# Building a V12 crankshaft



## ZAPJACK

Hello there,
I present to you my last work. It's the crankshaft ot the Rolls-Royce V12 Merlin at scale 1/4.
In the followed weeks, I will post the building process with needed pictures
LeZap


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## SilverSanJuan

That's all I can say...

Todd


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## Philipintexas

WOW!  Beautiful work. I don't even like to make more than one of an item. My hat's off to craftsmen like you who can do this kind of work.


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## dsquire

ZapJack

This looks like it is going to be a very interesting thread. I am sure that there are many that will be following this thread. I look forward to the next instalment.

Cheers 

Don


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## ZAPJACK

Manufacturing of a complex crankshaft​



First of all I wish to thank all the members of usinages.com and Blooo.fr who gave me advices and opinions in order to succeed in this matter.

I have neither history or work experience in manufacturing and I do not know anybody around me in this art. The methodology and the terminology used can thus surprise sometimes the professionals, thank you for not being irritated against me. However I manufacture by pure passion since 20 years.



The present document may inspire some builders for other works.



The followed process is based on my machines-park and can, of course, be modified with other more performance machines.

This crankshaft is the first step of the construction of the engine Rolls-RoyceMerlin V12 at scale 1/4. Probably the most difficult part to do. www.quarterscalemerlin.com

Datasource: 6 crankpins and 7 journals. Stroke:38.1 mm. Length 266.7mm. 3x 120°

Assembling with two connecting rods per crankpins. Fork assembling.

Selected materials: alloy steel type 34 Cr Ni Mo 6V (GER, BEL) 42 CD 4 T (FRA)

SAE4140 (USA)

It is structural steel to Chromium Molybdenum according to DIN 17200/1013 treated delivered. It allows the manufacturing of torsion bars strongly requested,axes, gears&#8230; 



Available tools :




Schaublin milling machine type     13 of 1964, DRO digitalization Mitutoyo
Sinus tilting table, directional     milling head, directional fast head with sensitive touch
Versatile dividing head & dead     center
Myford lathe Super7,     accessories and collets
Micro spray lubrication and Crouzet     sequencer
Cutting and milling equipments     with exchangeable plates
Metrology : Tesa, Mahr, Mitutoyo, etc &#8230;


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## Herbiev

Hi Le zap. Great looking project. Can you tell us a bit about the Crouzet sequencer. How you use it etc


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## ZAPJACK

Here's a picture of the micro spray lucrication. you're only need air pressure and use engine oil or equivalent
LeZap 

View attachment LUBROSTAR FR.pdf


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## old-and-broken

BEAUTIFUL ENGINE
this example built by [SIZE=+1]*Gunnar Sorensen*, of Denmark,[/SIZE]


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## ZAPJACK

Caution
Cutting a crankshaft from bar stock is a complex and dangerous work. Keep your machines clean, keep out chips or all other objects that may interfere during the various phases of manufacturing. 
Myford Super7 lathe has been used over its possibilities in dimensions and power.
During the manufacturing, it is important to check the amplitude of the movement by turning the machine manually. Do not hesitate to measure several times the same quotation. 
Keep attention of parallaxes errors during the reading with  calliper. Unsettle the part regularly andre-check after cleaning. Don&#8217;t forget to deburr, because smudges are sources of errors. Think of your safety by using glasses, emergency button, etc. &#8230;
For an easier construction, it&#8217;s necessary to foreseen special equipments such as : 
Jig bearing, grinding machine, steady, special tools.


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## ZAPJACK

First of all, distinguish high level precision quotations with those of acceptable errors tolerances.
Precision quotations:Cylinders centers distances, 4 virtual parallel axles, angular wedging between these 4 axes (3x120 °)
Secondary quotations: stroke,crankpin and journal diameter. If they can vary however they must have the same quotations, design and thicknesses of crank&#8217;s flanges. The secondary quotations can vary of +/-0.1mm and will not influence the good running of the engine.
Important remarks:
Still workin absolute measure, i.e. during a measure never refers to the quotation previously machined. In practice, manufacture the central bearing and its two crank&#8217;s flanges by working on the hundredth of mm. Then on this quotation basis (absolute reference table) add the quotations on the plan and postpone this sum on both side of the crankshaft.
If you workwith "relative" quotations postpone and add the errors so small arethem.
In this case of crankshaft, 0.05mm of error multiplied by 25 quotations = 1.25mm afterall!


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## MuellerNick

Bonjour LeZap!

That's certainly a masterpiece!
I'd like to know a bit more about it.

So you used 42CrNiMo6V, means it is in the QT state. Did you have problems with distortion while machining? You certainly first rough cut it. Did you temper it after roughing?

Did you turn it the classical way between centers? With center bores for each crank pin?

Do you intend to harden (nitrate) the race ways or leave them as they are?

Do you have pictures of your machining setups? You know, everyone drools for them!
Doing that work on a Myford looks like a lot of time you had to spend.


Chapeau!
Nick


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## ZAPJACK

Good Day Nick,
I have six pages of comments and more of less 80 pictures to post. But English is not my mother tongue, and I'm busy with the translation.
I will do it because I never find any information on the net about the building of a complex crankshaft.
LeZap


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## ZAPJACK

Think of markings:
The markings must be made in a continuous way and after every work. It is very important to avoid stupid errors when machines make noise and when it is very easy to lose concentration. Marker, Methylene blue, strips, milling, etc. &#8230;
Put a touch of white colour on any finished and validated size. (Picture 3, 26, 33, 92)


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## MuellerNick

> and more of less 80 pictures to post.



Ah OK, so I'll just watch and see. 


Nick


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## ZAPJACK

Think of calibrations:
The various processes of calibration must be made with the biggest accuracy. Mainly during changing position of the part or changing tool, etc. &#8230;
The use of  DRO gives more opportunities to zero setting the axles (X, Y, Z)
Quotations must always be "absolute" to avoid transfer or additional errors.
By every modification of the part, the machine and the tool have to be set up to zero. Zerosetting. (Picture 67, 68, 84,102, 103, 104, 120, 132)


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## ZAPJACK

Think of the cleaning:
Clean totally machines, parts and tools in every modification. Chips are also a big source of error and loss of concentration. Moreover a rolling-up of chips is a real potential danger.
(Picture 8 & 72)
Think of the procedures:
It is up to you to establish your own working procedures. These depend on the level of technicality of your machines and own skill, on cutting tools at your disposal as well as on instruments of Metrology. These procedures must be reflected then written. And of course follow these.
LeZap


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## ZAPJACK

STARTING THE PROJECT 



Picture 1 & 2: The starting bar haves 65x270mm and 7Kg. Reduction to 63.5mm and faces straightening. The bar has to have the same quotation throughout. Required precision: the hundredth of mm. The quotation in itself is unimportant. But if it is conical, you will never have a valid reference. This will influence the drawing afterward. Before the manufacturing,drill the centre with steadies or, in my case, in the air.


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## ZAPJACK

Picture 3: Start from the marble with the marking gauge as zero value, than add the quotations. These markings are is for deburing, During manufacturing stay "inside" quotations.
Picture 4: Milling a small flat on both sides of the block, in order to have a reliable reference during the drilling of the centres.To mill on the other side, do not unsettle the part.


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## Propforward

This thread is absolutely fascinating. That crankshaft is a work of wonder.


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## ZAPJACK

Picture 6, 7 & 8: Start at 80 rpm with a cutting tool of 2mm wide. The work is made in "staircase" i.e. by making several slots of 4mm deep on the required width. This is the first step, than doit again but 4mm deep, etc. &#8230; This is a long and hard work with a lot of tool claims.


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## ZAPJACK

Picture 11 & 12: Here is the first steps, the part have now 4.5kg weights and we already have 2.5 kg of chips.
Picture 13: Drilling the centers with centers drill. The four big one&#8217;s are corresponding to the axles of journal and crankpins. The small one&#8217;s are the future binding of the reductor gear. To make it easier, it is possible to program the DRO and have the right drilling postion following X &Y. As soon as the first face is finished, it is necessary to turn the part and to do the 4 centres once again. Take care at the right position of the milled flat it is very important!!!


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## ZAPJACK

Picture 14 : To increase the precision and the rigidity of the assembly, I totally have to unsettle the table of the milling machine.The part is thus directly fixed on the bench. The part has to be perfectly ofset square and the plate (Ph4)turned and perfectly parallel to the bench. Check with a rail of 30 cm atleast.
Picture 17: Fastening must be strong and hard.


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## rccubed

I hate to show my ignorance but what kind of machine is that?
Also I would like to say that this is some of the best education some of us Garage guys will ever get! Thank you for posting and explaining it! And it goes without saying, this is some awesome work!
LW


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## canadianhorsepower

ZAPJACK said:


> Picture 14 : To increase the precision and the rigidity of the assembly, I totally have to unsettle the table of the milling machine.The part is thus directly fixed on the bench. The part has to be perfectly ofset square and the plate (Ph4)turned and perfectly parallel to the bench. Check with a rail of 30 cm atleast.
> Picture 17: Fastening must be strong and hard.


 
Salut Zap tres belle ouvrage facinent a reguarde. Je reste de vant l'ecran et attand pour des photosth_wavth_confused0052

Luc


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## ZAPJACK

rccubed said:


> what kind of machine is that?


It's a SHAUBLIN 13 type milling machine. Swiss made. 
LeZap


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## ZAPJACK

Pictures 26, 29, 30 and 32: Now, on the milling machine, it is necessary to debur crankpins by milling it. Mill with a 3 sizes alternated of10x100mm plate-mill. 58 r.p.m. and 17 mm/min advance. The target is to obtain more or less six squared crankpins!!! 
Very visible on (Picture 32)
Picture 33: Marking of crankpins coupled by cylinders to avoid stupid error.


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## ZAPJACK

Picture 35 and 36:  Now, place the crankshaft between centers on the versatile dividing head
The centres used are of course those of the crankpins.
The milling machine must be fitted with milling head and 10mm end-mill. Now it is necessary to make round the square crankpins. Then move laterally the mill in order to adapt to the required dimension, we are still in deburing phase. Combine the mill rotation and the spindle manual rotation of the versatile dividing head until you get 0.5mm of the definitive quotation.
Note 1: The versatile collets holder willlet go back up the end-mill inside the holder which will falsify all yourmeasures. To avoid this phenomenon, use tool holder with single diameter.
Note 2: This method of milling (using atthe same time the end mill and manually the rotation of the versatile dividinghead) gives a shape of keg to crankpins. This phenomenon decreases when youmove the mill from the centre up to 5 mm. but keep in mind this.


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## Omnimill

Amazing work. :bow:


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## ZAPJACK

Pictures 37: This is the end of the deburing. See on picture that pins in the shape of keg as well as the first pin deburred in"square".
Picture 38: mounting between centers on lathe. The centre used is the one of the trunnions 3-4. To give the good thickness to the crank's flange, keep attention to manufacture still in absolute measure. Now trunnions can be machined at size +0.2mm. Keep attention, there is approximately 40mm offset.Working condition 200r.p.m.. You can, either work with tools from the left to the right, or re-turn the crankshaft in alternation. Weight 2925gr.


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## ZAPJACK

Picture 57: Now it&#8217;s time to grind journal and crankpins. If you do not have any grinding machine, you can manufacture one and adapt it on the lathe. This was a former circular saw
fixed  upside down under a table. I only had to modify the spindle and to adapt the wheel clamping flanges to the grinder. 3000rpm for the grinder and 200 rpm for the lathe. Both have to turn opposite. The grinder must be straightening with a diamond and must be perfectly perpendicularto the lathe&#8217;s spindle.
Remove step by step max:0.05 mm until you get the final quotation.
Think to protect your favourite lathe from abrasive dust.
Picture 66 & 60: Other view and finishing.


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## larry1

12 cyls,, and I feel lucky as all get to a 1 cyl to work right.  A beatiful piece of art.     larry


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## ZAPJACK

Picture 70 & 75: Now trunnions and crankpins must be drilled from one end to the other. This is a very delicate work. I choose to machine with the milling machine because the Myford is too small and not adapted forthis kind of job. To have more precision the milling table has been disassembled so that the crankshaft has directly been fixed on the milling bed.Check the symmetry of the angle of the top side of the drills (118°). The finished quotation must be X-0.1 mm. Finish after with a machine-reamer.


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## ZAPJACK

Pictures 79, 75 & 74: Now it&#8217;s time to machine the counterbores on both side of trunnions and crankpins (26 in total). On picture 79 you see the tool in action and on picture 65, you can see the result (testing plate). For this&#8220;blind&#8221; work, it is necessary to machine a tool as show on picture 64. The bar has exactly the internal diameter of the boring and the cutting tool must be positioned to have the good diameter on the counterbore. The "good &#8220;diameter of the bar must only be respected about 3mm before and 3mm after the cutting tool, this to guarantee an excellent guide and to avoid  vibrations of the tool. The rest of the bar is a little bit thinned to avoid a possible tightening. Lubricate a lot during these various operations. This tool allows making a counterbore forward and behind, however it is necessary to unsettle the plate in every change of flanges of the crankshaft. Note: these counterbores will later help to place corks for oil flow. At this step there is"only" 2500gr of material left.


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## ZAPJACK

Pictures 82, 83 & 138: *The crankshaft is now weakened*. It is absolutely necessary to build a versatile steady for any operations on the lathe or on the milling machine (fixed and moving steadies) by working between centres on the versatile dividing head. Try not to force during working "between centres",a light tightening is enough. 
In any case, this bearing must support the crankshaft without ever forcing either in vertical, or in side. This is to avoid distortion of measures.
Picture 86: At this moment, it is necessary to build small corks like a false centre, this to be able to work between centres while machining crank&#8217;s flanges. Obviously at this steps the real centres are definitively lost. But the precision of the external finishing of crankshaft&#8217;s flanges does not require a high level of precision.


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## ZAPJACK

_Reduction and shaping of thecrank&#8217;s flanges_
There is nothing complex in this work. Indeed, the precision is not very important.However by analyzing the more in-depth the problem it appears:

4 different standards,
A lot of material must be     machined
The crankshaft is very weakened     as far as its structure is concerned.
Combined work on the lathe and     on the mill,
need to build a jig bearing to     maintain the crankshaft,
Work complicated for the     extremities because of the nearness of spindle,     chuck, Vernier etc&#8230;

Picture 87: At first, reduce on the lathe all it is possible to reduce until quotation +0.1mm.    Use of tool at 200 r.p.m. Work as close possible to the jigs
Check your "freedom of movement" before starting to run
Pictures 107 & 106: Each crank&#8217;s flange has an important chamfer about 10 mm and under an angle of 11°. 200 r.p.m. and a maximum of 0.5 mm.


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## Peter57

Amazing work, Le Zap ! :bow:
Peter.


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## ZAPJACK

Pictures 89, 91 :
Turning between centers on the universal indexing head. The milling machine is fitted with its vertical milling head,with a sole carbide tip face mill.
Diameter : 12 mm. Speed : 1300rpm. Pulsed jet lubrication. 1.0 mm-wide passes.
Slow manual feed.
At this point, you have to rough form the flangesby removing all linear parts.
Precision is required (dimension + 0.1 mm).
The centers of the crank journals are theones to be used (center of the crankshaft).
Carefully mark the disc of the universal indexing head. Also, the crankshaft must be positioned according to the initial cut.
Mark the machining surfaces with methylene blue. This is important, as it allows you to get the right flange and roughly draw the final form.
It is extremely important to use both the dividing head and the Y-axis of the milling machine, as well as keeping your eyes on the DRO.
Zero the Z-axis on the digital readout.Place the zero on the central axis of the crankshaft, not on the work piece.This absolute zero is obviously tied to the swing of the indexing head.
By using this repository, you will be able to unmount the crankshaft or turn it over without losing your measurements.
Now perform the same operations, using the different centers of the crankpins (i.e. 3 times, with 120° intervals). Again,remove only the linear parts, and keep dimension +0.1 mm.


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## Brian Rupnow

Amazing work.--Perhaps I should consider flying you to Canada---I've got this single cylinder engine crankshaft thats giving me fits----


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## ZAPJACK

Pictures 95, 112, 120, 123 :
Go through the same operations, removing the round parts this time. In that case, you need to use the milling machine (Y-axis) and turn the indexing head at the same time. Remember to mark the disk of the indexing head. Remove 0.5 mm at a time, then 0.1 mm for the final pass.
For the finishing, using a face mill with 3 or 4 teeth (800 rpm) is recommended.
If you are careful, you can actually machine two faces and a rounding in one cut.
LeZap


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## stevehuckss396

That is some nice work there!!!!!


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## ZAPJACK

Pictures 129, 130, 132, 133 :
Drilling the oil channels is the last process requiring precision. As the crank journals are hollow, there will be no way to drill the various walls without the drill skewing and breaking. To solve that problem, you need to insert a mild steel « martyr » buffer (see picture 133). The buffer must be fixed using Loctite. This trick should enable you to drill the channels easily. LeZap


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## ZAPJACK

Pictures 134, 136,138,139 :
With the crankshaft completed, you now need to remove the templates located at the ends. Always use the under arm to minimize the flexion of the workpiece
LeZap


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## ZAPJACK

Picture 144 :
Check the run outs as well as the homogeneity of each crankpin, which must be below 0.2 mm on the central bearing.

Picture 146 :
To recover this run out, you need to set the crankshaft on the milling machine as shown in the picture. Place the crankshaft between two V-leveling pads and a brass axle to press the crankshaft. Zero the X-, Y- and Z-axis by just touching the central bearing. In order to minimize the stress on the piece, it is recommended to heat it in an oven (220°C, 20 min). Once the piece is hot, place it under the milling machine and start with a 1.0 mm deformation. Remove the piece and check with a Pupitast indicator. As the piece must not cool down, put it back in the oven regularly. Deformation can be gradually increased, but only by 1.0 mm at a time, and up to a maximum of 5.0 mm. A residual deformation of two to three percents is acceptable.
LeZap


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## John Rus

This is simply a work of art you have there!

Are you going to make the rest of the Merlin or are you stopping at the crank?

Keep up the fantastic work!
John.


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## ZAPJACK

John Rus said:


> Are you going to make the rest of the Merlin


 Yes, I will do it!
LZ


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## John Rus

If the crank is finished then you should start a "work in progress" thread on the rest of your beautifull engine. After you finish posting about your crank of course. Thm:

Cheers,
John.


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## ZAPJACK

Pictures 156, 162 :
Crankshaft finished. Final weight 777gr (7000gr at the beginning)
125 direct labor hours and 80 hours of indirect work such as: creation of a grinding machine, specialized tools, jig bearings, etc... 
LeZap


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## stevehuckss396

From what I can see, worth every minute.


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## FannBlade

ZAPJACK said:


> 125 direct labor hours and 80 hours of indirect work such as: creation of a grinding machine, specialized tools, jig bearings, etc...



And people wonder why one-off's cost so much!   :wall:

Nice work....I will be waiting for the upcoming portion.


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## gdrhbb

ZAPJACK said:


> Hello there,
> I present to you my last work. It's the crankshaft ot the Rolls-Royce V12 Merlin at scale 1/4.
> In the followed weeks, I will post the building process with needed pictures
> LeZap
> 
> View attachment 56977
> 
> 
> View attachment 56978


Hello, my name is Sun Guangye from China. Your work has shocked me. I want to be as good as you, but first of all I want to buy Rolls-Royce v12 engine. I don't care if it can be done. I love it. Please fulfill my little wish. Please


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## Jamie Barton

What a work of art! I've just destroyed my my second attempt at the tiny inline four crankshaft this weekend. Your pictures have motivated me to try a third attempt.

Fantastic detailed write up and photos.


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