Project Cove GNG-Spot build thread

ferret

1 kW
Joined
Aug 4, 2013
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477
Location
Israel
This build thread will document electrifying my Cove G-Spot FR bike using a GNG type motor.

The Cove frame was great fun going downhill but a pig pedaling uphill so I got a different bike for singletrack riding with my buddies. I still liked the bike so instead of letting it gather dust I decided to combine my MTB and electric RC hobbies and install a brushless/lipo system in it.

Cove G-Spot before starting the project, after fork and front brakes upgrade in preparation for electric power:

IMG_20131205_181840_755_30.jpg

I have been researching, planning, designing and gathering parts for the last few months and now actually starting the build.
I will post to this thread as I progress.

Avner.
 
I wanted my reduction to have a high ratio so I could lower the motor RPM (using a 50V battery) to match my pedaling . I preferred to avoid using belt or chain reductions that might catch on my legs or require fabricating a cover and I wanted the reduction to be as compact as possible.

Inspired by the Dogati build I saw here on ES, I decided to use Matex planetary reduction gears. My setup consists of 2 stages, a 5:1 and a 4.8:1 giving a total reduction of 24:1.

Thumbs up for ES member Gerard (comradegerry) that helped me source the Matex gears.

The following photo show (left to right) the parts used for the reduction.
Motor-to-reduction adapter plate
Gears and spacers
End plate

IMG_20131227_203216_269_30.jpg

Test assembling the parts:

IMG_20131227_204721_227_30.jpg

IMG_20131227_204800_837_30.jpg

I plan to use some RTV silicone or gasket maker between the gears, spacers and plates so I could pour a little gearbox oil inside to keep things lubricated like a car's gearbox.
 
That is a great looking bike to start with, electrically assisted, it is going to be very sharp indeed.

Really looking forward to see it evolve; great fabrication skills on the mount, is that the work of a well programmed computer or a patient perfectionist with a drill press and a file?

Subscibed :D
 
Nice, I have a pair of those 4.8:1 as well. Where did you get the mating shaft? If it was from Matex, What is the model number? Looking forward to the build. More detail on shaft connections and if you plan to use an inline freewheel, total width of final assembly. I'm also curious to the noise level and how well these planetary gears hold up in actual use.
 
I drew up the parts in Solidworks CAD software and had them made at a local machine shop.
Most of the parts involve shapes and precise dimensions that I am unable to achieve in my shed.

The 5:1 gears' input is a splined shaft that plugs into the output of the 4.8:1 gears. I will use 2 freewheels (3 if you count the one built in to the standard rear hub) so I will be able to use pedal power, electric power, both or neither without too much drag.

Total designed width of the final assembly is 156.3mm, to be squeezed between the crank arms of a Shimano ZEE 83mm crankset. I had to literally agonize over every millimeter when designing it to make everything fit. That is also one of the reasons that parts had to be fabricated by a shop rather than made by me.

As for the noise level and how well these planetary gears hold up in actual use, I am curious myself and hoping no to encounter any nasty surprises down the line.

Avner.
 
Hey ferret, I have those mates gears too. Was going to use a 80100 on them but dogati broke his putting too much power through them. Do you have the cad files for the rear of the matex transmission ? Have Subscribed gonna be an interesting 2014 build
 
This build is planned for around 1 KW and according to my calculations the Matex gears should be able to handle 1.5 KW (about 30 amps) so hopefully they will be up to it. Do you know how much power broke them in the Dogati?

I downloaded CAD files from the Matex site:
http://products.matexgears.com/viewitems/all-categories/planetary-gears-torque-range-45-300in--lbs-?forward=1
Select the part you need files for and on its page find the link for 3D in the VIEW CAD DRAWING box on the upper right part of the page.
 
That's a cool tip about the 3d on the matex website. The bit about the failing dogati transmission was early on his that massive thread. But he was doing way more than 1kw so you should be fine.
 
As I mentioned before, the jackshaft assembly includes 2 freewheels.
The inner freewheel and its sprocket will be connected to the rear wheel cassette by the main chain.
The outer freewheel and its sprocket will be connected to the chainring by a short chain.
This setup was inspired by the M55 bike and by builds I saw here on ES.

The parts used for the jackshaft assembly (top left to bottom right):
Jackshaft, inner bearing, inner freewheel adapter, inner freewheel, inner sprocket
spacer, outer freewheel adapter, support bearing, outer freewheel, outer sprocket

IMG_20131228_185032_721_50.jpg

After installing the inner bearing, the inner freewheel adapter is clamped to the jackshaft by 2 setscrew 90 degrees apart.

View attachment 1

The rest of the parts are then installed.

IMG_20131228_213428_153_30.jpg
 
Hello,

I would like to use matex gears as well, dependent on the pricing. May I ask you how much they cost? I can machine the needed parts myself. Do you know of a supplier in europe?

thanks,

Roel
 
Matex units are quite expensive in small quantities, through their usual channels. The ex Currie USPD ones are relatively cheap though: http://www.ebay.com/itm/Currie-Planetary-Gear-75mm-Planetary-Gear-for-Scooter-/281116107952?pt=LH_DefaultDomain_0&hash=item4173d364b0 They're made by Matex.
 
After some delays, I'm back on the job.

Work on the stator was:
Replacing phase wires.
Rerouting the phase and sensor wires.
Installing a temperature sensor.
Epoxying winding.
Countersinking bolt holes.
Drilling radial hoes for backplate attachment.

View attachment 1

IMG_20140110_221849_733_m.jpg

After the stock motor shaft got somehow bent, I had a replacement one machined from 4340 steel. I got some NSK bearings to replace the stock ones.

View attachment 4

Installed the new bearings in the frontplate and the new (thinner) backplate.

IMG_20140121_203311_861_30.jpg

Finally all he parts were bolted together.

IMG_20140121_211027_560_30.jpg
 
Cool project, I like the gear reduction and how compact you made it. How is the noise output? Vids?
 
This is really a nice build, I am very impressed so far. What are your plans for battery and enclosure?
 
For the build I bought 2*6s 8 Ah lipo packs. I hope that they (at 355 Watt hour) will give enough runtime.
I have some rough idea how to place them:



I don't want to invest the time building an enclosure before I know for sure which batteries I'll be using.

I have a rough idea of 3d printing brackets that will attach to the top ant bottom tubes with aluminum sheets protecting the sides. I would prefer to retain the ability to mount the bike on a hatchback carrier.
 
Seriously though nice build!
 
etard said:
I miss my G-Spot :(

Im sure some one will offer to help you find it :twisted:
 
I just realized those are planetary gears! I KNEW somebody had to make those!! Were they expensive? Where did you get them?

Edit: Just saw your replies above..
 
Miles said:
Matex units are quite expensive in small quantities, through their usual channels. The ex Currie USPD ones are relatively cheap though: http://www.ebay.com/itm/Currie-Planetary-Gear-75mm-Planetary-Gear-for-Scooter-/281116107952?pt=LH_DefaultDomain_0&hash=item4173d364b0 They're made by Matex.


Miles, what do you think max power handling for one of the Currie ones would be? To be honest it looks beefier than the Mac planetary! I have always wanted a planetary reduction instead of belts or chains. So much more elegant!
 
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