Anyone built an upside down kingpin ?

Hi all

I realised after a conversation with DannyC that I really need to know exactly where all my steering components will go before I commit to cutting steel , it is the one aspect of the build that can't really be diverted around frame parts that are in the way etc etc etc

This needs converting into a kingpin !

The kingpin can only really go in one place as can the steering control rods and some sort of joining bell crank.


So first up a scale drawing showing the cross beam and 1/2 wheel and rough position of kingpin [ I got the ground clearance wrong it needs to be 5" ]
The drawing assumes the kingpin is built along Brads lines from a head tube and has a tube [ not shown ] at the top for the axle to go through this replaces Brads tab solution.
First up it is obvious the kingpin is inverted compare to any of Brads designs this brings 2 problems:-
a) it will have to be inserted from the top and so rely on the normal head tube [non]locknut to hold it
b) the steering control somehow needs fastening at the bottom , ideally positively and yet still be able to be withdrawn upwards.

Just engineering problems , there will be solutions out there ?

I've seen them that way round before but most of the systems that way have gone to a simple bushing rather than a bearing headset. As you say the locknut system isn't great on a headset and in that configuration the main bearing is resting on that nut system. Going to a plain bushing allows a regular bolt and a nyloc or aerotight nut. I'd consider either a split plain bearing or oilite for the job.
yes I have been researching the old FleetTrikes site as 25hz built them that way ..

simple jig to weld a tube to the bottom of a bolt [ I would have to reverse the jig when built ]

then bush's and a head tube [ of sorts ]


The problem then becomes how to positively mount a steering arm to the opposite end of the kingpin ?
It needs to be like this :-


The arms need to come off the kingpin and go behind but not below the cross boom


I mean this bolt could just run through some rod end bearings , light and I don't struggle to find a tube/bush combination that works ?

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Just drop the arms down at an angle from the top axle mount to where you need them.

yeah that though occurred to me whilst dog walking last night.

However mornings this dog walking session made me think I was just using the wrong starting point ?


This could be easier although I would move the axle mount to above the top horizontal so it is removable , oh and not base it on a front wheel hub , but you get the gist ?


or this but with proper angles !


For the adaptation of a "PPP" for this purpose, although it could provide the kingpin and axle arrangement it would make this part....
ridiculously long if it were 5" from jaw to jaw.

So better scale drawing and a FAIL big time !!!


Lines as follows :-
Red dotted 15' Centre point steering angle
Parallel blue dotted standard head tube width
Blue hashed area SA 70mm drum brake
Black line probably spoke position
and it all fails spectacularly ?

A kingpin below the axle cannot avoid the drum OR the spokes.

Rethink needed or we go delta .....

First obvious question but why not pull the kingpin away from the wheel and just weld a slightly longer axle mounting tube on? Second obvious question what is wrong with the previous idea of a Kart type "C" bracket?
First obvious question but why not pull the kingpin away from the wheel and just weld a slightly longer axle mounting tube on?

Because I am being a t*t :D, I have become obsessed with the kingpin inclination being 15' DOH

Of course it isn't it , as ypu point out it can be any angle [ almost I choose ] as long as it's axis hits the centre of the tyres contact patch ....

Second obvious question what is wrong with the previous idea of a Kart type "C" bracket?
Pride ? I did think it looked very sort of ' home made ' , ' Heath Robinson ' ?

back to the drawing board !

Upside down Kingpin = USS, I finks! Same animal, just come in pairs, Ark like.
Sadly no gold star !
well I sort of made ' upside down king pin ' up !
It means the wheel is attached to the top of the king pin and not the bottom [ standard in most commercial trikes/quads ]
Oh and to make matters worse the steering control arm needs to be fastened at the opposite end of the king pin.
So the making of the king pin needs to be ' clever ' otherwise it will be impossible to take apart.