Hot Rods Hollow steering shaft question

I ground this 3/4 inch hollow steering shaft down to a double d, as you can see that won't work. I have to install a u-joint at the box and it needs to be removable. I could fill the center of the shaft with a piece of 1/2 stock and weld it at the top and the bottom and maybe put a plug weld in also. Any thoughts ?

 

As an Aerospace Test Engineer, my first inclination is, it's not worth the chance... The load is still mostly on the outer tube.
How heavy is the car (front of the car) ? How wide are the front tires ?

Mike

 

As a hot rodder, I'd say you have plenty of potential to make it work if you have the ability and think it thru.
Your idea of installing a piece of solid pressed in to the center hole is a good one, but you will need to consider say adding a little weld and/or a pin of two.
This is not impossible to fix, it just requires the right solution...
Take it slow and easy and see if any more ideas come in from our brains trust out there...

 

I would take a piece of 3/4 DD shaft and machine it down to slip in your worm gear, and weld it together. You should be able to insert the piece 3/4" and plug weld that as well.

 

It is a straight axle 1/2 ton 47 Studebaker truck. I do not have any weights for it. SBC the motor is behind the front axle for the most part. It will have 75 or 78 series tires on the front.

 

I like the idea of the pins , I had not thought of that. I could put a couple pins in the center and weld it at each end .

 

So your thinking turn a piece of 3/4 DD down to 1/2 and press it in and I could weld that at both ends and also would gain having a solid DD connection. That sounds good. I sure don't like what I have right now.

 

Nope...wouldn't do it, not on a truck.

You can put all the welds, pins, bonding, etc that you want.
You still have ONLY two little "ears" that are taking the load, that have no support. You put pins there, you will be weakening those two ears even more.

One method you could use if you could find a shop that would do it, is "vacuum brazing".
That is, putting a nickle based braze alloy paste between the new rod and the tubing shaft. Put into a vacuum braze chamber for "X" amount of time, depending on the braze alloy, then after the heat and cooling cycle, you'd have fairly strong part, suitable for your needs. As long as you didn't used some big heavy diesel engine down the road..!

Otherwise, I wouldn't risk someones/anyones life with that combination.

Mike

 

I wouldn’t even consider what you are doing.
Over here I doubt you could actually do that legally.
Start again !

 

Lots of more modern boxes out there that already have splines or double D shafts and would be much safer. Also, replacement parts are more readily available.

 

Maybe I missed the need to use “This Shaft”. The obvious solution is to replace the shaft or steering box with a known serviceable unit.

Retired Aerospace Design Engineer too.


Sent from my iPhone using Tapatalk

 

Subscribed to see where this goes. I have just the opposite. Hollow upper portion (steering wheel down) that has me not wanting to dd it for that very reason. I'll probably end up machining 3/4'' solid round stock with a tapered-keyed end for the steering wheel. It isn't any more work if not easier than trying to plug, graph onto.

 

Done right this repair would not scare me.
The two ears will have no where to go once a center hole is filled and the double D universal is over the outside.
The shaft can be pinned from the thick wall side.
Some DD universal also incorporate a bolt that passes thru it and the shaft.
If that breaks then you have more problems going on besides.
If you do decide to fix it, once installed get you and your buddy on the steering wheel and see if you can break it.
If you still have concerns weld the lower end of the universal body to the shaft.
That is done in race cars and others, how do I know, because they sell weld on universals and most are lighter that what we use in hot rods...

 

Anyone here a structural engineer ?

No ?

 

, machine design, and so far, the Marty soulution, or new box sound good.

 

Cut off what you have ground on already. Take a solid double D and turn it down so it fits inside what is there now. Weld it above and below the gear, and a plug weld or two above the gear. Done.

 

fiftyv8 wrote -
The two ears will have no where to go once a center hole is filled and the double D universal is over the outside.

Ever heard of "shear" ? These "ears" will eventually break and spin on the new god like center piece you seem to like. Any pinning or plug welding is just a disaster waiting to happen.
And yea, I am a Mechanical Test Engineer (retired after 33+ years).

Mike

P.s. - Sure, what BJR (above) said.

 

Cut the shaft open at the thin spots..Slide a snug fit bar in the whole length..Weld AT ALL PARTING LINES between the bar inserted and the 3/4 after releiving some so when you clean up the DD as necessary for fit you don't remove all the weld..Weld the bar at the far end..Heli arc would be the neatest, don't want to get the worm too hot [risk of losing hardness].

 

What's the deal with all the DD steering shafts being used nowadays, haven't people discovered Borgeson splined shafts and joints yet.

 

I use 3/4 DD, to convert some OEM steering shafts, just as I suggested above. DD has become the standard offering with many suppliers. I never use it when the DD is exposed, as I prefer the 3/4 X 36 spline, round shaft. My preference in u-joints is Sweet brand, they are not as big as Borgeson, and are NASCAR approved.

 

I think a couple of these approaches, done carefully, are viable. The concern about the "ears" is a good one that can be addressed in a couple of ways, as suggested.

I just want to go on record as being a fan of DDs

 

Marty
I knew you would have the answer but figured I would get a few different responses, just trolling as they say.
I realized early on why you saw a lot of them, from a commercial shop standpoint it is a quick way to get cars out and decreases the need to stock various lengths of splined shafts, also cuts down the wait time when ordering custom components.
Just buy lengths of DD shafting and cut to length.
I'm with you, those DD shafts with flats exposed the whole length seem to have the look of a "one size fits all" approach. It is more work and expense to keep the exposed splines to a minimum but it sure looks more professional in my opinion.
I also never liked how the DD shaft feels loose in rod end supports, due to reduced surface area I suppose.
Woodward has some really nice products also.

http://www.woodwardsteering.com/catalog2017.html

 

With all due respect,
I personally wouldn’t like to see this done.
You would want to have a good knowledge of different steel types involved, and some good welding ability, (referring to OP), and while I have access to all of that, I would not do it, there are safer options.

For what it’s worth,
And I know that it’s different over there, but I think that welding on any steering components is not allowed over here.

 

The OP contacted me, he has friends in the NASCAR shops, they will do it right, or not at all.

 

This is similar to what seems to be suggested by a preceding comment:

Machine a piece of solid bar, as shown in the first sketch. Bevel the "step" in diameter, and the end of the gears shaft, so that the V-groove to be welded will have a V angle of about 75 degrees. Tig weld, preferably with an inert gas blanket inside the hollow shaft. If possible, leave a slight crown on the weld (assuming you don't have a critical requirement to fit through a bearing or seal). This weld will have the same cross-sectional dimensions (i.d. and o.d.) as the shaft from the gear, and will have virtually the same torsional strength. Note that if the the joint is made by brazing in the "space" between the inner and outer pieces, the weakest point, hence highest stressed section, will be in the shaft just outside the brazing, at the point where the shaft o.d. is much less than the 3/4" nominal shaft diameter.

You could extend the small diameter end of the machined piece, so it could be welded to the far end, assuming the gear i.d. would allow for this. However, I suspect the inner extension would have much less torsional stiffness than the gear, due to smaller diameter, hence would not contribute much to overall strength.

 

I'm no engineer however I presume the load is on the shoulders, those thin strips are the weak link in the chain as is the area where the 3/4DD shaft runs into the worm area. It's not 'If' but 'When' shaft would fail. Do it right, do it once with brakes, steering and suspension.

Sent from my SM-G950F using The H.A.M.B. mobile app

 

Yes. Toss that part, and do it over properly.

 

Ditto on the solid bar...

 

you can make a double D with a grinder,. (whether or not it's a good idea for the application)

Cutting splines is a bit more involved. And would be the thing to do, in this case.