Lotus Europa Community
Lotus Europa Forums => Technical Articles and DIY tools and tips => Topic started by: Jmarkusic on Sunday,September 12, 2021, 12:52:03 PM
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Setting up CV joints on a Lotus Europa with a NG3 transaxle.
Though what we, we being the PO, Andy Harwood, and I, have done on this Europa has not been road tested, I thought it still might be of interest.
The NG3 transaxle was sourced from Banks and came with the correct transaxle side hubs. The CV joints were chosen based on that size, which is 100 MM. The CV joints are all VW parts as are the axle and the outer stub axles. Andy had purchased a couple of different sizes (flange Diameter) and a couple different stubs. The difference between the stubs is the length of the shaft and splines.
Another thing is that you need to add a suspension link to the rear suspension as the old universal half shafts are fixed length while the new CV jointed shafts float.
The first thing I did was make dummy shocks. These are nothing but simple adjustable steel bars that you can set the length to match the coil over working lengths. This makes it much easier to deal with the suspension and determine what mods are needed. To make them, simply take ¾ to 1 x 1/8 inch steel bars, slot one end, drill the other to fit the shock bolts and then use a bolt to connect them. I used two bars 11.5 inches long with a 3.25 inch long 5/16 slot for the front and two bars 9 inches long with a 3 inch long 5/16 slot. This gives you the basic suspension travel adjustments to check at full droop and full bump as well as setting your desired ride height. If you wish, you can make them a bit fancier and cut the slot a couple of inches longer so you can use two bolts, tacked in place, which would make it easier to move the suspension through its range.
Now that you have the ability to set the ride height and check suspension movement, you can design and fabricate the added suspension link. You do have to keep checking things like track and keep in mind how the suspension works on the rear. It is best if you can start with the stock suspension in place, move it through the travel and make as many measurements as you can. Then remove the old stuff and use those measurements as your reference. Obviously, you can come up with the needed dimensions in other ways if you get the car in pieces or it already has a difference transaxle installed.
The new link is pretty simple. The current common thinking on it is that is should be parallel and as close to the centerline of the new axle as possible. I take that to mean it needs to track with the axle such that its length and effect on the suspension should match that of the original fixed length axle. Its initial purpose is to keep the rear upright vertical as it naturally has a tendency to twist outboard. So I also think of it as adding an upper bracket to the existing upright. Andy had been following the current norm and had already made brackets that kept the new link pretty close to the axle. The outer brackets The inner bracket makes the mounting look simple but gets complicated due to clearance issues. Still, it works and should prove effective. The link itself should be sized at least .750 inch diameter and have a wall thickness of .156 inches. This gives you the ability to just thread the ID rather than make custom inserts for the threads. The heim ends are then ½ inch bore by ½ x 20NF thread and are heavy enough to do the job. You do have to drill the ends a touch bigger (.453 to .456”). If possible, use both right hand and left hand threads to make the link easily adjustable without removing one end or the other.
In determining which stub axles to use, I just did trial and error between the two. You need to include the new rear hubs as part of this trial fitting and insure that you do not end up with the axle binding and the nut and spacer interfering with the fitting of the wheels. In my case, Andy had purchased and modified a couple of different hubs. The outer spines are different between the stub axles so each has its own style of hub. The ones I believe work best are the ones that started life as drum/ hub units and Andy had turned them down to create a simple hub only. He did express some concern about strength but in reviewing the other hubs, others I have and doing a bit of research, I believe them to be a strong choice. The spacers I used are also VW parts, or at least from EMPI. You may have to turn a couple down to get the right thicknesses you need.
The parts, as far as I can tell are:
NG3 Transaxle CV custom (?) flanges from Banks. Use 100 MM CV joints
VW 100 MM CV joints and boots. Empi PN 87-9917-K ($49.95)
VW Axles: 16.25 inch IRS race axles Empi PN 16-2201 ($279.95)
VW 90 MMCV joints and boots Empi PN 87-9916-K ($48.95)
VW Type 1 and Type 3 stub axle SoCal Imports ($66.95)
VW Type I rear blank IRS brake Drum/ Hub SoCal Imports ($59.95)
No bolt pattern drilled, this is what Andy turned down to make the new hubs.
Empi Spacer/ Shim Kits PN – 16-2400 ($40.95)
VW rear axle Nuts EMPI PN 16-2425 ($8.95)
The brake discs used here are Acura Parts (1990's?) I'm not sure what they are off of.
The rear calipers on this car are Mazda (Miata?) parts with parking brake levers.
I left out the cost of the inner hubs for the NG3 from Banks as I didn't see a listed price and I don't know what Andy paid for them. The rest of the package, less the brake parts as well, looks like about $ 831.35. I used the mentioned sources for pricing but most of these parts are available from multiple sources. I suspect the inner hubs will add between $200.00 and $ 300.00 to that cost. That will also depend upon the choice of transaxle.
I believe you can be creative with the rear disc set up. There are many who have made those conversions. It seems like the only real difference will be the caliper mounting bracket and the size of the pilot turned into the new hub.
The axles have 10 MM + or – 1MM of play throughout the suspension travel. I used more (larger) spacers on the inside of the uprights to insure the stub axle did not interfere with the wheels. You also must insure proper engagement so it is a balance and I just made sure the stock wheels fit over the protruding stub and nut. The stub axles I got also had a splash shield that had to be removed to avoid interference with the upright.
The type 2 shorter stub axle can also be used, but I suspect it would require a different axle as it seems like I was bottoming the axle out when I tried that set up.
I did not provide any details on the new suspension link as this is actually what several others have done and that information seems readily available.
I can't add pictures at the moment but will later.
Please ask any questions you may think of as I'm sure I didn't think of everything here.
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Nice write up, jmarkusic!
I have a few questions (which will probably show my ignorance):
Do the areas where the bearings run on the VW stub axles line up with the placement of the bearings in the upright? If not, what did you do about that? Anything?
Which upright were you using? S2, TC, or TCS?
Which bearings did you use? Were they different from the bearings called out by Lotus?
Is the Empi spacer you listed for use between the bearings? I’m assuming no other spacers were required.
I’m anxious to see some pictures!
Thanks for the write up!
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Thank you very much for posting! I am will do something like this eventually and this is very enlightening. Are the CV much heavier than the original axles? I think the Elans get a 3lb penalty to go to CV
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Chuck, I suspect the weight difference is due to the need for the suspension link but I will weight both assemblies and post results here. I'm almost to the point to taking things apart again.
DBA,
The car still has the stock Lotus uprights.
The EMPI spacers take up the extra length the stub axles have. So, yes, the bearing area does line up as you adjust it so it does.
The uprights still have the custom aluminum bearing blanks that Andy made. To be honest, that's something I keep forgetting to check. Sometimes I just assume they will be stock bearings but then why the custom bearing blanks? Which then I assume to be simply because it is easier than installing the actual bearings with tighter clearances. But I can also assume they were made due to the bearings being a different size. I do know that the stock spacer in between the bearings is the stock one. But that too will depend upon what the final bearings end up being. I will add that info as soon as I figure it out. I could also just ask Andy.....
I can add pictures from the office/ shop. I'll try to get them up tonight.
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Here the pictures
The first one is all the pieces described above laid out. Then assembled. I included a picture of just the hub and stub axle. Last is the new par real link attachment and the solid aluminum dummy bearings Andy made.
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Thanks for the pictures, Jmarkusic!
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Nice!
Do you have a pic of the VW stub axle next to a stock one for a comparison?
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I’m out of town again. I’ll see if I can pull out the stock parts when I return and get those pictures.
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Kmarkusic,
Do you have any drawings of the steel plate that mounts the inner pivot of the upper link - the plate you have bolted to the bell housing?
Tom
74 TCS - 4605R
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I don’t yet. Andy did those but I’ll draw them when it comes back apart to have everything finalized.
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Jmarkusic - any luck in getting a diagram of the inner pivot attachment plate?
Tom
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Sorry, I've been busy. Instead of retiring we of course bought another business and expanded the others. We really need to go read the definition of retirement. Basically, I haven't had much time for the Europa.
I have created the rear mounting for the alternator and AC compressor and today I am working on the clutch slave cylinder issues. last will be the water plumbing. At that point, it will be time to take the thing apart and finalize all the parts, remake the ones pieced together to make them work so all parts at least appear professional and do all the painting. I will be able to draw up various parts if anyone is still interested.
I'll try to get pictures of what has been slowly, accomplished.
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It's been a while, and I fully understand the being busier now you're 'retired', but how's this project going?
I'm in the middle of converting a 'Federal' S2 into an EV. I was intending to install a motor using the Renault transaxle but have fortuitously discovered a better way with a dual transverse motor setup that uses a reduction box with CV jointed axles. Eliminating the Renault box reduces the powertrain weight creating more potential battery capacity/range but will require fabricating new radius arms and pickup points. I want to retain the Lotus drum brake installation as I don't need more braking when I've got powerful energy recovery braking from the motors, so will need to modify/fabricate suitable stub axles to retain the Lotus aluminium uprights.
Does anyone have a link to similar rear CV joint instalations?
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I'm completing (at least I HOPE I'm completing!!) a VW conversion and I'll be posting a report on my experiences later. Lotus 47 has a thread on his twin link setup including discussions about a CV joint conversion (https://www.lotuseuropa.org/LotusForum/index.php?topic=1724.msg15757#msg15757). I emailed him about what he had done and he ended up using Alfa Romeo parts with a BMW stub axle and hub. Unfortunately he couldn't remember which BMW the stub axles and hubs came from.
What I was unable to find in my investigation was how much torque different CV joints can be expected to handle. I think it's likely that regardless of your twin link design (unless you make specific accommodations for the outer CV joint) that you will be constrained to 90mm (78mm bolt circle) outer CV joints. Generally those are used low power sedans. Pegasus sells 90mm CV joints for high performance CV joints for use in Sports 2000 cars (https://www.pegasusautoracing.com/productselection.asp?Product=1471). They are however about four times the price of similar sized VW units but they are stronger. FYI: Sports 2000 cars use stock but race prepared 2.0 liter Pinto engines which I suspect generate 140hp or so. The cars were much lighter than a Europa, of course. The CV joints might end up being a bit of a weak point depending on the type of driving you do. It should be easier to accommodate stronger 100mm inner CV joints.
One of the complications you'll find is fabricating an inner drive flange for the inner CV joint. Drive flanges are available from EMPI and can probably be found at a junk yard or you can make your own if you have a lathe.
I will be using VW stub axles and half shafts from EMPI. Used stub axles can be found in junk yards but the EMPI units are a few thou smaller in diameter. This allows you to take the drive line out without taking the whole rear suspension apart.
As of now, I'm not quite sure how to measure the required half shaft length. I'll be including that in my report when I post it but I'm probably over thinking it.
I hope that gives you something to think about at least.
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Thanks you the insights. First, I'm lucky that the dual electric motors I'm using come with a 6:1 reduction drive built between the two motors. This provides the correct out put shaft rpm to suit the OEM wheel sizes. My source included the two driveshafts, with the inner CV joints to suit the transmission. The challenge comes with the outer CV jointed stub axles. They are too long to suit the S2 suspension dimensions. The CV jointed shafts were assembled by EMPI in California for the OEM that used these dual motor drives. Therefore I assumed, foolhardy I know, that I will be able to slide the original combined CV stub axles off and install what I'd hoped would be a set of VW stub axles that would leave me needing to machine down VW hubs to suit the Lotus drums. To test this out I ordered a stub axle of the sort specified in a CV conversion entry on here and find it is far too long. I'll try EMPI next week to see if they can suggest an alternative.
Your comment about being limited to 90 mm for the outer CV is interesting. As I will have no Renault transaxle to hang the necessary upper radius arms from I have ordered the Twinlink product sold by Europa Engineering(EE) in Britain. It will fit over the electric motor transmission and provide both inner and outer radius arm locations. It may serve, with some minor extensions welded on, for the inner lower radius arm pivots as well. When you mentioned CV clearance with the twinlink, were you specifically relating to the EE product?
Like you, I'll need to determine the shaft length as well. I plan to install the EE twinlink setup and add the inner lower radius arm pivot points I removed from the transaxle in the same position relative to the transmission output shaft. Then, with the rear springs removed, position the rear hub at the correct 'unloaded' ride height, take some careful measurements before ordering suitable length shafts. The ones that came with the motors look to be close so I may get lucky. But probably not. :(
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i have an early version of Richard's twin link suspension so I can't comment on his later version. If the upper link is mounted high enough on the upright, you might be able to get a bigger CV joint there but most of the twin links I've seen don't allow it. Replacing a CV joint isn't that big of a deal so if it has a short life, it's less of an inconvenience than say replacing a u-joint.
The EMPI Type 1 stub axles are longer than the stock stub axles by about an inch, maybe less. I would think that most wheels would be able to accommodate that. Using the Type 1 stub axle will require the use of the 94mm (I may have called them 90mm earlier) CV joints.
The problem I'm having to deal with now is a hub. Jmarkusic suggested machining a blank drum (https://socalautoparts.com/product/brake-drum-rear-blank-pattern/). My machinist was concerned about a cast hub being brittle and didn't want to risk it. I would note that the stock hubs are cast (I don't know if they are iron or steel). Looking at the stock hubs, they are beefier around the splines so I'm a little concerned about the torque they'll handle. I plan on calling SoCal Auto Parts to ask them how they are used. and I'll report back.
Another option is these centers (https://dansperformanceparts.com/jamar-db-center-6-bolt-splined-long-axle/). They come in 5 and 6 bolt flavors. They are actually centers that are meant to be bolted on a larger, more complicated hub. The idea would be to machine a plate to be bolted onto those centers to accept wheel studs. Because of the OD of the center (about 4.2", they would have to be machined to make room for the wheel studs. If you designed the plate well, I believe this would be bullet proof but it's expensive - not just the price of the centers but also the steel round to machine the plate.
There are other options like rear brake discs but I'm not sure they are any better options than the blank brake drum. Unless you make your own hub (which would require machining your own splines!), there aren't any other options for a hub that I've seen.
Measuring axle length
I asked the guy (a guy?) at Blind Chicken Racing (their website was referenced by Jmarkusic: http://blindchickenracing.com/How_to/CVJoints_Axles/axles_and_cvs.htm) about that and here is our conversation:
me: First, is the listed length of the axle the distance between the circlip grooves? or the total length of the axle?
Then, how should I measure the length of axle I'll need? I assume I would measure between the outside face of the inner race of the outer joint and the inside face of the inner race of the inner joint. Should I position the inner race in any particular way (eg. each inner race in the center of the joint or one inner race at the outside and on at the inside of the joint)? Since this is for a street car, I won't need to accommodate a lot of plunge.
mark: Axles are measured in total length. Most aftermarket axles have extended splines so they can be trimmed to fit the application.
To measure axle length, assemble your axles with stubs and put your trans in place with flanges installed. With the stub and flange horizontal to each other measure from the bottom of the flange cup to the bottom of the stub cup and subtract 1/4” to 3/8” depending on how much flex you get with your trailing arm. You could go a bit more in your case as travel is not important.
me: From your description, it appears you are saying that the "faces" of the CV housing are the important distances. Because I'm not using a VW transaxle, I have tranny drive flanges that are fabricated and as it turns out, the "cup" of the flange is much shallower than the stub axle flange (I'm using EMPI stub axles). I've attached a pictures. Should I deduct, say 0.2", from the measurement to mimic a deeper cup dimension?
mark: The old school way of checking for axle length is getting a wooden dowel and trimming it until you have ¼” of clearance for the axle.
I sent Mark the photo of my drive flange depth to give him an idea of what I'm dealing with. I've attached other pictures of it in case it would help you fabricate your own (Thank you SwiftDB4). If I were to make a change to them, I would make a taller "lip" around the circumference to better support the CV joint. I'm not sure if I understood Mark's answer so I included the entire conversation.
I also asked him about the capacity of the CV joints. Here's what he said:
With bug CV’s (94mm) you can probably do 100hp as long as you don’t try and pop the clutch. A four cylinder engine is more forgiving as it has less rotating mass. You put a V6 in there you will probably blow the CV’s or axles (or both) if you are on it. If you can stuff 944 CV’s in there it will take a lot more power.
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BDA,
There are chromoly hubs on EBay .... https://www.ebay.com/itm/126125151369
Not sure this is what you are looking for but they may have it...
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Yeah, those are the "centers" I mentioned and linked to at dansperformanceparts.com but at a slightly better price.
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I got an email from SwiftDB4 and he pointed me to this (https://www.taylor-race.com/products/94mm-standard-lobro-33-splined-cv-joint). Thanks Swift! It didn't occur to me that "FT" in the "Common applications" refers to Hewland FT200 transaxles used in 240 hp Formula Atlantic cars which should handle most any engine someone is likely to put in a Europa (except kram350kram) so if I have to replace a CV joint, I'll replace it with one of those. I would advise them for anyone starting down this road.
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I just talked with a guy at SoCal Auto Parts that sells the blank rear brake drums. He wasn't very specific or technical with me (I may have expected more than I should have) but he did say that they are used in high performance applications - including drag racing and dune buggies. I said I was most concerned with stress in cornering and he was dismissive of my concerns. I figure the beating that is most similar to the beating we might give our cars is a dune buggy (think of a buggy taking a hard turn in deep sand).
I've done some measurements but I can only compare them to the hubs I have which were made by Richard at Banks (they are very stout steel pieces) and pictures of the stock hubs (which are cast (steel? iron? - I'm guessing iron). They seem like they should be stout enough. I would also mention that while the Jensen Competition Manual suggests replacing the stub axles regularly, there is no mention of any worry about the hubs, which if I remember the production car rules from that period correctly, were required to be stock.
In any case, I also asked a buddy of mine who was one of Shell Oil Company's rotating machinery experts what he thought. I haven't heard back yet but will post his comments when I do.
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Unfortunately he couldn't remember which BMW the stub axles and hubs came from.
If I recall correctly, Richard used BMW 2002ti or 2000 axles.
I have his installation notes around here somewhere.
The problem I'm having to deal with now is a hub. Jmarkusic suggested machining a blank drum (https://socalautoparts.com/product/brake-drum-rear-blank-pattern/). My machinist was concerned about a cast hub being brittle and didn't want to risk it. I would note that the stock hubs are cast (I don't know if they are iron or steel). Looking at the stock hubs, they are beefier around the splines so I'm a little concerned about the torque they'll handle. I plan on calling SoCal Auto Parts to ask them how they are used. and I'll report back.
Agreed, I'd be concerned about machining the outer drum section from the hub. I expect the drums would be cast iron. I'd say wheel stud support is reliant on that drum being present
The stock hubs are a steel forging.
There are quite a few flavours of VW CV joints (link below) and be mindful that BMW spec. CV's sometimes call for 8mm bolts and some use 10mm bolts.
https://www.jbugs.com/VW-Tech-Article-CV-Joint-Specs.html
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If you find out which BMW stub axles Richard used, please post it. It won't help me but it could help someone else. The nice thing about using BMW parts is that they have a normal hub which Richard said he modified for his conversion.
Forged steel makes a lot more sense than cast! Thanks for the correction. That pretty much solidifies my decision to use the hub centers I mentioned (https://dansperformanceparts.com/jamar-db-center-6-bolt-splined-long-axle/) with a 1/2 plate turned to fit and take wheel studs.
Thanks for the CV joint information! I looked back at what Richard said in his email to me about his conversion. He used Alfa Romeo (Spica) CV joints. He didn't remember what size but he was sure it was less than 100mm. He drove his car hard (as you might expect :) ) for 20 years without issues.
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G'day, BDA,
Found it . . . but lo and behold, my computer search also brought up instances on the interwebs. It looks like Richard had already uploaded the procedure to lotus-europa.com - (link below)
http://www.lotus-europa.com/manuals/misc/suspension/BMW%20STUB%20AXLE%20AUG%202005.html
Re the hub, are these suitable?
https://www.heritagepartscentre.com/au/311501581-rear-wheel-hub-4-130-pcd-left-or-right.html
Looking at Jmarkusic's hubs, it seems like they may be similar. It also looks like his are cast, so I dunno but they also appear to be decently thick. In my mind, a brake drum wouldn't be all that thick.
Jmarkusic mentions spline differences, too. Are Type 1 and Type 3 different in the spline department? :confused:
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Thanks for the links to Richard's BMW stub axle conversion. I had seen that long ago but at the time it was just a curiosity. I also don't think I appreciated what he was describing. That will make a good fall back if I can't get my hubs to work. I'm a bit worried that my center will be hardened and will have to be ground rather than just machined. I really hope to be able to use the EMPI stub axles since that would allow me to take the drive train apart without a press or taking the radius arms off.
I got one of those hubs. My machinist didn't like it because the rib that reinforces the places where the wheel bolts are would have to be cut down more than he'd like because the wheel studs are on a smaller bolt circle. I had assumed they were cast but I have a call into the place I bought mine to see if they can give me some information. It turns out there are two other similar hubs but I'm not sure that they are any better. They still have more of the one I have but the others are out of stock at the moment.
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I have found the perfect hubs for the VW conversion! A company called ISP West sells chrome moly hubs with thick sections that take the place of the Type 3 rear hubs and are designed for high HP applications. (https://vwispwest.com/rear-hub-4-x-130mm-ga-501581/). Before I took the rear suspension apart I measured the distance from the face of the hub to the brake caliper mount (I have rear discs) and using a couple of spacers and the type 3 hub I have, I'm within about 0.020" so those hubs would be perfect! Unfortunately, they don't have any in stock and they're looking for a machine shop to make more. They hope to have some "sooner rather than later." We'll see how long "sooner" is.
They are really pretty - hard anodized and with two sets of wheel stud holes, for VW bolt circle, of course. It occurs to me that since if I were to order a pair before any are made, they might be willing to make them without the anodizing and either blank or holes for the Europa bolt circle.
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Hmmmmm …. hard anodizing is used on aluminum, magnesium etc. not 4130 steel, are you sure it’s not a black oxide finish?
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Yeah, I thought they were confused. I’ve known anodizing was for aluminum but thought I had heard of a reference to anodizing other materials. Maybe I should have said I was quoting them.
But now you have me curious. This is what Wikipedia says about anodizing:
Electrolytic passivation process used to increase the thickness of the natural oxide layer on the surface of metal parts
So maybe you can anodize steel, though it sounds more like bluing when we’re talking about steel, but “hard anodizing?” Should we expect the anodizing to be harder than steel? That seems unlikely…
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Yeah, here's another one (link below) of their similar bespoke parts which they describe as:
Finish: Black Zinc
https://vwispwest.com/rear-hub-5-x-130mm-ga-501581p/
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That’s probably accurate. Who knows why he didn’t write the description for the other one!