Tired of broken & twisted CVDs?

[redshift]

Last Saturday I went to a local sandpit, was hoping to shred a bit and get some video. I put it in first gear, started rolling and I saw the left rear wheel stop.... what the?

I was into the run all of 30 seconds.

So come to find out I wedged a rock between the inner wheel and the knuckle and thoroughly mangled my CVD.

Let me just say my MIPs have about a million miles on them and the basic design is great. So this is not an attempt to bash MIP. In fact my truck would never have moved without them, it's a 3906 which came with the spindly original drives that twisted with even stock power.

My CVDs have been straightened countless times, just with a hammer and a flat hard surface, but it has gotten tiresome. And with this last episode I had a simple choice- buy new ones or try to come up with something else.

Problem with that is not the cost, but that the original Emaxx CVDs were about .1" too short because my A arm pivots are out that much further than the drive cups. So all this time I have been using the ragged edge of engagement with the drive cups. Ok most of the time, except when something overstresses the A arms and the dogbone falls out of the cup.

Then when the arm straightens out, the bone usually doesn't fall back in and that resulted in my CVDs being severely bent many times. And before I had aluminum knuckles, this would often be enough force to pop a ball out of the knuckle- and that is just annoying

So first, the carnage hehehe

[squeeforever]

Just get 3905 knuckles, turnbuckles and Summit sliders. Should hold up to anything you throw at em.

[redshift]

I did ya one better Squee

Gotta love turning scrap into very useful goodies

I found some 5/8" bolt stock that had the heads cut off, so was unsure of the grade before drilling into it. It did machine a bit gnarly but I managed to get it to work. I then used .120" gage pin, .0005 oversized for the dogbone end. And drilled 8 holes instead of 2 into the CVD end. I figured I might as well make some extra holes to use once one pair wears out.

I did a fairly hard trial run with them tonight, and I am very pleased

[redshift]

The issue with the old CVDs being too short was easily fixed, I just added about 1/8" to the hole centers. I made the dogbone pin a bit longer too. The inside bore is full length, and I turned the wall down to about .045, so they are lighter than they look. And I am pretty sure it is grade 8 material, which should give excellent wear characteristics. I plan to paint them flat black and heatshrink over the paint, they look nice but I'm sure rust is nobody's idea of bling

[lincpimp]

Nice, you should make some for me (and maybe other people too).

[redshift]

I'd be willing to do it on a limited basis, as I only have access to conventional equipment. These took over 3 hours each to make, so I don't stand to profit from it.... ie, the ball ends were filed to fit....but it certainly isn't all about profit in this hobby I'm well aware.

The other thing is, I can't even certify material!

Without getting too specific, prices would be in the three digit neighborhood (pair) but pm me about that if you are interested

[lutach]

Originally Posted by redshift

I did ya one better Squee

Gotta love turning scrap into very useful goodies

I found some 5/8" bolt stock that had the heads cut off, so was unsure of the grade before drilling into it. It did machine a bit gnarly but I managed to get it to work. I then used .120" gage pin, .0005 oversized for the dogbone end. And drilled 8 holes instead of 2 into the CVD end. I figured I might as well make some extra holes to use once one pair wears out.

I did a fairly hard trial run with them tonight, and I am very pleased

Very nice. How much do they weigh over the other unit?

[redshift]

Thanks lutach. I have them installed at the moment, but I think they are roughly twice the weight of the bones.

I considered minimum wall thickness to be around .030, so I left some headroom going with .045, partly because I was concerned about distortion and "ring"- chatter, because you can only go so thin without having internal support when turning, and the ceramic insert I used was not liking it much. And yes it was a new insert.

However the narrowest point of the 'bottleneck' on mine is .030 thicker than the .170 diameter of the MIP bones, so I beefed it where it made sense to. I could have lost a few more grams drilling, but was cautious about drilling through said bottleneck. The heavier end is the inner end now as opposed to the outer cup on the old ones. Unsprung weight will be almost identical, not that it's a huge concern for me..... "weight is no object"

[Bondonutz]

Very Very Nice Work J. !!!
Since it ben 5+ months I can only assume they're still holding up well becaue they are so beefy ?

[redshift]

They actually are not

One of these steelies failed at the neck.
Out of a second pair of Ti drives, both failed at the neck.
I just installed the third set (2nd Ti set) and we'll see...

There needs to be torsion to soak up shock loads, there is no torsion in these, being a tube, and they will always fail eventually at the thinnest point. Which was my initial concern, and was justified obviously.

I had failures both with a diff, and a spool.

Did give me some experience working with titanium at least. Most unusual stuff, drilling to make the tube end was a huge pain. Not sure what grade I had because it was given to me, but it acted like 3 different metals. It files very easily, almost like aluminum, but it machines like high carbon steel. Drilling produces intense heat, far more than any material I've worked with.

Over the course of making 3 sets I determined that about .002"- .0025" interference fit is needed to secure the large pin (dogbone end). The first set of steel drives I tapped the end for a 3mm setscrew, not knowing the proper amount of pressfit I wanted a way to secure the pin. Those were made to be only about .0005 pressfit, not nearly enough and they did loosen. So the neck being hollow on the first pair with the relief drilled ended up being weak. One steel drive survives, but it is rather rusty. I think after this it will be back to either regular bones or possibly making some bones. But the tube CVD I think would be an excellent way to do custom length centerdrives, but for outdrives bones are still the best way to go.

[magman]

have you tried these...I had a set on my Revo. They are sweet

http://www.rcalloys.com/pricelist/pricelistshafts.html

[redshift]

Haven't seen that one magman, thanks. How do they keep the double-dogbones centered?

Is it like the old days with a little spring in each cup?

I might try some stainless if I make more...

[magman]

I used a small piece of fuel tubing to center the bones. They make custom sizes so just give them the size you need....very reasonable to

[redshift]

Ok I thought silicone tubing would be better long-term, see!

I got your PM, prices look decent indeed.

I put the site in my favs. Graci...

[magman]

anytime!