Three broken spiders later.....

[aeronca65t]

Yep, running double-bearing hubs (from Frontline).

I've been pretty good about cleaning and assembling the rear seals, but I have to agree....it's an art! I've tried with and without the gasket.

I agree that the standard diff is probably OK stengthwise......my guess is that many of them have just run low on oil at some point.

I've noticed a lot of the Spridget axle housings are slightly bent and I've considered having them straightened, but again, more $$$. Right now I have my straightest housing on the car, but I wouldn't say it's perfect.

By the way, I seem to recall that you guys added Ford outer bearing to Spridget axles at some point (or did I dream that up?).

Anyway, the Datsun rear axle seems like such an easy, cheap, bulletproof swap (if it works) so I guess we'll see. Axle ratio is 4:1 so close enough.
I'm not adding it for any performance advantage, so I don't think the tech-inspection guys will care (at least not in vintage).

 

[Guest]

I'll be darned if I will pay a shop to properly set up a new pinion and crownwheel based upon a cracked housing.

How 'bout buy a used complete center chunk, drop it in and drive the car?

If you're not careful, you can OCD the fun right outta these things. I was REALLY bad about that. I actually now enjoy the fact my motor isn't "right" but runs like a top.

 

[Westfield_XI]

Nial, the rear of Spridget, hub wise on a race is almost a art from to seal up, but first on race car, you must go for DB hubs, has your car got them, if not that's probably contributing to your problems. I use to drill my race axle in 4 places, as for hub retention, the drill and tap 4 palces on the DB hubs as well, use no paper gasket, a new o ring and Permatex Ultimate Balck, I would do this n a drained rear end, and I would even flood the bearings with spray can brake clean to get them from oozing rear end dope in the area I was sealing and let it all sit up for 24 hours to seal. With this routune I got where I hardly ever had a hub/axle leak.

As for the cracks rear diff cases, I cant really comment there, but I can say that I raced a Spridgets (4 different Spridgets in total) in well over 100 SCCA races, and told you all here of the only diff failure I had in all those years, and it was my fault, and lets safely say, we talking about well over a dozen different diffs used on these 4 different cars, not counting all the buudy and customer cars I worked with as well. My commnets on the PG was it totally failed under race conditions, I was given tougher springs to try, and they failed as well, the well known vendor that sold me this unit, now no longer offers the PG anymore, I'm not alone, several other experienced exactly what I did, did the PG break your rear end, I don't know, I just know as LSD, they don't work. AS for your expereicne with cracked cases, Ill trust you in your expereience to read cracks, can't dispute that one way or the other, its just in almost 3 decades of doing this, I never seen anyone have this much trouble with these diffs. SO do I think it is something wierd, based on decades of experience, yep, you betcha I do.

No one is "having this much trouble with diffs" these diffs would probably have run quietly for years, but were crack checked because I do not put broken parts on my car. Period. I had the crankshaft magnafluxed and I would have had the rods checked if I reused the OEM parts, why wouldn't I have these parts checked too?

Hap in your decades of experience how many times have you or your customers used magneflux to check these specific parts? The cracks are not visible to the eye, so unless you use proper NDI how would you know if your units have not been cracked too? If you have been magnafluxing these all along over the years, then I yield to your demonstrated factual knowledge. But if you have not been checking them how would you know? How would anyone know?

What's seems weird to me is that people will spends thousands of dollars on performance parts and services for their engine, more thousands on bodywork and paint and then turn around and just bolt in any old used diff and hope it works for a while. And if it doesn't, just throw in another junkyard unit and drive on...... It just makes no sense to me at all to spend all that money on the rest of the car and then cheap out and lower standards to put unknown junkyard parts in the axle. Sorry, but I just don't get it.

 

[Westfield_XI]

I'll be darned if I will pay a shop to properly set up a new pinion and crownwheel based upon a cracked housing.

How 'bout buy a used complete center chunk, drop it in and drive the car?

If you're not careful, you can OCD the fun right outta these things. I was REALLY bad about that. I actually now enjoy the fact my motor isn't "right" but runs like a top.

I have been working since 2007 on building this car, I am not going to lower my standards in the last two months just because it would be easier. Besides, your suggestion is the route I took to get here. I just dropped in a used gearset of the correct ratio to avoid the expense of a rebuild and it howled. This required the entire 4link axle to be removed from the car to get the diff out which required the disassembly of the entire rear of my car, removing bodywork, inner fenders, luggage compartment and brake lines. And of course, the rear brakes have to be removed and the axle pulled. This is not something I intend doing again in 6 months or a year.

 

[Trevor Jessie]

Let's suppose you find one that is not cracked. Given how many you have found cracked ... it seems likely that it too may develop similar cracks. Maybe you should consider going with another type of diff/axle?

 

[Guest]

[ why wouldn't I have these parts checked too?

Hap in your decades of experience how many times have you or your customers used magneflux to check these specific parts? . But if you have not been checking them how would you know? How would anyone know?


It just makes no sense to me at all to spend all that money on the rest of the car and then cheap out and lower standards to put unknown junkyard parts in the axle. Sorry, but I just don't get it.

It was "checked" every time it went out on the track. I understand what you're saying, it just doesn't apply here. Rods and a crank endure much more forces than a diff.


It seems you have stumbled on a "weakness" of Spridget diffs. Apparently they all crack. Sometimes things like this happens. IIRC, it was Audi that had a tolerance for cracks on a diesel head. If this is true, and they all crack, then Hap have proven it doesn't matter. 1500's wear thrust washers badly but they still run. These cracks didn't cause the howl.

As far as cost, here are your two options: A. put in a used diff that apparently they all crack; B. spend the $$$ and get a brand new carrier. You've already spent thousands, what's another grand?!

How about this, if the 3.90 I just got looks good, I'll install a new seal and put it in my car. If it sounds good, I'll then drive ~100 miles to BMC restorations. I'll throw Peter in the car and take him for a ride. If he give the thumbs up, I'll then pull it out and sell it to you. How's that sound?

 

[Guest]

It just makes no sense to me at all to spend all that money on the rest of the car and then cheap out and lower standards to put unknown junkyard parts in the axle. Sorry, but I just don't get it.

As a guy who used to comb the fringe on his oriental rugs and send oil pumps back for the slightest of marks, I truly understand your desire for perfection.


The point is, how enjoyable is it just sitting there broke in the garage? :confuse:

Yeah, I know, it won't be as "good" as it can be, but it'll be good enough to enjoy. :thumbsup:

My car may need paint, a proper rebuild and some better tires, but I'll take a fuctional but cosmeticaly challenged Midget over a perfect but broke Lotus replica anyday.

Mine may not be the prettiest girl at the dance, but at least I get to dance. :banana:

Part of ownership of these things is the continued improvents and repairs. These things were marginal when new. Factor in a that it's all in a replica and man, have you got some wrenching to do!

Sometimes in life things are as good as they're ever gonna be. (sometimes just for the short term.) The trick is knowing when to just accept it and move on. Trust me, you can drive yourself nuts with things like this.

Yeah, it's cracked, but if it holds up then all is well. Apparently this is normal. I do understand it's a pain to keep changing them out. :madder:

If you're in doubt if what you have will hold up, send 'em to Hap, Nial or me and we'll "test" them for you. :hammer: :wink:

 

[Westfield_XI]

Let's suppose you find one that is not cracked. Given how many you have found cracked ... it seems likely that it too may develop similar cracks. Maybe you should consider going with another type of diff/axle?

It appears to me and to my axle guy that the reason they crack is due to stress risers focusing stress in an as cast part. We intend to blend and smooth the radius and edges where all the cracks appear to try to prevent this. Will this work? Who knows? The principle is sound and is similar to polishing a rod. At least I will be starting with parts known to be serviceable.

 

[Westfield_XI]

It just makes no sense to me at all to spend all that money on the rest of the car and then cheap out and lower standards to put unknown junkyard parts in the axle. Sorry, but I just don't get it.

As a guy who used to comb the fringe on his oriental rugs and send oil pumps back for the slightest of marks, I truly understand your desire for perfection.


The point is, how enjoyable is it just sitting there broke in the garage? :confuse:

Yeah, I know, it won't be as "good" as it can be, but it'll be good enough to enjoy. :thumbsup:

My car may need paint, a proper rebuild and some better tires, but I'll take a fuctional but cosmeticaly challenged Midget over a perfect but broke Lotus replica anyday.

Mine may not be the prettiest girl at the dance, but at least I get to dance. :banana:

Part of ownership of these things is the continued improvents and repairs. These things were marginal when new. Factor in a that it's all in a replica and man, have you got some wrenching to do!

Sometimes in life things are as good as they're ever gonna be. (sometimes just for the short term.) The trick is knowing when to just accept it and move on. Trust me, you can drive yourself nuts with things like this.

Yeah, it's cracked, but if it holds up then all is well. Apparently this is normal. I do understand it's a pain to keep changing them out. :madder:

If you're in doubt if what you have will hold up, send 'em to Hap, Nial or me and we'll "test" them for you. :hammer: :wink:

An interesting philosophical difference. You feel that I am being compulsive and picking nits, I feel that you are impatient and too willing to settle for good enough. It is a good thing we don't own the same car.

Actually it is quite enjoyable to have a chance to pull apart and detail some of the major subassemblies while I am awaiting the resolution of this situation. So far in the 10 or 12 days I have been working on this I have finished up 6 or 7 little tasks on the car. Things like moving the throttle pedal over an inch to help with heel and toeing, replacing the oilpan gasket, welding studs on my headers for the heat shield and building an alloy firewall to replace the warped Fiberglas on the scuttle. If I have time I will also fiberglass some foam stiffeners into the forward bodyshell and add some ducting to reinforce the tilt mounts and assist with cooling. It is not like the time cannot be well spent and it is not like these tasks did not need doing.

 

[Guest]

[ It is a good thing we don't own the same car.

:lol:

Not exactly. My point is it never ends. Actually I'm being patient. I use to be really impatient. Now if there is a problem that I know I can't do anything about at the time, I resolve myself to deal with it later. I don't do without just because.

I can't build the motor I want now, do I let the car sit till I can? What about paint? It looks like it was painted with a hammer. I can't do anything about it. That doesn't mean I shouldn't enjoy it now. It doesn't mean I'm impatient either. (Gotta remeber, I still haven't installed my 3.55's yet. Now that I have an extra diff I can)

Take Nial for example. He frags the 1500 in his racecar and installs a bone stock 948. Will he be able to run up front? Will he be able to win? It doesn't matter. He is enjoying himself and the car. He does it just for the love of it. What some might consider imapatience I say is dedication.

Nit picky is a slippery slope if you're not careful. Like I said, how many men you know who brushed floor rug fringe? My place was spotless, did it really matter if my rug fringe wasn't at a 90 degree angle?

This is what I meant about vanity. Not that people are trying to look good, but rather struggle for perfection in an imperfect world. Like when I used to clean bugs off my windshield every time I stopped. Sometimes I would stop just because of bugs. I soon discovered all of my efforts were in vain.



I know what it's like getting bad parts time after time. I know how fustating that can be. All I'm saying is the possiblilty seems to exsist that all used diffs may have this condition. The possibilty may also exsist that it doesn't make a difference.

I do hope you'll be able to enjoy your car soon. I enjoyed mine tonight and will again tomorrow.

 

[Westfield_XI]

I think I see the difference in our approaches: when I placed my order for my kit back in 2006, I did it with the clear understanding that once I was done playing with it and I had as much fun as I could stand, I would have a car to drive at the end. In other words, the journey and not the destination was what compelled me to start this project. I enjoy building things just as much as I enjoy using things.

Back in 88 I bought a used Laverda motorcycle, rode it a few thousand miles and took it apart right down to sandblasting the frame. I then assembled it the way it should have been, in the color I wanted and with the quality I expected. I did everything except the powdercoating myself including painting and machining. This took the better part of 18 months, but after it was done I rode it for thousands of miles all over the small highways of the west for decades. I still own it and I still ride it.

I expect that things with this car will go like they did with the Laverda, I will enjoy the building and learning new skills and practicing old ones. And then I will put it in the garage and use it for what it was intended as often as I can. Much like the .45's, the broomhandle Mauser and the FAL that I built after the bike: I built them and tuned them myself and I still take them to the range and put them to use. Which gives more satisfaction, building or using (driving)? Well, the build only happens once, the using(driving) goes on for years, why not take the time to get it right the first time?

 

[nomad]

I think you probably hit the nail on the head. The cracks are probalby caused by stress riser's designed into the original casting. Probably most of the ones that are currently running have the cracks and no one has gone looking for them. Apparently they don't cause much trouble but if you want to go to the enth degree, go for it!! Its your car (and a d**n fine one at that!!!)


Kurt.

 

[racingenglishcars]

This is a really cool thread

Cracks are things that show up in all types of parts regardless if they were cast, forged welded or whatever.

The front spindle tends to crack on these cars too. In the old days people would crack test a whole lot of them to find non-cracked pieces for their race cars. Turned out about 1 in ten weren't cracked. I suspect a similar ratio for diff carriers.

Blending has been the standard method for repairing leading edge damage on propeller and turbine blades for years. It works, as long as the root of the damage is removed.

In your case this would mean polishing through the root of the crack. If the cracks are long, the part may not serviceable except as a standard used component. But if they are short, the durability of the part would be increased many times by blending.

Welding "can" cover cracks but creates residual internal stresses. These will be removed by normalizing, but then the entire carrier would need re-machining. Poor quality welding will allow internal defects, undetectable except by eddy-current testing. You would probably be better off without welding.

All ferrous parts will fail eventually if periodically stressed to more than 30% of the elastic limit. Though at 30% it will take a very long time. Stressed to more than 60% the part will fail a thousand times faster.

The choice is therefore:
Keep stresses below 30%;
Use a design where the stress is never too high for the durability needed;
or accept that the part will fail - eventually.

Cracks create stress concentrations - period. Therefore blending cracks reduced the concentrations and lowers the maximum stress making the part more durable.

BTW, Over-dimensioned parts don't have high stresses, but they weigh a ton.

 

[Guest]

So what you are saying is grind it out, right?

 

[Westfield_XI]

Grind it out, blend and smooth the entire area and then polish as much as possible. Check under mangaflux and repeat until crack is gone.