Bobs 2024 Build Off Build

[bob58o]

I like this a lot.
Very “meat and potatoes”

I’ll arrange some steel in a minibike shape later and then start adding engine and gofast fan and Jack shafts and sprocket and pulleys and wheels to get an idea of spacing.

I was originally trying to put the weight of the engine as far forward as possible in an attempt keep center OG gravity at about the mid point of the 48 or 50 or 52” wheel base.

I might just try to keep JS close to axle with short chain and engine as close to jackshaft as available lengths of Comet belts will allow.

In the photo from before… the JS is very tight to the engine but spaced from the axle. I might slide the [engine + jackshaft] back and accept that the center of gravity going to be closer to the rear than I wanted.

I’m just going to repost a bunch of previous mock up photos…

 

[Master Hack]

Why do ya say ya have to move the engine back?
Change the angle and/or bend the front down tube. Go forward til the front wheel hits if ya want.

Am l missing sumpthin?

 

[bob58o]

Never mind about that.
I won’t explain what I was thinking because it was wrong. And won’t try to draw because it requires 3D.

Now the only advantage of pushing it all the way back if keeping the riders left leg in front of the belts and pulleys.

I can keep these as short as 24 inches.
I noticed I had marked them previously to cut to ~ 35 inches.

I believe the 35” length allowed the supercharger, carb and air filter to fit and keep a simple single down tube attached to front at a natural looking angle. Sorta shown in first photo.

 

[Master Hack]

I'm done adding confusion to the plan, I imma gonna shut up and see what ya come up with.
But its fun tossing ideas around just see what goes wro...err ahh I mean happens.

 

[Whitetrashrocker]

I'm done adding confusion to the plan, I imma gonna shut up and see what ya come up with.
But its fun tossing ideas around just see what goes wro...err ahh I mean happens.

Bob seems to over-think things enough for all of us. Don't need to add more thinking than necessary.

 

[Master Hack]

Bob seems to over-think things enough for all of us

Thats weird! I haven't noticed.

 

[bob58o]

Do I lose points if a cut off wheel is required to change belts?

 

[Denny]

Do I lose points if a cut off wheel is required to change belts?

Yes, as many as 85 out of a possible 100.

 

[bob58o]

Yes, as many as 85 out of a possible 100.

I’ll look for another way to change my pants

 

[bob58o]

I think it’s safe to add this “tail bone” to the “back bone”

Im gunna use the 1x1.5” for it. 15” long so it’s the same length as the width of the bottom (outside to outside).

I’ll notch out 1x1.5” in the back and top of the 1x3” backbone and sit the cross tail so the top of the tail is flush with the top of back bone. Leaving a nice “T” when looking from the top to mount a seat.

Does this seem like a reasonable joint?
Better than just sticking the one tube on the back of the other (without the notch)?

 

[bob58o]

I assume the “correct” / “fancy” way involves cutting and bending the side of a tube to close off the end of it?

 

[Master Hack]

And/or angle cut if ya want a straight down tube and any combination of bends and angle cuts that satisfy yer inner design mogul.

 

[bob58o]

I think the tubes coming down from that cross tail thing might both be angled. Haven’t decided yet.

Im my head I am imagining “those down tubes” with the 1.5” side in the vertical plane and the 1.0” side in the horizontal plane.

 

[Master Hack]

Ya could even get fancy: two parallel down tubes. Parallel when viewed from the side spaced a couple inches apart. Then ya could even get some laser cut stainless sheet to go in between the two tubes.
Oh, I wasn't gonna....
stir the pot....

 

[Master Hack]

Yer planning on using the 1 x 3 tubing for all the frame members? If there is a major earthquake predicted, can I come and hide under yer bike?
Have you figgered out the final weight?

There I go again....

 

[bob58o]

Nah, still going with 3.03 lb per foot (IIRC) 1.5x2.5 x0.125” x ~6 feet for the bottom of this thing.

6 ft x 3.03 lb / ft = at least 18.2 lbs of bottom rail

9.5 lbs for 3 feet of 1x3x1/8

Or something like 30 lbs so far in just those three parallel tubes.

2.5 lbs for 15” of cross tail @ 1x1.5”

12.5 lbs for 80ish inches of 1x1.5” for 4 down tubes from cross tail.

Another 5 lbs for head and down tube?

About 50lbs for frame without engine mount?

BTW, I believe I’m going to have the cross wing directly able the jackshaft… which is about 9” from the end of the bottom rail.

 

[bob58o]

I’m guess the steel frame alone will probably weigh close 60 lbs naked.

 

[Master Hack]

It's plenty stout!
Thats the way I build, tough, but heavy!

 

[bob58o]

About 7 lbs of pillow block bearings.
Didn’t realize they were that heavy.
2lbs for a 1” bearing?

2x UPC202-10 (5/8) for jackshaft
2x UPC205-16 (1”) for live axle

 

[Master Hack]

Then ya add in things like engine, tires and wheels seat, handle bars, yada, yada, yada.