When Did It Become OK to Mount R&P on I Beam Axle?


The "Hot Rod" version of the K and KB truck

Golden Jubilee
Golden Jubilee

Posts: 8937

Joined: Thu Dec 27, 2012 12:45 pm

Location: Canada's left Coast

Post Sat Sep 10, 2016 1:35 pm

Re: When Did It Become OK to Mount R&P on I Beam Axle?

https://www.hotrodhotline.com/sites/def ... 60-01-lg(1).jpg
http://www.unisteer.com/
Unisteer make a rack and pinion unit that is a direct replacement for an original steering box. Does they make something for your vehicle? Click the link and ask them.
Try to remember that you are responsible for any changes that you make. Should something, of your design, fail and cause injury or death to another person, you will be liable. Your insurance company will walk on you so fast. It is in the "fine print".
You may be able to reduce your liability if you have your "repair" inspected by a certified person that your insurance company recognizes.
A mechanical inspection is the law, here. These inspections became law after home made junk became an embarrassment to some elected official when his voters were being hurt or killed by flying junk.
I would rather have tools I do not need than to need tools I do not have
Thinking risks being controversial and possibly being offensive

Yard Art
Yard Art

Posts: 95

Joined: Wed Dec 30, 2015 9:43 am

Post Sat Sep 10, 2016 5:02 pm

Re: When Did It Become OK to Mount R&P on I Beam Axle?

Ok to boil it all down the only real issue here is that the slip joint might be unsafe.

I don't see any issues with mounting the R&P safely to the front axle. It doesn't really matter if a regular car manufacturer does it or not. That's not the point. The point is making an older vehicle that you own safe and fun to drive. The more of those two things in a vehicle the more use it gets. Case in point. I love driving my 47 around but hate the fact that it takes forever to get anywhere.

As far as the slip joint goes I would never use a stock style joint as that is definatly not what it was designed for. At the same time I'm going to say that it shouldn't be difficult to design a slip joint that is perfectly safe with a R&P mounted onto the solid front axle.

PS I'm going to ignore what I perceive as baiting in my comments. I want some honest fair discussion here. As far as me getting my Irish up... if that's the way you feel about my comments then maybe you need to read them a bit more carefully. I enjoy a good argument but it seems that most of the time they just degenerate the thread.

Golden Jubilee
Golden Jubilee

Posts: 5170

Joined: Thu Nov 29, 2012 9:28 pm

Location: Lyman, IA

Post Sat Sep 10, 2016 5:19 pm

Re: When Did It Become OK to Mount R&P on I Beam Axle?

I think the best choice would be to look to a heavy truck steering slipshaft. They are formed like a + with "glidecoat" on the shaft (a heavy plastic type coating to reduce friction). Truckshaftss have the lower end of the outer shaft that fits snug around the + shaped inner shaft. The upper end of the inner shaft is not supported, and I think this may be a problem on a shaft that has a lot of movement. The shaft has a grease fitting on the lower end to keep the joint between inner and outer lubed.
I think a shaft subject to a large movement will tend to "sea-saw" in the bottom bushing. If you could make the bottom bushing longer, it would tend to counteract the tendency to sea-saw.
One problem is getting the parts to make them. My local truck supplier can not get the pieces and con only order complete shaft assemblies. The reason is liability.
I don't see it being a big problem making a rack mount that is strong enough connection to the beam axle.

Golden Jubilee
Golden Jubilee

Posts: 2028

Joined: Fri Apr 08, 2016 4:52 pm

Post Sat Sep 10, 2016 6:00 pm

Re: When Did It Become OK to Mount R&P on I Beam Axle?

PMS, no, it doesn't just boil down to a "slip shaft" issue.
The R&P main steering mechanism is being bolted to a seperate, UNSPRUNG part of the chassis. I know of no stock steering mechanism bolted to anything but a contigious or welded frame member.
No, you do NOT know more than ALL the vehicle manufacturer designers, EVER.
At best it's cutting corners.
I guess I came from a different automotive repair place than you.
I complelely understand old trucks and their lack of "agility".
I've said THREE times now that if this practice gets the thumbs up from the old-car community, I'll be the first to put R&P on my old stuff. I like being able to steer easily, too.
I'm not BAITING, I'm trying to get folks to think about the appropriateness of this modification. It LOOKS scary. Maybe it's OK.

Golden Jubilee
Golden Jubilee

Posts: 5170

Joined: Thu Nov 29, 2012 9:28 pm

Location: Lyman, IA

Post Sat Sep 10, 2016 6:36 pm

Re: When Did It Become OK to Mount R&P on I Beam Axle?

From a steering point of view, from the rack to the wheels, it makes no difference if the rack is bolted to the frame or the axle as long as the anchor points are good enough. The forces are the same. Anchor points have to be ridged and strong enough to take anything the wheels can transmit, or in short as strong as the tie rod connection is. The rack has to be spaced back as far as the steering arms so the geometry doesn't change on hard turns. So in short the weak point is the connection from the pinion to the steering wheel and the need for that connection to expand and contrast as the suspension moves.
As far as bump-steer, mostly that can be minimized with steering box placement and drag link angle. I once drove a modified chassie where someone had move the steering box from in front of the axle to the rear, which in itself isn't the problem, but they left the fixed end of the spring in front and the shackle at the rear, every bump the truck jumped side to side, only way to drive was to allow the wheel to spin inside you hands, only keeping a very loose grip on the wheel.

Golden Jubilee
Golden Jubilee

Posts: 2028

Joined: Fri Apr 08, 2016 4:52 pm

Post Sat Sep 10, 2016 6:59 pm

Re: When Did It Become OK to Mount R&P on I Beam Axle?

CB, you wouldn't add a "safety" travel-limiting device? Something to keep steering splines engaged?

Golden Jubilee
Golden Jubilee

Posts: 5170

Joined: Thu Nov 29, 2012 9:28 pm

Location: Lyman, IA

Post Sat Sep 10, 2016 7:24 pm

Re: When Did It Become OK to Mount R&P on I Beam Axle?

I'm not sure I would do it in the 1st place, I just don't know if even a heavy truck slipshaft is up to that kind of use.
I think it would be possible to make a slipshaft with enough extra travel that it couldn't separate unless the springs fail, and at that point, it is moot.
My cabovers have a long enough shaft not to disengage even when the cab is flipped all the way over. My Conventional Marmon has a shorter stub as it only has to contend with the air suspended cab, and that has the fixed connection at the front, so very little movement.

Yard Art
Yard Art

Posts: 95

Joined: Wed Dec 30, 2015 9:43 am

Post Sun Sep 11, 2016 1:23 am

Re: When Did It Become OK to Mount R&P on I Beam Axle?

So I did a bit of thinking about this while driving to Medicine Hat tonite.

I see no issues with mounting an R&P to the front axle beam and it being unsafe. Yes you are right in that I will never know as much as car manufacturers engineers. But I don't have to follow in their ruts either.

The issue of adding more unsprung weight to the axle is a valid one though I seriously doubt that it's an issue. My thought's are that if you install an R&P on a beam front axle you really aren't concerned about ride quality. It's not the forefront issue. People would do the conversion for other issues than ride quality. Furthermore unsprung weight can be reduced by changing from drums to discs and changing wheels to aluminum.

The issue of steering shaft movement reliability has already been addressed so that's not an issue either. I'm sure that 99.9% of you have seen it in action. Next time your going down the road and you see a semi with the rear of the cab on airbags bouncing up and down think of the steering shaft between the steering wheel and the steering box on the frame. There won't be as much movement as an R&P mounted on a beam front axle but that's not the point. The point is that it has been reliably done on a lot of trucks.

When I got home I remembered that there was an R&P conversion done on a 4x4 Cummins or similar. I couldn't dig up much on that other than in a race truck but I came across this which I couldn't find much out about either. "Freightliner Coronados have a R& P setup.. mounted on the drop beam front axle..." Maybe someone can dig up more info. If it's true then the question of a factory R&P setup mounted on a front bean type axle is answered.

So really the only question I have left on the safety of this setup is this. Can the bearing of the input shaft on the R&P handle the constant friction of the slip shaft moving in and out? I'm assuming it should be able too because there is always a bit of movement between the frame and the body on frame type vehicles.
User avatar

Golden Jubilee
Golden Jubilee

Posts: 1887

Joined: Thu Nov 29, 2012 10:40 am

Location: Wichita, Kansas

Post Sun Sep 11, 2016 8:53 am

Re: When Did It Become OK to Mount R&P on I Beam Axle?

Wildmanbill uses a manual R&P setup on his IH.

viewtopic.php?f=28&t=5030&p=37732

I think the key is having a slip joint with plenty of travel and overlap. I believe he said his slip joint was for a 4x4 with long travel suspension.

Dean
Lifelong Kansan
Grew up with red paint
Moved off the farm 33 years ago.

Yard Art
Yard Art

Posts: 95

Joined: Wed Dec 30, 2015 9:43 am

Post Sun Sep 11, 2016 10:55 am

Re: When Did It Become OK to Mount R&P on I Beam Axle?

Just read through this. http://www.ford-trucks.com/forums/91138 ... eport.html No Limit is making a kit for early Ford trucks. There's some good ideas in that forum for our trucks if that's the way that somebody wants to go.

Also was on this site. www.borgeson.com They sell bulk double d collapsible steering shaft.

I was also on Flaming Rivers site. I didn't do any reading yet but it looks like there are good articles there on how to set up steering components.

Somewhere too I have an article on how to correctly build your own steering shafts but I haven't found it yet.
PreviousNext

Return to The Modified K-KB

Who is online

Users browsing this forum: No registered users and 3 guests

Powered by phpBB® Forum Software © phpBB Group
Designed by ST Software for PTF.