Home Built Knuckle Centering Tool (1 Viewer)

[Tokamak]

I need a sanity check on my home built centering tool. After building the tool and making the measurements my numbers came out different that what was in originally. It looks like the PO just put in shims equally spaced. I’m doing my measurements with the old bearings just to keep from goofing up the new stuff until I get the tool verified.


First picture: I made the shoulder of the tool the same length as the existing bearing holders.


Second Picture: The bottom shoulder block location is fixed to the shaft with the set screw collar as the reference.

Third Picture: The top block is tightened with a ¼-28 bolt to get the preload. Grade 8 bolt into a steel shaft with moly lube should be able to handle the preload.

 

[Tokamak]

The rest of the story

Picture 1: The axle marking pin is 3/8” transfer punch in some bushings in the axle opening adapter. No up down slop on the pin. I did some ciphering and determined that diameter at the marking location needed to be .637 to have the same 3mm offset (number subtracted from “D”). This is based on a 10.5 degree shaft angle. If the angle is different, I can recalculate the offset to subtract.

Picture 2: Similar and separate marking pin holder for the knuckle.

Picture 3: Reference block is on the bottom bearing. Any other combination gives a negative number.

The measurements I got were .138 and .157 for right and left. That comes out to .030 and .041 for the bottom shim. The originals were .040 bottom and .041 top. They were the same on both sides.

Does it look like I forgot anything?

 

[kiwidog]

knuckle Bearings

Hi Tokamak,

I think you have it.
I have never used the centring tool . Just relied on Mr t to machine the parts within couple of thou. (and using original housing parts with axle)
Once you set one set of shims top or bottom then just work from there, to get the pre-load right. If you have 0.040 in one side ( say top ) them if you put 0.040 in the bottom and the preload is loose by say 0.002 them if you remove 0.002 from the bottom and the pre-load will be correct. The centring is the split by 0.002 to the top and bottom. If you are within 0.001 of being centred then call it good.
The centring tool just does exactly what you have done. The bearings are made with a certain amount of precision so even if you keep the shims from the factory setting and change the bearings to new ones I bet you are with couple of thou assuming it was centred from the factory setting.
If you are starting blind with lots of different parts then the centring tool is great because it give you datum to work from to get the pre-load correct from that datum.

The shim setting tool is just like a level. If you are out by 1/16 per foot and you reverse the level you will be out by 1/16 per foot the other way so level is 1/32 raise or lowered depending in which end you are working from.

Good luck with you tool, looks exactly like some I would make. Think I will make one using your idea. Mr T's SST are over engineered a lot of the time and there are far simpler ways of doing lots of operations Mr T call ed for a SST.
If you separate the centring from the preload, I think it is way easier to understand what you are doing.

Thanks for sharing.
jb

 

[pbgbottle]

nice job on the tool
looks good to me . Monrovia?
how many landcruisers are there in Monrovia ?

 

[cruiserjunkie]

Looks good when can I borrow it

 

[Tokamak]

Not sure how many TLCs are in Monrovia. It would be nice to know.

I'll loan it out locally mainly cause it's custom made and may not have the tolarence slop to fit all inner axles or knuckle bushings. I may need to shave it down to fit.

I'll try to get a Drawing posted if anyone wants to make one.

 

[Tokamak]

Centering Tool Dimension Request

Does anyone know the dimensions of the centering tool related to the attached picture. If I can find out the generic dimensions then my tool will fit any FJ40.

Also does anyone know the actual angle of the king pin. I measured mine with a digital inclinometer but the real value may be different. Kinda anal but may as well make it right.

Once I get this info I can post a drawing for machining.

 

[Tokamak]

The Picture duh

Here is the attachment

 

[pbgbottle]

looking at your tool again .how are you measureing the distance for A (see pic ) with your tool .
it looks like the SSt has a special shoulder machined in it to get a accurate measurement.for A
A-B = total shim thickness used to get desired preload. or are you just finding center and then messing around with shims to get the desired preload. or does it not matter.

 

[Tokamak]

Measuring for preload shims

Looking at the picture of the tool installed on the axle you can see that the underside of the shoulder is where it will touch the knuckle. You can use inside calipers on the under side of the shoulder to get one of the measurements. This is why distance A1 is so important. I used my existing pin as the reference.

The distance between the shoulders should be greater than the distance between the flats on the knuckle.

I think that the SST tool uses a machined flat at the same level so outside calipers can be used.

I'm getting some calipers that measure more than 6" so I can confirm the measurements tonight.

 

[Tokamak]

Preload Shim Measurements

I'm using old bearings just to test the tool. The bearing races are about as smooth as a corrugated roof.

The measurements were.

Right:
Axle = 6.601"
Knuckle = 6.499"
Total Shim = .102

Left:
Axle = 6.601"
Knuckle = 6.501
Total Shim = .100


The original shims totaled .081 per side. (.040 bottom .041 top) Loose by .020"

I'm think I'm pretty comfy with the tool.

 

[pbgbottle]

nice ! i see. i forgot to add pic in post above ,i edited my previous post .


,,,

 

[Tokamak]

Possible tool modifications

All that extra aluminum on my tool was for mistakes and such. I could mill a step above the shoulder to make the A an outside measurement instead of inside.

When I trim off the excess I'll look into a top cut. Right now i just want to get my knuckles installed so I can move on to the rear diff.

I would like to hear from someone that has a tool or built one before.

 

[chevurai]

I recently did a mini truck knuckle on the front end of my fj55 using the "real" steering knuckle centering guage and your numbers look good. I don't see any problems with your design or application of the guage that you made. Looks like high quality work.
This tool should be used when installing knuckles onto a different axel tube to come up with the proper preload and shim thickness.
Also, as you discovered, it dosn't hurt to ckeck the previous mechanics work.
Maby I missed it but did you copy the guages dimentions from a factory tool or did you come up with the design on your own? Nice work.

 

[Tokamak]

I measured my knuckles and axle then made the tool to fit with no slop.

Don't have a "real" tool so I don't know what the average dimension is that would fit all so I'm afraid to loan it out cause it may not fit someone elses truck.

Thanks for the feedback, it all helps.

 

[jagota]

Not sure how many TLCs are in Monrovia. It would be nice to know.

I'll loan it out locally mainly cause it's custom made and may not have the tolarence slop to fit all inner axles or knuckle bushings. I may need to shave it down to fit.

I'll try to get a Drawing posted if anyone wants to make one.

Not sure about Monrovia, but there are a few in Duarte.

 

[numby]

I've always wondered about using the OEM SST (or equivalent) to determine preload especially as it's ultimately determined by a spring scale. And the start number (4.4 - 5.5 lb using the SST) doesn't directly correspond to the final number once everything is all bolted in place (4.0 - 8.4 lb). Is this just to ballpark the numbers before centering?

When a friend helped me do my new front knuckles we just added shims equally to the top and bottom until we got the correct preload measurement via the spring scale. True, the knuckle wasn't centered vertically but, hey, that's what a Marlin EcoSeal seal is for.

 

[Tokamak]

When I built the tool I made the arm for the spring attachment exactly the same length as the steering arm (not sure of the length of the SST). This way I was measuring the same spring scale distance on all measurements. When asembling the first knuckle the shims calculated with the tool gave me exactly the same spring scale preload with the knuckle assembled. The other side was light and needed .002" removed to give the same spring scale reading as the tool. I chalk this up to the accuracy of the caliper measurements plus how parallel the flats are on the knuckles. I know that I'm probably picking fly s*&t out of pepper but just want to understand why stuff is the way it is.

When using the tool I measured "A" with each spring scale reading and found that the preload is approximatly .001" per 1/2 lb of preload. This was around the 4 to 5 lb preload range since the higher the preload the less the knuckle ball compresses.

If the bearings weren't preloaded the upper bearing would unload as soon as you put the weight of the vehicle on the lower bearing. This opens up another inconsistancy. My July '74 FSM calls for 3.9-5.0 lb final preload but the Max Ellery Manual calls for 6.6-13.2 lbs. This is quite a difference. The preload should relate to the weight of the vehicle + the additional pressure when hitting a bump. Additionally if wheel spacers and/or wheel offsets are used the point of force is moving further from the bearing creating more leverage and therefore more pressure on the bearing. This would imply that the preload may need to be increased to compensate.

I am waiting for my front ARB locker so I have time on my hands to make more measurements. I plan on reinstalling the tool and measuring the torque required on the tool to apply 5 lbs of preload. The torque and the thread rate will relate to the pressure against the face bearing which should relate to the weight of the vehicle.

On a different but related subject I am testing to see if Moly Assembly (Sta-Lube) lube is compatable with Mobile 1 Synthetic grease. If compatable I can use Mobile 1 every where on the knuckle and spindle with the addition of the moly + Mobile 1 on the birf. The soap in the two greases are the same so it should not liquify or cake.

Later I will post some stuff I discovered related to the two types of knuckle bearings available. The PO used KOYO 3030D and I installed KOYO TR0305A. These 2 bearings are have some measureable differences.

 

[Tokamak]

Trunion Bearing Pre Load

I needed to disassemble the knuckles once again during this rebuild to put Loc-Tite on the stud threads in the knuckles. While disassembled I did some measurements of preload vs pressure on the trunion bearings. The data is interesting but no startling revelations.

My centering tool uses a 1/4-28 bolt to apply pressure. The bolt threads are lubed with Moly. Torquing a 1/4-28 bolt lubed with Moly to 7 ft/lbs will preduce 2325lbs of clamping pressure. I torqued the bolt to 40 in/lbs, measured the spring scale preload, measured the distance between the bearings, and calculated the bearing pressure. Then increased the torque in 10 in/lb increments taking readings until the spring scale read 6.2 lbs.

On the attached chart the Bearing Pressure (blue line) and the Spring Preload (red line) shows an even rate as the bearings are being squeezed together in .001" steps. At about 5lbs of preload (redline) the pressure vs preload starts to change. Additional .001 inch changes increase the bearing pressure at a faster rate than the spring preload. This leads me to believe that a 5lb preload is the area where the flex of the knuckle ball has been removed and it is at a stable pressure. For what ever it's worth.

I then reassembled the knukles with Loc-Tite on the studs. Pulled out my seals for the back of the knuckles and realized that I needed to remove them again to install the seal components.

The test of mixing Sta-Lube Moly with Mobile 1 Synthetic is looking promising.

 

[numby]

.001 shim thickness per 1/2 lb of preload up to (roughly) the 5 lb mark is interesting. That's the low end of the spectrum but, assuming factory spec unsprung weight, perhaps that's the ideal number.

I don't have it in front of me but I think the Ellery manual is aimed more at later disc brake models so there may be differences from your '74 manual.

This was around the 4 to 5 lb preload range since the higher the preload the less the knuckle ball compresses.

This was around the 4 to 5 lb preload range since the higher the preload the less the knuckle ball compresses.

I guess I don't understand why there's no expansion in the knuckle itself as the arms and bearing caps are tightened. Both the ball and the knuckle are cast and machined. The knuckle is beefier and supported by the spindle but I'd think it would still flex during initial assembly.

The preload should relate to the weight of the vehicle + the additional pressure when hitting a bump. Additionally if wheel spacers and/or wheel offsets are used the point of force is moving further from the bearing creating more leverage and therefore more pressure on the bearing. This would imply that the preload may need to be increased to compensate.

I have heard of folks both increasing AND decreasing preload when running really large tires to either make turning easier or prevent bearing wear depending on the camp each was in. All parties were commonly breaking things and thus doing a fair bit of disassembly/reassembly. I was never offered any proof or survival rate stats so it was pure shovel conjecture to me.

Oh - are the bottom numbers (preload in .001 increments) in your graph backward or am I a dumbass?