# Kostov 11" spigot clearance



## TTmartin (Feb 7, 2012)

Can anyone advise on motor spigot to adaptor plate bore clearance?
I have a 4"/3.998" motor spigot, planning on machine shop boring hole in adaptor plate to give nice snug fit. Does 4.002" sound about right?
Thanks in advance


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## DIYguy (Sep 18, 2008)

TTmartin said:


> Can anyone advise on motor spigot to adaptor plate bore clearance?
> I have a 4"/3.998" motor spigot, planning on machine shop boring hole in adaptor plate to give nice snug fit. Does 4.002" sound about right?
> Thanks in advance


Hi TT.
What is a motor "spigot"? Please describe your quandary better.


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## TTmartin (Feb 7, 2012)

DIYguy said:


> Hi TT.
> What is a motor "spigot"? Please describe your quandary better.


Hi,
Motor location flange is probably a better description.locates motor centrally to gearbox.
I have now measured motor flange at 3.998" so having gearbox/motor adaptor plate hole bored to 4.000" think this should be fine,
Sorry don't know why I put post up, it's just me thinking aloud (measure twice cut once)
Thanks for your interest


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## DIYguy (Sep 18, 2008)

TTmartin said:


> Hi,
> Motor location flange is probably a better description.locates motor centrally to gearbox.
> I have now measured motor flange at 3.998" so having gearbox/motor adaptor plate hole bored to 4.000" think this should be fine,
> Sorry don't know why I put post up, it's just me thinking aloud (measure twice cut once)
> Thanks for your interest


A picture is worth a thousand words they say. I'm still not exactly sure what you mean. . . but I'm thinking maybe the DE (motor drive end bell) has a raised section? Anyways, 0.002" to 0.003" is considered a precision slide fit.


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## TTmartin (Feb 7, 2012)

DIYguy said:


> A picture is worth a thousand words they say. I'm still not exactly sure what you mean. . . but I'm thinking maybe the DE (motor drive end bell) has a raised section? Anyways, 0.002" to 0.003" is considered a precision slide fit.


Yes thats right, motor drive end raised location flange, but the 0.002" to o.003" precision slide fit is the reassurance I wanted to hear.

Cheers


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## piotrsko (Dec 9, 2007)

I'd go a wee bit larger, say 5 to 10 thousandths: say 4.005". Back in the day.... .003 was considered a interference fit in aluminum requiring either a torch to warm up the female part or a large press to force it. Now since you say 4.005, the machinist is going to think you want really precision machining which will be expensive. I'd let him bore the adapter plate to 4.00 +/- .010 and hand hone myself it until it fit, unless the machinist went and did 4.010 in which case it is just about perfect. a cheap auto cylinder hone is ideal for this.

BTW .010 is an .005 error which is about .035 closer than what your dowel pins and bolts will position the plate to on the transmission


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## DavidDymaxion (Dec 1, 2008)

There are charts online that have recommended clearance for the hole size and type of material.


piotrsko said:


> I'd go a wee bit larger, say 5 to 10 thousandths: say 4.005". Back in the day.... .003 was considered a interference fit in aluminum requiring either a torch to warm up the female part or a large press to force it. Now since you say 4.005, the machinist is going to think you want really precision machining which will be expensive. I'd let him bore the adapter plate to 4.00 +/- .010 and hand hone myself it until it fit, unless the machinist went and did 4.010 in which case it is just about perfect. a cheap auto cylinder hone is ideal for this.
> 
> BTW .010 is an .005 error which is about .035 closer than what your dowel pins and bolts will position the plate to on the transmission


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## piotrsko (Dec 9, 2007)

yup there are such charts, BUT, if the OP shows up and asks for a 3 place accuracy hole, which ISN'T needed, the cost to machine goes up about double. BTW the charts don't account for temperature differentials, which on a 4" hole could be as large as .008. 

Leave the drive end sitting in the full sunshine while you fiddle with the adapter plate in the cold shade and it is going to take a bunch of banging to fit the adapter. How could I possibly know this?


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## TigerNut (Dec 18, 2009)

piotrsko said:


> yup there are such charts, BUT, if the OP shows up and asks for a 3 place accuracy hole, which ISN'T needed, the cost to machine goes up about double. BTW the charts don't account for temperature differentials, which on a 4" hole could be as large as .008.
> 
> Leave the drive end sitting in the full sunshine while you fiddle with the adapter plate in the cold shade and it is going to take a bunch of banging to fit the adapter. How could I possibly know this?


Lakewood specifies 0.005" as maximum runout:
http://www.priveye.com/images/lakewood.htm
And I'm pretty sure that factory bellhousings are typically machined to half that tolerance or better. Motor shaft to transmission input shaft alignment is pretty critical and if you were out by 0.040" then the trams input shaft or it's bearings would not last a year - if you were even able to put it together in the first place.


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## MikeB (Jan 2, 2012)

I worked on an motor to flywheel adapter last week. The poor customer ran a piece of junk aluminum adapter that fit at least .005" loose on the motor shaft and ran out at the flywheel locating surface over .015". Guess what ?? it vibrated so bad he decided to drive it to the repair shop. Wow total waste of money for that and the bell housing adapter took more than .090" to cleanup parallel. I really didn't want to give the junk back to him but some people are convinced if they want it to work bad enough it will.

The energy in the mass of the flywheel and clutch bent the motor shaft of his 9" motor over .002" in the 1.5" it stuck out from the bearing. I held the adapter by the flywheel locating step in fresh bored soft jaws in the lathe and skined the outside to clean it up and bored a tapered socket in the oversize 1.125" bore then made a matching taper sleeve for the motorshaft we held the thing together with the 5/16 - 18 thread in the motor shaft with a grade 8 bolt. The big end of the bushing bottomed out on the bearing and we helped to make sure the assembly was tight with a few taps of the hammer with a block of aluminum to protect the face of the adapter. The runout was about .002" which I attribute to the bent motor shaft. The bores I turned were dead nuts concentric because I turned the inside and outside in the same chucking and there was only .0002" as close as I could get to the bearing and .002" at the end of the adapter. 

The parallelism of the motor and transmision mounting faces has to be as close as possible. The centerlines should be no more than .005" tir for long bearing life. And the flywheel and clutch assembly should run as true as possible or the vibration load will take out the motor bearings.

Please use an indicator to check runout and don't waste money on junk that will just wreck the transmision and electric motor. This crap gives the whole DIY EV scene a bad rap.


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## piotrsko (Dec 9, 2007)

Can you calculate true position? Do you even know what it is?

If lakewood's stuff is so precise why do they sell bell housing locating kits made from adjustable eccentric dowel pins? Then include instructions on how to adjust them?

yup +.005 RUNOUT sucks. Both directions; but so does a .090 parallelism error. BTW did you check to see if the customers flywheel was an external balance? Hope you pulled the bellhousing to check for concentricity to the motor shaft before you slapped it back together.

Yup he has a crappy set-up and thank you for repairing it. Bet you didn't do it for free either.


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## TigerNut (Dec 18, 2009)

piotrsko said:


> Can you calculate true position? Do you even know what it is?
> 
> If lakewood's stuff is so precise why do they sell bell housing locating kits made from adjustable eccentric dowel pins? Then include instructions on how to adjust them?


I'm not a Lakewood spokesperson, but I think they fully recognize that their stamped steel scattershields don't hold a candle to the OEM aluminum or cast-iron bellhousings when it comes to concentricity between the dowel pin holes and the transmission input bearing register, and that's why they tell you that you must measure the alignment of the bellhousing and the crankshaft end, and fix it with eccentric dowel pins if necessary. They also tell you how to measure it (although the quality of that measurement depends greatly on how well you can set up the dial indicator on the flywheel). It doesn't matter whether or not that measurement is difficult to do; if you don't do it right and you mess up the alignment, then the bearings in either the motor or the transmission are not going to last, and you will probably have significant vibration.

The single fact that all vehicle OEMs use multiple snug-fitting dowel pins to fix the alignment of the bellhousing to the engine block should tell you that this is a fairly critical thing. It may be that you can still get half the bearing life if you're only off by 1/4 mm (0.010"), and that should be within the capabilities of a careful home DIY fabricator. But if you're out by 1 mm then I think you'd be lucky to get 1/10 of the expected service life out of the bearings, and less if you push any kind of significant power through the assembly with any regularity. That may still not matter if the normal life of the bearings is over 200,000 miles and you're good at R&R of the driveline; but just because repair is easy doesn't mean it's OK to settle for a borderline alignment of the motor and transmission.


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## z_power (Dec 17, 2011)

Thanks MikeB for pointing some good data on tolerances. I'm currently measuring/designing/testing adapter plate and would like to know your opinion on my testing method. Photo isn't of best quality but shows the idea; dial indicator is mounted to input shaft and I'm trying to locate it's axis relative to factory guide bushings. Do you think I can reach satisfying concentrity with 0.01 mm indicator? (yes, it's plastic template - first "iteration" cut with plotter  )


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## MikeB (Jan 2, 2012)

Z power, you are on the right track there. I saw a build thread of someone doing a Passat and I was real impressed with his setup you should try to find that and check it out. I am new to this posting thing so I don't know how to link it for you. I think the indicator you have is probably good enough. The trick the passat guy used I liked was a 2 piece adapter. With the bell housing side pinned and bolted to the bellhousing then adjust the motor side with the indicator just like what you are doing now. Then you can pin the 2 plates together and know for sure the alignment is good. That way neither piece has to be made perfect but if you are carefull you can end up really really close.
I think I might do it this way then I could put the combo plates in the cnc to probe the hole locations for making a one piece adapter with the cnc machine a lot easier that trying to fixture the damn transaxle in the machine to measure it. But you still need the 2 dowels in the bellhousing to be the right distance apart to start with so maybe the transaxle in the machine is unavoidable to make one with a program. One off stuff is different than cnc but not inferior, it just takes patients and sometimes a do-over or 2.
Mike


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## z_power (Dec 17, 2011)

I think you meant two build threads actually, Passat from etischer and Jetta from azdeltawye, both very impressive. My shop equipment really sucks but I've access to cheap laser cutter service so my approach is rather like "measure with whatever-i-have, make prototype from pvc or 1 mm sheetmetal, test fit, correct, repeat..." Here you can see what I did to find proper distance between bushings - holes are in pairs, every pair has slightly (0.1 mm) changed spacing. Only one pair fits so I know the distance is 251.2 mm. Fitment is really tight, you cannot lift this flat stock on one end only because it jams. Now I need to find coordinates of shaft centerline and I'll have three most important points caught


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## TTmartin (Feb 7, 2012)

Well,
I did not think there would be so many responses to this post, I was just looking for confirmation of my thoughts, been in engineering for 36 years and have aligned many motor drive couplings over the years in an industrial environment but this will be (my EV) so want it right.
I measured motor spigot accurately at 3.998" had adaptor bored to 4.000" that's 002" clearance, that for me was maximum clearance, the fit felt good, I clocked adaptor plate to gearbox shaft until it was ooo" spot on true, then doweled in two places, removed plate then refitted, clocked again with dowels fitted it was 005" out, re-adjusted without dowels until 000" again, added third dowel, removed and refitted adaptor plate with all 3 dowels all now spot on true.
Anyone that suggests within 005" to 010" is ok is accepting probable vibration and premature bearing failure, also expansion / contraction is not really an issue if both parts being fitted are of same material.
Thank you for all your input much appreciated.


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