Switched to a GNG style "big block" swingarm coming soon!!

[2moto]

looks quite compact, but the center of gravity seems to be quite high. I felt a lot of difference when mounting my motor in front of the BB rather than above, handling the bike feels much better with the motor mounted in front.

I would try to get the heavy parts far more down, there is plenty of space.

That's just one of several, significant flaws in this desgin. But hey, let the ball roll.

 

[dustyearlobe]

bowlofsalad...

This has been discussed at length in a similar thread about building frames. If sufficiently over built, others have had great success with not heat treating. Their bikes are used on and off rode and at hight speeds and have had no problems.

I am not wanting to start a debate or derail whip's thread, just stating that it has been covered in depth and if one prepares for it, heat treating is not always necessary. But certainly one must be aware of the effect of welding aluminum.

Clay

This was a big headache for my build although there was a place near by that could do it for me i desided to over build but give the frame a couple of weeks to age harden,cant say if this was right or wrong way to go but hasnt failed me yet

 

[bØb]

Of course if you are dealing with flat surfaces, you can always "7P" rivet them together.

bØb

 

[Whiplash]

The thing is, bicycle frames are typically MUUCH thinner than mine in fact 1/4 of the thickness is common. If you do the math using the typical tensile strength of raw 6061 is still approximately 18,000lbs/sq.in. and since I will have SEVERAL inches of weld contact area in the high stress areas it is MORE than strong enough. Also of note is the fact that my box style frame is far stiffer by design than any tube design. Finally, it has been proven by several builders on the sphere that its perfectly fine so I am not going to waste the time. Eventually when I am trying to shave lbs off the final design and possibly go to a thinner sheet thickness, I my look into heat treatment but for now its fine..

 

[Whiplash]

That's just one of several, significant flaws in this desgin. But hey, let the ball roll.

I thought I had remedied the swing arm, its almost exactly inline with the drive sprocket now, and I moved the motor back significantly. And what other "flaws" do YOU see now? You know, I try very hard not to criticize others in their threads. If there is something to say, pm the person, don't try to make yourself look smart at anothers expense...

When designing anything, there are compromises to be made for performance or weight or ease of manufacture. As long as it all works, nothing else matters and there is no flaw.. If it does not work, I'll change it, but I don't see it being a big problem and I'm not building a top competition downhill frame, it just needs to be fun to ride period.

 

[bowlofsalad]

I am sure nobody wants to hear this, but I recommend http://www.cineventions.com/steel_aluminum.html giving this a read.

 

[flyinmonkie]

bowlofsalad...

Good info and well explained. That is why a steel bike rides so well vs an aluminum one. In whip's case, he is going to make the frame a box structure in which the sides add to the strength and rigidity of the bike. The sum is great than the parts.

The strength/weight in steel vs aluminum is always an interesting one and often comes out near equal. That is of course unless you have access to expensive manufacturing processes and cad design that can determine actual stresses on components. That way you can build strong where you need it in the direction you need it. Like high end bikes and aircraft.

Clay

 

[Whiplash]

Well said! Yes I am likely giving up at least a couple lbs. in exchange for the added strength the extra weight will give me and the piece of mind.

I found some extruded aly that I had laying around that makes the perfect jig to hold the sides while I tack it together. I just need to cut the top section and bend it into shape and I can get it to start looking like a frame! I'll try to get it cut tonight if I have the energy after work...

 

[crossbreak]

The only thing you exchange is design work for weight. Alloy is in fact more lightweight as steel, since complex stress conditions gain from more greater cross section and more distributed material even if the material has the same stiffness to weight ratio. Alloy will not rust. There IS a reason why planes are made from alloy.

Anyway i would redesign the weight distribution of your bike. Handling will be horrible the way it looks now. Also the high pivot point leads to differing wheel base, when your suspension engages. But weight distribution is much more important. Redesign or you'll build it twice

 

[Whiplash]

I played around with battery/controller mounting and I can get them much farther back and lower than my existing functioning bike, so even though the motor is a few inches higher than my current test bike, the CG should be the same or lower than my bike so handling should be fine as my test bike is great the way it is. I may be able to get the motor a bit lower than the mockup when I actually mount it. As for the swing arm, yeah it only changes about an inch over the 8" of travel and I plan on playing with it more when I get to mocking up the swing arm for real..

 

[crossbreak]

That sounds promising... waitinh keen for pics of the reworked design! What about a seperate battery box like the one KTM uses on its eGnition 88? Weight distribution looks perfect on this bike, I sadly never drove it

 

[Whiplash]

I was considering a range extender pack similar to the KTM for very long rides, but the STD battery should be plenty most of the time. I could offer it as an option or something..

 

[Kepler]

That's just one of several, significant flaws in this desgin. But hey, let the ball roll.

I thought I had remedied the swing arm, its almost exactly inline with the drive sprocket now, and I moved the motor back significantly. And what other "flaws" do YOU see now? You know, I try very hard not to criticize others in their threads. If there is something to say, pm the person, don't try to make yourself look smart at anothers expense...

Totally agree Whip. Bloody rude in IMO.

Been following this thread since the start and I think you have gone to great lengths trying to optimize this design while at the same time taking on board the valued suggestions by the many talented builder's on this forum. Looking forward to the results. 8)

 

[crossbreak]

I totally agree with 2moto. He said something that had to be said to HELP whip with his build, even if 2moto may not have found the right words for that. He, as well as me, wants to help whiplash make a great bike. If whip would not appreciate that he would not post anything here besides the result, like many do who can not stand any critics btw, a lot of BS builds are shown around, one should not take as an example :? I like whips builds even if there are flaws, at least he took care and got a better one in the end

I talked to 2moto in the meantime... looks like he does not have time for this :? Sometime guys are as bitchey as girls... hope you can stand the critics 2moto

 

[Kepler]

Seriously crossbreak, you really think that was fair comment. We obviously think very differently. :?

How about you and mr moto draw it up and show how it should be done then

Hope that didn't sound too bitchy.

 

[Whiplash]

To be fair I appreciate most comments but if someone offers their opinion and I either decide to go a different route or not they should not post rude comments. I don't mean to step on toes but I am the type of person that follows his gut for the most part and I think the design will work. If not, I will fix it. I take every comment into consideration but that does not mean I am going to do it someone else's way. Please all I like any input it helps me figure it out but if I decide differently, please don't be offended, there is often more than one way to "skin a cat".

Thanks Kepler for the support!

 

[crossbreak]

Seriously crossbreak, you really think that was fair comment. We obviously think very differently. :?

How about you and mr moto draw it up and show how it should be done then

Hope that didn't sound too bitchy.

I would use the same geometry that his old build uses. Motor is already mounted perfect. The battery is mounted directly above. Controller as close to the motor as possible, it should be mounted in front of it. The space around the upper tube stay free. Nothing should be mounted here to keep the CG down. I have no mspaint on my phone, I'll draw for you when I have

 

[Whiplash]

If I wanted that I simply would use that frame and box it in. Problem is travel is very limited and not tough enough for my taste. I also want to be able to wash the bike without fear of ruining it. The box frame will allow pressure washing if need be! 8)

 

[Whiplash]

Small progress but progress nonetheless. I cut the top plate tonight and ordered my bottom bracket so I'll be able to get it looking like a frame soon!

 

[Whiplash]

OK guys, I had an idea pop into my head last night of putting the MAC back to its original design and using the axle as both the motor mount and the swing arm pivot like I have seen in another builds design ideas. I would simply bolt sprocket to the left side and thread on a sprocket on the right side and tack weld it in place as I did on my test bike! I am thinking this would be ideal for the chain growth and hopefully cancel any squatting from acceleration. Any opinions on this before I put the motor back to original?

 

[bØb]

That will eliminate most of the torque induced squat and you will have no chain length issues. BUT, your internal gear ratio will go back to 5:1, you loose the ability to shed more heat from the stator, you will loose some throttle response because the motor housing is now a flywheel, the motor will continue to drive the rear wheel for a while when you close the throttle, how are you going to use pedals?

Have you ever driven an old farm tractor with PTO driven bush hog with no overrunning clutch or a two stage clutch? You mow along FD&H till you come to the ditch and push the clutch in and the bush hog drives you right into the ditch :-(

bØb

 

[Whiplash]

Lol! Like the image. I was going to use a freewheel on the right but the left side would be tricky I suppose.. any ideas?

 

[dustyearlobe]

OK guys, I had an idea pop into my head last night of putting the MAC back to its original design and using the axle as both the motor mount and the swing arm pivot like I have seen in another builds design ideas. I would simply bolt sprocket to the left side and thread on a sprocket on the right side and tack weld it in place as I did on my test bike! I am thinking this would be ideal for the chain growth and hopefully cancel any squatting from acceleration. Any opinions on this before I put the motor back to original?

thats a great idear but would you be able to fix the motor in place add cogs and sleve the axle for external bearing (could be internal threaded bar so doubled as nut)for swingarm and still have room to bolt up the swing arm bearings ,,could be a big ask, also how would you remove swing arm unless in two halves but workable i should think ,,would be good to see the motor in side veiw with measurments cogs ect

 

[bØb]

Lol! Like the image. I was going to use a freewheel on the right but the left side would be tricky I suppose.. any ideas?

HD Front Freewheel & 5/8" bore FW adapter (right hand threads). Threads on FW adapter needs to be shortened because they bottom in the Front FW adapter.



All available from sickbikeparts.com . The pedal cranks and BB cartridge are also available from SBP.

bØb

 

[dustyearlobe]

is that the cyclone bb with some mods