Downhill project motorcycle transmission

Hi everyone,
Along with half the planet,I've been reading this site for some time now in efforts to gather as much info on a build idea.
I stumbled across this seemingly horrendously awesome idea of motomoto and a few others of running an astro 3220 or similar through an existing small bore dirt bike trans.
Has anyone done this successfully as yet?
The 'gearboxes are awesome conclusive proof' thread seem to divide camps in the pro v anti gearbox right down the middle with no clear right and wrong that I could tell.
So how's this for a start. I've scored a Trek session 10 as the blank canvas. Take a ktm 65 engine,remove the crankshaft along with all other unnecessaries,kick start, water pump set up and machine off unwanted fixings. Weld the the clutch inner to outer and machine off clutch basket fingers etc. fit the astro motor where the crank was(yes it fits) and turn up adapter bosses to fit the primary drive gear onto the astro shaft to drive the clutch basket, effectively making it an electric crank.
As motomoto and others have mentioned the nature of a two stroke bottom end would easily lend itself to a liquid cooling set up.
The purpose of this build is an alternative to my beloved RMZ450 and would be used for some tight technical riding up steep enduro type hill limbs and high speed forestry trail work.
I've mucked about with these little motors aplenty and with the crank,head, barrel and other ancillaries removed wouldn't be that heavy.
It would have to be grafted into the frame in front of the bottom bracket, drive would be left side off the disc rotor mount using a 420 type chain or similar.
This would be a complex and lengthy project that'd no doubt take a few attempts, delving deep into the unknown with many one off parts. However a gutsy power unit in the one housing with 6 gears and liquid cooling potential is worth a thought.
I'm a metal fabricator, build motorcycles and have friends in the cnc game. I haven't ruled out a hub motor build by any means just yet but this seemed a tad more appealing.
What do you guys and gals think? Any ideas would be grand.
Cheers Richard

Whilst i do believe the ultimate EV drive would be direct,..no gears, no reduction,..i do not believe we have the right motors or controllers to achieve that situation economically yet.
Having said that, my experience with a mid drive ( through the gears) Ebike has convinced me that very few gears are necessary, even with a relatively low powered system ( < 1.5 kW)
a low gear for hill starts, medium gear for hills generally, and a high "cruise" gear , is all that is necessary.
A higher power/torque set up would probably need even less ratios.
But , im sure you will find your own answers from riding you own set up.

Yes true enough. If a modern mx gearbox came as a 3 speed I'd go for that for sure. All that is available is 6 speed, 5 on very old models. A 3 speed would possibly have less drag too. Ktm and Husqvarna amongst others have released wide ratio 125 engines,this maybe a better way to go.
This concept is very fledgling and may stay at that, good to investigate all alternatives. It would be 'possible' to mod the box and shift mechanism to only select 1st, 3rd and top but that would be murder of a task.
No doubt something out there exists but as a compact, strong and fairly cheap solution it may well work.
Thanks for your reply

I am in total agreement that we need a simple, light, strong two or three speed trans for any high powered mid drive bike! Can a single speed climb AND have a good top speed? MAYBE, but its not going to do either one as well or as efficiently as it could. I wouldn't trade my gears for 20,000 watts given my compact battery, it might climb but it'll overheat eventually no matter how good the motor and it'll use tremendous power doing it. Gears are the way to go for any off road bike period...Good luck with this I'll be watching! Also, you could lighten the trans up by actually removing a gear or three. Its usually not too hard to do sometimes cutting gears of is required though... I bet you could get it nearly half the weight though!

Ecobogan said:

Yes true enough. If a modern mx gearbox came as a 3 speed I'd go for that for sure. All that is available is 6 speed, 5 on very old models. A 3 speed would possibly have less drag too. Ktm and Husqvarna amongst others have released wide ratio 125 engines,this maybe a better way to go.
This concept is very fledgling and may stay at that, good to investigate all alternatives. It would be 'possible' to mod the box and shift mechanism to only select 1st, 3rd and top but that would be murder of a task.
No doubt something out there exists but as a compact, strong and fairly cheap solution it may well work.
Thanks for your reply

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hi mate i am not an engineer at all in the slightestnow i have cleared that up,what about a 3 speed gearbox from a honda c90 or cub i think its called?

they are 3 speed and have no clutch.
any good?

Not entirely convinced that a rc motor/gearbox is a better or more efficient setup than an appropriate sized motor/controller running direct drive. That said good work was done here and it has a certain kool factor to me.
http://endless-sphere.com/forums/viewtopic.php?f=12&t=35865


-edit
I've confused the linked thread with another similar build thread.
I'm searching for it but I'm having a tough time finding, and I just ran out of time.
I'll continue the search and update later.

Here is the build thread is was thinking of.
The motor and gearbox action start on page 2, but enjoy page 1, it is full of great creativity.
Not to mention the inspiring metalworking skills.
Construction of Electric Chopper

Thanks for the link Brentis, that is very similar to what I had in mind power plant wise.Very slick machining work too. I wonder what type of 50cc engine that was, looked water cooled in its original guise, perhaps an RM80 actually? Good to know it has been done before.
You're right cheekybloke on the 3 speed alternatives. I got a bit hooked on the mini mx idea partly because of the design specifically aimed at severe off road abuse, compact size and can be power shifted. Will certainly explore all alternatives though. Hondas Z50 is a 3 speed along with many old school scooters as you mentioned. Also some mini thumpers.
The frame and swingarm will have so be radically modded to accommodate the drive set up. Removing a large section of the lower tube in front of the bb and plating it over. The engine cases would serve as a structural brace as per many motorcycle set ups. The swing arm I'm thinking would need to be plated from the inside with 6 or 8mm so material could be 'carved ' from the cast section on the outside for chain clearance.
I'll post some pics of the bike and super imposed scribbles.
At this point a 4 turn astro 3220, 44v 25ah 25c seems like a good start, haven't settled on a controller as yet.
I've already started shopping around for a bike engine and will have something in the next few days or so.
This rig will be no 450 mx eater that's for certain but ballistic fun in the bush doesn't always need 50+ hp and it'd be pretty cool to show certain hardened dirtbikers that e power doesn't have to be a soft cock option. I've owned and loved dirt bikes for years but the time is nigh for change so keep the ideas and criticisms rolling in chaps and chapettes!!! This'll be fun.
Cheers Rich

I think that if your serious about integrating a moto tranny to a downhill bike, you would be better served building or having built a custom frame based on D.H. geometry. You will be modding that Trek to a point that custom will not be much more expensive nor much more work. Then use the dh parts of your choice to kit it out. The Trek is worth a fair dollar that could be used towards a custom frame. You could then integrate battery pack as well.

What sort of skills do you have? Weld?

Interesting point and always an issue when doing something like this. What to use and what to make. The Trek in my view is a bit of a head start to a scratch build in that it could well be used as much for its bits as being a modded downhill bike. The changes to the frame would have to be extensive but not far enough removed from what this bike is to justify a full custom build in my opinion.

I'm certainly in no position to be paying anyone to make a frame for me and will be doing all the work myself. There will be a moment of sacrilege taking to the poor Trek with the grinder and plasma cutter that's for sure.

I spoke to a bloke today regarding a KX80 whole bottom end for $150, probably check it out tomorrow with a crucial eye on dimensions and weight of course. These will be the defining factors -skinny and light.

Have been into a fair bit of metal sculpture over the years, mostly mild steel but stainless, bronze, aluminium and copper as well, forming organic shapes. At work we do a lot of one off custom installations for peoples houses and the like and have all the respective metalworking gear. I'm trained as a blacksmith.
If my frigging lap top would keep its act together I'd load some photos, might have to take it out the back and hose it out again.
Will have some definitive answers in the next few days as to whether this is a brain dead idea or not.

Thanks for that link, it was worth every second to read about that build!

if your set on a gear box, ThuD has upped plans for his two speed dog box
that can be built with basic tools...I have two of them one hooked to a Turnigy 80-100
the other on aTurnigy ca120 bloody fantastic!! do a search for 2 speed dog box

best of luck

KiM

Ecobogan said:

...
I'm a metal fabricator, build motorcycles and have friends in the cnc game. I haven't ruled out a hub motor build by any means just yet but this seemed a tad more appealing.
What do you guys and gals think? Any ideas would be grand.
Cheers Richard

Click to expand...

Brentis said:

...

What sort of skills do you have? Weld?

Click to expand...

I'm paying attn. I swear.

Sounds like you have the skills needed.
Will be nice to see a custom build rather than the common retail hub kit. Plug and play is great for the beginners.
Custom builds offer engineering ideas and often new solutions. Creativity blossoms.
Customs keep me coming back to ES excited and inspired.

AussieJester said:

if your set on a gear box, ThuD has upped plans for his two speed dog box
that can be built with basic tools...I have two of them one hooked to a Turnigy 80-100
the other on aTurnigy ca120 bloody fantastic!! do a search for 2 speed dog box

best of luck

KiM

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Agreed. That 2-spd will be much easier to integrate to the Trek frame.
Check out both Thud and AussieJesters builds. Great info and many pictures available.
Slick, small, simple unit.

Start thinking about battery size and placement. There are a few builds here where they chopped and boxed the frame of DH bikes. Seemed to have had good success. Adding a moto tranny to the mix will make you a bit of a pioneer though.
I still think you should sell that Trek. It has bolt on drop outs, great for the hub crowd. Gotta to be worth at least a grand.
That buys a lot of tubing. Maybe a tube bender, a few other tools. :wink:
Anyways I'm just being selfish for full tube customs.
Love the artistry.

Best of luck. Excited to see pics and more plans.

View attachment 1That two speed is pretty small! Nice, not too pretentious or exotic either. What does it shift like? I'm sure this has been discussed just haven't read about it yet.
On the Trek itself I still believe, based partly on experience, that using as many factory parts is a huge help. It'll basically end up as a Trek rear end and headstem, but that's cool.The Trek has a decent gutsy well thought out back end with 10'' travel with an option to bolt on a wheelbase extender. The front ends of many DH bikes are in some ways a bit generic it's the rear set up that is most interesting and a decent one is something that I don't have to redesign.

As you mentioned Brentis incorporating the battery pack into the frame is the way forward, weight distribution wise and aesthetically. I was thinking of ovalising the top and bottom tubes to house two battery packs. The lower tube would start off at head tube thickness and taper out to meet the trans set up at the BB end like a long oval trumpet with a plated removable end. I need to do some more drawings. The top tube could be ovalised upwards using perhaps a yachting boom or mast extrusion, there are some pretty funky alu extrusions out there, used aircraft bits etc. Which alloyed metals will weld with which along with the normalising and heat treating process will also have to be considered. These two frame mods will allow fairly respectable battery space and still look vaguely factory afterv powder coating and stickers. This part in a lot of ways is the easy fun bit, it's the learning more about electrics, electronics and what'll fry first that will sort me out.
I'm still going to look at this KX motor just to rule the notion out if nothing else. Very keen to look inside at the gears clusters to see what can be removed lightened or what ever. To use 1st, 3rd and 6th would be the hot ticket.

Not real sure why the roadbike came out twice, maybe I got nervous. Anyway I finished it some months ago. Good old fashioned hearty fun that thing is. Modern cafe racer type situation with a supercharged 1000cc motor and other bits with 170hp at wheel at 7lbs boost. Wheelies in 3rd etc, my licence has a coronary whenever I start it up. The wrongness of petrol fun.
And the virgin Trek.

So......a bit of progress, if not a little stilted. I picked up the KX motor the other day and began immediately pulling it apart to see what could be shedded. Stripped with the crank out, kickstart gear and other unwanteds it tips the scales at a tad over 3 kg. After much trying of all possible mounting locations and positions, I think I've found one that works. It's 265mm long by 150mm high and 165mm wide at this stage.
It is basically sitting in the orientation that it would have been in the original bike. The barrel studs would make a secure engine mount fixing and a good water inlet, along with the existing engine mounts.
The only real hurdle at this point is fitting it between the cranks, they need to be widened.
The Trek runs an ISIS splined Bontrager King Earl crankset made from 7050 cold forged aluminium alloy.

I don't know what you guys reckon but getting a one off bb axle made will be prohibitive so i was thinking of cutting and shutting two cranks together.
The 7050 is unweldable so I'll have to find two sets of 6061 cranks, cut one pair down and overlap weld a second crank onto the first effectively widening them by about 15mm each. Cutting off unwanted bits first of course. With a bit of careful grinding and shaping it wouldn't be too ugly and having a 50mm or so overlap would weld up plenty strong. Any suggestions?????
I'm sure the bearings in the Astro motors are up to standard but the crankshaft main bearing in the engine cases could be adapted to support the shaft as well taking some strain of the 12mm drive shaft.
Well that's where it sits for now and when I can sort out the crank clearance fiasco it'll be time to fit it all up.
I calculated at 7500rpm with a final drive ratio of 3:1 1st gear would come in at 30kph and top would be 95kph. Which could be a bit high for hill climbing but is a start.
More to come. Cheers

Ecobogan said:

So......a bit of progress, if not a little stilted. I picked up the KX motor the other day and began immediately pulling it apart to see what could be shedded. Stripped with the crank out, kickstart gear and other unwanteds it tips the scales at a tad over 3 kg. After much trying of all possible mounting locations and positions, I think I've found one that works. It's 265mm long by 150mm high and 165mm wide at this stage.
It is basically sitting in the orientation that it would have been in the original bike. The barrel studs would make a secure engine mount fixing and a good water inlet, along with the existing engine mounts.
The only real hurdle at this point is fitting it between the cranks, they need to be widened.
The Trek runs an ISIS splined Bontrager King Earl crankset made from 7050 cold forged aluminium alloy.

I don't know what you guys reckon but getting a one off bb axle made will be prohibitive so i was thinking of cutting and shutting two cranks together.
The 7050 is unweldable so I'll have to find two sets of 6061 cranks, cut one pair down and overlap weld a second crank onto the first effectively widening them by about 15mm each. Cutting off unwanted bits first of course. With a bit of careful grinding and shaping it wouldn't be too ugly and having a 50mm or so overlap would weld up plenty strong. Any suggestions?????
I'm sure the bearings in the Astro motors are up to standard but the crankshaft main bearing in the engine cases could be adapted to support the shaft as well taking some strain of the 12mm drive shaft.
Well that's where it sits for now and when I can sort out the crank clearance fiasco it'll be time to fit it all up.
I calculated at 7500rpm with a final drive ratio of 3:1 1st gear would come in at 30kph and top would be 95kph. Which could be a bit high for hill climbing but is a start.
More to come. Cheers

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how wide do you need your bb?cyclone do a square taper bb at 190mm if thats wide enough
darren

Cool idea.

Tom

How wide depends on how much further I can tuck the primary drive gears into the cases thereby narrowing the gearbox. 180mm would be bucket loads, cranks are currently 160mm, g/box is 163!!
I've seen the cyclone wide axles and that's definitely an option. It'd mean changing the bb over to square drive though.

So I'm going in. All measurements have checked out and time for cautiousness is done. I'm going to order an Astroflight 3220 4 turn and start the machining work. As you could imagine I have a few queries.

Can anyone tell me if the 169kv spec for the 4 turn 3220 is wye or delta? Couldn't find that in my searchings
Is the 'sealed' body sealed enough for the water cooling?

So.......she's on now! Any Astroflight distributors in good old Oz? Didn't think so

Why not just cut and extend the crank axle? It will be steel (or you can easily get a steel ISIS axle), so should be fine for welding?

Ecobogan said:

Can anyone tell me if the 169kv spec for the 4 turn 3220 is wye or delta? Couldn't find that in my searchings

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Wye.

Sellick said:

Why not just cut and extend the crank axle? It will be steel (or you can easily get a steel ISIS axle), so should be fine for welding?

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Not necessarily. The ISIS BB axle sure is weldable but it's a lot of torsional force on not a huge weld area. It'd be fine for footpegs mounted straight off that point but add 170mm of leverage and things change somewhat. Compare 60mm of weld surface to 150 odd mm by overlapping the cranks.
I'm looking into fitting a crank lock which would fix the cranks in either fore/aft position. I'm factoring in coming off a big jump all horribly wrong and landing with one foot on the pedal, it happens, and has to be able to stand up to this kind of abuse. Have a set of 6061 FSA cranks in the mail

Wye.
Cheers

I have extended a steel Isis works a treat, insert tube inside after cutting then weld it up..
re: how does the dog box shift.... fast! at any speed

you should hit up tooman2 he's modded a ice gear box and fitted a Turning rc motor to it, there's
video floating around of him whipping a ktm dirt bike with it, easily.

KiM