After shipping more of these than I expected, and talking to a few people about the install here's a few notes.

1. The loop can be installed without dropping the driveshaft on cars with short transmission tailstocks. The loop needs to be able to be pretty close to the crossmember, where the tunnel widens out, in order to flip it over the top. Even then it's a close fit. Start with the loop horizontal and the open end facing the crossmember. Then roll the loop over the top. It may help to rotate the driveshaft to a better position.
It's not going to happen if you have a long tailstock on your tansmission. Sorry for not realizing that at the begining.

2. The short version will fit TH400's TH350's and Muncie 4 speeds. The long version is for TKO etc.

3. Make sure you torque the bolts to 25 ft/lbs espesially the cossmember mount bolts, yes it is hard to get at the nut inside the crossmember, but it's possible. Really.

I guess that's it.
Anyone else have any install / usage comments?
Keith

 

Do you have any pictures?

 

 

Do you think that hollow square stock is strong enough to contain a driveshaft that is whipping around after it breaks the u-joint? The loops I've seen are made from some pretty thick material suggesting the brackets needs to be pretty stout.

 

Regards from Down Under

aussiejohn

 

I think it's stonger than the 24 gauge floorboards most driveshaft loops are bolted to.

It's 3/4" 14 gauge.

How thick do you think it should be?

 

I know there is no way to test this but i dont think thats going to prevent all damage to the floorboards if the u-joints give. Its getting ripped straight up and to the sides. You need at least one more bolt on each leg mounting to the crossmember, and possibly somehow having more square tubing from the top of the crossmember.

Im just being honest, trying to help not just bash this product. That being said i would not think I am totally safe with just this on my car. If I was worried about my driveshaft giving i would weld something up a little more significant than that.

Right now the week spot is where it mounts to the crossmember

 

I'd rather have negative feedback than no feed back, really.
I like to know what peoples concers are.
I do plan on a rev B on the design, so I'd like to know what concers I should address.

So would you expect a driveshaft loop to completely protect your floorboards from any damage at any speed?

 

I don't see alot of force exerted in any direction, if the u-jpint goes the driveshaft will just spin in the bracket, at least that's what will happen on my car

 

Well if i was to make one for my car i would want that. I dont think your going to make anything that will 100% protect the floorboard and be 100% bolt on. I think a lot of people know this and know for total protection they will have to sacrifice and get something welded on.

Heres a suggestion for you:

Use what you have so far but instead of bolting the square tubing straight to the crossmember make a mounting bracket.
Take a piece of 14Ga and weld on two pieces of square tubing with a slightly bigger diam then the tubing for the ring. Then slide the ring tubing into those and bolt together.

This would get rid of the side to side play you are going to have and the longer length of tube you have slid in the more it will brace it.

This would also make it adjustable for where to protect as I myself would probably put it as close to the end of the driveshaft as possible.

EDIT:
Im pretty much known for going overkill on everything, Your product may in fact be plenty enough for this purpose.

Quick cad drawing: mounting plate from underneath

 

Why would you place the hoop very near the tranny output shaft? Lets say that the drive shaft sheared in the very middle. Then you would have a long tube flailing around.

I really thought about where the hoop should be placed for max safety. mine is a good 1/3 of the way down the drive line. If the front u-joint or shaft sheared you still have a rear end turning the drive shaft. If it shears in the middle it will be contained. If the rear goes it is much more contained than if the hoop was right near the front u-joints.

It is also BS that a car will pole vault if the drive line breaks and comes down and snags the pavement. I've been there and done that. Myth busters should show you that drive lines are not strong enough to lift a 3000+ pound car off of the ground

 

the shaft will slap around in the loop, by then I'm sure your speed is going to decrease....and it will scare the $%^& out of you!

 

too!

 

I designed it from what the NHRA requires. They say within 6 inches of the front U-joint. I figure they know somthin.

I've seen fast cars with 3 loops, so I'm sure there is room for improvement!

 

The safety hoop design looks excellent.
The purpose of a driveshaft safety hoop is not to protect the floorboards or the vehicle. Its only purpose is to prevent the forward end of the driveshaft from hitting the ground and pole-vaulting the car in the event of forward u-joint failure - whether or not that could really happen is irrelevant, because that's what NHRA requires. NHRA does not require that the hoop guard against driveshaft breakage - only forward u-joint failure. With these design requirements in mind, the hoop shown looks very good, and satisfies all requirements for safety.
Lars
Mechanical Design Engineer
Lockheed Martin Space Systems

 

The greatest leverage on failure of this part would be if it moved quite a bit out of its alignment. The loop keeps it in a narrow range until the driver can get out of trouble and stop (hopefully).

 

Quoted-for-truth

 

Not trying to bash your design, my mind envisions an unconstrained shaft whipping around violently, and breaking the brackets if they're made from stock that's too thin, but if Lars says it's good then it must be good.

I can't see a C3 Vette pole vaulting because the rear cross member supports the shaft before the front can contact the ground, at least that's the way it is on my car. Therefore I was thinking the purpose of the loop is to keep the shaft from damaging the fiberglass floorboards/tunnel and occupants.

This one looks pretty strong and I'd be more inclined to purchase:

 

Keith,
I am a Steward and Technical Inspector with the Australian National Drag Racing Association (ANDRA) and we basically use NHRA Rules when it comes to safety items. My understanding is that the sole, or at least main, purpose of the loops is to protect the driver if a front U-joint fails in a car with a fabricated floorpan. Below a certain e.t. they are required whether the floorpan is modified or stock.

If the car is "pole vaulted" or not in the case of a driveshaft failure is less important than if the driver is protected from harm. Most "normal" cars have steel floorpans and usually there is a steel channel section in this area that may be used for any combination of floorpan stiffening, seat mounting, seat belt mounting and transmission crossmember mounting. This would give the driver a lot of protection from intrusion of an errant driveshaft, but not be as safe as a car fitted with a properly fitted loop.

The Corvette, of course, is a different kettle of fish. The crossmember goes from frame rail to frame rail and doesn't touch the floorpan. The front seat mounting bracket is flimsy at best, and the floorpan is fibreglass up to '77. On the upside is the fact that with a solidly mounted third member, there is minimal lateral or vertical movement of the driveshaft, only rotational.

Having said all that, I would feel safer with an NHRA approved loop in my 1974 Corvette and the Corvette Engineering one looks good. However, I would be prepared to pay extra for one with a mounting bracket like shafrs3 showed us. Would you be prepared to go that far with your "Mark II" version?

Regards from Down Under

aussiejohn

 

Now thats something i would put on my car.

The pole-vaulting thing is a little rediculous with the crossmember there, and there is no way your driveshaft is shearing in the middle. The ujoints will give before the shaft.