Current Cycles Prototype Buildlog...

OK I have been doing some research on this, and I have decided to build my own gearboxes for now. I have a design worked up and I played with some ratios and with a 3 stage gearbox, I can keep the form factor really small while still having all gears with decent tooth counts for strength. I plan on simply welding the gears onto the shafts and having the shafts on high speed quality bearings. I am planning on three stages with a 16T drive and a 48T driven on each stage. This will give me a total reduction of 27:1 which is only slightly lower gearing than my current box of 25:1 so I am really excited about this! PLUS the motor will be more or less part of the box and require no adjustment for chain tightness, ETC! this is the way to do it for sure! I just hope they are fairly quiet, but if they are a bit noisy, I think I could run some lapping compound through the box just to mate all the surfaces and hopefully quiet it up, plus the fact that it's enclosed and in oil will really help as well. Oh and the box is only going to be approx. 3" deep by no more than 6-7"now and have no exposed sprockets except the freewheel for the output shaft, and the motor itself! I am doing a side job this weekend that will pay for the ears, so I can get started building, it will take a bit to get it figured out I am sure, but this is a much better option and with nice sized gears at 3/8" wide, I think it will be plenty sturdy as well! The 27:1 ratio combined with the new rear 11/34 cluster I am going to get (VS my current 11/32) should give me WAAY better climbing power than even before! I wanted to slow it down since it was still a little fast going up big stuff! Lookout goat trails here I come!

If anyone is interested. initial figuring for production quantities puts the box sale price (WITH 2,500ish watt MOTOR) at around $300ish as long as I don't run into any problems, so it should be very reasonable for a bolt it on and go setup! Even if it goes up a bit... And believe me, that is MORE than enough power when going through the gears! I had 1200-1500 watts before and it would climb ANYTHING!! Even straight up big rocks!
 
I finally got to order my gears! Hopefully they will show soon, I am anxious to get started! I also am getting help from Gwhy on my halls, it seems I lost one, so im going to make my own set to his design...
 
Well, I am not too much of a CAD guy, so its in the napkin stage! LOL! I will be drawing it up in cad though so I can be sure of fitments and such, it might be a bit though..... On second thought, maybe I'll try it soon though, since I will not have the gears for a bit....
 
Okay guy I need opinionS if I use a chain to put power into the box, or possibly a belt, does anyone see a problem with this versus putting the motor directly in the box ? I am having trouble packaging the box with the motor inside of it because of the necessary seals and what not. So my question is do you see a problem with a belt or chain input, that will make the box much narrower? I think this system will be much better this way But I would like to hear your comments! Thanks!
 
Nobody? Just curious, I would like to know what you think...
 
I thought that was what I was doing? I had over 200 miles on the last design and it failed. That's why you do R&D. This is what I am doing here, R&D.
 
True, I was actually not putting it "inside" just driving the gears directly through the case. I thought I would be able to make ti thinner than I actually could. I think this setup will be good as well since it will leave the option of different ratios of primary drive before the box if someone wanted. I will give a good amount of adjustment in the motor mount slots so someone could change the input ratio if they wanted. I plan on a simple 1:1 to start with, just so I can get the power to the box. I will hopefully get some Sketch-up renderings of my idea up soon so you all can critique.
 
Did a bit of work tonight. I got the gears all laid out in Sketch-up. I have all dimensions and such now, I can actually build it! Hopefully some progress this weekend. I will continue to finish the whole box in CAD tomorrow night....
 

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  • Bike Gearbox Layout details final.jpg
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From a noob standpoint, I would think the less complicated it looks, the less maintenance there should be, right? So, if there is a magic box that then a chain puts power to the rear wheel might be less intimidating than one chain in to the gearbox and another out. On top of this, add in the spinning motor which could possibly pick up dirt and muck and you have a rather complex mechanism. But hey, if you can make it work for you and look clean, there really is no other option out there right now. I'm just thinking in terms of the possible buyers you might be catering to that aren't board members. People that just want to hop on and ride.

What exactly was the fatal flaw with the original design? Would it have survived at a lower power input?
 
Yeah, it basically handled about 1200 watts until I tried taking off in 4th gear to skip a few gears. It sheared a tooth off and that was it.
 
You can get some fairly good performance from 1000W since the motor has the use of the bikes gears (being a BB-drive). You could add limit switches or use halls to create lock-outs. This would be especially easy with an IGH on the rear wheel and some type of gear lock-out could be added to the shifter knob.

If you coasted a while and slowed down, a power lock-out would require you to downshift before you could apply power again, but...it might be a worthwhile idea.

There must also be some way to allow power, but limit it by linking it to your speed, but doing that would require some electronics modification, and I prefer solutions that involve big hammers.
 
LOL! You think like I do! I am hoping to just add a small switch to the rear derailleur that will be connected to the brake switch on the controller and if you are in high gear it will not supply power. I also want the box to be able to handle the power I want which is at least 2500 watts, so I am hoping the new design will do it, we will see, it's MUCH more robust than the little tiny box I had before, but only slightly larger, and I dont need the big sprocket reduction anymore, so it will actually be MUCH smaller!
 
Thanks!
 
I was planning on doing some machining today, but I have to go to a funeral for an older friend that passed, I should have a little time tonight and tomorrow is all Machining! How thick should I make the box walls? I was thinking of using .125" thick aluminum for the sides and .250" thick for the top and bottom to add rigidity torsionally. I am currently using only .125 for my side plates, but the little box in there is stiff, so I am not sure... But I want it as light as possible..
 
Have you considered putting some sort of dampening designed into your system? I used to have an old Kawasaki motorcycle that had a triangular rubber piece shaped like a peace sign so when power was slammed from the motor to the rear wheel the dampener acted inside the wheel to smooth out the power coming from the sprocket. It's hard to describe, but it seems if you put something like this inside your output shaft it would take the bite out of your gear changes on the cassette. It would work much like Thud's dog clutches, only you would have a piece of rubber between the two engaging components. I'm all for building the gearbox yourself, but if you are gonna try to market these, there is no way you will ever pay for all the man hours you would be putting into every single gearbox, unless you up your price a good $200. I liked the cheap off the shelf gearboxes nested, I don't think you are solving any problems by building it yourself, the shock loads are still there. I wonder how the Cyclone setup deals with this, maybe being below the BB after the cranks insulates it more. A slipper clutch would actually be the best solution, IMHO, but that's gonna be tough to do on the output shaft of your setup. Ask Thud, I bet he has over 20 hours into each 2 speed box easy. I also think he uses .375" aluminum.
 
Yeah, I thought about that, they are called a cush drive I think. They are used in jet skis as well from the motor to the prop shaft. The main reason I went away from the little boxes, is A) I wanted the setup to be more compact. B) I wanted it quieter. C) The gearboxes vary in bolt pattern slightly from one maker to the other and you never know what you are going to get, I have bought 4 of them now and they are all different, and I go them from the same place! D) The gears they use for the pinion are junk and in any kind of hard use WILL break no matter how nice you make the drive. I actually think they will break even without any shocking, simply from the vibration... You will see, my new box is going to be much improved, I am going to harden my own gears and everything, It will be a bit more cost to make but truly not too much more. I figure about another $50.00 in materials and about the same in hours to make. It is a fairly simple design, I just am taking my time designing it so I can get a good finished product. I got the gears from Mc Master Carr for $125.00 and I will heat treat them myself this time, but they sell them hardened already for future builds, I was not sure I would need the hardening so I opted to save the cash for the upgrade. It is really pretty easy to do anyway and will take little time. In production (assuming the drive works well) I will do multiple sets together to save time. I may even build a kiln to do the heating..
 
I got the driven gears all machined up except for drilling the final drive gear for the half inch shaft it will receive, and I am getting ready to start on the shafts for the box. I didn't want to go pay a bunch of money for shaft material, so I decided to simply turn down some all thread I had laying around. I figure being bolt material it should be fairly strong and pretty rigid. It is definitely harder than the 1144 material the gears are made of, so it should suffice. Here are a couple pics of the gears and the layout for them in the box once its complete...

416395376_photobucket_71529_.jpg


416395376_photobucket_71530_.jpg
 
looking good, I looked into gears for mybuild initially, but they were wanting about 400 bucks for the gears you have there, so I opted for chains and belts instead. The axle should be fine, not a heap of distance between the gears for it to shear in, and you would think bolts would have the cell structure for that kind of force.

I am very interested in seeing your final product it should be inspiring. So good luck and be sure to post many pictures of the finished drive.
 
Will do, I tried to machine the all thread but to my disappointment, the deeper I cut the harder it got until I could barely get it to shave it, and I am using a carbide cutting tool! SOOO, I guess I will be getting some hot rolled steel at the local hardware store instead, but like you said, there is hardly ANY unsupported shaft between the gears, so I think it will be fine. the box is only 1.5" wide so that is very narrow and I think it will be OK. I MIGHT try to get some better material for the output shaft since it is going to be hanging out there with a freewheel on it to drive the cranks. Possible some chromoly or something unless you all think it does not need it at 1/2" diameter?
 
I understand the desire to get parts as quickly as possible so you can finish the next phase of testing soon, but...

I have had good luck with McMaster-Carr case-hardened shafts. Heres the link from my files...

SHAFT, 1/2" diameter, case-hardened, available off-the-shelf in one-inch increments, arrived in mailbox less than 5 days in an envelope, less than $10 ea
http://www.mcmaster.com/#catalog/116/1058/=8sk0ir
 
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