What makes a front radius rod appear too short?

[richc]

I’m building up a 1918 TT chassis and have the front end done with the wheels attached. Now I’m at the point of being ready to installing the rear end assembly and look forward to having a chassis that I can roll around. With the long driveshaft tube of the TT, I placed an oil pan with transmission cover on the frame to give the forward end of the driveshaft tube its proper support. Being a pre-1919, the front radius rod is type mounted above the front axle, and thus needed to be installed before I placed the oil pan on the frame. But… I find myself unable to attach the radius rod ball in its bracket on the oil pan – it doesn’t want to reach! I tried loosening the nuts at the front of the radius rod to scoot it back a little, but it’s acting like the radius rod is too short. I know it isn’t, so what do I need to adjust to get everything to fit?

For background, most all the brackets at this point are still loose so the fit has some wiggle room. The front motor mount allows the springs to be lifted up and down on each side and spring shackles swing up and down easily.

The photos below show how the front radius rod ball doesn’t want to seat back into the support bracket on the oil pan even after “moving” the radius rod back by loosening the front attaching nuts as far as I dared knowing I’ll need some threads protruding when the time comes to pull it back into place.

Have any of you had this dilemma and found what was needed to get the front end to fall onto place?

Thanks in advance,

Rich C.

[Humblej]

Hard to tell from the dark picture, but it looks like your front axle perches are on backwards. The boss on top should be offset to the rear.

[Bruce Compton]

If Jeff is correct, you can just reverse the placement of the axle. Remove the two steering arms, the wishbone, the spring to frame clamp(s) and turn the whole axle 180 deg. Trying to remove and reverse the perches is difficult to impossible. I've seen this situation before......on a National show winner 1913 touring at Hershey....

[Mark Nunn]

I noticed the same thing, Jeff

[George House]

To the best of my knowledge Rich; a TT never had an ‘above the axle’ wishbone. Much has been written on this Forum on techniques to insert the wishbone ball into the pan socket. My technique is wrapping the center of axle with leather glove or rubber mud flaps and adjust a large pipe wrench over the material. Having your wife step on the pipe wrench will move the axle to usher the wishbone ball into the crankcase socket. And the axle will have the correct ‘rake’ when everything is removed…Is that a 30x3 tire in your pic ?

[kmatt2]

From your picture I can’t tell if the 1918 type spring perches are on correct side or not. But in the past with the later 1919 type front end I have had to put some weight on the front to compress the spring some to get the radius rod attached. Ford first used the 1919 type spring perches and radius rod on the TT truck because of the better front end geometry. I remember something in the 1918 Ford service bulletins about all trucks using the below axel radius rod and new , (1919 ), type perches.

[Jerry VanOoteghem]

Hard to tell from the dark picture, but it looks like your front axle perches are on backwards. The boss on top should be offset to the rear.

I don't believe "above the axle" wishbone perhes have the boss you're referring to.

Okay, I see now that some do... Oh well.

[Jerry VanOoteghem]

From your picture I can’t tell if the 1918 type spring perches are on correct side or not. But in the past with the later 1919 type front end I have had to put some weight on the front to compress the spring some to get the radius rod attached. Ford first used the 1919 type spring perches and radius rod on the TT truck because of the better front end geometry .

Correct. This is not an uncommon thing. It can also be caused by the front crossmember being a bit bent and by the spring being installed a little out of alignment. Loosen your front spring clamps a bit and see if it helps by allowing you to draw back the wishbone until it enters the socket. When it's all buttoned up, confirm that you have a negative caster angle.

[Erik Johnson]

RE: determining the front and rear of an early perch

It's very simple: the early perches are designed in such a manner that the prongs of the wishbone can enter the perch socket from only one direction. The front of the perch socket is flat so the castle nut can be snugged up to it and the rear of the perch socket is tapered/chamfered to accept the wishbone prong

If you have early perches which have been installed backwards and were still able to completely install the wishbone, then the prongs and/or the perch sockets are worn out.

Also, in order to install the wishbone into the pan socket, chock the front wheels and have someone push the truck forward. There should be enough combined play in the front spring, perches and shackles that will allow the bottom of the axle to tilt rearward which will shorten the distance between the ball and the pan socket. (Hope this description makes sense.)

[TRDxB2]

Same issue was noted a few weeks ago viewtopic.php?f=2&t=41856&p=321100&hili ... ne#p321100
but the root cause may be different. The first thing to do is to make sure the perches are on the correct side. The boss on the top of the perch should be towards the rear of the car. The easiest way for the early ( two hole) perch is to look at the radius rod hole. Also make sure that the correct nut is used, easy to use the later nut when the perches are facing the wrong way.
--

perch orientation.png (353.75 KiB) Viewed 2344 times

--

[Allan]

If you do take the axle and swap it end for end rather than swap the perches, you will need to consider the spindles also.
The left hand thread spindle goes on the right side, and vice versa.
The spindle arms go into holes in the spindles set up just like the holes in the perches in the previous post. The arms have a slight radius behind the shoulder and the hole in which they fit needs a corresponding chamfer/relief to allow them to seat properly.
This correct fit of the spindle arm dictates the spindle required at each end of the axle.

This is a long winded way of telling you that just swapping the arms will not work!!!!

I once supplied a new front wheel bearing on a tour for a car which had two RH thread spindles.One had an ill fitting spindle arm.

Allan from down under.

[richc]

Gentlemen – thank you for the suggestions on my front radius rod dilemma.

I too had considered that I made the mistake of having the spring perches swapped and I actually disconnected the shackles on one side and withdrew the perch and made sure the angle tipped the axle forward. It did.

In the end I think Kevin M had the correct idea which was the need to add weight over the front spring. With the spring compressed the vertical distance between radius rod and the oil pan would be reduced, and thus less swinging up the rear end of the radius rod to mate with the bracket on the oil pan. I placed an engine block on the pan which did compress the front spring a bit. My spring is a standard seven leaf spring, but still sits fairly high above the axle. I guess I’ll have to wait until I get the wooden cab on the chassis before the front radius rod will be happy.

With respect to the usage of the early above axle radius rod on TT trucks, the 1919 Ford documentation says:

APR 14 1919 Acc. 235, Box 39, #385
“From this date two distinct designs of front radius rods, together with front spring perches, right and left, one on the Model T and the other on Model TT.
The Model TT design will be assembled beneath the axle, instead of above the axle through the spring perch as heretofore.
Although it would be possible to use the Model T design on the Model TT, we request this be resorted to only in case of a shortage serious enough to threaten loss of production.”

Since the engine I plan to use has a March 1918 block, I’m good.

Rich C.

[Allan]

So Rich, your TT must have been one of those assembled in a time of shortage of the under axle wishbones. Ford indicated that this was only to be resorted to in times of such shortage. I think that advice tells us that the factory was averse to the over axle wishbone on TT's. That, and many years of combined experience in forum members with over axle wishbone problems,is enough to make me heed the factory advice.

Rather than hang my hat on a loophole that means a less satisfactory part could be used, I would opt for the recommended safer route. Just MHO.

Allan from down under.

[Jerry VanOoteghem]

I actually disconnected the shackles on one side and withdrew the perch and made sure the angle tipped the axle forward. It did.

Do you mean maybe "tipped the axle backward? The top end of the kingpin should be tilted back, toward the rear of the car.