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dmac257
06-09-2014, 12:17 AM
I spent two days on fit up for axle tabs and I am very happy with the center of the fork crown pointing directly at the contact point. They actually came out better than I thought.

THEN I spent another two days trying to get the steering tube mounted to the cross boom. After fit-up SEEMED perfect I put a tack on opposite corners of the boom ... then the fun started.

Lined up both front wheels so they are parallel to each other and as straight ahead as I could .. and both wheels are toed in at top. Grind one tack on each side and re-position and re-tack. Line up everything and after 3 cycles get everything straight up and down.

Here I disassembled the bearing and fork steering and carefully welded the steering tube all the way around following the instructions in the plans. Everthing looked good and I put the front wheels back on to check the angels after the welds cooled.

With three wheels on the bench .. the caster angle is the same on both sides but not quite what the plans call for. I figure when I am sitting on the frame the weight on the back will shift caster to the correct angle.

Now I check if the wheels are straight up and down .... and they are not :(

Every TINY shift in steering DIRECTION also changes the angle. I tried very hard to move ONLY one wheel but every time the steering angle of the opposite wheel changed also. If I put a framing square on the ground the wheel is straight up and down ... unless I turn it a little bit right or left.

Is this how it is supposed to work? Am I worrying too much about this part of the build?

dmac257

Twinkle
06-09-2014, 03:28 AM
Hi Dmac

With the compound angle of the head tube in the cross boom the straight ahead position is the ONLY one that needs to be RIGHT , as the wheels move from the straight ahead position the angles change and allow a little positive/negative camber , This is correct BUT at the straight ahead position the wheels MUST be at right angles to the ground and the cross boom should be parallel ,

I only built one streetfox as per the plan as I found the setup too time consuming and devised my own way of jigging the tabs into a parallel position and ensuring the head angles were right ( Pythagoras - tan made drilling the boom angles perfect ) and jigging the tabs in the straight ahead position made tacking the tabs into position simple .

Without being equal and with the correct amount of toe-in, tyre wear and looking odd are just two of the problems you will get any you will be left with a "wonky 3 legged donkey" for life .

Trying to weld up the individual units on the bench seems to be the way that allows the most discrepancy unless you make a left and right hanged jig

It is worth getting the tabs into the right position to ensure the trikes handling to not compromised by its steering geometry

regards emma

dmac257
06-09-2014, 04:15 PM
Thanks Emma,
I have already finished welding the steering tubes so I was mostly worried if the movement I am seeing is "normal" or not. This Streetfox is my first recumbent and my first flux core welding project and I have learned a lot. I will probably ride this trike for a little while and see what I would change for my next build. When I get a gas bottle I will build another one designed from the ground up.
dmac257

Twinkle
06-09-2014, 04:57 PM
This is the way I did it so the wheels were straight ahead and parallel then I jigged the boom parallel to the reference bar .
it was a little easier for me as I used a straight cross boom which made jigging less fiddly

http://s11.postimg.org/5ulkkmtsz/front_jigged.jpg (http://postimage.org/)
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