Model Engine Maker

Engines => From Kits/Castings => Topic started by: michelko on December 22, 2020, 03:04:45 PM

Title: Holt 75 from Germany
Post by: michelko 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
Title: Re: Holt 75 from Germany
Post by: michelko on December 22, 2020, 03:06:18 PM
boring tje cylinder holes and taping some threads
Title: Re: Holt 75 from Germany
Post by: michelko on December 22, 2020, 03:06:55 PM
milling the end plates/bearing holders
Title: Re: Holt 75 from Germany
Post by: michelko 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
Title: Re: Holt 75 from Germany
Post by: michelko on December 22, 2020, 03:11:15 PM
and here is the short video from the boring job


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Title: Re: Holt 75 from Germany
Post by: Roger B on December 22, 2020, 05:57:42 PM
You're off to a good start there  :ThumbsUp:  :ThumbsUp: One to follow along with  :wine1:
Title: Re: Holt 75 from Germany
Post by: fumopuc 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.
Title: Re: Holt 75 from Germany
Post by: michelko on December 27, 2020, 02:55:54 PM
Hi guys,
worked a little on the crankcase/sump. Unfortunately i didīt 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.
Title: Re: Holt 75 from Germany
Post by: michelko 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.
Title: Re: Holt 75 from Germany
Post by: michelko on January 03, 2021, 03:43:16 PM
and some more pics
Title: Re: Holt 75 from Germany
Post by: michelko 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
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Video camshaft
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The boring bar and the cases where setup into the lathe for boring.

Title: Re: Holt 75 from Germany
Post by: propforward on January 05, 2021, 01:43:41 PM
Very impressive work michelko!   :ThumbsUp:  :praise2:
Title: Re: Holt 75 from Germany
Post by: Admiral_dk 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
Title: Re: Holt 75 from Germany
Post by: Foketry 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
-cLmn0B9Tj0


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

well done Michael  :ThumbsUp:

Title: Re: Holt 75 from Germany
Post by: Art K 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
Title: Re: Holt 75 from Germany
Post by: michelko on January 10, 2021, 11:43:46 AM
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
Hi Per,
the bar is an ground drillrod. i just meassured the hight of the cutter bit above the rod. So for example to bore a 14mm hole i set the cutter tip to 2mm above the rod surface.
I still have to measure the achived diameter but in the end it is not critical because of the bronce inserts. i will fabricate them to meet the bored hole.

Regards Michael
Title: Re: Holt 75 from Germany
Post by: michelko on January 17, 2021, 12:28:13 PM
Hi Guys,
worked a little on the cams. I made them from Drillrod and they will be hardened also the followers.
I mainly used the profile like in George Brittnells plans but instead of a tangent between base and nose i used a radius.
So the  follower will not do abrupt movement.
The bar was setup in my rotary table (not used as this just as holder) and milled with the cnc function of my bf20.
The cams came out nice and just needed a little sanding/polishing.
The cams has a little noth of 2 mm, these is used to index the cams on the shaft. The cams will be fitted with loctite to the shaft, the pins will also be an additional security against loosing /rotating of the cams.
The shaft will be an anharded drillrod of 6mm like i similar used in the bugatti.
Title: Re: Holt 75 from Germany
Post by: michelko on January 17, 2021, 12:31:29 PM
here is a short vido from milling

https://www.youtube.com/watch?v=dfswU4RaAdI
Title: Re: Holt 75 from Germany
Post by: michelko on January 17, 2021, 12:37:48 PM
Here is a drawing with the meassures of the cams
Title: Re: Holt 75 from Germany
Post by: Vixen on January 17, 2021, 02:38:25 PM
Hello Michel

I believe we all have a problem with videos no longer showing.

Nice work on the Holt engine

Mike :ThumbsUp:

Title: Re: Holt 75 from Germany
Post by: michelko on February 01, 2021, 12:10:20 PM
Hi Guys,
here is a little update on the cams and the shaft.
With the indexing table i drilled the holes into the shaft . The little pins are indexing the cams and also give a little safety against loosing. The cams are loctited io the shaft after hardening.
The cams are made from drillrod, heated to 800 °C and quenched in oil. Then annealed at 290°c for 1,5 hours.
Also turned the outer bearing and did a testfit with the shaft.
Just have to make the split middle bearing.

Title: Re: Holt 75 from Germany
Post by: michelko on March 16, 2021, 03:34:22 PM
Hi,
here is a little update on the holt.
I made the cylider jakets. They are turned from some free turning steel. For this i used my temporarely to cnc converted lathe.
I also fabricated the big gear for the cam shaft.
Unfortunately i had some problems to make the hole to spec. i aimed for 6 H7 but something went wrong while reaming.
At the end i bored it out on the lathe to fit the camshaft.

Regards Michael
Title: Re: Holt 75 from Germany
Post by: gbritnell on March 16, 2021, 03:50:45 PM
The engine is coming along great! Thanks for the videos on your progress. That was the main reason I split the crankcase so it would be easier to machine the main bearings.
gbritnell
Title: Re: Holt 75 from Germany
Post by: michelko on January 10, 2022, 10:25:21 AM
Hi guys,
long time no post.
Yesterday i found some time to work on the rockers.
Made them from freeturning steel.


Regards Michael
Title: Re: Holt 75 from Germany
Post by: gbritnell on January 10, 2022, 01:09:31 PM
I'm glad to see you are getting back to your Holt build.
Title: Re: Holt 75 from Germany
Post by: michelko on January 10, 2022, 03:24:32 PM
Hi George,
yes i am too. But in the meantime i had another toy to play with that took my whole focus.

Greetings
Michael
Title: Re: Holt 75 from Germany
Post by: michelko on May 30, 2022, 08:30:39 AM
Hi guys at least i found some time and inspiration to work on the holt again.
I started on the crankshaft. I decided to build it up from pieces.
The main shaft is from 12mm drill rod an the rod shaft s are from 10mm drillrod.
The webs where milled and drilled/reamed from c45 Steel.
All pieces will be glued together with loctite and additional pinned.

I made some good experiences on my bugatti build with the loctited crank so i am hoping this will also work for the holt.

Michael
Title: Re: Holt 75 from Germany
Post by: michelko on May 30, 2022, 08:33:56 AM
Here is ashort Video from milling the webs with my BF20 CNC

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Title: Re: Holt 75 from Germany
Post by: Admiral_dk on May 30, 2022, 11:36:02 AM
Distractions - yeah there can be many of those  ;)  great to see you back here  :cheers:

Per
Title: Re: Holt 75 from Germany
Post by: michelko on June 14, 2022, 02:36:07 PM
Here is my setup for gluing the crank.
Later i will additionaly pin it. Just to be sure the connection  wonīt come loose.
Title: Re: Holt 75 from Germany
Post by: michelko on July 07, 2022, 06:10:17 AM
Crank is finished.
i additionaly pinned the webs to the shafts with 3mm drilrod bits. they are also glued with loctite and slightly hammered.
Then milled out the parts between the webs.



The crank looks nice. I am happy with the result.

Title: Re: Holt 75 from Germany
Post by: Roger B on July 07, 2022, 08:45:29 AM
Nicely done  :praise2:  Multi cylinder engine crankshafts are not easy  :ThumbsUp:
Title: Re: Holt 75 from Germany
Post by: Admiral_dk on July 07, 2022, 12:40:31 PM
Great looking Crank  :ThumbsUp:

Are you going to put Split Bronze Bearing-Shells in the Block ?

Per
Title: Re: Holt 75 from Germany
Post by: gbritnell on July 07, 2022, 01:11:36 PM
The engine is coming along great!