Specialized Big Hit FSR with midmount

[Tench]

Just blows me away.

You ever think of taking orders for frame builds? I'm saving up at the mo'.

Cheers,
Chris

It is not something i had intended to do but wouldnt rule it out, first though i have to finish this one, get the gearing right and then the throttle responce tailored so i can climb trees on it, power is nothing without control, who said that?

Cheers Simon.

 

[morati]

Incredible job, simply beautiful work!

 

[Justtoby]

Thanks guys, Toby, this is my first venture into Lipo and it was important to make it fool proof when switching from series (running) to Parralel (charging) i didnt want to make any mistakes and fry anything, coming from Life bats plug and play was the only way i knew so i worked out a way to do it.
I am just trying to source some new chain wheels then design and make a new carrier for them, possibly with another bearing to take some load off the Dicta freewheel, My CA has a fault aswell so that needs to be replaced then we can get some video!!
We should have a UK rideout this summer, there is getting to be quite a few of us now.

Simon.

Sounds good to me, I hope to get some good group rides together this year, as you say there are a few of us now. I have got a week in Barnstaple riding and whizz kid is bringing down his fighter for a few days too.

 

[Trackman417]

Crazy build!
The color scheme just rocks! I bet you don't need to worry about that motor over heating anytime soon . Idk if anybody asked this, and if so I am sorry for askin it again. How fast are you going on this thing? And could you put up some more pics of the charging block you put together? That would be great! Thanks!
Once again great work! It beats the hell out of my plastic battery box ebike. 8)

 

[Tench]

Crazy build!
The color scheme just rocks! I bet you don't need to worry about that motor over heating anytime soon . Idk if anybody asked this, and if so I am sorry for askin it again. How fast are you going on this thing? And could you put up some more pics of the charging block you put together? That would be great! Thanks!
Once again great work! It beats the hell out of my plastic battery box ebike. 8)

I dont know how fast it is yet, allthough i have had a few spins round the block on it i have a few details to sort out before i take it for a proper ride, i expect 40mph as top gear equates to very slightly over 1-1 ratio which would be the same as it being in the wheel, actually it is at 1-1.09 at the moment but will be 1-1.05 when it has had the chain wheels changed for my final size choices.
I dont have any good pics of the rest of the charging connector, i will take some tomorow.

Cheers Simon.

 

[deecanio]

Absolutely top drawer 8)
Really looking forward to seeing how this bike goes, if it's half as good as it looks expect a lot more mid drives to show up, beautifully executed.
Can't wait for the video, offer up some frames, please, pretty please?
One quick question, with such a great quiet setup could you get away with a smaller hub? I have the hs myself and it's a bit weighty, with this sublime drive setup maybe a lighter smaller geared hub like the bmc might suffice?
Totally non critical btw I'm just curious how having the hub mid drive translates when powering the crank? It would seem a shame to go rc unless there's one that runs as quiet and without the need to gear down?
Kudos on an sublime machine Tench, it's bike like these that really move us forward.

D

 

[Kepler]

Up there with the best builds ever posted on this fine forum. Fantastic work.

Now I am with Deec on this one, a geared Hub like a BMC or a Bafang would be a great option for this bike. Not that there is anything wrong with the choice of motor on the bike. They are a powerful motor DD and will have crazy power through the gears. The hardest part will be keeping the power under control. It will just about need a current limit based on what gear you are in (now there's an idea )

Are you sure it weighs 85lb? That's heavier then I would expect especially considering is an aluminium frame. A Fighter that has a full CoMo frame and swing arm, higher battery capacity, and same motor is around 77lb.

There is so much I like about this bike. I especially like the series / parallel plug. Absolute gold.

 

[full-throttle]

Now I am with Deec on this one, a geared Hub like a BMC or a Bafang would be a great option for this bike. Not that there is anything wrong with the choice of motor on the bike. They are a powerful motor DD and will have crazy power through the gears. The hardest part will be keeping the power under control. It will just about need a current limit based on what gear you are in (now there's an idea )

Just to rub it in - the internals of Bafang BPM are 150mm dia, 60mm wide and weight less than 3kg

I'd be very interested in knowing how much power can a bicycle drivetrain handle continuously. 2kW?? So, keep us updated please

A parallel drive would prob be ideal for anything higher than that.

 

[Hyena]

Very slick build Simon!
I'm working on a very similar charging plug for my fighter at the moment. I've always used 45a anderson blocks for series/parallel discharging/charging but they don't carry enough power for the new set up. I'm curious though, your charging set up only seems to have the main power lead going to 1 of the 3 packs - is that the case ? Or are the other bullets internally connected inside the plug ? Or is it only charging slowly through the paralleled balance taps ?

As others have said a smaller DD hub like a 9C or better still a mac/bmc would be great. Do you reckon the H35 was really necessary ? Not having it in the back wheel is great but they're still a pretty heavy beast and as full throttle said I wonder just how much the rest of the drivetrain can take.
If you're looking to make further weight reductions check out the milling Keyne did to his - he removed quite alot of the alloy and steel material which I think shaved around 1kg off it.

 

[flathill]

Bravo! Such attention to detail. My cousin was a WRC mechanic and they would fire guys for not clipping a zip tie flush (no sharp edges allowed near wiring). He thought it was crazy until a driver took him on a mountaintop gravel road with no railing and a 1000 foot drop at 120+ mph

 

[Tench]

Bravo! Such attention to detail. My cousin was a WRC mechanic and they would fire guys for not clipping a zip tie flush (no sharp edges allowed near wiring). He thought it was crazy until a driver took him on a mountaintop gravel road with no railing and a 1000 foot drop at 120+ mph

Clipping cable ties i would fire someone for that, they should be cut off perfectly flush with a sharp blade!! i,m not kidding!

 

[Tench]

Up there with the best builds ever posted on this fine forum. Fantastic work.

Now I am with Deec on this one, a geared Hub like a BMC or a Bafang would be a great option for this bike. Not that there is anything wrong with the choice of motor on the bike. They are a powerful motor DD and will have crazy power through the gears. The hardest part will be keeping the power under control. It will just about need a current limit based on what gear you are in (now there's an idea )

Are you sure it weighs 85lb? That's heavier then I would expect especially considering is an aluminium frame. A Fighter that has a full CoMo frame and swing arm, higher battery capacity, and same motor is around 77lb.

There is so much I like about this bike. I especially like the series / parallel plug. Absolute gold.

I used this motor because i was familiar with it, i know nothing about any of the other you have mentioned, maybe there could have been a better choice?
As for the weight, i only weighed it on a set of bathroom scales, i will see if i can it weighed on something more accurate, i can grab this by the fork leg and seat post and pick it up and carry it at head height, if the bomber is 116lb as claimed this does feel closer to 65-70.

 

[Tench]

Very slick build Simon!
I'm working on a very similar charging plug for my fighter at the moment. I've always used 45a anderson blocks for series/parallel discharging/charging but they don't carry enough power for the new set up. I'm curious though, your charging set up only seems to have the main power lead going to 1 of the 3 packs - is that the case ? Or are the other bullets internally connected inside the plug ? Or is it only charging slowly through the paralleled balance taps ?

As others have said a smaller DD hub like a 9C or better still a mac/bmc would be great. Do you reckon the H35 was really necessary ? Not having it in the back wheel is great but they're still a pretty heavy beast and as full throttle said I wonder just how much the rest of the drivetrain can take.
If you're looking to make further weight reductions check out the milling Keyne did to his - he removed quite alot of the alloy and steel material which I think shaved around 1kg off it.

The pins in the charging plug are linked with brass bars so it charges through all the pins, i will try and show it on some pics later. I have got .75kg off the motor allready, i could take some more off the O/D of the steel outer ring but is the small saving in ultimate weight worth the effect it might have of making the motor more lively, if it where lighter it may pic up too quick and lose some smoothness? I have pulled 3000w at 18s and the transmission didnt complain, i think if the whole system is maintain well it should stand upto to it ok, time will tell just how long the components will last.

 

[flathill]

Bravo! Such attention to detail. My cousin was a WRC mechanic and they would fire guys for not clipping a zip tie flush (no sharp edges allowed near wiring). He thought it was crazy until a driver took him on a mountaintop gravel road with no railing and a 1000 foot drop at 120+ mph

Clipping cable ties i would fire someone for that, they should be cut off perfectly flush with a sharp blade!! i,m not kidding!

Haha you got me there. I like the razor myself but a flush cutter can work in a pinch

 

[Spicerack]

Do you have a temp sender on the motor windings? That would be a concern of mine especially when the motor is enclosed like that. You could also do an oil wet bath inside the hub if heat does prove to be a problem...

 

[Tench]

Do you have a temp sender on the motor windings? That would be a concern of mine especially when the motor is enclosed like that. You could also do an oil wet bath inside the hub if heat does prove to be a problem...

No i have not put a temp sensor in it, i did think about it but decided if it becomes a problem i would go the oil bath route as that apears to be quite effective from the info that has beeen posted on here. I will keep my eye (or hand) on it and see how it goes.

 

[knoxie]

Really looking forward to seeing the videos of it running Simon sure there are other motors you could have fitted in there but I reckon you are fine with what you have done to be honest, you could fit a geared motor (BMC/MAC) in there but then thats more reduction more mechanical losses not to mention noise and serviceability with the gears not sure what you loose in weight that it would be worth it? DD hub motors are great for their simplicity.

Thermal management might be an issue, you have options there you could mill out the motor covers with holes but then fit fine mesh over the existing holes in the plate / cover to stop crud getting in there when your out on the lanes

Drive train will be fine although you will go through chains fairly quickly and alignment will be critical to stop it skipping under hard acceleration, if you can get any video and you want it editing and posting I am more than happy to do that for you on my youtube channel.

 

[Tench]

Knoxie, Dave is going to come over on Sunday if he gets the chance, he can do a vid and host it for me so you can all see it running, no doubt he will have a spin round on it while he is here!

 

[Kepler]

I used this motor because i was familiar with it, i know nothing about any of the other you have mentioned, maybe there could have been a better choice?

I think the choice of motor has its own merits and am quite sure it's going to provide amazing performance. The geared hub motors have their own set of merits. I started using them a few months back and am constantly amazed by the performance you get from such a small light package. Improved efficiency over DD motor is another bonus.

For me personally the perfect bike is your amazing build but with a code 12 bpm motor driven off a 6FET mini monster set at 2000W. Battery would be 18S 8 ah to keep things really light and a second front mount 18S 8 ah auxiliary pack only fitted when more range is required.

Power might be slightly less but a geared hub at 2000W down low, pulls like HS35 at 3000 W

So basically your bike but 15lb lighter.

 

[knoxie]

Knoxie, Dave is going to come over on Sunday if he gets the chance, he can do a vid and host it for me so you can all see it running, no doubt he will have a spin round on it while he is here!

ahh great stuff!! so looking forward to seeing it in action your man should be able to get the front wheel off the ground then! and again I think your choice of motor here is fine, I have loads of experience with the BMC geared motors and DD hubbies like the X5, I like them both but haven't found the geared motors to be any more efficient in fact I would say they are less efficient from my experience with them, your going to have fun keeping things running smooth under high power as it is without worrying about shredding the gears in the motor I love my geared motors but they aint made for going off road and hard starts and stalls they don't last if you treat them like that the gears shred, the clutch bearings go, the key-way on the shafts break, keep it simple even if its a little heavier

 

[billsy]

Tench this is seriously impressive. I feel like you just jumped up and Tangoed me

I'd deffo be up for a ride out in the summer. Please give me a shout if and when.

Cheers

[youtube]H6yCgtehwUE[/youtube]

 

[Tench]

Pmsl, i have not seen that for some years, the expression on his face when he got "Tango'd" was rather like my lads expression when he had a go on it in a low gear today!!

 

[Tench]

Took a few more pics, this shows how slim the bike is and the amount of steering lock, so many frames converted or made to carry batteries are in my opinion made too wide resulting in a reduction in the turning ability, this was one of my goals to retain as much lock as possible;

Here are some pics of my plugs, the first is the socket.
The pins in the socket on the frame are as follows, top group of 3 all - bottom group of 3 all + the 2 on the right side are top - feed to the controller and below it the + controller cable, the 3 negatives counting from the left are (each battery is a parralleled pair) batt 1, batt 2, batt 3 below them from the left are the positive terminals from batt 3, batt 1, and batt 2. The "run" plug connects the first vertical pair on the left together also the middle vertical pair together and the pair on the right of the group of 3 are connected horizontally to the controller, this put the 3 batts in series and hooks them up to the system.

The charge plug has the horizontal groups of 3 connected together, top 3 - bottom 3 + and each of these connected to the charger cables, the controller plugs are isolated.
The 25 pin d-sub connector on the bike has the 3 sets of 7 balance port wires from each permanently parralelled pair fed into it, the plug on the charger when plugged in connects the 3 sets of 7 wires into one set of 7 so the pack can be balanced and charged as a 6s6p pack. I used a heavy cable for this to ensure minimal voltage drop between battery and charger which has worked.

 

[Kepler]

Knoxie, Dave is going to come over on Sunday if he gets the chance, he can do a vid and host it for me so you can all see it running, no doubt he will have a spin round on it while he is here!

ahh great stuff!! so looking forward to seeing it in action your man should be able to get the front wheel off the ground then! and again I think your choice of motor here is fine, I have loads of experience with the BMC geared motors and DD hubbies like the X5, I like them both but haven't found the geared motors to be any more efficient in fact I would say they are less efficient from my experience with them, your going to have fun keeping things running smooth under high power as it is without worrying about shredding the gears in the motor I love my geared motors but they aint made for going off road and hard starts and stalls they don't last if you treat them like that the gears shred, the clutch bearings go, the key-way on the shafts break, keep it simple even if its a little heavier

All extremely valid points knoxie. Will need to agree to disagree with the efficiency thing though.

Please dont view my last post a negative comment against this bike, it certainly wasn't meant to be. Just simply an insite to what would be the perfect bike for me

 

[Kepler]

The attention to detail on this bike is just amazing. The excellent steering lock (lack of being my least favorite feature on my Bomber), carbon mount for the CA, water proof on/off switch in the perfect place, 3 speed switch just to name a few.

The charging block works as an emergency cut off too being so easy pull out if you need to. This bike has given me heaps of inspiration and lots of new ideas to consider.