First trike build engineering questions...

[DELTA V]

Greetings to all. Working on a new trike design and have a few (HUNDRED) details to work out.

Design layout more or less set so far:

Tandem seating, rear drive.

3.8L GM FWD Automatic drivetrain (220HP) putting the track in the 60 inch hub to hub range.

Wheelbase in the 132 inch range due to the seating. 24-26 inch rolling diameter tires.

Center of gravity somewhere near passenger rear seat bottom.

So now the questions:

1. Is there an issue with overturn angle with these specs?

2. Having almost unlimited choice of Rake, Trail, and fork length at this phase, how to determine the best geometry for these?

3. What kind of steering stop angles are needed lock to lock to be able to have decent turning radius?

That will keep me busy for a while! Thanks.

[rhino 2]

Welcome to Trike-Talk, Rico...........From New Jersey......

[Zammy]

Welcome to the forums Rico, you probably will get more answers posting your questions over in the home built section. Sounds like quite a project.

http://www.triketalk.com/forum/forum...e-Built-Trikes

[David357]

Hey Rico,

to Trike Talk from South Florida.

Please keep us updated with some detailed pictures.

Your concept design sounds awesome.

[DELTA V]

Started out as a fairing, got a little carried away.

[Gorilla]

welcome aboard

[peteg59]

Welcome to Trike Talk Rico.

Not a design or structural engineer, so no help in the "paperwork" or CAD stage of your project but there are others on the site who might have some worthy ideas for you.

The "enclosed" style bodywork you are showing is relatively unique. Most conventional motorcycle based "trike" designs that you see on the street are somewhat more open to the elements.

From my limited building experience that design does lend itself to automotive drivetrains, as you are planning, much better than trying to adapt a motorcycle engined base to an fully enclosed bodied, rig.

Best of luck in your project, & I think I speak for some others on here in saying: please feel free to post pics of the eventual build if you feel like doing so.

[Loner]

Sounds like an enthusiastic start to designing a fun and safe trike. I think your basic layout will need to be a bit more defined to really offer good recommendations. My early comments; if a conventional engine forward arrangement is envisioned, then the CG falling under the passenger seat seems to be estimated a bit too far rearward. Once some [rough] overall starting point dimensions (frame length, motor/tranny positioning, seating placement, etc.) are drafted, then the other specs can begin to be evolved. CG placement can be more accurately estimated, which will influence front end particulars (fork lengths, front end suspension style, rake, etc.). Sketch what you envision for a layout to go under your sleek body and share it with us and then we can begin to help with the tech stuff. Unless you are well-versed in CAD you are probably at a good point where a few #2's, some erasers, and some fine-lined graph paper will serve well to capture your ideas for posterity. Once roughed in, then graphic layouts can prove out your ideas and visualize them handily.

Early response with what you've shared (just so it doesn't seem like I'm copping out to everything) would be: short front forks with some type hydraulic damping if feasible, low angle neck rake (24-26 degrees from vertical might be a good starting point), low mounted drivetrain (= low CG). With what you describe - a 60" width and 130" wheelbase, tip factor should not be a big concern so long as there is not an unusually short distance between engine CG and front axle (motor/tranny weight needs to stay well inside the axle-axle-axle triangle).

Good start - keep conceptualizing and keep us up to date. We are all interested in new designs and builds whether we can contribute much help or not.

[desertclassic]

Welcome, I admire someone that builds from scratch. Looking forward to the pictures. Jim

[Jack Klarich]

Welcome to Trike Talk

http://trikerdon.50megs.com/raketrailtrike.htm

Look here for starts

[DELTA V]

Thanks for all the responses! Links provided a ton of info as well. The rake and trail calculator got me on target quickly.

Moved the mindset quite a bit from motorcycle to car like. (I have never driven a trike)

Did not find info on the "axle-axle-axle triangle" mentioned?

7 degree triple trees get me to 2.5 degrees of trail.

Opinions on getting that all from the trees or splitting it with offset raked neck cups?

[DELTA V]

Got the rake and trail starting point using the calculator. A little less rake than with the 7 degree trees and better trail (I think).

Any opinions would be welcomed.

[Loner]

After looking at your chart, I offer this recommendation for your review:

Facts used - 1) 40 degree effective rake, 2) tire diameter 25.5", 3) desired neck height 32.79".

1. 1/2 tire diameter = 12.75", so axle is 12.75" from ground.

2. You then need to get 32.79" - 12.75" = 20.04" rise from the fork tubes.

3. At 40 degree angle, each inch of fork length = (90-40 degrees) divided by 90 = .555" rise.

4. So 20.04 divided by .555 = 36.1 inches of fork length needed.

5. So your forks will need to be 8" longer than the anticipated 28".

As a crosscheck, 28" fork length yielding .555" each inch = 15.55" plus tire radius of 12.75" = 28.3" top of tubes/neck height, short of the desired 32.79" by 4.43". 4.43" divided by .555 = 8.05" additional needed.

By your chart, you can see that you can't take a starting fork length of 28" and kick it out another 6 degrees and it still be 28". So your New Fork Length in the table should be 36".

You asked for a check on the numbers - so I hope you take my comments with a grain of salt. I think you are well on the way to doing a great design. Keep up the great work, and if my numbers are all wet for some reason please point it out.

I look forward to seeing this project progress.

[DELTA V]

Hi Loner, I'm not much of a mathematician so here is what I came up with on graph paper. 1 square = 2"

(Just noticed graph lines not showing up in scan) I'll work on that.

My measured fork length is 29" top of trees to axle center.

Started fork at 40 degree rake.

Backed out 6 degree tree to locate neck.

As it sits it has 10" ground clearance and wheels are 26" diameter in the sketch.

I guess my drawing does not match how the rake calculator works.

Thanks for helping on this and check my drawing against the numbers if you could.

[Loner]

From your new numbers:

Top of tube height will be; 29 x [(90-40)/90] + (26/2) =

29 x .555 + 13 = 29"

Neck height will be; 29 - (2.5 x .555) = 27.6"

Does this compare with your graphical depiction? It deviates quite a bit from your target neck height of 32.79" in the first chart. What are you using for your objective (fixed) points - neck height, tube length, etc.? With that target fixed data established, everything else is a variable that can be calculated and adjusted.

One note from a practical side, testing that I have done in the past has shown that hydraulic tube forks generally lose their compression and begin to flex at rakes above ~37-38 degrees. You might consider using a leading link type fork for your design that will allow total flexibility in setting fork dynamics.

Again, my calculations are always to dementia at any given time.

[Sidecarbill]

You don't need raked trees if you're building an inclosed body. Adjust the trail by the angle of the steering head. It won't look odd because its hidden.

[DELTA V]

Some of the confusion seems to be the calculator (which I have deemed more or less useless). The neck height was not an input, the calculator did that.

Maybe I'm working backwards to the norm.

First was the wheel tire location with the 29" forks attached and leaned to wherever the neck ended up. It was not a variable. Everything else was derived from that location. Thought the trees would bring in the trail to an acceptable level.

As far as a no rake fork goes, that was my first thought but could not find short enough forks to fit within the body. The 29" overall was the shortest I could find leaving me with the 40ish rake. I will try to back it off a few more degrees. Hopefully the forks will compress.

I have seen quite a few long forked, highly raked choppers that seem to function. Do they use a weaker spring?

As long as it has stable turns and does not tip over, I'll be happy.

[Loner]

I agree that the rake/trail calculator numbers are somewhat muddying the conceptual layout. That myriad of calculations prompted a bit too much drill-down on my part. So for the sake of simplifying let me offer a bit more reserved comments and considerations.

One of the trikes I have built in the past was called a Trimuter, roughly based on a design originated by R. Q. Riley (do a search to find his website). Absolute poor quality since this photo was taken before the digital age came about, here's mine:



Google 'Trimuter' to get better photos of others built from those plans. Not easily seen in my photo, but it uses a front fork that lends itself to a flexible layout to fit a variety of designs. The fork and frame layouts can be better seen in these images:



The leading fork link is single sided with an automobile type hub. That allows easy removal of the front wheel and flexibility in choosing wheel types and sizes.

If you are fabricating your own frame, this would be an easy addition. Check out Riley's site where he has a truckload of information as well as design concepts. I also will refer you to a similar thread here on TrikeTalk where we discussed front end configuration for a low, enclosed trike design; http://www.triketalk.com/forum/threa...forks-on-GS650 .

Great progress, keep it going!!

[DELTA V]

That is pretty kool

Wish I would have found that before dropping a grand on the forks Sunday

Will have to make it work now. No time to waste, on to the next dilemma...

Are there any existing drawings or examples of connecting a tilt steering column/wheel to the triple tree? I know the angles are not ideal, but don't want a "Bus" steering wheel angle.

Aircraft Heim joints? Small CV joints?

Guessing I need about 30 degrees Left and 30 degrees Right. (?)

Really appreciate all the input so far, keeps me moving. (Deadlines ya know)