RC downhill bike design -

[HAL9000v2.0]

Hi Matt,
Yes, I am fan of space frames too, but it is Pita to weld it. Initial plan was to do it with lot of 10mm round tubes 0,8mm wall thicknes. Then after first sketch I changed it to 20 x 1,2mm And only few of them is required and the weight is almost the same.

 

[CroDriver]

WOW, this looks extremely cool! Hal, we have to buy some Aluminum welding equipment

 

[recumpence]

Hi Matt,
Yes, I am fan of space frames too, but it is Pita to weld it. Initial plan was to do it with lot of 10mm round tubes 0,8mm wall thicknes. Then after first sketch I changed it to 20 x 1,2mm And only few of them is required and the weight is almost the same.

I love welding, though.

The big problem for me is not overdoing it with too many tubes. Either it gets too heavy, or access to components becomes impeded by all the tubes.

Matt

 

[12p3phPMDC]

That KTM is awesome...
But that is a huge angle on the rear CV joints...!

 

[HAL9000v2.0]

Some progress. I actualy manage to do about 15 minutes/day... it is so frustrating...

But the frame is allmost finished, have too make BB and some small pieces then welding and grinding then chains, brakes,tensioners and shifter... then paint...then...

 

[CroDriver]

I knew that it would be something odd when you mentioned that rear suspension position yesterday but this is sick

Is unsprung mass an issue in bike design?

 

[HAL9000v2.0]

Not any more.

 

[johnrobholmes]

That is wild! How do you think the rear brakes are going to act since the long chain is transmitting the forces?

 

[HAL9000v2.0]

That is wild! How do you think the rear brakes are going to act since the long chain is transmitting the forces?

The force in chain will be simmilar to coaster brake system so I don't se issues there. the rar chain tensioner will be problem because it will have forces in both ways. Also the brake will interfere with suspension travel, not sure how or is that good or bad but we will see...

 

[Miles]

Looks incredible, Hal

I like the straight arms....

 

[deecanio]

indeed, very impressive frame hal.

D

 

[AussieJester]

WoW... very unique design indeed Hal...where are the batteries going?

KiM

 

[HAL9000v2.0]

in Batpack...

 

[johnrobholmes]

have you crunched any numbers on the antisquat when the suspension is at ride height? I know it all changes when incline/decline and rider position/ weight changes, but I would be very interested to know how it will act under acceleration/ braking. From just an eyeball, I would guess that the A/S% is very high and it will lock out the rear suspension under power and squat down when you hit the brakes.

 

[HAL9000v2.0]

I gave a lot os toughts on this problem. Still thinking on this and can't wait to try... so on breakind there are basicly two momentums in opposite directions. One is when you push handlebars around front axle and the other is your feet pushing frame around swingarm pivot axle. The ratio of this two momentums is dfferent and it depends on how hard you breake and where are you leaning. Ideal is when they are the same and in different directions. I this case that os when on hendlebar os 65% and on pedals 35% of my weight. And that is pretty hard braking. On "slower" brakeing the bike will probably dive with rear end. and that is why I put BB highet then front axle to make momentum in different directions. I made quite complicated calculation in Mathcad with 6 vectors on this bike geometry and my weight and hight. The result is quite good but I am not sure i take all variables in. Another thing is why I put swingarm axle so high; I tried to reduce dive on hard acceleration. Seat maybe looks high but now is in position like lowest position on 19" frame. There are missing headtube berarings so actualy the frame will tilt back little more...

 

[johnrobholmes]

Indeed, there are so many variable it is hard to know what will happen until you ride it. I had not considered the pedal and handlebar weight bias, and seat weight is another consideration too. It is much harder than finding antisquat on a truck!


It is certainly best to have some antisquat under acceleration so that traction is good. I think it will be extremely difficult to build a bike that is neutral at all times without complicated suspension pivots that will make the bike more flexible and prone to repair. Beyond that, even changing the rider weight will change the antisquat, so a designer must make a lot of guesses!

 

[mikebikerad]

sick frame!!!

 

[AussieJester]

Howz that weather Hal? anymore to reportz on the bike? We needz our Hal-a-fix

KiM

 

[HAL9000v2.0]

The Spring came as someone switch off the winter and swithced on the Spring, The temperature raised over night for 20°C and all the snow is gone. The frame is finished and now I have to dissasembled it and powdercoated. I run over my camera with a car so pictures will be after next paycheck. I have few other things to finish before can come back to this one. First is mold for new canopy for greyborg RC and swingarm jig...and must finish drawings of "Ctrl+C" bike...also the cruiser is waiting...days are so short lately...
I ordered scorpion controller 200A and rucksacke for batpack. I loved the idea of batteries in backpack so much that I will make few versions of that.

hooroo, Kim.

 

[AussieJester]

The Spring came as someone switch off the winter and swithced on the Spring, The temperature raised over night for 20°C and all the snow is gone. of that.

hooroo, Kim.

Woohooo we too can celebrate here in West Aus Hal..our Summer officilly finished March 1st !! and we went from 42c to 38c overnight lovely stuff ..... :-|

Look forward to more update Hal you now have NO excuse ;-P

KiM

 

[HAL9000v2.0]

Still someone playing with that switch, snow and sub zero are back...
I almost finished the frame, I have to make extra wide bb first to see where can I put the motor...

 

[Miles]

That is like no other, Hal....

Would it even be recognised as a bike frame, without the saddle?

 

[AussieJester]

That is like no other, Hal....

Would it even be recognised as a bike frame, without the saddle?

Looks like a Transformer to me! ...im just waiting for it to unfold into a finished bike and starting killing thingz

KiM

 

[etard]

That is like no other, Hal....

Would it even be recognised as a bike frame, without the saddle?

Looks like a Transformer to me! ...im just waiting for it to unfold into a finished bike and starting killing thingz

KiM

Or maybe a battlebot that "pecks" you to death with the seat!! :lol:

I am loving the position of the rear shocks, I have a Fox Triad on my Specialized that has a lockout and propedal feature, I would much rather have it there for easy access to lockout. It looks like your rear hub is stationary, shouldn't it be horizontal dropout for chain tension? I'm sure you have thought this through already, just trying to figure it all out....

 

[j3tch1u]

I gave a lot os toughts on this problem. Still thinking on this and can't wait to try... so on breakind there are basicly two momentums in opposite directions. One is when you push handlebars around front axle and the other is your feet pushing frame around swingarm pivot axle. The ratio of this two momentums is dfferent and it depends on how hard you breake and where are you leaning. Ideal is when they are the same and in different directions.

good to see everything coming along. one potential problem i see may be twist/flex of the swingarm in relation to the frame (especially if you stomp on the pedals). you may need to add another linkage where the swingarm intersects the cranks. good work--very unique build!