# Lovejoy couplings



## jaspersk (Jun 26, 2008)

I have searched this topic and found that most folks say these are not tough enough. I saw that there were some folks with 72V systems using them successfully but also several folks that had torn them up. I am curious about this. I have a 144V system.

When I look at a motor spec for the ADC 9", I see peak torque that ranges from 80-225 ft-lbs for 400-900 amps at 120V (my Zilla is set to limit to 600A):
www.evparts.com/cms/picts/products/mt2120peakmotoroutput.PDF

The L255 spider (which I can find on eBay and Amazon) shows a rated torque of 195-519 ft-lbs depending on material. The coupler itself has a rated torque of 195 ft-lbs.

It sure seems like this should work if you believe the ratings. Is it possible that folks that had problems either weren't aligned properly or selected undersized components?


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## onegreenev (May 18, 2012)

Don't use them. Period. Not worth the hassle. They may seem simple but stay away. For low power systems they may be fine but for a good street vehicle, no. I would not even use one in a golf cart.


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## electro wrks (Mar 5, 2012)

What kind of setup are you using them in? Front wheel drive, front engine/rear wheel drive, etc.? The shafts connected by this type of coupler need to be well supported. The typical front engine/rear wheel drive setup does not have enough support of the transmission input shaft for just about any flex coupler to work.


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## jaspersk (Jun 26, 2008)

I have a 95 Jetta that is direct coupled today. Taper lock on the motor and custom machined part with old clutch spline welded into it. I am upgrading my transmission to a 4th generation (1999). It is a near perfect bolt up except, the input shaft is 3/4" longer. I can't use a spacer to move the motor out because there is no room on the back side. I have enough material in my existing coupler to cut it down but that means cutting a new taper. Machine shops large enough to understand how to do the taper don't want a job that small and small shops don't know how to do it. The person that original built it (Craig at EVsolutions) no longer has the equipment and got out of the ev business. At the end, a whole new coupler seems cheaper. Although Craig was kind enough to dig up the plans from his files and send them to me so maybe I should keep looking for a machine shop.

I could push the coupler onto the transmission shaft further if the splines went further. Plan B is I use a grinder to carefull take off 1 mm around the diameter so I can slip the cloupling on 3/4" further.

I also talked to a couple of other guys that could build a new coupler for reasonable cost. I am trying to get my hands on an old clutch in order to do that.

I sort of liked the Lovejoy idea but it is hard to ignore the advice on this forum. The past posts seem to also say "don't do it."

Steve


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## electro wrks (Mar 5, 2012)

So, just to clarify, the setup you have now works to your satisfaction? How long have you been running it? Has a problem with the original trans. required the trans. change? If so, there might be some alignment issues that need to be fixed before you bolt up a different trans. or modify the coupler.

Some pictures would help: the coupler, adapter plate(s), trans. input shaft,etc.


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## jaspersk (Jun 26, 2008)

You are asking a fair question. The setup has been working for over 20,000 miles so why change. I really just don't like the metal on metal coupling. It just doesn't seem like good engineering practice. Getting a custom built coupling puts a lot of faith in the machine shop to get it centered and balanced perfectly. I am confident that the adaptor plate I have centers the motor dead on but the idea of a soft coupling just seems better long term for the motor and the transmission. I also didn't like the idea of spending another $300-$400 for a new coupling. In theory, an off the shelf coupling designed as a coupling should be better.

My primary reason for replacing the transmission is that it is just a poor design with several known problems. For example, it often pops out of second gear. Secondly, the syncro on 3rd gear was starting to go out. I know that you could blame that on my direct coupled setup but I don't think that is the case since I rarely start out below third gear and it was the syncro below third that was going.

I am attaching a couple of pictures. The first is my existing coupler:









The second is a copy of my "new to me" transmission. You'll note that the shaft has already been cut down.









I have someone shipping me an old clutch so I can have a new coupling built. If I could find a Lovejoy that was an exact match for the transmission spline, I'd be attempted to try it despite the advice here but the truth is I was going to have to count on a shaft lock device which is admittedly much worse than any custom built coupler even though it is rated for the torque. 

Thanks for advice. I really need to spend more time on these forums.


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## electro wrks (Mar 5, 2012)

The trans. problems you describe probably comes from the syncros having to deal with the much larger mass of the motor's rotor compared to the original clutch disc, as you shift. 20,000 miles of syncro life might be all that can be expected, if you do a lot of shifting. What's been other peoples experience?

Your coupler looks like a good design. A picture with more of a side view, with the parts disassembled, along side your tape measure, would be more helpful. It's hard to beat the involute tooth type spline design (like yours) for power transmission capacity. Keep the teeth clean and lightly greased and the splines should last a very long time. You might consider adding a grease fitting to the coupler, accessed through the clutch lever or starter opening. Keep the openings covered to keep out water and dirt.


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## TheSGC (Nov 15, 2007)

In my first EV I tested a Lovejoy connection at 96 volts and it was torn up within 10 minutes. The Lovejoys cannot handle the startup torque of an electric motor, they are rated in Inch-lbs at high RPMs.

I now have a full clutch setup in my EV and I would not have had it any other way. I need a lot of fast shifting because of the traffic conditions and hills in my area and waiting 5+ seconds for the syncros to line up is not an option. It's a Stage 4 Clutch so it wont slip while accelerating and it's been working great.


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## jaspersk (Jun 26, 2008)

I really wanted to make a Lovejoy work but in the end I decided against it. I was absolutely convinced that Lovejoy made couplers that were adequately rated for the torque. However, when I finally found ones that were rated for the torque, I realized that their size was larger than would fit in the transmission and the added weight would have made shifting with syncros that much harder. Everyone here was correct. Just don't do it unless you have a low power system.

If case you are curious, what I did to solve the problem is a bit ugly but it worked. I ground down the input shaft just enough so I could slip on my existing coupler a little further. Thanks for the advice and guidance.


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## PZigouras (Jun 5, 2010)

I've seen a Lovejoy on an engine dyno hold back almost 600 horepower with a supercharged Chevy V8 on in. I think they can hold the load just fine; the problem is that people often select the wrong size coupler for their application.

I met a local EV owner who kept blowing his Lovejoy spider, and he didn't understand why. He removed the motor for me, and sure enough the coupler he was using was about 2-inches in diameter (not sure what the part number was).

The dyno I saw was using an L276 coupler, and it held just fine. And keep in mind that the L-series couplers are nowhere near as strong at the C-series (I think the C-series goes up to over 3000 ft/lbs or torque). Then, there is the H-series which handles more load than a solid 3-inch-thick steel shaft.

I feel that the correct size/type of coupler should have a decent lifespan in an EV. That said, the cost of the correct part will probably be more than simply aligning the motor up perfectly. Also, when using smaller couplers, keep in mind that the load always varies in an EV. In most motor/pump/winch applications, the load stays pretty much constant. This will probably lead to a shorter liftspan in an EV application vs. a pump application, for example.


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## electro wrks (Mar 5, 2012)

Your modification is one way of doing it. How much of the spline is engaged? If it's too little, the teeth will strip out. Let us know how it works out.


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