# building an adapter - measurement or blueprint?



## rwaudio (May 22, 2008)

brainzel said:


> To get an adapter so precisely as possible, I would love to take blueprints / drawings of motor and transmission with exactly dimensions but I can't find them or no where to find.
> An exact measurement is quiet difficult to get the last hundredth.
> 
> So my questions are:
> ...


I'm in the process of designing an adapter plate right now. I have a small CNC machine that's pretty accurate, so you are correct in wanting the best "input" data possible to get the best results out. I'm going by measurements plus a bit of cheating. I have two options for my car, make an adapter plate that attaches to the bellhousing, or scrap the bellhousing and attach to the torque tube. The torque tube measurements are easy, the bolt holes line up on on even mm distances, so I don't have to measure to 3 decimal places. (and it's a simple rectangle) If I keep the bellhousing I will scan it (yep just put it on a scanner and import as a PDF) my CNC software will allow me to scale the image if necessary to physical measurements taken of the bellhousing, and accuracy depends on one or two critical measurements, not one for every hole in reference to every other hole and getting every angle correct.

My motor has documented mounting holes, so that part I don't have to worry about, but if you are using a forklift motor or something similar it would be a bit more difficult. However unlike the bellhousing there is a good chance they are all uniform in distance from center and spacing.

Because I don't have a lathe, I'm having the coupler made for me, that only required providing a clutch and some measurements.

****warning, my bellhousing is detachable and weights about 6-10lbs so it won't break my scanner, use common sense if using this idea****


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## DJBecker (Nov 3, 2010)

The easiest approach depends on the situation.

The usual case is making an adapter plate for a manual transmission where the bell housing mounting surface is on a single plane and the input shaft projects slightly beyond that plane.

The easy approach is to make a template out of foamboard or fiberboard. Start by drawing centerlines (horizontal/vertical alignment lines), drill a snug hole for the input shaft, and trace the outline of the bell housing.

The challenge is getting it precisely aligned. Transmission input shafts are often supported and aligned by the pilot bearing on the engine side. While there is some tolerance for minor misalignment, we can't be so far off that we preload the input shaft gears.

Each transmission is different, but there is often an obvious centerline and projecting dowels or sleeves that set the exact alignment. These are the only points that need precision. The rest of the bolt holes should be large enough to allow some movement -- non-sleeved bolt holes are not alignment points.

Again, it depends on the exact parts you are using. The Miata we are converting has bell housing bolt holes that are just a few mm lower than the horizontal centerline -- close enough that I was convinced that they had to be the centerline until precise measurements showed that not to be the case.

When you transfer the template to the plate you are going to cut, score both the centerlines and several concentric rings. These will make subsequent measurements much easier, since one of the first steps is removing the centerpoint.

We left our transmission adapter plate over-sized, with lifting holes on the top. As long as it fits in the engine bay or transmission tunnel, there isn't a reason to make it conform to the bell housing. You can cut it to the exact profile later, once everything is working.


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## EV-propulsion.com (Jun 1, 2009)

I always recommend measuring off of the engine, if you have it. The crankshaft is precisely centered, so there is no error from a trans input shaft wobble as mentioned above. If your vehicle has a sheetmetal plate between engine and trans you are in luck, as this is usually a precision fit to the dowel pins (which really are the only two holes that need to be precisely measured to the center). Just solidly mount a scribe to the crankshaft, this could be as simple as a transfer punch pushed through a tight hole drilled in an aluminum bar, bolted solidly to the crankshaft. Now turn the engine 360* and you have a perfectly centered circle to measure off of. There are many variations of this depending on vehicles (like extending the bar so the scribe goes through the center of the dowel hole,etc) If you don't have a sheetmetal plate factory, just make one up and securely mount it to the block.
Now you have an accurate template.
This is how we did it in the early days, before hi-tech measuring equipment!
Mike
www.EV-propulsion.com

DJB- you are right about the alignment dowels on the miata being just off the centerline-it would make things a heck of a lot easier if they were!


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## F16bmathis (Jun 6, 2008)

Looks like you want something that looks profesionally made. When I made the adapter plate for my Ford Probe, I first made the adapter for the motor to transmission by taking the very end of the drive shaft where the flywheel bolts to and cut it off so I had a perfect flywheel bolt pattern. I also pulled the forklift motors output gear, made a centering tool that fit in both adapters and welded them together. Now that I had the adapter made, I put everything back into the car and lined it all up. I had about 1" of a gap with everything in place, so I bought a 1" aluminum plate, placed it against the tranny and marked it for cutting. I then had it cut at Coca-Cola (work) by a machinist, but I could've easily done it. It wasn't CNC but it looked good and worked great!


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## Woodsmith (Jun 5, 2008)

There have been two piece adaptor plates made.

One plate is drilled to fit the bell housing and a large hole made in the centre.
The second plate is mounted to the motor and has bolt holes in it to bolt to the bell housing plate.

The trans is then stood on end so the bell housing plate is flat and level. The motor is then coupled to the trans but the plates are left free floating.
12v is applied to the motor and then it is nudged around until the shaft, coupler and trans sounds quiet and smooth. The two adaptor plates are then drilled and bolted together in that position.

It seems to have worked for a few people.


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## carambo46 (Oct 12, 2010)

EV-propulsion.com said:


> I always recommend measuring off of the engine, if you have it. The crankshaft is precisely centered, so there is no error from a trans input shaft wobble as mentioned above. If your vehicle has a sheetmetal plate between engine and trans you are in luck, as this is usually a precision fit to the dowel pins (which really are the only two holes that need to be precisely measured to the center). Just solidly mount a scribe to the crankshaft, this could be as simple as a transfer punch pushed through a tight hole drilled in an aluminum bar, bolted solidly to the crankshaft. Now turn the engine 360* and you have a perfectly centered circle to measure off of. There are many variations of this depending on vehicles (like extending the bar so the scribe goes through the center of the dowel hole,etc) If you don't have a sheetmetal plate factory, just make one up and securely mount it to the block.
> Now you have an accurate template.
> This is how we did it in the early days, before hi-tech measuring equipment!
> Mike
> ...


WOW Mike I like the way you set this up, I think I could even do it that way!
Thanks car
now how to get a coupling


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## rfhendrix (Jan 24, 2011)

Buy something like this or similar (16" x 1/4 steel disk): http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=320522082859&category=29402&_trksid=p5197.c0.m619

Then match it using one of the methods described on this thread. You may be able to get two pieces out of it by cutting a smaller disk out of the middle and using that to match the motor (as described by woodsmith) then welding the pieces together or whatever depending on the spacing you need.


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## rfhendrix (Jan 24, 2011)

By the way, you can cut steel with your circular saw with a metal cutting blade. Of course you cannot make a circle but you can easily make a hexagon or whatever and then finish the cuts with a saws-all.


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## F16bmathis (Jun 6, 2008)

Who's using steel? Aluminum works great and is easier to cut. Did I miss something somewhere? Oops no smiley face icon?


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## F16bmathis (Jun 6, 2008)

I didn't have the engine, so I cheated and got my errors of letting the motor/adapter settle down, then lifted it up, halved my distance and figured that was a good enough center. Side to side was easy enough to judge the same way once centered up and down.

Its really not as hard as people make it out to be.


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## F16bmathis (Jun 6, 2008)

Woodsmith said:


> There have been two piece adaptor plates made.
> 
> One plate is drilled to fit ... drilled and bolted together in that position.
> 
> It seems to have worked for a few people.


I like this idea best! There's the smiley face!


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## Woodsmith (Jun 5, 2008)

F16bmathis said:


> Who's using steel? Aluminum works great and is easier to cut. Did I miss something somewhere? Oops no smiley face icon?


I did a search on Ebay for aluminium plate for my original MR2 adaptor.

I searched based on the thicknesses I could use and found that there are a lot of fabricators selling the bigger offcuts from their scraps bin.
I also found big bits of aluminium plate at my regular scrap metal yard.

It works out a lot cheaper this way if you don't mind a few additional holes. Just make sure the pieces are flat though.


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## rfhendrix (Jan 24, 2011)

Aluminum is easier to work with but more expensive so I guess it depends on what you have laying around.


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## Yabert (Feb 7, 2010)

Hi

I build right now an adapter for coupled an ADC 9" to a Ranger 94 transmission.
You can see how I align the center of the ADC shaft with the transmission shaft. You can find some kind of dial Indicators for 20$.
Because I don't have the original hollow dowel pin coming from the transmission, I put two new 1/4" dowel directly in the transmission frame.


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## Woodsmith (Jun 5, 2008)

That looks a good method, Yabert.

Is there any radial movement on the gearbox primary shaft?
On some there is a little slop as there is only one bearing on the shaft and the front end is then held in the pilot bearing.


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## Yabert (Feb 7, 2010)

Woodsmith said:


> Is there any radial movement on the gearbox primary shaft?


Yes! Around +/- 0.010" for this transmission shaft. But you can find the center with appropriately accuracy when you play with the shaft.

The front end is support by the pilot bearing in the fly wheel and this one is support by the motor shaft. The bearing with blue seal on picture align the fly wheel (transmission shaft) with the coupler mount on the ADC shaft.


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## DavidDymaxion (Dec 1, 2008)

I used steel for mine. Racing rules require a 1/4 inch steel scatter shield, so the adapter is doing double duty. It seemed a waste to drape 1/4 inch steel over an aluminum adapter. Also, steel was easier to weld for Mr. Amateur welder here. Here are a couple links on how I made mine:

http://explodingdinosaurs.com/9electric/adapter/

http://explodingdinosaurs.com/9electric/adapter2



F16bmathis said:


> Who's using steel? Aluminum works great and is easier to cut. Did I miss something somewhere? Oops no smiley face icon?


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## Yabert (Feb 7, 2010)

I drew some parts to help people to perfectly understanding the use of an adapter plate....

I think people from school that I build this adapter will like these drawings!


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## Jimdear2 (Oct 12, 2008)

Yabert,

Beautiful job. 

This should absolutly be placed as a sticky or go to the WIKI

Do any others of you guys agree?

Jim


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## DavidDymaxion (Dec 1, 2008)

Yabert, those are great pics. I would 2nd putting them into the wiki.


Jimdear2 said:


> Yabert,
> 
> Beautiful job.
> 
> ...


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## Duncan (Dec 8, 2008)

Hi Yabert

Lovely adapter system

Just a suggestion 
Take that flywheel and cut off everything outside the area the adapter bolts onto 

That will cut down on the inertial mass and reduce nasties like whirl which can put significant unexpected side-loads on your bearings


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## Yabert (Feb 7, 2010)

Because this conversion used the originale clutch, I can't remove lot of weigh on the fly wheel exept the starter teeth and some unnecessary steel.

For my personnal Smart convertion, I think build an aluminium fly wheel!

You can see here an other nice picture of an adapter (from Cro driver).


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## neuweiler (Nov 6, 2012)

Very nice post, thank you very much! I'm currently in the same situation as the original poster was and I found your post and this one very helpful. In order to be able to go with one single plate instead of two, I've come up with this approach. Don't know if it will work. Would be interested in your opinion:

Measure the exact distance between the two dowel points (if possible to 1/10mm or even 1/100 mm):









Perform a precision drill for the two dowel holes and insert the bolts. The plate (blue-grey) is fixed exactly against the gearbox:









Approximately measure the center from one of the two dowel holes. (e.g. perpendicular to the previous line) :









Drill a small hole (black) at the estimated center. Use the hole to mount a circle to the gearbox shaft and scratch a ring into the plate -> exactly centered (red circle). Or use a precision measurement tool (e.g. one of those needle distance-o-meters) :









My motor uses a beveled ring in the front plate for lateral fixation (up/down and left/right). Mill a concentric ring into the plate -> motor position is fixed:









All that’s left is drilling the holes for the motor and the remaining holes in the gearbox (doesn’t need to be a precision job) and to reduce the plate to the outer shape of the gearbox:


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