Dual Suspension 'Roo'

Theon · Jun 15, 2014

[/IMG]Dual Suspension 'Roo'.
Today my new 'Roo Print' motor is to be posted from 'Screaming Roo'.
This motor is said to come with all the best 'bits', and have an Australian assembled Computer balanced Crank Shaft.
I felt it deserved a nice bike, I was going to put it in my Goat, and see how it compares to the motor I built for it. I may well still try it out in the Goat, but I've been looking for a suitable Dual suspension bike to mount it in.
I've realized that I will have to build my own as I can't afford to get a flash new 'Top End' bike and I can't find anything secondhand that looks like what I want.
Besides by making my own I can negate the need of a shift kit by repositioning the swing arm pivot.
I picked up a duel suspension girls bike a while back not suitable for mounting a motor, but I could see potential in the parts.
Here's a mock up of the bike to get an idea of what frame dimensions I'm looking for in a donor bike.
Tomorrow I will head into the City and see what I can find.
Looks like I'm wanting a fairly standard medium sized mountain bike similar to my old Mongoose. I cut up an old Apollo a while back that would have been close.

Theon · Jun 15, 2014

I feel I may need to find two more Donor bikes for this build, a cheap steel 19" mountain bike for the frame, and another more expensive bike for the componentry.
I'll see what I can find, I still have a stash of old bits and pieces, and would be good to get out of this cheaply but once you start buying individual components things can add up quickly.
I like the idea of getting some decent forks, as well as a decent rear shock.
These can be bought individually, but I may be able to buy a complete secondhand alloy dual suspension bike for a couple of hundred and just swap in my steel frame?

Theon · Jun 17, 2014

Well after spending the day navigating the city, which is not something I'm all that good at or do very often, The only bike I could find that was close to what I was looking for was an old 'Dunlop' cheap crap Kmart bike that wasn't really as good as what I had hoped for. It was in an Opp Shop for $70, it couldn't have been more than $89 new and had a broken shifter and mis matched wheels! It was probably worth $30, So against my better judgment I offered $50 for it, Which was declined!
So I'm still looking.

mrfubs · Jun 19, 2014

i actually just stumbled across that Australian website a couple weeks ago, theyre crank are computer balanced? i wonder if they true them too even though truing these cranks with out welding the pins after is pointless. let us know how the vib's on that motor are once you get er screaming!

Thats pretty neat, i hope the Frankenstein bike works out well for you im very ceriouse how it comes together. If you can make it work that would be sweet because you could put a big sprocket on and do trail riding!

HotRodRob · Jun 19, 2014

Cool ideas Theon. I'll be checking back in on this one. What is an "Opp shop"? Is it like a second hand store or something like that? I've never heard of that. Keep the pics coming mate!

Theon · Jun 19, 2014

Opp Shop is Ozzie slang for Life Line or other church based recycling stores.
I have not found the donor frame still, but will try and get a start on the swing arm based off my other bikes, Been planning to draw something up for reference.

Henshooter · Jun 19, 2014

Looks like it going to be a great but technical build Theon , can't wait to see the progress , all my projects are on hold while the funds are raised ,had to move for unforeseen reasons ( basically rental property got sold under our feet , I'm slowly polishing the ally frame ,she's coming up fairly sweet surprisingly .
Good luck anyway mate hope it all comes up good

Regards Sean

Theon · Jun 19, 2014

Cheers Sean, Rob , mrfubs.
I've been spending more than I should on my bikes and for me this hobby is suppose to be about recycling. I thought it would be easy to find a suitable frame, however my remote living can make these things hard.
There have been a few hold ups with my new motor, concerning Chinese suppliers. However should be in the post today. I plan to give this motor a review stock, then see what I can get out of it. My RSE 'balanced' crank in the Goat motor is a bit average, in fact I'd have to say it is the worst crank I have. So my new Roo will likely go in the Goat for now while I build a frame for it. But I'm getting too old to be bashing a hard tail, and will likely give the goat some road tyres and make it my Urban Assault Goat.

HotRodRob · Jun 20, 2014

Its easy to spend more than you want on this fun hobby of ours. The cool thing is parts are usually super cheap. Its hard to beat 5-10 dollar parts like we have. On a motorcycle it would be way more expensive. I like the recycling idea and its always better than new parts if you can find what you need. You'll find a frame. Ive found that parts seem to find me haha. Usually just when I need them too which is always a good thing.

Can't wait to see some pics and hear your review of the new motor you are getting. I know what ya mean about the hard tails. Im only 30 but my dr said my body is in worse shape than his 65 and older guys. A nice spring seat helps a lot too. I like your Urban Assault Goat idea.

Theon · Jun 20, 2014

Very easy to spend more than you should have.
I have 4 'complete'(well almost) bikes, and another 4 projects.
I have certainly spent more than I had planed on this hobby.
And then there is the tools that I have bought,
That is why I didn't buy the disc braked GT and little steel framed Trek the other day, I probably could have got the two of them for $250, My missus would have had a fit!
Thought best to sleep on it.
I will likely have to strip the Goat for the wheels and what not once this frame is together, and I plan to sell of the Phantom once I get her tidy, 3 bikes are probably enough, I really fast one, a cruiser and a dirt bike.
I will then be left with a spare motor!

Theon · Jun 20, 2014

I want to extend the swing arm by less than an inch, Allowing a neater fit to a wide knpbbie tyre.
I'm also moving the linkage brace down an inch and a half closer to the tyre to allow for better frame fit and plenty of travel.
The swing arm wasn't quite straight/square, and it seems the thing may have been made like that, but I'm correcting it as I go.

curtisfox · Jun 20, 2014

likeing this more and more, now wll keep a closer eye;on it.......nice work.........Curt

Theon · Jun 20, 2014

I'll try and get a bit more done on the swing arm this weekend.
I did a quick sketch of the basic 4" of travel, but hope to get another 2" of un laden travel as well. Unless I can get hold of a better rear shock, I had a quick look and it seems these 'Fox' Shocks are dear.
I havn't done any proper calculations or checks, but I'm guessing this linkage rear should give me a multiplier of around 4:1?
But will work that out soon.

Theon · Jun 21, 2014

I got something mocked up,
Gives me an idea of the perfect frame dimensions, I saw a steel frame Trek when I went to the city, and looks as though it might work, at least now I have a definite ideal.
I tested the suspension travel on the rear, and with the cranks dropped 70mm from highest possible position, 320mm down to 250mm I got a bit over 40mm of spring compression, and so an effective rear suspension travel of around 6" with around 2" off spring compression.
This mock up has also given me a good idea of what top tube angle I'm looking for, as that will affect the rake, this Apollo frame had a fairly horizontal top frame which has messed with my rake. I hope I can find the right frame for it,
It appears to me the swing arm mount needs to be lifted relative to the motor by a little for perfect chain tension with rider weight, but it's pretty close.

Theon · Jun 21, 2014

I hope I've done the right thing!
But this morning I got up, dragged the Phantom out, stared at it for quite some time, then proceeded to strip it and take angle grinder to the frame!
I was going to have to sell it otherwise!
This is a sweet little motor, that it seemed a shame to have to detune for the angle fire head, and a good strong, compact and steel frame. However it rides a little rough on the 24" wheel chair tyres and didn't have room in the frame for anything wider.
Pedal is a little close to the front tyre, but I don't plan to need much pedal power.
The mock up, looks to give good wheel base, good rake, good ground clearance for the crank arms, just enough room to fit a center fire head with a tidy, compact, strong and reasonable weight frame.
This looks like it!

Theon · Jun 22, 2014

I got a bit more done,
I Would love to put this on 24" Rims, it looks to have plenty of clearance, but will go with 26" for now.
A few more Photo's.

Theon · Jun 22, 2014

I've got the frame together, got a few rods in the oven and I'm just waiting for the missus to go, as I've been told to wait.
There is a piece of sway bar with a 3.2mm wall running the length of the seat tube and also functioning as a lay back seat post, It feels as though it's doubled the weight of my bare frame and gives a sturdy anchor for the swing arm, photo's on the way.
Next thing to think about is the rear shock mount.

maniac57 · Jun 22, 2014

I'd be damned sure your seat is where you want it for your test ride...I suspect it will become VERY difficult to remove. Using swaybar for strength is a great idea as well. There's no way that tube would live without something. I'd be scared of crushing the engine case on big air! But your solution sounds bulletproof if a bit chunky.
You might want to think about popping a couple holes in the seatpost tube down low so you can tie the swaybar to the BB with some plug welds...I'd be worried about ripping the BB off the seatpost next.
Maybe a strap gusset around the whole assembly? Idk.
Looking VERY clean and sanitary so far! Good lines and geometry from the look. Your engine chain will move very little with the pivot so close to the output shaft. All the slack will be on the pedal side where the derailleur can deal with it. Good thinking!
Keep us posted!

Theon · Jun 22, 2014

I got a bit more done on the frame, pic's soon, the frame back on it's wheels looks to have enough crank clearance to run 20" BMX Wheels, which would be awesome, I have a nice old set of BMX rims here, but will need some suitable Hubs. I'm thinking a 36t on a 20" wheel should give me some good torque, how does that compare to a 44t on a 26" wheel? should be close?
I need to see her on 20" wheels!, I'll be the envy of all the young fellers down the skate park!
It has a good seat height for myself with the 26" rims, It would be nice to have a set of each, the 26 for a bit of road racing and the 20's for dirt.
She's very close to taking for a pedal and the day is getting on.

Theon · Jun 22, 2014

Thank's Maniac, I didn't get your post till after mine,
Seat post to rear wheel is good, may have to take another trip to the city to get the bits to finish her off, but got plenty to go on with and hate leaving the house for the city, see how I feel tomorrow.

Dual Suspension 'Roo'

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Old, Fat, and still faster than you

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