ppc

Hello all,

I finally finished modifying my beater bike, and I now have a fully functional two-speed retrodirect drive bike. Well, not a true retrodirect system, as I use two chains instead of just one, but close enough.

The fast gear is obtained pedalling normally, and the granny gear pedalling backward. It really can climb, but honking backward will definitely take some getting used to I can't wait to try the bike on rough terrain though...

Here are some photos, and a couple of video of yours truly accelerating away Hirondelle-style:





The videos:

https://users.skynet.be/ppc/retrodire..._backward1.mov
https://users.skynet.be/ppc/retrodire..._backward2.mov

(Note the derailleur that I re-use as a chain tensioner for the forward chain: it kept skipping off the chainring without it, I couldn't adjust the chain tension as my dropouts are vertical)

frameteam2003

Wow,that great!
I've just finished with mine also(the drive part)--I used the one chain style.Took the rim and frame over to a friend to have them trued up---I'm not good at wheelbuilding.Will post photos when I finish the frame etc.---sam

gmason

Pretty neat. And why did you do that?

ppc

Neat. Please post photos of your bike when you get it back. Maybe we should start a list or something

The 2-chain design seemed better for me, because (1) it requires no modification to the chainstay, (2) it allows me to use two different chainrings (i.e. more gearing options), (3) if one chain fails, I can limp back home on the other, (4) both chainlines are perfectly straight and (5) I already had 3 chainwheels and don't care about the extra weight.

ppc

My half-arsed official reasons:

- I can ditch both derailleurs/cables/shifters, and I don't need to adjust anything
- It won't derail when the cogs get jammed up with snow this winter
- I've been contemplating going single-speed for a while now, but I do have 2 bits of hill going to and from work that I didn't want to tackle with only one gear.

My real, hidden reasons:

- It's different
- I really wanted to try pedalling a bike backward
- I expect the bike to be a great conversation starter
- I had nothing to do this week-end

urban_assault

cool

gmason

The real, hidden reasons are much better.

grolby

Whoah! Neat! But... um... how does it work!?

Mentor58

Well done. I'm sure that will cause more than a few double takes when you petal by. I'm trying to think what my reaction would be seeing that for the first time, not knowing the story. I think I'd just figure that I'm WAY dehydrated, and best get some water right away, since I'm obviously seeing things.

Again, congrats.

Steve W.

frameteam2003

Did you weld the extention onto the BB for the front idler?--sam

bostontrevor

That's so awesome.

I really enjoy the first video where you start from rest by pedaling backwards and then smoothly transition to forward. The others could just be some guy spinning the cranks backward on a freewheel, but that one demonstrates the thing for real.

Little Darwin

Ditto!

Especially one question. Do you have in essence two independent freewheels in the back? If so, does the clicking drive you mad?

I think I figured out how the chain routing gives you the two gears.

For the other poster working on their own, how does a single chain version work?

frameteam2003

The single chain version (original style,this dates to the teens) works same as the pics of two chain except the chain is doubled at the rear sprockets not the front and takes freewheels of different sized for the gear reduction.PPCs version is very inovative as it uses the different size front chainrings to get the gear reduction.
PPc please contact me at samclingo@hotmail.com I've some ideas on a web article for retro-direct,maybe we could team up on this---sam

ricardo kuhn

Who cares if It works,,,,
when is so much fun, thanks for the posting, for sure made my night and the videos man they are great...now taking seriuslly, that is a really smart and intuitive way to solve a dual speed auto sistem..

MIT here I come kind of brain....

thanks again for getting my Sprockets moving inside the big old melon.

ppc

No, this extension is in fact an old table leg that I shortened, then drilled to pass a 10mm bolt, and bolted to the bike using a hacked kickstand. It doesn't move sideways because the top of the leg had a larger plate that I hacksawed to the width between the chainstays, so it acts as a guide. As you can see, it's very high-tech

Regarding how it works: yes, there are two freewheels at the back. One of them is driven backward while the other goes forward. The "fast" chain runs normally and drives the outer freewheel, the "reverse" chain is crossed and drives the inner freewheel. The only reason for the 2 idlers and the weird routing for the reverse chain is because it's not practical to cross the chain directly. The single chain version uses the same principle. There's a good description of the system here: https://www.m-gineering.nl/retrog.htm

Because I use a second chain that runs on the innermost freewheel and the innermost chainring, and because the bike is a mountain bike with wide chainstays, I didn't have to modify the frame to add clearance for the reverse chain. That was my main incentive to go with 2 chains instead of one.

And yes, it makes one hell of a racket It goes clickety-click softly when going forward, and the noise becomes totally unreasonable when pedalling backward, due to the speed difference between the two freewheels. But the main reason for the noise is that I use super-cheap freewheels from the local supermarket. If I installed very nice, expensive BMX freewheels, I'm sure it would be quiet(er).

MMACH 5

I'm impressed! Good on ya for this one!

FlatTop

I'm loving this. Can't wait to see the writeup.
ppc, Would a synthetic lube (or a thicker lube) cut down on freewheel noise? Might make it more reasonable. Although it probably draws attention to the bike, and people will yell stuff like, "Hey! You put your bike together wrong - the pedals are s'posed to turn the other way!"

MMACH 5

Excuse my ignorance, but how do you mount two freewheels on one hub?

ppc

Well, the writeup is here, if you can call it a writeup: https://users.skynet.be/ppc/retrodirect_drive/. Nothing new there, just a random compilations of what I already posted here and there on this forum. I'm hoping to get more people to try the conversion

Grease might cut on the freewheeling noise, but I don't really care. Pedalling forward, the bike isn't much louder than a gear hub. Pedalling backward, well, I already look strange, so the noise isn't gonna make the situation worse. Lubing might improve things, but you know, that beater bike of mine is already so noisy with the top-case rattling like hell that it just doesn't matter at all. I see it as an early warning system for old ladies.

Re people's reactions: I do get stares, but almost no laughs or comments. I'm used to be on the receiving end of some stupid comments as a recumbent rider, but strangely enough the Retrodirect bike seems to attract mainly silent stares and quick looks, like people notice something odd, but they're not quite sure what to think of it. The few laughs I got were from my colleagues, nobody in the street started laughing or commenting stupidly like they do when I ride the bent. We'll see how the cycling club guys react this weekend...


When you screw a freewheel on a hub, there are leftover threads, especially with a multi-cog freewheel. I simply made a hollow steel cylinder with the proper thread on the outside that screws on the leftover threads of the inner freewheel, and screwed the second freewheel on it. According to another Retrodirect rider, it's quite possible to reuse an old BB cup to screw the two freewheels together instead, since a BB and a freewheel share the same thread, but I didn't feel a BB cup could take the torque with my weight honking on the pedals.

speaking of which, I finally got the knack of honking backward. The bottom line is: lean forward on the power strokes, or prepare yourself for early knee surgery. Also, it's amazing how different pedalling in two directions can be, and how the art of pedalling is subconscious and taken for granted: with the Retrodirect bike, I always have to double-check where my pedals end up when I stop, so I can restart quickly. It's different if I stop downhill or uphill, so it requires some thinking. If I plan to restart backward, I need the pedals almost vertical, with the one I intend to start on slightly back, beyond the deadspot. Then when I start, I lean forward and kick back hard to get going. It's not difficult, but pedalling backward definitely requires new reflexes. The new skill is fun and novel to me, and all the guys who tried the bike today at work had a good time with it. At any rate, it seems like a great workout for the glutes. God they hurt since yesterday

MMACH 5

Thanks.

"You got a sweet bike...
Lucky!"

ricardo kuhn

I have a idea for you,,,

how about ussing a similar sistem like the MRP chain guide


I'm pretty sure you can move the "bomerang" forward and replace the Uretane pulleys(maybe even keep them) and secure the bomerang so the chain loads will not move it around..
with this sistem you don't need to modified the frame and just use the bottom bracket to hold the device tight,,

but a Even better sistem is the ISGI(i think is the name of the 3 bolt standard mount for bash guards) so you can have a much more solid and reliable mount,, you can actually Weld the 3 taps to the bottom brakcet shell or get one of this adaptors like the small silver piece on the left side of the photo


I hope this helps to simplified your prototype process and make it a more viable alternative for others to follow..

The Knave

I don't know you, but I like you style. A+ Very neat.

The Knave

Install reversed?

Company Dirtyparts boomerang Not ISCG -no guard\plates, 2 arms only. Inexpensive.

ricardo kuhn

You know with the Arms of the guide going forward to achive some how the *V* shape like on the original prototype.



the rest...
i have no idea what you are trying to say (I guess the same way that happend to everybody about my posting do to my lammeA^^ ingles) actually i'm not saying he need to buy a whole guide and for sure not a new one, but some how aply as similar concept so the frame does not need to be modified diminishing the amount of comitment like if you need to weld part to the frame and then somehow don't don't like the results to much, plus simplified the adaptavility to diferent type of bikes and frame configurations.

ppc

Ricardo,

Actually it's a lot cheaper and simpler than you think: the extension you see at the bottom of the bike isn't welded at all, it's bolted onto the bike: vertically it's held exactly like a kickstand, with a plate to press against the stays from the topside (in fact, it is from a hacked kickstand), and it's guided sideways with a bolt that goes through the mudgard hole in the small crossmember between the two stays. I could install this boom on virtually any bike.

The boom is an old table leg, so it's definitely cheaper than a chain guide. Besides, the guide wouldn't work because the idlers need to be quite far apart to make the chain describe a large enough "V" to go around the granny ring. Also, the top idler (the one attached to the seat tube) is used to tension the chain by sliding it up and down the tube. Not sure I'm very clear here, but believe me, a guide wouldn't work