Tadpole Reverse Trike Idea

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lowracer

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Oct 17, 2008
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Hi all,
Whilst pedaling my local roads early morning getting my exercise, I stumbled upon a jogging stroller being thrown away along the curbside trash. I took it apart made a quick pull behind trailer with its two wheels, pulled my daughter & doggy around the neighborhood for a few laps, then disassembled it since I really dont need a pull behind trailer & I had no space to store it. Then the item got thrown in my car trunk (not much room left for more bikes in my house, per wifey...lol).
I'm thinking again about a new project using the fairly stout axle piece that the two wheels plug into. The wheels have 1/2" (13mm) axles. I think they are solid enough for my purposes?
With the bicycle front wheel removed this piece can be mounted to a piece of wood and a U-channel. U-channel bolts to the fork with a long 3/8" bolt w/spacers. I've been successful with this U channel mount on '2-High' my motorized tall bike. I'll probably need to find a piece of throw away 2 X 4 (18" - 19") to mount across the aluminum axle, u-bolt to the wood and then bolt up to the u-channel.
I know this isn't how tadpole trikes steer (or cars or that matter). There will be no Ackerman compensation or centerpoint steering.
As a kid, I built an 8' oak motorized go cart using 4 skateboard trucks, 8 sticky skateboard wheels (Kryptos) w/ foot steering & a 2 hp Briggs for power. The go cart handled like a race car with that foot steering, low center of gravity and awesome traction (had to hold the sides very tightly on hairpin turns or risk getting thrown off).
If this steering arrangement works somewhat well on an upright bike with its higher center of gravity, I might then construct a DIY, No Weld, recumbent platform around this very simple steering arrangement.
Here are some mock-up pics with the aluminum posts left uncut (they will get cutoff).
Cheers,
-Lowracer-
 

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Theon

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Jan 20, 2014
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I think you may need less steering rake, you may find it strange to steer as the bike will tilt the wrong way as it steers due to the rake.
 

lowracer

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Oct 17, 2008
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Theon,
To reduce rake, I could mount the fork lower onto the axle dropping the front end of the bike. What do you think of reversing the fork as well (brake posts facing rearward)? I did that on a bike conversion to stand-up scooter and it helped higher speed stability but made low speed stability get floppy.
-Low-
 

lowracer

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Oct 17, 2008
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Theon,
I see what you mean by less rake.
I found this pic of a trike mod and can see that the std head tube rake has been changed.
My foot steer go cart had about zero rake w/trail built into the skateboard truck offset.
Also, I was thinking that at slow speeds both front wheels stay planted on the ground, but at higher speed, the inside wheel for the turn initiated could carry all the weight and the outside wheel could lift up off the ground (while its an upright w/higher center of gravity, if changed to a lower recumbent may not be possible)?
-Low-
 

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Theon

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I'll get my Tadpole out of storage very soon, It tends to take up a fair bit of the bench and makes the place untidy.
Unless your only looking at very low speeds, this is something that really should be done properly.
Low center of gravity would be my preferred plan as you will not get the required tilt to balance the side ways forces of turning and you will likely highside.
Trail is very important if you want any sort of higher speed handling, Rake may be better slightly negative if your planning a solid/straight front axle. Reversing your forks will help give trail to zero or negative rake and is worth a try.
I would also look at some triangle braces, your suspension forks are likely to jam with that sort of side loading, I would probably make a solid front end?
 

2door

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Sep 15, 2008
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Lowracer,
My gut feeling is that you're not giving a lot of attention to the steering geometry of what you're planning. As Theon said, it might be okay for very slow speeds but I think this thing will prove extremely 'squirrely' at anything over 10 to 15 mph. It might be a handfull at even lower speeds.

I'm trying to invision what happens to the front end when you steer. My feeling is that the outside wheel will try to rise off the ground leaving you unstable on three wheels.

I'd have to actually see the trike and move things to have a better idea but I'm afraid I can't be optimistic about this concept. And yes, I had wooden carts too that I steered with my feet. But they had four wheels and a very low center of gravity.

I wish you luck and ask that you report on the progress of this build. I'd like to be proven wrong and see you design a whole new concept to three wheeled vehicles.

Tom
 

Intrepid Wheelwoman

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Oct 29, 2011
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Lowracer, the bicycles you build are ingenious and I always enjoy seeing what has sprouted from your active imagination, BUT in this case I feel I must join with the two learned gentlemen who have commented so far and counsel caution.
 

Theon

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If done properly, a tadpole trike is a lot of fun, but I strongly recommend reading up on steering geometry, and following what you read. Ackerman's steering although not necessary is the only thing you have , which makes for a great trailer.
Correct caster is one of the most important aspects, if you plan any sort of speed, otherwise your wheels will likely start 'dancing'. I think your idea may work, to a point, It's never going to handle real well, but as long as you put careful thought into the rake and caster?
 

lowracer

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Oct 17, 2008
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Thanks to all for pointing out handling concerns.
I found a piece of wood to cut & begin mounting this contraption.
As with most of my builds, I put it together and then see what happens...lol
If it handles like garbage (which it most likely will) I wont be adding the gas engine to it.
It could end up morphing back into a foot steer motorized wooden trike with (2) skateboard trucks & (4) skateboard wheels doing the steering, & (1) 12.5" scooter wheel out back for powering & braking. I'd like to keep this project consistent with no cost ghetto engineering.
-Low-
 

cannonball2

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Oct 28, 2010
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Colonial Coast USA.
LR, I had a similar thought on using standard bike frames for a trike. I had a plan to weld the fork straight(could be bolted too), build a steel tube axle that welded/ bolted to the fork with king pin steering and tie rods. The handle bars and stem would have an extension through the fork to the tie rods for steering. I read about king pin inclination, Ackerman etc., then S canned the idea as a lotta work if I didn't get it right. Gotta hand it to you. You aint afraid to try anything with bike parts! Go LR! Just don't get hurt!
 

lowracer

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Oct 17, 2008
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Charleston, SC
CB2,
LOL Thanks!
As its been said, 'Crazy is as Crazy Does'.
2 days ago I found a little pink Razor Sweet Pea electric scooter being thrown away sitting on a curb with a 'Free, just needs batteries' sign on it so I picked it up.
Now I have another gas conversion project on my hands (daughter loves it).
Not sure yet if it'll get friction or chain drive but probably chain.
I'll get a new thread started once building commences.
-Low-
 

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lowracer

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Oct 17, 2008
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Charleston, SC
CB2,
That was a cool contraption & I really liked the use of the threaded pipes.
I could imagine building a lowracer recumbent using that same method.
Appreciate the link
-Low-
 
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lowracer

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Oct 17, 2008
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Ok, I finally got this simple front end mounted up. I found a small piece of 2X4 and bolted the fork mount to it & then used 2 aero handlebar type clamps to bolt the axle to the underside of the wood. I took it for a short slow ride around my neighborhood to test the steering geometry.
This thing is messed up!
The angle of the steering head screws the handling up to about an almost unrideable state.
Perhaps if the steering head angle was perpendicular to the ground it would handle better but I won't be working on this design any further.
Chalk it up to failed experimentation...
Cheers
-Lowracer-
 

cannonball2

Well-Known Member
Oct 28, 2010
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Colonial Coast USA.
Well you stuck it out to the proof stage. Kudos LR! Its kinda like my Jet Ski with an outboard aberration. Sure looks like its gonna work and it might if I pushed it further, but aint gonna. Like the term failed experimentation. No such thing!
 

BarelyAWake

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Jul 21, 2009
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Agreed, the experiment a success in proving the concept - in this instance "almost unrideable" ...can't fault the trying, only the result. Someone had to try it to be sure after all ;)

I came across this pic in my wanderings & thought of your interest, your experimentation with bicycle forks/front ends for making a tadpole, the two wheels in front steering w/o full fabrication - it's not ideal ofc, there's still be higher speed oddities, but still somewhat simple to build w/what's at hand... the rear wheel or wheels depending on your wants ofc;