how to locate each holes positions relative to the center of engine shaft?

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howardyin

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How about an abitrary reference point ,three feet from my center,find my bolt hole,extend
the line out to the same diameter as my reference,measure, compare to the same
radius as my bolt, repeat as many times as nesessary to get a grouping,throw out the outliers and average the rest.
Its slow,but it works.
would you please paste a pic to show the way ,thanks
 

Geraldc

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Hello , guys here ,

how to locate each holes accurate positions relative to the center of engine shaft ?


I am a homebuilder now modifying my Honda L15A , I am wondering how to make sure the shaft center position relative to the holes those used to hold the plate which hold shaft of output gears. (to keep engine shaft Coaxial to belt gear shaft)
View attachment 113508
If you are making a one off.
I would remove the flywheel.
Machine hole A in your photo to fit neatly over flywheel flange.
Buy or make one of these pins shown below to fit in each hole.They are called dowel transfer pins used for woodwork.
Transfer hole centers to plate.
The large hole that is located on the flywheel can be used for a bearing housing.
1628311204940.png
 

wsimpso1

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You have good guidance on several ways of doing this.

I feel like a couple of background points are needed.

The pilot bore in the end of all automotive crankshafts is there to support the pilot on the centerline of torque converter or the input shaft of a manual transmission through a pressed in pilot bearing. This has to center the TC (25-35 pounds in this size range) or the front end of the input shaft and the clutch disc. There is a tolerance on the size and position of this bore, but it is pretty small or we would have all sorts of 1st order vibe - very bad modes. Tolerance is only a couple thou IIRC.

The crankshaft to main journal radial clearance is also pretty small - a couple thou. So, simply making a center that is a firm slip fit in the crank bore will typically get you within 0.002” on crank centerline position.

As for the dowels, they are spring pins typically in two places and designed center the transmission case on the RFOB. Again tolerances are pretty darned small, or the misalignment would mess with tranny install and bearings, gears, and in many cases, the coaxial oil pump that is finally going out of favor.

All other bolt holes should have enough clearance that the bolts do not pilot the PSRU, only the dowels.

At the automakers, this is all checked with CMM, but those of the toolmaker craft no doubt can measure bore diameters, distances between bores, angles between dowel bores, then through some trig, check that the radii indicated from center are the same.
 

pfarber

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Ever wonder what the ballpeen end of a hammer is for? My dad showed me how to do it for a auto transmission. Using strong cardboard, Cut or drill an accurate hole matching the drive shaft, use a ball peen hammer to tap out carboard for the remaing mounting holes.
Where do I find tool room quality cardboard?

For a gasket? Sure. Done it dozens of times.

For a precision layout of +/-.002? No, I think not.
 

TFF

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There would be no hot rods in Hot Rod magazine from inception to about the 80s, without cardboard templates. I would surmise no Indy cars through the mid 70s. No Ferrari’s, no Cobras. The best of our engineering history, pretty much had no computers and when they did, they were just adding machines, not CAD/CAM. Now it seems we can’t measure hole to hole without NASA workshop.
 

PMD

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There would be no hot rods in Hot Rod magazine from inscription to about the 80s, without cardboard templates. I would surmise no Indy cars through the mid 70s. No Ferrari’s, no Cobras. The best of our engineering history, pretty much had no computers and when they did, they were just adding machines, not CAD/CAM. Now it seems we can’t measure hole to hole without NASA workshop.
I think I already described how to get the X-Y co-ordinates without any computers earlier in this thread. You can just work the backwards with mechanical measuring tools to preproduce the original dimensions with reasonable accuracy if you are any good at layout. Also, the Ferraris, Cobras, etc. from the '70s fell a fair way short of anything I would want in an airplane when it comes to engineering, materials or craftsmanship. Try restoring a few and you will know just what I mean.

BTW: I don't claim to be an expert nor am I an actual machinist or toolmaker, but I routinely do size-on-size bolt patterns all by measurement and layout - just the nominal bolt size vs. actual bolt diameter for tolerance to allow for fitup. I do not have a digital readout on any of my drills, lathes or mills. BTW: that includes many engine/transmission adapters.
 

wsimpso1

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There would be no hot rods in Hot Rod magazine from inception to about the 80s, without cardboard templates. I would surmise no Indy cars through the mid 70s. No Ferrari’s, no Cobras. The best of our engineering history, pretty much had no computers and when they did, they were just adding machines, not CAD/CAM. Now it seems we can’t measure hole to hole without NASA workshop.
I am certain that a lot of things were measured and then built using simple techniques. When the drag racers were figuring out that a stock flywheel inside a stock bellhousing could result in high speed pieces of cast iron, some of those new scattershield bellhousings had to have been measured and drilled. At Ferrari, Porsche, Shelby, etc, the tranny and engine folks know each other and will share dimensions for stuff like what we are talking about.

In fairness, I suspect that many of the racing teams, hot rodders, and performance builders had somebody inside the car companies who would favor them with the dimensions for the radius, angle, and diameter of the dowel holes on the RFOB, as well as a lot of other specifics.

At Ford auto trans well into this century, the SVT folks and race teams were always querying us for dimensions, offsets, custom torque converters, etc. When we did not answer fast enough (more than once we told a guy "tomorrow" and he was pissed we did not have the number "right now"), we even saw some amazing failures that came out of impatience over a 1-to-2 day response time. That included custom bell housings with radial offsets, rigid "flex plates" that caused 10 minute crankshaft thrust bearing failures on their expensive race engines, and once in a while some unusual colors on the torque converter and/or seized pumps due to high temps when the race shop talked their reluctant TC shop into an overtrim of a stator or impeller instead of waiting for us to assemble a few for them for free.

This sort of help might be a little harder to get out of Honda or Toyoto than from GM, Ford, and Chrysler, but with some careful calling and chatting, I bet it still happens.

Billski
 
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Aviacs

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There would be no hot rods in Hot Rod magazine from inception to about the 80s, without cardboard templates. I would surmise no Indy cars through the mid 70s. No Ferrari’s, no Cobras. The best of our engineering history, pretty much had no computers and when they did, they were just adding machines, not CAD/CAM. Now it seems we can’t measure hole to hole without NASA workshop.
No doubt some versions were and are constructed along those lines, and some people are just astoundingly lucky.

Notheless, I'm pretty sure anything that counted on performance and was durable used actual precision location methods based on techniques going back to the late 19th c (mid to late 1800's) Precision measuring methods predate that, NB Maudsley and contemporaries in England & USA at the end of the 18th c/early 19th c.

You can find (locate) a lot of close work with dowels and gage blocks. Often conveniently augmented with dial test indicator(s).
Useful gage blocks are an early 20th c invention. But precision end measurement to tenths goes back much earlier; adjustable rods and end-stops can work in the hands of someone who knows what they are doing. Then tooling balls (cylinders), trig, and single point boring to place the holes.

It might even be argued that swatting a sturdy paper pattern with a ball bearing is as accurate as it gets.
The problem is that you can't read it, or transfer the location points reliably.
Even with spray adhesive, perfect non-distorting paper, and a single point boring head and loupe, i doubt .002 everywhere.
As has been pointed out, only the dowel pins have to be perfect, but the rest matters. I'd want hard dowels for generating locations not spring pins. Spring pins are an assembly expedient for eventualities (such as minor dings); and they accommodate more accumulated tolerance than should be accepted for initial machining.

smt
 

pfarber

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There would be no hot rods in Hot Rod magazine from inception to about the 80s, without cardboard templates. I would surmise no Indy cars through the mid 70s. No Ferrari’s, no Cobras. The best of our engineering history, pretty much had no computers and when they did, they were just adding machines, not CAD/CAM. Now it seems we can’t measure hole to hole without NASA workshop.
I think you need to go back and actually look at the accuracy available 'back in the day'.

We built IMUs and turbo-pumps for actual rocket ships using just a slide rule and 'primitive' techniques that cannot be duplicated today. Every wonder why they don't make another Saturn V rocket? They simply can't. There is no way. To knowledge of the craftsman has been lost and modern technology has erased the years of experience those craftsman had. Some kid now a days only know what a CAD program can do... not what is actually possible.

So no, your cardboard fantasises were not building high tech precision machines. Stopping a leaking water pump? Sure. But don't ever say out loud that your 'precision' ball peen hammer is anything close to a trained scraper or machinist.
 

Geraldc

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And lining up a redrive plate with a dial gauge on end of crank then drilling reaming and dowelling is no different to a toolmaker using "buttons"
 

AdrianS

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I am certain that a lot of things were measured and then built using simple techniques. When the drag racers were figuring out that a stock flywheel inside a stock bellhousing could result in high speed pieces of cast iron, some of those new scattershield bellhousings had to have been measured and drilled. At Ferrari, Porsche, Shelby, etc, the tranny and engine folks know each other and will share dimensions for stuff like what we are talking about.

In fairness, I suspect that many of the racing teams, hot rodders, and performance builders had somebody inside the car companies who would favor them with the dimensions for the radius, angle, and diameter of the dowel holes on the RFOB, as well as a lot of other specifics.

At Ford auto trans well into this century, the SVT folks and race teams were always querying us for dimensions, offsets, custom torque converters, etc. When we did not answer fast enough (more than once we told a guy "tomorrow" and he was pissed we did not have the number "right now"), we even saw some amazing failures that came out of impatience over a 1-to-2 day response time. That included custom bell housings with radial offsets, rigid "flex plates" that caused 10 minute crankshaft thrust bearing failures on their expensive race engines, and once in a while some unusual colors on the torque converter and/or seized pumps due to high temps when the race shop talked their reluctant TC shop into an overtrim of a stator or impeller instead of waiting for us to assemble a few for them for free.

This sort of help might be a little harder to get out of Honda or Toyoto than from GM, Ford, and Chrysler, but with some careful calling and chatting, I bet it still happens.

Billski
A friend of mine had two gearbox input bearings die before he measured the aftermarket gearbox adapter and found it wasn't centred on the crank.
 

dwalker

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There would be no hot rods in Hot Rod magazine from inception to about the 80s, without cardboard templates. I would surmise no Indy cars through the mid 70s. No Ferrari’s, no Cobras. The best of our engineering history, pretty much had no computers and when they did, they were just adding machines, not CAD/CAM. Now it seems we can’t measure hole to hole without NASA workshop.

I was using cardboard templates in the race shop right next to the FARO "arm" until I retired in 2015-16.
 

Aviacs

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No doubt we (machine builders of all kinds) all use "Cardboard Aided Design" on a routine basis for many assemblies.
Using it to locate bearing bores, gear centers, or matching alignments to same by "CAD" method borders on certifiable optimism. :)

It's a good start for rough location. Then out with measuring equipment suitable to the alignment specs.
The equipment does not have to be all that "high tech". But it needs to be rigorously applied & of a resolution and confidence level (ridgid, repeatable, etc) that exceeds the tolerance. Now about temperature....

smt
 

Winginitt

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From looking at the picture you provided, it would be nice to know what the holes you are asking about actually do. I say this because what it will be used for can make a difference in what is an easy and precise means to locate the hole.

As an example, are those outer holes for bolting some type of housing to the plate OR for bolting the plate to a mount in the airplane?

If its a housing of some kind, then simply set the housing against the plate and indicate it on center of the crank. Then clamp it in place and put a drill bushing each hole and drill the pilot hole for the location. Also drill and ream a couple of dowel pin holes to keep it centered when disassembling and reassembling. The bolt holes are not locating holes.

If the outer holes are for physically mounting the engine in an airplane, Then there is a lot more tolerance and you could probably make the locations whereever its convenient to your airplane.

The above is just an example, as I don't know what the purpose of each hole or set of holes is. Please explain the hole patterns and maybe some idea of what you plan to adapt to it (picture). I think you can get better answers that way.


I once had an engineer design a part that had 8 locating dowel pins. Anything over 2 is redundant and makes manufacturing much more difficult. They were .001 true position locations. Without going into a lot of details, I found out that the part we were making was simply to locate a mounting plate for a hydraulic cylinder shaft. The plate could have been mounted 1/2" or more off location and it would not have mattered. Thats why I'm suggesting that you identify the purpose of the holes you wish to locate, as that can have a big effect on ease of manufacture. Even a rough sketch would help.
 
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stanislavz

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My two cents. Put engine vertically. Remove all sparks. Turn some adaptor on you shaft which protrudes 10-20mm sbove you gearbox mounting plate. 20 mm in diameter. Mount it and dial it. Move it into horizontal postion. And dial it again. If it is off centre - you will have to find bare engine block and make new shaft in place of crank shaft. Machine close fitting bolts or tubes for all holes which you would like to transfer. Measure all distances minus radiuses of used pins/axes.

Only big problem - you need an 500mm caliper.
 
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