Steering Arm Taper

[Matt]

I'm looking to use some minor steering arms in a different way...

Does anybody know the taper angle where it goes in to the swivel/leg?

Thanks!

[bmcecosse]

Get hold of a track rod end and measure the taper on that - it will be a lot easier than trying to measure the internal on an arm.

[Matt]

I have arms kicking about (several of them) not already in the swivel. I don't have suitably accurate equipment for measuring it correctly...

[Matt]

Aha - just made sense of your reply BMC, but its not that I am interested in - its the taper where it goes in to the swivel pin, not the TRE

Does anybody know the taper angle where it goes in to the swivel/leg?

[bmcecosse]

[philthehill]

Matt
You say that you have spare arms so why not measure the large dia, the small dia the distance between where you measure and then you can calculate the taper.

[Matt]

Yes I can do that - but probably not accurately enough to get the right angle... digi calipers are the best I can manage!

[MarkyB]

Shamelessly nicked from elsewhere on the internet
The Taper of a Shaft can be measured by Measure the diameter of the shaft at the beginning and end of the taper, Measure the distance between the beginning and end of the taper, Subtract the largest diameter measurement from the smallest, Divide the distance measurement by the difference between the distances.

[bmcecosse]

Yes indeed - the difficult lies in measuring accurately enough. Come on - spill the beans - what on earth are you going to do with the arms????

[philthehill]

I got an old Minor steering arm which had a paint rim at the larger end of the taper so the length of the taper was reasonably easy to measure.
Used the following formula:-

Large Dia (D1) minus small dia (D2)
______________________________ this gives the depth of taper (T1)
2

and then

Length (L) between D1 & D2
_________________________ this gives the taper
T1

The above calculation gave a taper of 1 in 16 which looks about right! But please check with your own measurements!!!!

It is a bit like trying to work out the steepness of a hill.

[Matt]

When I get to the garage I will have a measure up...

I told a slight porky TBH - Because of the way my minor is modded (rack is moved), the steering arms need to be in the top boss (ala riley 1500) and you can't get new arms with the hole there any more. Also, given that I am using marina stub axles now I am trying to future proof (esp. as one of the lower threads on my swivel is pretty worn!)

[smithskids]

Put in a lathe between centres and measure it in degrees from the topslide using a dial gauge or a friends lathe

[Matt]

Intesting idea that...

[philthehill]

Regarding the use of a lathe to determine the degrees of taper - all you can do is put the thread of the steering arm in the chuck as the arm cannot be held between centres and then angle the top slide to run parallel to the taper and read off the degrees of offset as described by smithskids.
Do not forget that there will have to be a woodruff key slot cut as well to stop the arm from turning.

It may be easier to fit the Peter May Engineering Rose Jointed T/R/E Pt No: 1.29 with some packing/spacer to raise the joint to the required height.

[Matt]

That would be quite expensive and need a lot of packing Phil!

In terms of accuracy of angle for the taper - how accurate does the angle need to be? to get a good fit?

I haven't forgotten about the woodruff key. I am confident I can put the required slot in.

[philthehill]

Matt
I did not think that you had forgotten the woodruff key but just wanted to make sure.
Now not being funny but if you feel confident enough to cut a woodruff key slot in the upright you should be able to make a tapered hole in the upright to accept the steering arm and this is how I would do it: apologies in advance as regards the depth of detail.
Measure the small ID of the steering arm taper hole and then drill a hole 1mm smaller than the measurement through the centre of unused boss making sure that the drill is square to the boss.
Measure the large ID of the steering arm taper hole and use a tapered drill (available from Clarke's Machine Mart order code No: 060230382) and drill down so that the largest diameter of the taper is 1mm smaller than the measured ID of the large hole.
Offer up an old arm and carefully remove small amounts of metal between the two diameters to develop the taper.
Use engineers blue on the old arm to identify the high spots which you can then remove.
When the engineers blue covers all of the taper then lap the arm to the upright with fine lapping paste which can be finished with brasso if so desired.
Yes it is important that the both tapers are a good fit and even if you get a machine shop to do the taper I would still lap the tapers together.
It may take a little while to achieve the tapered hole but that is how It would have been done years ago by a proper mechanic

[bmcecosse]

Or just track down a couple of Riley/Wolseley king pins......

[Matt]

Phil - yes thats what I am intending!

I work away from home and only get access to my bits and bobs every other weekend - hence asking if anyone knew! It means I can get things sorted for when I get back I don't want to buy a drill/reamer with the wrong angle to start with. Who knows what angle those machine mart ones are??? It would take quite a lot of time to lap it down if those are (for example) 10 degrees and the arms are 7 degrees! (I'm also quite impatient when doing things like this - so getting something with the correct angle to start with makes much more sense!).

BMC - I have a pair of riley swivels on the car, but as I am sure you know they are not common, and you can't get new ones! Whereas you can get new minor ones, and by drilling the correct hole they become the correct swivel! (I also have a number of minor ones kicking about). Knowing the angle would also allow modification to turn normal swivel in to an 8CWT one!

[philthehill]

Matt
I have one of the Machine Mart tapered drills and though it is not the same angle having checked against a Minor steering arm/taper it does go a long way to getting the job done and does not leave a great deal of metal to remove.
A ordinary reamer will not do as it will be too soft to cut the metal used in the production of the upright.
As you most likely know that if you want to use 8cwt van steering arms (which is what I use on my Minor) you will need an even bigger taper/drill because the taper is bigger and it cannot be assumed that the steering arm taper is the same as the non 8cwt Minor.

[Matt]

I have both arms to measure ;) But I wasn't planning on using the 8cwt arms

I'm looking at drills/reamers from the states for ball joint tapers etc - im sure the materials used in swivels there are the same as here?