3D dirt bike cake

i would use a t-pin looking something that is firmly planted into foam that is resting quietly under the bottom board

either pvc pipe or something metal like copper tubing that is food safe

how big is it going to be?

you can get pretty small pvc

if you get an elbow joint

http://www.made-in-china.com/showroom/sissybao/product-detailybQxhzYdLjVO/China-PVC-Pipe-Fitting.html

see the t shaped joint and the one in the bottom left corner? i'd use those for handlebars and insert the pvc pipe in there--this all comes in a most confusing array of sizes so have fun with that

but the big box hardware stores have it all out where you can mix & match and think yourself into a coma

that's how i do it

but i've also gone to plumbing stores and those guys were real helpful too

your step sister has a great step brother

that's gonna be a huge bike sculpture!

too cool

i've done a large enough tire for that, but it was laying down

for family birthday--they are so forgiving

esp since it was a red velvet cake and white chocolate cream cheese cake

sometimes my shabby on the outside is offest by the chic inside

and there was some kind of liqueur too

spaghetti spokes

But for your venture i would use foam for the tires

or cast solid chocolate

then i'd cover that with candy clay aka modeling chocolate to make the treads

hope you post a picture!!!

 i think i saw your vehicle in another post--well done! very cool

i mean you def could carve tread on the cast chocolate but every time you touch it you'll leave a mark

you could cast it with popsicle sticks coming out of the bottom of the tire

(where they can be inserted into foam for stability --located under bottom board)

but yeah it'll be fragile

i'd have extra hands to hold it during delivery

and valium

edited to say:

oh gosh now i wanna cast big chocolate tires

oh man, what fun!!!!!!!!!!!!!!!!!!

so exciting!

i used rice krispie treats for that tire and this was a good idea and a bad idea

that dang rkt would not stay in shape--it flexed  <grimace>

even though i let it setup overnight

somehow i arm wrestled it under the fondant  <rahr>

copper tubing would work great

you need some structure for the tire--unless you cast the chocolate

big learning curve working with choco, but doable

foam would work...can't eat that though

can't wait!!!

here's a low key 2-d  scooter

My 2nd ever 3-D cake was a motorcycle, also 2 feet high (in my pics).  Although I didn't have foot pedals I had pvc supports for them. I did use RKT for the wheels and the entire thing was covered in chocolate clay.  I used pvc supports and foam core for support in the wheels  and then covered the rkt with chocolate.  Plywood and foam core for support (with pvc) in the main cake.  It feed 200 people at that size.  My best suggestion is to make a scale drawing first, that helped a great deal with proportions.
 

sweetflowers.

so like five feet long

omg

wow wow wow wow wow

truly amazing

and the dual smokin' pipes---get outa here!!!

<chorus of applause>

thanks..,   I'll just say it was 45 hours of work, not counting all the planning.  It is 4 feet by 2 feet and 2 feet high.  k8 is right about the support for the RKT, which I did do.  The wheels were 11" round approx. and the RKT will collapse if not supported.  If you have the time, do a practice one first.  Your step-sister is one lucky girl and although this is a ton of work...you'll have a blast doing it! 
 

been wondering how you were doing

i mean in this thread you have from the simplest to the bad a$$inest

i do let my cakes fully freeze

are you used to rice krispies? that's another learning curve

~~~~~~~~~~~~~~~~~~~~

do you have a pattern?