View Full Version : steering boom angle

02-09-2014, 05:47 PM
got my plans, getting parts together, modifying a bit. i understand Akerman and caster but is there a reason the steering booms are swept forward and up? the angles for the front tire pivots can be be maintained with out doing so, ie teeing straight off the center out. i have see other tadpoles that dont to this and some that do.... what am i missing? here is a rough sketch i did that might help explain why i am asking, i really need to sweep down and also parallel to the center bar would be easier. thanks much.

ps. 110mm inline speed skate wheels


02-09-2014, 07:03 PM
Assuming you are building a tadpole trike , nothing is written in stone EXCEPT the caster and camber angles of 14 degrees from vertical ( worked out by drawing out the centre point angle and the caster of 76 degrees from horizontal , I have built 2 trikes similar to the streetfox using a straight boom and a stepped straight boom .
See the leaner meaner thread for the stepped boom and the MKII tadpole trike threads . Both trikes used a straight boom to reduce the wheelbase by 4 inches .

the other dimension is the height of the bottom bracket spindle from the ground of 14 " to stop heel strike .

with 4" wheels hope you find somewhere smooth to run on !

hope that helps

regards emma

02-10-2014, 06:32 AM
Just a thought, how do you turn 5x110mm inline wheels without scrubbing them. I'm assuming you are having front wheel steering.


Radical Brad
02-10-2014, 07:20 AM
You could modify your caster angle as needed if you are going with the skate wheels. As tomelect mentioned, there will be much dragging when steering, and possibly a few other things to deal with...

Much greater rolling resistance.
Very bumpy ride.

You will also need some kind of lockout on your pivot point, as a good bump in the road could force the entire wheel assembly to turn over and that would be a bad scenario.


02-10-2014, 11:17 AM
thank you all for you input. my AZ plans say 20 deg caster. 14 is better? also, since my steering rod will be directly over the front wheel contact point there should be no reason for camber angle.... right? 110 mm are the large speed skates, the bike is for paved trail only. each side will have a shock so shouldnt be to rough, also rear has shock. i am really interested to see if speed skate wheels have less or more rolling resistance than a flexible bike tire. 5 wheels might scrub to much, then i will try 4. (actually sold in sets of 4 anyway) will have bump stops in. working on a break. if is works might try adding 'leaning' into the mess. also, if it bombs, i will go back to tires. just really want to see if this is faster.... maybe this is all a dumb idea, but people said that about recumbents.... lol

02-10-2014, 12:33 PM
Faster is usually accomplished by reducing resistance. More wheels-more bearings. It appears you are going to be adding 8 to 10 wheels totals if you hold with the tadpole configuration. That is 1/4 to 1/5 more resistance to moving down the road in bearings alone. As to caster angle each plan is built on its own merit and Brads experimentation with what works. Streetfox and Warrior each have the caster that work for them.
The sweep forward design was to help with keeping the Center of gravity lower of the bike as designed. It also allowed the ease of getting the Rake and Trail correct on the Warrior when assembling. Which affects steering. So your design your center of gravity is going to be really high in comparison to the center of the front axles. Also I have no idea of how your rake and trail are going to work out. Playing with the design is fine if that is what you want. But COG issue have defeated a few riders here. As well as the Rake and Trail affect how much work you will have to do to hold the trike straight. If built to plan the Warrior and Streetfox will travel straight without much input to the steering. A bad rake and trail will have you force the trike to keep straight as it will tend to go all over the place.
Lowering the frame as drawn could be problematic as any rise you go over including speed bumps will have you scrapping bottom of the frame. Not to mention the drag of the chain across the ground. If you take a good look at the photos your chain will drag the ground. If you add too much tubing to reroute it, it will give far more resistance to pedaling. The other issue I see with your lower the frame is the pedal to ground clearance. The pedals barely clear the ground when built to plan. By building to your lowered design your probably going to hit the ground with your feet all the time.
And Just an FYI- Shocks tend to absorb power and speed. So good luck in pedaling this. I'm not saying it is impossible. But I don't think your going to like the results.
but this is just an opinion. Go ahead and keep us updated with photos. There could be something we are all missing that your drawing is not reveling. After all it is your creation. and if it doesn't work you have a grinder a welder and can rebuild it anyway you want. Ticktock had done this several times to build his perfect ride. It is perfect for him anyways.
As an inspiration I refer to the movie "Meet the Robinsons" Keep moving forward. It did not take Thomas Edison 999 times to fail to make a light builb. It took him 999 times to figure out how not to build a light bulb.
The point is have fun however you make it.

02-10-2014, 12:35 PM
Another point is the rear brake is not an effective form of braking
front brakes are more effective as the rear locks up

regards Emma

02-10-2014, 02:22 PM
Just my take on this.....
The forward sweep on the Warrior steering booms is primarily to make it easier sitting and getting up from it without catching your legs on them, not an uncommon fault on some trike designs,the upward rake makes cutting the codsmouth an easy 90 degree cut.
You are correct that your idea needs no camber angle or very little, but your sketch shows caster angle which unless you have a pivot point above the wheel carriers will make turning very difficult.you will in effect be lifting the rear skate wheels off the ground and loading the front skate wheel only.
I rather think this is going to produce very heavy steering but if you only want to go in a straight line will work rather well but good luck with your build