# 2001 VW Jetta Homemade Coupler and Adapter Plate



## azdeltawye (Dec 30, 2008)

*Coupler overview*

Since I spent a majority of my EV conversion budget on a Lithium battery pack I needed to cut back the spending and save money wherever possible. One of the areas I figured I could save a few bucks was on the home fabrication of the coupler and adapter plate. 

I started my quest for a DIY coupler by searching the catalogs of commonly available industrial taper lock bushings. After looking over the many different products that use the taper lock setup I selected a synchronous gear belt pulley and split taper bushing combination made by Browning. I chose the synchronous gear belt pulley to make the coupler since it was made out of steel instead of cast iron and would be easier to machine. The pulley was Browning part No. 24HP100 (Grainger No. 2L700) which had an outer diameter of approximately 3.8” and thickness of 1.25”. The bushing was Browning part No. P1 X 1-1/8 (Grainger No. 3X483) for a 1.125” keyed shaft. I chose the split taper style bushing over the Q-D style bushing because the split taper type has an external key which mates with the pulley for positive drive and greater torque carrying capability. Whereas the alternate Q-D style bushing does not have an external key and relies solely on the friction of the taper and the bolts to transmit the motor torque to the load.










Bushing and pulley as purchased










Coupler CAD dwg

One nice aspect of using a later model donor vehicle such as the A4 Jetta (4th generation) is the pilot-less input shaft in the transaxle. No pilot bushing is required for the transmission input shaft. This eliminates the need to fabricate and install a bushing in the end of the motor shaft or coupler body.


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## azdeltawye (Dec 30, 2008)

*Reverse mounting of bushing*

One problem with the split taper style bushing was that it did not have the reverse mounting capability (bushing flange towards motor) that other style bushings have. This problem was easily solved by installing threaded inserts in the bushing through-holes. I used 5/16-24 fine thread thin walled key-inserts with a 7/16-14 outside thread for this purpose. Reversing the bushing mounting scheme also required drilling and counterboring the existing threaded holes in the pulley to sink the fastener heads below the surface of the pulley which is used for mounting the flywheel. I used a 31/64” endmill to a depth of approx 0.750” for the counterboring operation. After this I trial-fitted the bushing and pulley together to verify proper fitment and that the 5/16-24 socket head bolts would be below the surface of the pulley after the facing of the pulley was complete.









Threaded inserts installed in bushing


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## azdeltawye (Dec 30, 2008)

*Turning the pulley – Flywheel mounting surface*

Next I removed the belt guide rings around the edges of the pulley and mounted the pulley and bushing on a dummy shaft so I could turn it on the lathe. I used a 4-jaw chuck instead of the 3-jaw chuck to minimize runnout. Before removing any material from the pulley I verified the pulley and shaft were true with a dial indicator. I took 0.375” off the face of the pulley leaving a protrusion or hub in the center of the pulley to properly locate the center of the flywheel. My goal was to mimic the shape of the flywheel mounting surface on the crankshaft while maintaining the proper flywheel depth when using a 1” thick adapter plate. The flywheel locating hub on the crankshaft had an outer diameter of approximately 1.693”. This measurement was smaller than the inner diameter of the bushing opening in the pulley (1.856”). This meant that the nose of the bushing and not the pulley would be responsible for locating the center of the flywheel. I realized this was not an ideal method of locating the flywheel since the outer diameter of the bushing nose could vary somewhat depending on the diameter of the motor shaft it was mounted on. With this in mind I made sure the dummy shaft I used had the same diameter as the motor shaft to within 0.0005”.









Machining complete on pulley face


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## azdeltawye (Dec 30, 2008)

*Drilling and tapping the pulley*

Once the material was removed from the face of the pulley and the flywheel hub was sized appropriately I aligned and marked the 6 flywheel bolt holes on the pulley for drilling and tapping. The flywheel bolt holes were not all evenly spaced at 60°. One of the holes was set approximately at 49° / 71° from the others. Initially I was worried that this meant the engine was externally balanced by the flywheel. But close inspection of the flywheel assembly revealed no external weights or non-symmetric features on which meant the flywheel was not used to balance the engine (this was later verified by trial assembly and spin test on the motor). I drilled the flywheel mounting holes in the pulley to 8.75mm and tapped with a M10-1.25 tap. The original flywheel bolts had a 1.0mm thread pitch but I could not find a M10-1.0 tap with a rear centering dimple locally. I used M10-1.25X30mm grade 12.9 socket cap screws to mount the flywheel to the pulley. 









Flywheel bolt holes marked and center-drilled









Tapping flywheel bolts holes in pulley









Finished coupler – Front view









Finished coupler – Side view









Finished coupler – Rear view


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## azdeltawye (Dec 30, 2008)

*Adapter plate overview*

Since I did not have access to a CNC milling machine I figured I would use a two piece adapter plate (one plate attached to the transaxle bellhousing and the other plate to the motor) rather than one thick plate. I lucked out and found some scrap ½” aluminum plate for $1.50 per pound at the local metal recycling yard for this purpose. Prior to removing the flywheel from the gas engine I measured the ‘critical distance’ behind the flywheel to the transmission mounting surface. This measurement was 0.175”. My goal was to accurately duplicate this distance while using a 1” thick adapter plate and have the taper lock coupler fully inserted onto the motor shaft. 

Due to the limited space in a transverse engine compartment (19.875” between tranny bellhousing and frame rail) anything much greater than 1” for the adapter plate thickness would prevent the use of the Kostov 11” motor which has a length of 18.05” from the mounting surface to the end of the fan housing. Motor options for transverse engine applications are limited due diameter and length restrictions.


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## azdeltawye (Dec 30, 2008)

*Transmission plate*

I temporarily removed the two hollow locating dowel pins and RH side CV drive flange from the transaxle so I could trace the bell housing outline and locate some of the mounting bolt holes onto the aluminum plate. Once the plate was marked I cut it to size with a jigsaw and smoothed out the edges with a belt sander. I used a 5/8” counterbore drill on two of the mounting holes to mate with the locating dowel pins in the transaxle. Once the plate was mounted to the transaxle I marked the location of the remaining bellhousing bolts and input shaft center onto the plate. I cut a 9.125” diameter hole in the center of the tranny plate to clear the motor mounting bolts in the motor plate. 









Tracing outline of transmission on aluminum plate










Index holes drilled and outline marked










Cutting center of tranny plate










Finished tranny plate mounted on transmission


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## azdeltawye (Dec 30, 2008)

*Motor plate*

I selected the Kostov 11” DC motor for this conversion project. Since the Jetta bellhousing was not much larger that the body of the motor I decided to make the motor mounting plate outer diameter the same as the motor drive end plate diameter (11.45”). Centering of the motor plate to the motor was accomplished by a 4.0” diameter hole to accommodate the nose of the motor. The mounting bolt holes were drilled oversize and subsequently not used for centering the motor. Special attention was given to the allow clearance of the CV drive flange so it would not interfere with motor plate or motor. In fact both the motor plate and faceplate of the motor had to be notched to clear the CV drive flange and CV joint mounting bolts.









Notching motor plate for CV flange


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## azdeltawye (Dec 30, 2008)

*Centering the motor plate on the tranny plate*

Since this transmission had a pilotless input shaft there was minimal radial play associated with said shaft and therefore it could be used to center the motor plate with respect to the tranny plate. I mounted a dial indicator to the transmission input shaft and used it to center the 4” circular cutout in the motor plate. 









Centering motor plate on tranny plate with dial indicator

Once the motor plate was properly positioned I clamped it to the tranny plate, drilled and installed four 5/16” roll pins to securely and precisely locate it in this position. Note: prior to this step I made sure the motor was properly oriented with respect to the transmission (lift eye on top). After the roll pins were installed I removed the plates from the bellhousing and drilled holes through both plates for eight 3/8-16 socket head cap screws. I installed threaded inserts into the tranny plate to accommodate the cap screws. I also had to counter bore the holes in the motor plate to prevent contact between the cap screw heads and the motor face. These fasteners are used to solidly clamp the motor and tranny plates together. 









Finished adapter plate – motor side










Finished adapter plate – tranny side

At this point I trial fit the finished adapter plate assembly onto the tranny and temporarily bolted the motor faceplate to the adapter. This allowed me to gauge how much material needed to be removed from the motor faceplate to clear the CV drive flange. 









Trimming motor faceplate for proper clearance of CV flange and bolts


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## azdeltawye (Dec 30, 2008)

*Final assembly of adapter plate, coupler and flywheel*

With the motor plate and tranny plate bolted together I attached the adapter plate assembly to the motor using eight 3/8-16 socket head cap screws. Once the adapter plates were installed onto the motor I installed the coupler on the motor shaft and trial fit the flywheel. Special attention was given to the method used to torque the three taperlock clamping fasteners. This was performed in a repeated sequential fashion to the desired value of 192 inch-pounds. The first attempt at positioning the coupler depth was not correct so the coupler had to be loosened to allow axial adjustment of the coupler on the motor shaft. This took a few times to reposition the coupler and get the correct distance of 0.175” between the back of the flywheel and mounting plate. 









Adapter plate and coupler installed on motor










Verifying correct flywheel position with feeler gauge


Once the coupler was properly positioned and torqued I installed the flywheel and verified the axial runnout and wobble was acceptable with a dial indicator (< 0.001”). The A4 Jetta 1.8L Turbo engine and possibly others uses a dual mass flywheel assembly which adds a size constraint to the head of the flywheel mounting fasteners. Because of this I had to reduce the height of the socket head to approximately 0.325” with a bench grinder to clear the movement of the friction surface portion of the flywheel. After the flywheel was mounted onto the coupler the next step was to install the clutch disc and pressure plate. This was followed by the tell-all spin test of the motor – no vibration!! 









Final assembly and spin test of flywheel and clutch


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## azdeltawye (Dec 30, 2008)

*Final assembly of motor to transaxle*

After I was satisfied that the flywheel and clutch were vibration and wobble free I installed the motor onto the transaxle. Once the motor and tranny were mated I then could install the right side CV flange which was removed earlier. The final test of the assembled motor and tranny was to energize the motor with a moderate voltage and cycle the clutch a few times with the motor spinning. This verified proper alignment of the motor with respect to the input shaft of the transmission. All was good…









Motor and tranny – Top view










Motor and tranny – Front view










Motor frame and faceplate modified for CV flange clearance


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## DIYguy (Sep 18, 2008)

Excellent workmanship! I like it! REally nice job there azdeltawye...!


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## O'Zeeke (Mar 9, 2008)

azdeltawye, I agree with DIYguy that IS excellent work. Great project.


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## Woodsmith (Jun 5, 2008)

Excellent work and a great write up.

I'm sure that this will be a great guide to others on how to make their own adaptor plate. Maybe it could be kept somewhere, Wiki it perhaps?


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## azdeltawye (Dec 30, 2008)

Thanks for all the positive comments!

After I get the vehicle on the road early next year I'll post a similar write-up/build thread of the whole process.

This forum has been a great resource and has helped tremendously with my first EV conversion!!


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## gdirwin (Apr 7, 2009)

Great job and explanation!

I also chose a Browning P1 bushing with reverse mounting and designed something very similar ( http://www.diyelectriccar.com/forums/showpost.php?p=149545&postcount=70 )- I am just a little slower than you (and do not have a lathe), so mine is still at the machinists... I had not thought out how to re-use/thread the 3 bolt holes for the reverse mount - I agree that it is better to fill/tap them with inserts and keep the original alignment with respect to the split (instead of drilling/tapping new holes).

I assume that to push the bushing off, you threaded some of the flywheel bolts all the way through?

Also, do you think the tapered hole in the adapter should be the full length of the bushing? I see the bushing extends through the end of the adapter...

Well done!


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## grayballs (Aug 27, 2008)

I think the use of the dial indicator is the important part and worth mentioning,again,, I've read of quite a few couplings (of all types) failing and have always thought that a mis-alignment, however slight, could be the reason.
Well done!


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## Woodsmith (Jun 5, 2008)

Yes good point.
I used to rely on gauging and trial and error measurement but when I got my lathe I decided that I had to get a dial gauge. I found 10 assorted types on Ebay for very little money and now use them where ever I can to check accuracy. What a difference!


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## MJ Monterey (Aug 20, 2009)

Thank you for this clear, concise, and consolidated post. You have given me a fantastic procedure to follow when I start my conversion(s).

Did you need to clearance the motor for the CV joint?

Jack


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## dtbaker (Jan 5, 2008)

nicely done!
man that is a MONSTER motor!


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## azdeltawye (Dec 30, 2008)

gdirwin said:


> I assume that to push the bushing off, you threaded some of the flywheel bolts all the way through?


Yes, I threaded all the flywheel bolt holes through the pulley and just used two longer bolts to push the pulley and bushing appart and remove the coupler from the shaft.



gdirwin said:


> Also, do you think the tapered hole in the adapter should be the full length of the bushing? I see the bushing extends through the end of the adapter...


 
Ideally I would think that the the tapered hole in the pulley should be the same length as the bushing but I was trying to reduce the overall length of the coupler and had to compromise. As you well know, space is at a premium in a transverse engine application and a compact coupler is essential...

Thanks for the comments.


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## azdeltawye (Dec 30, 2008)

MJ Monterey said:


> .....
> Did you need to clearance the motor for the CV joint?


Yes I did. I tried to show it in one of the pics but the lighting wasn't good. I had to remove about 3/8" of material from the motor frame where the CV joint goes. You can see where I repainted this area on the motor - higher gloss paint...


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## electromet (Oct 20, 2009)

Darren,

I'm glad to see you finally decided to post your Jetta in the Garage. How's the wiring coming along? PM me if you need a couple extra hands.


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## GizmoEV (Nov 28, 2009)

Nice looking build. A comment on your placement of the fire extinguisher. What happens if the trunk batteries are on fire and you can't grab the extinguisher because it is in flames? Wouldn't it be better to place it at the back of the trunk by the opening or inside the cabin under a seat?


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## azdeltawye (Dec 30, 2008)

GizmoEV said:


> Nice looking build. A comment on your placement of the fire extinguisher. What happens if the trunk batteries are on fire and you can't grab the extinguisher because it is in flames? Wouldn't it be better to place it at the back of the trunk by the opening or inside the cabin under a seat?


Thanks.

Good point on the fire extinguisher...


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## cts_casemod (Aug 23, 2012)

I had to say, I just loved your design. Will be a good insiration for my Polo. Keep up the good work!


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## azdeltawye (Dec 30, 2008)

cts_casemod said:


> I had to say, I just loved your design. Will be a good insiration for my Polo. Keep up the good work!


Thanks!
24,000+ miles and counting...


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## jaspersk (Jun 26, 2008)

Darren-

That is a really nice job! Your workman ship puts me to shame. I have a 95 Jetta that I would like to upgrade to the MK4, probably a 2003 as there are a lot of them for sale right now. The folks on the vwvortex forum suggested that the 5 speed 02J transmission (yours) has the same shaft and bolt up pattern as the 020 (mine) so I am thinking it is a good car to upgrade to. I also want to have a 4 door since I spend a lot of time shuttling kids around. 
http://forums.vwvortex.com/showthread.php?6082308-020-to-02J-housing-Electric-Car-Upgrade

I wanted to ask you a few questions if you don't mind:

You said you used a "stock VW/Audi electric vacuum pump." Does the Mk4 Jetta have this vacuum pump or did you need to harvest it from another vehicle? 

Did you get the Toyota MR2 Spyder EHPS from a junkyard? I seem to remember looking for one on my first build and never found one. Ebay doesn't yield much help either.

I have the same battery pack as you (45 - 180ah). However, I have gotten 95 miles on a couple of occasions with a little bit of room to spare (driver plus 3 kids). The EPA mileage is listed as 21/28. The manufacturer's listed curb weight is 2647 lbs for my Jetta. Your EPA mileage is also 21/28 although the curb wight on your car is 2974. Do you think that added 300 lbs is the difference between the range we are getting? I know that Calib said in their testing, they were actually getting 200 AH out of their batteries at the time (a year ago) so maybe that is it. The other difference is I have a direct coupled motor so reduced weight there as well I suppose.

I plan to use 9" motor. I'd be surprised if I needed to upgrade the motor mounts because it has been fine on my current vehicle.

Your evalbum post called the car "a horribly unreliable donor vehicle." Can you comment more on that? Any general advice you'd have for or against this conversion? Had anyone else that you know of converted a Mk4 Jetta? Any other warnings you'd have for me before I go this route?

Thanks!
Steve
http://www.evalbum.com/2199


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## azdeltawye (Dec 30, 2008)

jaspersk said:


> Darren-
> That is a really nice job!… I wanted to ask you a few questions if you don't mind:
> 
> You said you used a "stock VW/Audi electric vacuum pump." Does the Mk4 Jetta have this vacuum pump or did you need to harvest it from another vehicle?
> ...


 Thanks for the positive comments!
I got both the VW vacuum pump and MR2 electric PS pump from the junkyard. I always use the following site which networks most major junkyards throughout the country: 
http://www.car-part.com/



jaspersk said:


> Your EPA mileage is also 21/28 although the curb wight on your car is 2974. Do you think that added 300 lbs is the difference between the range we are getting?


 The total weight of my finished conversion is 3540 lbs and my 33k mile overall average energy consumption rate is around 385 Wh/mi (AC). This seems to be consistent with the ballpark rule-of-thumb for homegrown EV conversions of 10 - 11% of curb weight in Wh/mi.
 


jaspersk said:


> Your evalbum post called the car "a horribly unreliable donor vehicle." Can you comment more on that? Any general advice you'd have for or against this conversion? Had anyone else that you know of converted a Mk4 Jetta? Any other warnings you'd have for me before I go this route?


The Mark IV VW Jetta is a very heavy and extremely unreliable vehicle. I could not in good conscience recommend anyone convert this car to electric drive. Some of the failures I’ve had with this vehicle are as follows: door position micro-switches, door release cables, window regulators, power door locks, trunk release mechanism, airbag ECM, seatbelt release latches, seat adjust cables, sunroof drain tubes and stock dual-mass flywheel. In addition I’ve had chronic front end alignment issues due to premature strut mount failures (likely due to the extra weight). I’ve replaced the struts and strut mounts twice in the past 33k miles of electric driving and am overdue for another set of strut mounts again...  

Despite all the issues I’ve had with this vehicle I still enjoy driving it on a daily basis. But if I were to do it again I would steer clear of the MK4 Jetta. Perhaps the MK5 would be better, I don’t know. Better yet, go with something more reliable like a Japanese Donor… But if you are stuck on German engineering go with an Audi or BMW. 

Just my 2 cents… 

Thanks again,


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## Roderick (Dec 8, 2013)

Hi, I've looked through your thread and you have done great work! 
I actually came across your thread from your garage. I am wondering if you are going to do any update on this thread or just on the garage page?? 

I just want to know what happened to your Kostov motor that's apparently melted


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## azdeltawye (Dec 30, 2008)

Roderick said:


> Hi, I've looked through your thread and you have done great work!


 Thanks!



Roderick said:


> I am wondering if you are going to do any update on this thread or just on the garage page??


 Really nothing new to report in regards to the topic of this thread – I did have to add a 3/8” aluminum spacer to the adapter plate to accommodate the switch to a NetGain motor since it doesn’t have a hollow front DE bell like the Kostov. But that’s about it.



Roderick said:


> I just want to know what happened to your Kostov motor that's apparently melted


 The self-destructing Kostov 11” motor debacle is fully documented in this thread:
http://www.diyelectriccar.com/forums/showthread.php/kostov-k11-catastrophic-failure-93478.html


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## Moltenmetal (Mar 20, 2014)

Thanks for the informative thread. What you've done is what is required for the precision of the task, if you expect the device to last long term. Further proof that pushing the "easy" button and buying a pre-made tranny/motor adapter plate + coupling is the right thing for me to do- although I have access to a lathe, I have nowhere nearly the patience to carry out all the steps you've gone through!


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## Al-turbo (Aug 13, 2014)

Excellent write-up on how you machined the coupling, thanks for that azdeltawye.
One question: did you consider to use a standard taper-lock hub instead? It would only have required enlarging the centering hole in the flywheel and drilling 6 new bolt holes. 
Example: http://www.boltonbearings.co.uk/bf12-bolt-on-hub-taper-lock-1210.html
Thanks, Albert NL


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## azdeltawye (Dec 30, 2008)

Al-turbo said:


> Excellent write-up on how you machined the coupling


 Thanks!



Al-turbo said:


> did you consider to use a standard taper-lock hub instead?


 I guess I never considered a ‘standard’ taper-lock bolt-on hub because I didn’t know they existed. It certainly looks like it would be easier than all the monkey business I had to go through. I will definitely consider using the bolt-on hub for my next build… 

It looks like Fenner carries them.


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## jefsmk (Dec 12, 2019)

Al-turbo said:


> Excellent write-up on how you machined the coupling, thanks for that azdeltawye.
> One question: did you consider to use a standard taper-lock hub instead? It would only have required enlarging the centering hole in the flywheel and drilling 6 new bolt holes.
> Example: http://www.boltonbearings.co.uk/bf12-bolt-on-hub-taper-lock-1210.html
> Thanks, Albert NL


Hi Albert, can you clarify what your describing here? Designing my motor to transaxle connection for a VW bug, and this sound interesting, but not sure exactly how the connection would work. Got a quick back of the envelope sketch? Thanks so much for any info you could share.


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