2021, 11:21:22 AM »
Hi Guys,
the lineboring is done. I am realy happy with the result and how the boring bar worked.
I made some brass plugs to fit in the formerly bored holes at the end s of the case. these plugs had an 10H7 boring to guiede the 10mm drillrod. In the drillrod i made a 3mm hole and 90 degree to that a m3 thhread for an set screw to hold the cutter.
The cutter is ground from an broken mill schaft.
The surface of the bored holes came out realy nice , no chatter or something.

Video crankshaft

Video camshaft

The boring bar and the cases where setup into the lathe for boring.


Offline propforward

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Re: Holt 75 from Germany
« Reply #11 on: January 05, 2021, 01:43:41 PM »
Very impressive work michelko!   :ThumbsUp:  :praise2:
Stuart

Forging ahead regardless.

Offline Admiral_dk

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Re: Holt 75 from Germany
« Reply #12 on: January 05, 2021, 08:39:19 PM »
Hello Michel

I have just watched the video - I knew how it's done, but this is the first time I really could see how well and cleanly the cutter removed the material - thank you  :ThumbsUp:

I guess that this is a homemade tool, so did you use any tricks to set the depth of the cut ?  And how accurate could you set it for the diameter you aimed for ?

Per

Offline Foketry

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Re: Holt 75 from Germany
« Reply #13 on: January 05, 2021, 11:30:14 PM »
Hi Guys,
the lineboring is done. I am realy happy with the result and how the boring bar worked.
I made some brass plugs to fit in the formerly bored holes at the end s of the case. these plugs had an 10H7 boring to guiede the 10mm drillrod. In the drillrod i made a 3mm hole and 90 degree to that a m3 thhread for an set screw to hold the cutter.
The cutter is ground from an broken mill schaft.
The surface of the bored holes came out realy nice , no chatter or something.

Video crankshaft



Video camshaft

The boring bar and the cases where setup into the lathe for boring.

well done Michael  :ThumbsUp:


Offline Art K

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Re: Holt 75 from Germany
« Reply #14 on: January 06, 2021, 03:58:12 AM »
Michelko,
I am very impressed with your work on the Holt. I have heard of line boring but have never seen it in action. I have seen George run his at the NAMES show in Michigan. Look forward to seeing yours proceed.
Art
"The beautiful thing about learning is that no one can take it away from you" B.B. King