What are the chances?

[DannyC]

Hi folks (← me being gender neutral, inclusive and totally PC here)

... back to the plot..

I have 2 previously made steerer's (threaded headset fork heads with tabs on for attaching axles) (like for a Street fox etc.).

Problem: They are not both at the same angle, there is a 2° difference between the angles their axle mounting tabs are at in relation to the axis of the steerer tube.

Q. What's the best way of getting them at the same angle?

• Do I hack one tab off and try to get the angle the same as its twin when replacing it?
• Cut a slit in the outside of one tab at the root and open the gap and then fill with weld?
• Run a thick bead on BOTH but on opposite sides of their tabs to get the contraction on cooling to take 1° out of each but in opposite directions?

Which method have you had success with/believe will be more successful?

Thanks in advance.

 

[undertoad]

With #3, you're just guessing that X amount of weld, will result in X amount of pull - Maybe, but not very predictable.
And it'll only make more work, cutting both of them off later.

I'd try #2 first - If it fails, then just fall back on #1

 

[DannyC]

With #3, you're just guessing that X amount of weld, will result in X amount of pull - Maybe, but not very predictable.
And it'll only make more work, cutting both of them off later.

I'd try #2 first - If it fails, then just fall back on #1

Good call, I want to do as little as possible to get the best result.
I "might" be able to slit and jig the thing at the correct angle and clamp it hard and then put a big bead on either end of the slit and let them cool and act as "immovable" spacers and then fill it back up from the centre outwards a little bit at a time. ;-)

 

[Popshot]

Agreed. Cut a slit, hammer and weld.

 

[stormbird]

Can you weight the completed item ready to have the outer head tube welded to a cross member of some sort ?

This is [ to my mind ] a much simpler [ and I hope lighter ] kingpin that looks deceptively easy to make ....

Although maybe upgrade it from M8 to M10 rod ends ?

As the Royce cars had a bit of a rough time last weekend , over 2 days racing these M8 rod ends suffered 4 bent , 3 broken and 1 seized.
Under normal circumstances a non event really , the car would benefit them being changed and it is a simple task until it is during a race laid on it's side under a gazebo !

Paul

 

[DannyC]

Can you weight the completed item ready to have the outer head tube welded to a cross member of some sort ?

This is [ to my mind ] a much simpler [ and I hope lighter ] kingpin that looks deceptively easy to make ....

Although maybe upgrade it from M8 to M10 rod ends ?

As the Royce cars had a bit of a rough time last weekend , over 2 days racing these M8 rod ends suffered 4 bent , 3 broken and 1 seized.
Under normal circumstances a non event really , the car would benefit them being changed and it is a simple task until it is during a race laid on it's side under a gazebo !

Paul

Oh, they will definitely be heavier, but infinitely better as their bearings will all be in the proper alignment and as god intended.

 

[Popshot]

It may be just a simplified drawing because of the drawers CAD limitations but given the professional look of them that seems unlikely. The top left drawing shows the upper and lower rod ends with separate axes (2x axis not 2x axe). This just can not swivel. Each axis will resist the other. The plan shows a common axis which is necessary intersecting the tyre line but each bolt is vertical not canted to the pivot line.

I've used M10 before in a similar way and they bent immediately. The threads have to take all the forces including about 80% of the weight of the rider and machine in heavy cornering. A lot will depend on the quality of the rod ends and specifically whether they are HT or not but just like we generally regard 12mm as the minimum for an axle I'd regard 12mm and HT in the same manner for such a kingpin. There's also the issue of using them in misalignment. 12 degrees at first seems well within most rod ends capacity UNTIL you actually try to tighten a bolt or nut. Anything that touches the rod end's spherical part on the inside or outside eats into the stated rod end maximum misalignment. Even purpose made misalignment spacers eat into this figure. You can easily find this works well until you tighten everything up and it locks.

A better system is to angle the rod ends so the bearing works with zero misalignment. There is nothing lost and a lot gained by doing so. There's still the problem of them bending though. Using M12 or bigger quality rod ends plus a M12 or bigger kingpin bolt is then starting to add up to a lot of metal compared to an AZ type kingpin, especially if you don't weld a tab on the bottom but instead weld a tube on. A 3mm wall tube for an M12 bolt will weigh less and because it is prevented from distortion by the bolt is perfectly adequate.

 

[DannyC]

I had another look at the two steerer's with tabs that I have and it struck me that just making them the "same" might not be the best course of action. Determining which one of them currently has the best angle for alignment with the contact patch might be a good idea, so I fitted both of them with axle-tubes, backplates and wheels and gave both a darned good looking at.

Now, one is more or less "spot-on" the other points out beyond the wheel. I remember that the tabs for the axles were applied only when the completed steerer was fitted in the frame and a disparity in the frame meant that the tab on one side was at a different angle.

So I guess I will try and adjust the one that points out beyond the contact patch to match the one that's correct and try not to mess up a frame next time these get deployed.

 

[stormbird]

It may be just a simplified drawing because of the drawers CAD limitations but given the professional look of them that seems unlikely. The top left drawing shows the upper and lower rod ends with separate axes (2x axis not 2x axe). This just can not swivel. Each axis will resist the other. The plan shows a common axis which is necessary intersecting the tyre line but each bolt is vertical not canted to the pivot line.

I've used M10 before in a similar way and they bent immediately. The threads have to take all the forces including about 80% of the weight of the rider and machine in heavy cornering. A lot will depend on the quality of the rod ends and specifically whether they are HT or not but just like we generally regard 12mm as the minimum for an axle I'd regard 12mm and HT in the same manner for such a kingpin. There's also the issue of using them in misalignment. 12 degrees at first seems well within most rod ends capacity UNTIL you actually try to tighten a bolt or nut. Anything that touches the rod end's spherical part on the inside or outside eats into the stated rod end maximum misalignment. Even purpose made misalignment spacers eat into this figure. You can easily find this works well until you tighten everything up and it locks.

A better system is to angle the rod ends so the bearing works with zero misalignment. There is nothing lost and a lot gained by doing so. There's still the problem of them bending though. Using M12 or bigger quality rod ends plus a M12 or bigger kingpin bolt is then starting to add up to a lot of metal compared to an AZ type kingpin, especially if you don't weld a tab on the bottom but instead weld a tube on. A 3mm wall tube for an M12 bolt will weigh less and because it is prevented from distortion by the bolt is perfectly adequate.

I understand a tiny bit of this ....

Those broken M8's were the first I had seen in over 11 days of racing with the Royce , and were spread over 7 cars.
Some where definitely accident damage , there was some hitting tyre walls and the rumble strips at the side of the track where lethal for 20" bike wheels
This what the kingpin looks like :-

Can't find a better picture yet.

Paul

 

[undertoad]

I feel your pain, Danny -
Remember these lovely, carefully machined axle tabs I made?
I had tediously drawn out the whole head / steerer tube / axle assembly, full scale, measured the needed angles, and kingpin center point, and blithely proceeded to machine the axle tabs, and cut the compound angle notches in the cross tube.

Ain't I clever ?
Apparently I was pretty un-clever, and was blindsided by trigonometry ..........
When I mounted the axles and front wheels, my stupidity was obvious - The trike had so much positive camber, it looked knock-kneed.

After I recovered from beating my head against the wall, I figured a way to fix it - Sort of.
Since everything was welded - Cross tube to frame, and head tubes to cross tubes, I decided to see if I could fix it by making new axle tabs.
I jigged up the frame on my welding table, so the cross tube was dead-nuts horizontal, and then re-figured the difference between the head tube angle and a projected, horizontal axle angle, by using one of those little electronic angle / level boxes.

It actually worked, almost -
Unbelievably, both sides were the same, and so I turned off the old tabs, and milled and re-welded new ones, with the new, adjusted angle.
Result - The wheels are perfectly vertical now, but now the kingpin angle does not quite meet the tire center point - It's about 1/8"+/- inboard.

But I'm choosing not to worry about it, at this point -
The trike is almost done now, and if it turns out it goes into a death wobble at 10mph, or something...........
Oh well, I'll just look at it as a learning experience .......... Maybe

 

[stormbird]

It actually worked, almost -
Unbelievably, both sides were the same, and so I turned off the old tabs, and milled and re-welded new ones, with the new, adjusted angle.
Result - The wheels are perfectly vertical now, but now the kingpin angle does not quite meet the tire center point - It's about 1/8"+/- inboard.

I would not sweat that some of the cars and commercial trikes are like that , apparently it has some benefit.

Both yours and DannyC's problems are related to the difficulty for us home builders to get the build accuracy to meet the measured accuracy.
Not sure it there is anyway to fix that ?

Rod ends could ? allow some adjustment in one plane I think , but not both ?

Paul

 

[stormbird]

Popshot

I assume you are talking about this ?

Was your vehicle particularly fast or heavy or both to break a M10 rod end ?
HD rod ends were mentioned as NOT being used as they simply snapped instead of bending first.

Paul

Sorry DannyC thread hijack in progress

 

[stormbird]

DannyC

If your tabs are thick enough can't you just machine the 2' off using your mill ?
Maybe fill the axle hole first with weld then redrill after the above operation ?

Paul

 

[DannyC]

DannyC

If your tabs are thick enough can't you just machine the 2' off using your mill ?
Maybe fill the axle hole first with weld then redrill after the above operation ?

Paul

Easiest is the slit, bend and weld up. Milling would be too complicated to try and get 2 fresh parallel faces. My little mill probably would really struggle (I would struggle too).

 

[DannyC]

OK, so armed with a generous selection of Anglo-Saxon words, a hacksaw, a grinder and a Tig Torch I altered the steere, and we have a result!
I now have 2 steerers that both point to the general area of the contact patch.

Note the purposely vague wording there.

I tried my hardest but I could not get them exactly the same. There is a 0.34° difference.
For a nanosecond I was distraught beyond mere words.

But then I remembered the seemingly wise-words of another lunatic on this forum (you know who you are Pike).

He said "But we aren't NASA!".

So I am cutting my losses and calling it quits. There will probably be more than 0.34° error in the head tube angles anyway.

 

[undertoad]

We can try for rocket science, but need to accept our (Insert appropriate language, here) limitations.

 

[stormbird]

So I am cutting my losses and calling it quits. There will probably be more than 0.34° error in the head tube angles anyway.

How short do you think the head tubes could be and still work ok ?

Paul

 

[DannyC]

How short do you think the head tubes could be and still work ok ?

Paul

I'm not sure Paul, I think 3" is not impossible. The tadpole has 3" headset tubes and threadless inserts, but the basic principles of the bearings are the same. I have a 1" 24TPI die to put additional thread on the stem rather than cut & shut when shortening them.
What I like about standard 1" threaded steerers is the fact that they offer opportunities to insert goose-necks with lights and mirrors on top which I see as a real bonus.

 

[Popshot]

Popshot

I assume you are talking about this ?

Was your vehicle particularly fast or heavy or both to break a M10 rod end ?
HD rod ends were mentioned as NOT being used as they simply snapped instead of bending first.

Paul

Sorry DannyC thread hijack in progress

Yes. That's what's needed. The trike I bent M10s on was a tilting prototype that didn't work and covered less than a mile. In that short time the M10 rod ends had all bent. The trike wasn't heavy though I am.

I use M12 HT bolts in a few of my contraptions and they haven't snapped by being HT. Maybe HT rod ends are much harder than bolts?

 

[DannyC]

Just out of curiosity I weighed a complete wheel, backplate & kingpin.
3.06Kg, so 6+Kg for front wheels. It all adds up doesn't it?