Join Date: Jun 2004
Location: PERTH WESTERN AUSTRALIA
Bikes: TADPOLE TRIKE
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I am making a tadpole trike and I cant get my head around the king pin and axle location.
I know what camber and caster/trail are.
I think I have looked at nearly every available web site on this including Ricky Horwitz's excellent site.
I have taken the following two paragraphs into consideration when trying to get it all correct. they are quotes from sites I have found on the net.
KINGPIN TO WHEEL AXLE ORIENTATION
The placement of the wheel axle, in relationship to the kingpin, drastically affects the steering. If the wheel axles are placed in front (lead) of the kingpin axles, the 'caster effect' is defeated making the steering unpredictable and extremely unstable. However, if the wheel axles trail too far behind the kingpin, the steering may be influenced by road shock and brake steering.
Just like a two-wheeler, a trike's steering needs to self-centre if it's to handle well, and especially to be stable at speed. And just as on a two-wheeler, this is usually achieved by inclining the steering axis (the steerer tube on a bike).
Clearly, this inclination is in a plane at right angles to the centre point steering inclination we've just mentioned: that is an angle seen as viewed from the front of the trike: the caster angle is as viewed from the side.
Around 10-14 degrees of kingpin caster inclination seems to work OK on most designs.
Caster effect can also be achieved with no kingpin inclination, offsetting the axle mounting points from the kingpin axis instead. Read up about 'trail' at, for example, Sheldon Brown's splendid website if you're interested. But most commercial trikes seem to just mount the axle right on the kingpin axis.
I want to put front brakes (v brakes) on the trike, therefore I need somewhere to mount the brakes
I will use steering similar to the new Greenspeed and the Logo. ie from rear of steering knuckle to the same side of handlebars.
the kingpin has a 11 degree camber which is the correct angle to give me centre point steering.
so from the king pin which I will weld to a piece of 30x30x1.6 x 180 (sq tube)
I want to place the axle (12mm grade 8 bolt) 45 mms to the rear of the kingpin centre. (this will give me my caster)
Directly above the axle I want to weld a 20-25mm pipe that is bent so it goes over the wheel and down to the other side on to the axle with a fork arrangement. this gives me a place to mount the brakes on the top of the tube.
I will mount the steering tie rod to the rear end of the sq tube
I have toyed with this for weeks now. I have looked at other designs but I think what I have come up with is the best for me.
I know the brake mount will work ok but i'm not sure about the axle placement.
all the factory trikes I have seen mount the axle under the kingpin. the only one that I know of that does not is the Anthrotech. they mount the axle forward of the kingpin see pic (anthro wheel) this goes against all the rules (unless i'm missing something) they have crossed steering rods. This might be why they remain stable.
Forward or rearward would suit me I only need enough room to mount the brake tube to weld the brake mount on.
I can still get a good amount of turn without hitting the (brake tube) on the cross boom.
also good for mounting mudguards (fenders), mirrors,
the only other way I thought of is put a tube horizontally forward of rearward.
can anyone please tell me if I will have problems mounting the axle 45mms behind the kingpin.
I have drawn some pics might explain it better (hopefully)