--Wayne's Mac Giant DH to mid drive--

[waynebergman]

View attachment 1
I am going to convert my Giant DH to a mid drive. One bonus with the Giant is I have the option of placing the motor within the front triangle instead of with in the swing arm should I end up going for a front triangle placement of the motor.

I am making some progress on converting the mac 10t thanks to the "crossbreak" thread and "spiningmagnets" detailed step by step walk through of the process explained on….. http://www.endless-sphere.com/forums/viewtopic.php?f=28&t=45245&start=450 . The plan is to first convert an old Mac 10t for this build and if it goes good then I will take my newer Mac 10t and do the conversion to it and use it in this project for the final drive.

Shown in the photos attached is my Giant in its current state with a mac 10t in the wheel. 48v 20ah 35amps to give 1600 watts. Also shown is the start of the conversion process to make this mac motor spin a drive sprocket from its axle. The stock in the lathe chuck shown will be turned to replace the aluminum collar shown in the same photo.

The motor conversion is clearly spelled out in the link above from the cross break thread so I will take care of that first. What I am not sure on at this point is to go with the FW on the left side of the motor which is the best solution for FW issues but I worry this FW placement could cause suspension chain line and chain growth problems when it comes to working with a full suspension bike. I feel the easiest for me is to place the motor in the front triangle and then drive my crank assembly with this converted motor and then the crank assembly drives the wheel with out any suspension surprises to the chain line. So I am still looking into the best crank assembly FW solution to make this work and I also would like to use an internally geared bicycle hub to help with chain line issues. I may just stick with a common derailer system to start with as the rolloff rear hubs are a bit too pricey for me. If the bike works real well then I may spring for a nice internally geared hub down the road.

 

[waynebergman]

Photo shows my crank assembly and work on the heat bridge to date. I still have to drill out the 6 holes for the M4 bolts but dont have the right drill bit right now.
I have thought about things and I will go with the hollowtech left drive to motor FW as crossbreak has done. Looks too clever to not to try it.

Any one have any idea the best place to shop for the hollowtech BB for shipment to Canada?

Also wondering the best size of sprockets for both crank assembly and the FW on the motor?

Coming back from the motor on the right side to the wheel I am also not sure of the best size of sprocket to go with? I am fine with a top speed of 25 mph as long as it climbs well and stays cool. Mac 10t running 48v 35amps.

Thanks for any advice.........wayne

 

[crossbreak]

hi waynebergman,

great to see you're in! As for your gear calc: There is no graph for 10T MAC on ebikes.ca/simulator, so I'll do the math for 8T (similar to BMC_V2_Spd) and ´do some adaptation: 10T MAC @48V/35amps behaves like a 8T @ 38.4V/43.75amps.



So you should tune your gearing, that the rotor sees 235rpm*5=1175rpm@85rpm crank cadence. That is a bit too much IMO, but will work ok I guess. Max is 1000rpm for the MAC IMO, to keep eddy current loss down to an accepatble degree.

Viel Erfolg!

 

[crossbreak]

The MAC-shaft speed will be 1175/6=196rpm. So if you want 85rpm avarage cadence, you need 196rpm/85rpm= 2.3 overdrive ratio between motor and cranks, for example

42T chainwheel and 18T freewheel, or
39T/17T or
37T/16T,
32T/14T even
30T/13T is possible, if you use the wider 1/2x1/8 inch chain, there are 13T freewheels available that can be threaded on small 30x1mm threaded hubs. Personally I would go for 32T/14T, since both 32T chainwheels and 14T freewheels are commonly available for the 1/2x3/32 (=common 6,7,8-speed) chains. A 14T freewheel with 20mm inner dia hub can be ordered from cyclone for example. I use the same.

As an output sprocket we will find something that fits the 25mph speed you want. That is 321rpm for your 26" outer dia wheel. If you use a durable 13-34T cassette, you will need a 321rpm/196rpm*13T=21.3teeth sprocket. 22T should still make a very good hill climber.

BTW, I have no idea where to get hollowtech cranks in canada :? As long as you have 68mm bottom bracket width on your frame, there shouldn't be any problems with mounting your motor, using 2.5mm /0.1" steel sheets.

 

[crossbreak]

Spreadsheet

 

[waynebergman]

Thanks for this Crossbreak! This is going to be a huge help when I am ordering my sprockets etc.

Photo attached shows an older Rocky FS frame I just may use instead of the Giant. The black hard tail in the background is a Cove Stiffee I have owned for several years that I will strip down for its components. They should all fit over onto the Rock Mountain OK so if I scare up a rear shock for it and can take my time building this frame up and leave my Giant to ride while I am at it. If I mount my converted mac motor in the frame things may take a while so this will make a more relaxing project. Also with this bike I would be happiest with a lighter bike even if the suspension is not as good as the Giant. I think it will be a 5 inch travel bike which is fine by me and more suited really to the slower speeds I am also fine with.

 

[bose]

Hi Wayne!

You cannot leave the giant middrive to the side, was looking forward to see it with your machining skills. I'm going middrive too on my dh now. Actually ordered a headline kit, some Isis try all crank arms and I will try to push it onto the existing bb.

Looking forward to see the rest of your build but please, convert the giant!

 

[waynebergman]

Thanks Bose, yes I am sure I will convert the Giant also after this first mid drive gets up and running. This way I will have a second bike for friends to ride and I can take my time on my first mid drive and see if it goes well.

Photo's attached show the heat bridge and testing for its line up. The little plug shown on the left of the heat bridge in the third photo is just something I made up to sit into the outer hub plate bearing and then center my heat bridge on it so I could accurately mark and drill my holes through the side plate to fit the other parts. With the holes in the side plate and heat bridge needing to be very close in size to the M4 machine screws it is tricky to get everything lined up and matching the threaded holes in the stator. The second picture shows everything lining up OK. I had to fudge one of the holes with a slight oversized drill out to make things work.

I have bought some 4140 3/4" diameter solid stock for making a new axle like Greenmachine's. Thanks Ron for posting the photos of this http://endless-sphere.com/forums/viewtopic.php?f=28&t=45245&p=735959#p735959 I will be watching Ron's progress to follow along, with regards to the spacing out of the different components on the axle that may need special attention before I go ahead with the machining of the axle.I pulled most of the dimensions from the stock shaft, and estimated the rest from Ron's pic.

 

[crossbreak]

great to see your progress, I like your "center-tool", looks like you made it for centering the heatbridge, was that spinningmagnets idea or yours :? Anyway I like it. Still, best would do a phase that centers the stator in the hub housing. You could make such a phase by just using some epoxy putty on the side cover

 

[waynebergman]

Yes crossbreak, I thought of the little plug to help me get the heat bridge hole locations transposed onto the hub shell. Once the little home made centering plug and the heat bridge were snugly fitting into the outer motor side plate I was confident I could clamp it together and with a hand drill lightly mark my drill locations. Then I finished the drill outs on the drill press.

 

[crossbreak]

ok.. now I get it. I just used the original axle and bearing for that purpose. Anyway, a phase for centering the heatbridge/stator makes assembly more easy, especially if you open the motor frequently to check on the gears like I do. I found that 30amps@45V is too much for my bafang SWXB, the gears got damage after only 1000km, now use 25amps@45V and it does fine. Sorry, I have no picture of that phase.

I drilled the holes free hand. Does not looks that good, but fits quite nice. Of course you need to mark the holes to make sure you always use the same allocation.

Hope you found a source for a hollowtech2 crankset. I really adore mine, it's the best you can get IMO.

 

[waynebergman]

Yes crossbreak I picked up the hollowtech crank and BB. I like them, very nice.

I am taking a short break on the conversion of the motor as I need to sort out which frame I will use before I order my battery pack. The green rocky I now noticed does not have disc mounts so I have scrapped that idea. Now that I have the Hollowtech BB assembly I can work on picking a frame for this project. I have a super nice Banshee Legend MK1 shown in the attachments here but the BB shell is 83mm. If I grind it down to 80mm and slide out the left crank arm (shown in third picture) to its outer most position on the axle I can get away with it I think but then I would have to use a different motor mounting system then crossbreaks method which I may be OK with. Lots of meat on this frame to work with for motor mounting but lots of other stuff with this frame that will cost me a lot to get up and running like super wide rear drop outs at 155mm so special DH hub etc and a 1.95" head tube. All my spare parts I was hoping to use are regular cross country mountain bike stuff so it will cost me a lot to buy special stuff for this bike. It may be worth it however as the frame is very nice. Also I dont have a shock for it......on and on it will go for costly purchases if I choose this bike.

I am half thinking to just convert the black hard tail shown in the above picture as it will be nice and light and much simpler to build but the issue here of course is it is a hard tail. It will be the easiest to convert for sure and may be the route to go. I need to sort this out first of all as it may take a while for batterry pack to arrive and I want to make sure the battery pack will fit in front triangle. It sounds like the cellman 50v 14.35ah may just fit both of these bikes with in there front triangles.

 

[crossbreak]

The green rocky I now noticed does not have disc mounts so I have scrapped that idea.

IMO on the rear wheel a disc brake is not really necessary. if you enlarge your wheelbase by elongating your swing arm, your can make an IS2000 brake mount quite easy. I do this mod next week (I hope) when my ordered AL-7075 sheets arrive, maybe you get some more ideas when you see the pictures. I would start on a bike that is 68mm BB width, since you can swap the frame easily in the end.

80mm+ BB is to much to grind it down i'm afraid :?

 

[waynebergman]

The hollowtech 2 assembly will give me a 2.5mm on each side of the frames BB shell for my motor mount plates based on a 68mm BB shell. PERFECT! The hub shell is just zip tied in the general location for now. After the axle is made and installed and I get my FW mounted on the axle I can design and make the motor mounts.

The plan is go with with crossbreaks suggestions on the tooth counts

LEFT SIDE OF BIKE.......32t @ crank.....14t FW on the pedal assist input side of the motor shaft....EDIT...I COULD ONLY FIND A 16T FW TO FIT MY ADAPTER SO I AM NOW RUNNING A 36T AT THE CRANK AND AN INEXPENSIVE 16T FW. SHOULD BE FINE.
RIGHT SIDE OF BIKE.......22t for the motor drive back to my 13-34 cassette.

If I can get around 50v 14ah in the front triangle I will be go with it. Its appears the cellman 50v 14.35ah batteries measure out at 75mm x 276mm x 138mm according to his web site. I will confirm these sizes before ordering as it looks like it should fit in this frame just fine.

I think this will be a good choice for my first mid drive as its much easier to put this together as a hard tail. If it works well then I can leave it as is for an extra bike for when my kids come up to visit me or for introducing friends to electric trail riding. Then I can convert the Giant as originally planed based on what I have learned on this first mid drive.

 

[waynebergman]

I am trying to source out my FW stuff and drive sprocket for the motor. FW components like these are new to me so I have some questions to help me get my head around the different directions of FW you can order and how they will work.

The adapter shown in the left of the photo looks like it could be a good starting point for the left side motor FW. I can turn my axle down to 5/8" and slot in a keyway slot for it. I just want to make sure that under power things don't fall off or unscrew because I did not understand the different components threading and freewheel action. For the left side of the motor I know I would need a clockwise Freewheeling freewheel but I am not sure if I need to worry about the threads on the adapter when it is run on the left side of the bike. Will the freewheel fall off of this adapter if I pedal assist from the left side. I will be giving pedal assist in a counter clockwise direction to this Freewheel assembly of course following crossbreaks lead. So far its looking like I can get the adapter shown on the left of photo from Sick Bike Parts and then scare up a 14t FW from somewhere else as they do not have a 14t FW that I can see on there site.

I will leave my right drive side question for a later post as the wording above may be confusing enough for one post.
Thanks Wayne

 

[crossbreak]

hey wayne,

your right, the right hand freewheel will work on your left side drive. But the 14T freewheel needs a 30mmx1mm threaded adapter, I guess the one shown from SBP is BSA threaded and I'm afraid it wont fit. If you own a lathe it should not be a problem to make one yourself, Otherwise I can make some of these and sell them them here for a fair price.

For the right side I made my own adapter. There is no freewheel needed, so I use Shimano Sprockets made for 3/32" chains for the Nexus internally geared Hubs.
http://www.sjscycles.co.uk/images/p...t-for-nexus-geared-hubs-322-0320-IMG23008.jpg
For the sprocket Adapter I used a 40mm Holesaw do make a round plate and then I just filed 3 keyways into it. For the connection to the axle I just bored a 10mm hole and then enlarged it with the file, till it has fit the Hubmotor shaft. Some more sideplates for a bit support, and you got your sprocket adapter made yourself. I can post some pics tomorrow.

If more people like you need these adapters, we could talk about selling these , but yet there is too little interest.

 

[spinningmagnets]

but yet there is too little interest.

I've gotten the impression that a lot of builders are waiting for more road-data before committing to such a new idea....

 

[crossbreak]

I guess the one shown from SBP is BSA threaded and I'm afraid it wont fit

smallest one that fits on your chosen adapter is a 16T

 

[waynebergman]

The photos here are what I am leaning towards so far for the left side pedal assist FW on the motor shaft. I had hoped for a 14t but a 16t should work OK. I will just have a slightly faster cadence than 80 at top speeds but that is OK. I don't see if the eno 16t freewheels in the clockwise or counter clockwise or if I have a choice. I will phone and ask them if I can get this FW to freewheel in the clockwise direction.

If I can get this 16t FW shown in the photos here to coast in the clockwise direction am I heading in the right direction for the two pieces shown here to work together for the left hand side FW?

And thanks crossbreak for the tips on getting the right side to work. I realize I do not need a fw on that side so I am feeling I can work that one out no problem.

 

[crossbreak]

You can use a cheap and very common right hand Dicta FW saves money for lipo 36T/16T or 38/16 are combination worth thinking about. 32/16 is a bit fast IMO, but try it, you can change this easily.

 

[waynebergman]

Looks like the above items from Sick Bike Parts should do the trick. So the new tooth counts are 36 t from the crank to the Freewheel adapter c/w a dicta 16t FW. Then the right side of the motor shaft will get the 5/8" non FW adapter to 24t sprocket from sick bikes. This will mean the top speed will be a bit over the 25 MPH but that is fine. From Sick Bikes I could only get a 24t for the non FW adapter so I went for it. Its in the mail so I can move on with the axle once the parts arrive.

 

[crossbreak]

I thought a nit about your project. Guess you would also be fine woth a 32/16 overdrive to the motor. You then gain 85rpmx2x6 =1000rpm

thats fine if you have got a good throttle device like the CA, you will run efficient.

I say this couse 32T is more common and maybe lying around

 

[crossbreak]

this is how I make my output sprocket adapters... I do not own a good lathe http://endless-sphere.com/forums/viewtopic.php?f=28&t=45245&p=746789#p746789

Any progress?

 

[waynebergman]

I am waiting for my sprockets and adapters to come from sick bike. In Canada you never know what gets held up at the boarder. Good tip with the hole saw crossbreak.

 

[waynebergman]

View attachment 3View attachment 6Lots of goodies arrived in the mail over the last little bit.
I have picked up some down hill heavy duty tubes and a nice rear tire. BB Motor Mount plates arrived from Spinningmagnets, my FW and adapters have also arrived. Now that I have these pieces I can sort out the issues of how to make my axle & locations to space out my sprocket adapters etc. Picture shows first dry fit of things so I can get a feel for how the motor sprockets will line up with my crank assembly and the rear cassette. I can see I will be able to shorten up the motor mounting so the motor is about 1 inch closer to the BB and still leave room for my pedals etc.Purple tape shows the location of the down tube reinforcing mounts I will attach to the rivnuts in the frame that were originally for the water bottle mount. Got a good tip from the bike shop yesterday for rim tape. They use the clear hockey tape shown on the floor in one of my pictures. It stretches and its fairly thick and its cheap. I can see the 14.3 ah battery I am getting for this project is going to fit into the main triangle very nicely. I am glad cellman is making a pack with this ah and size. It should let me run my 35amps no problem as I think it is a 5 c Lith Mang and the 14.3 ah range is just right especially if the mid drive gets the effenciency I am hoping for.

The photo shown of my milling attachment shows the flat bar I have got to modify the milling attachment so it will fit my lathe. Of course as luck would have it, I need a mill to make the mods to the attachment. I need this milling attachment up and running so I can cut my key slots in the axle so I may take a bit of a break in the project to get this sorted out as I would like to have it up and running for the completion of this project. I have a very nice neighbor that has a mill so I will tap him on the shoulder for help on this one.

Feel good to be making some progress on this. I am starting to have a good feeling about this project. I may not be the full suspension mid drive I would one day want to build but I feel it should be solid.