Knoxie to try Draper Conversion

[knoxie]

Thinking about doing a Draper style conversion to one of my old bikes so we can compare notes! ha ha and erm well I am not sure I can do it without maybe a freewheel cluctch on the motor?

the Kol motor takes a bit of turning by hand, this will be even worse when connected to the battery, I ride without the motor sometimes for 20 miles to get a good workout, I would have to use the motor all the time as I would think it would be pretty tough to peddle against the motor.

I am sure with Randy's system he does not employ a clutch on the motor shaft end as per the currie drives, I guess it isn't really important if you don't peddle or you intend to have the bike as an "always electric bike?" otherwise peddling with no motor will drive the motor around.

I am going to have a go at doing it as I think it will be an interesting experiment if nothing else, I can get any special parts and brackets made up on the CNC machines at work, just need to get me a nice cheap Sram 3 speed! that's the tricky part so far all the other bits are cheap or can be made.

I don't have a volcano to climb but I do have a 16% 1 x mile long grade near me that is a good test on a hot day, It will be interesting to see how it compares to a hub motor, I have an X5, the Puma a stock Currie and a Randy style bike in time so it will make for an interesting test setup!

I need a bigger garage!! I am sure the Randy bike will be the best hill climber no doubt esp as I can run the Kol up to 2KW should I need to and it should operate at lower rpms which will be good for the magnets, I need a nice summer project so this will be good fun, flatland speeds I doubt there will be too much difference, I cant slap a Randy motor in there although I can get a Sevcon controller should I have to, If I get somewhere near Randy can always lend me a motor to try out :wink:

Ill keep ya posted

Knoxie

 

[Jozzer]

Wouldn't using the kollmorgan make it more like an electrodrive than a Randiedrive? What would be the difference, except that you would gear it down right onto a big sprocket instead of using curries gear reduction?
If I were you Paul, I'd take the easier route and just stop looking at randies posts! He's only trying to get a rise! On the other hand, I bet he hasn't fully experimented with hub motors, could be the only way to get a really OBJECTIVE comparison (for a change).
Just be carefull not to feed the trolls!

 

[xyster]

Don't know how Draper's freewheels, but I do remember somebody employing a tandem-bike's crank-gear freewheel.

 

[knoxie]

Hi

i am pretty sure it doesnt free wheel when you peddle, it may be possible to get a clutch like the curries to drive it I am sure, will have a dog about to see what I can find.

This is nothing to do with trying to get a rise out of Randy I just fancy a go at doing it as i agree with Him on a lot of what he says, yet he seems to continually point the finger at me which I don't mind at all.

Nobody can say i haven't tried then as well, I am sure it will be a great hill climber I just fancy trying it out as the Kol is a strong motor and should if properly geared perform well, I don't know how it would compare to a Randy motor as I don't have one, but I have loads of the Kols so it makes sense to use them first, I can always bolt bigger better more efficient ones to it at a later date.

We shall see!

Knoxie

 

[fechter]

The Kollmorgen should be good for a test.

A BMC motor is probably the closest "available" motor to Randy's motor. The efficiency of the motor and controller combination is around 89%. It can do 1kw all day without burning up.

I think he has a freewheel on both sides of the hub. This means one of them has to be installed reversed somehow. Left handed threads?

 

[maxwell]

Left hand freewheels are available for MTBs

 

[eP]

Left hand freewheels are available for MTBs

Where ? For what a hub ?
I've seen only for bmx hubs.

 

[Miles]

Randy uses 2 freewheels, side-by-side, on the splined driver of the Dual-drive. Either 2 BMX freewheels or a BMX freewheel and an overunning sprag type bearing.

.

 

[knoxie]

Hi

Right I see we grafted a BMX freewheel to the Lemco bike in the same way, shouldnt be too hard to sort that out, I will break down what I do so anyone can have a go at it, I will list all the parts and where I get them with super close up photos, its more work than most would want to do but it wouldnt be to hard to offer the basic parts as a kit in order to do this, made suitable to the common or garden BMC or KOL format would make coupling a motor to it fairly generic and simple.

Knoxie

 

[geoff57]

Hi all
from what everyone has said randy system is as follows on a 26" moutain bike:-

rearhub consisting of a dualdrive hub with 6 hole disk brake mounts.

disk brake system on right side of hub (where it would normally be found) using said 6 hole disk brake mounts.

on left side of hub insted of a derailler he has fitted 1 very large sprocket for the motor chain drive and 1 small sprocket for the manual chain drive.

the 2 sprockets are amle to freewheel independently of each other, one using the dual drive built in freewheel the other haveing an independent freewheel.

the derailler arm of the dualdrive is either fixed so it can't move (screw down the stop bolts) or totally removed and a chain tentioner used in its place ,this would be on the manual drive chain.

possably multiple chainrings.

This would give an end result of, 3x number of chainrings for the manual drive. 3 gears for the motor drive. the 3 gears being the 3 internal gears found in the dual drive, low 0.66:1,medium 1:1,high 1.33:1.

the 3 gears would be linked to both motor and manual drive.

from what randy has said he also can increase motor speed by haveing a series to parallel switch on his battery pack, so giving him 36v or 72 v(I am not sure on this).

Does this sound about right guys?

 

[Miles]

Geoff.

The built-in freewheel on the Dual-Drive is redundant. The only way to have independence, is to have 2 freewheels on the splined driver (you could have a clutch bearing on the motor shaft, of course)

You can buy the Dual-Drive separately from the derailleur and cassette.

Randy uses #35 chain for the motor drive. On his last example, this goes to a sprocket clamped to an overunning clutch bearing.

 

[geoff57]

hi miles
thanks for that,other than useing 2 compleatly seperate freewheels have I got the system correct?

 

[Miles]

hi miles
thanks for that,other than useing 2 compleatly seperate freewheels have I got the system correct?

Yes, that's pretty much it.

If you have a bike with a horizontal drop-out, you won't need a chain-tensioner.

Smaller wheels are an advantage, because they reduce the reduction needed from the motor and also reduce the torque going through the Dual-Drive - they increase the lineal chain speed, though....

 

[EbikeMaui]

Now if Miles will lend Knoxie his motor and explain to Knoxie how to make the parts needed you may get a 48 volt version of my system
The high rpm Kroll or BMC motors will NOT have the same efficiency due to the need of a much larger reduction to produce the same torque at the same great efficiency with a single reduction that can be employed by a 94% efficient higher torque motor that is not required to need high RPMS to be most efficient.Without a higher torque motor at about 57 RPMS per volt for great efficiency you will not match my performance. There are 3 Types Sram dual Drive Hubs. The latest version is the best as can be expected. Composite Gocart wheel hub Sprockets mounted on a freewheel are also recomended to have the quietest and most efficient system.
Substiution of ANY parts or motor/controller will NOT perform as well.
You will learn this if you start from anything less and fallow the R&D process through till it can get no better and being the most cost effective for production at the same time.
This is a system that works equialy well on wheels from 10" to 27"

 

[CGameProgrammer]

Freewheels can be very noisy... mine is. I plan on removing it as soon as I feel confident in my estimation of range and don't need pedals as a backup anymore.

 

[Sturdly]

I've been following the whole "Draper Special" discussion and been tinkering, trying to reverse engineer this system. The way it appears to me is that to adapt the BMX freewheel to the splined SRAM drive one could use a single speed conversion sprocket with a 7mm thickness. Milled down to fit in the four slots used for the freewheel installation socket. The thicker cog would keep the wear down on the hub spline. The freewheel to hub spline seems a very tight fit so I think the threads on the freewheel need to be carefully ground away.

I've also spent countless hours looking for the proper auto transmission clutch bearing to have broached, still no luck there. Dial up and spec sheets don't mix well.

Were I to try to assemble this myself I would probably duplicate the above and have the cart sprocket hub drilled out to match the external dimension of the freewheel I chose to use. For the motor I would probably go with a White Eno trials freewheel as these seem the highest quality available.

Should Randy ever decide to sell custom machined bearings and adapters I would sure pay the premium and buy some. The nearest volcano is Mt. St. Helens about 120 miles away but Seattle has some pretty nasty climbs which I wish I could summit easier.

Since my last couple of surgeries I just don't have the stamina or strength (or all the body parts) of my youth. In the mean time I'll keep messing with the concept and hopefully crack the code for the mechanical portion. The electrical portion seems fairly straight forward, big motor, big controller and the best batteries I can justify buying.

 

[Miles]

Freewheels can be very noisy... mine is. I plan on removing it as soon as I feel confident in my estimation of range and don't need pedals as a backup anymore.

Pedals aren't a "back-up", for me... I shall be pedalling all the time.

If you use a sprag clutch bearing for the motor drive it should be quieter, when you're using pedal only.

 

[Miles]

Sturdly et al,

My present plan is to use a CSK35 one-way bearing for the motor drive and an ENO freewheel for pedal drive.

The CSK35 is rated for 140Nm, which should be enough... It has a bore of 35mm which will be a loose fit on the splines of the cassette driver. 3 keyways will secure it.

I've just taken apart my ENO unit. It's all case-hardened, have to cut the spline slots with wireEDM, or something.

If anyone's interested in joining forces to create a set of parts, let me know.

Randy, any thoughts on the above?

 

[Miles]

Now if Miles will lend Knoxie his motor and explain to Knoxie how to make the parts needed you may get a 48 volt version of my system

Sorry, I need the motor for my own project...

Presumably, David made a small batch and then lost interest?

 

[TylerDurden]

In case Y'all missed this...

Do you know how to mount two freewheels at the same side ?

I understand a bottom-bracket plug/cup can be used to extend the hub...

http://members.westnet.com.au/rjharrop/recumbents/retro-direct/Retro-Direct2.htm

Custom stuff is pricey. A BB cup and threaded freewheels are cheap to experiment with. Not as strong as a sprag clutch, but easy to find.

 

[Miles]

Custom stuff is pricey. A BB cup and threaded freewheels are cheap to experiment with. Not as strong as a sprag clutch, but easy to find.

Tyler,

It's useful info, but not for coupling to the Dual-Drive...

 

[TylerDurden]

Tyler,

It's useful info, but not for coupling to the Dual-Drive...

Ah... the Sram freehub cassette setup. Ja.

How about cutting threads into the freehub splines?

 

[Miles]

How about cutting threads into the freehub splines?

You could do that, if you put it on a lathe, but the o.d. of the splines is just too small. Also, the freewheels that I want to use are not threaded right through.

 

[kisshu]

i'm all excited about drapers bike but i can't find any info on it
what motor does he use, how is it mounted etc...
where are all the details??

 

[fechter]

Here's some of the info:
http://endless-sphere.com/forums/viewtopic.php?t=953

There's more pics scattered around the forum somewhere.