streetstomper

Is there a list of all the models that had such reverse action, preferably with short cage? I'm looking for one to use as a ghetto IGH chain tensioner and don't know which models to look for. I figure low normal would be best for a tensioner because then I could just pull it outward with my hand to make wheel removal easier.

demoncyclist

You would pull towards the rear to remove the wheel, not outwards. So, it makes no difference if it is high normal or low normal- you will be locking the derailleur in place with the set screws either way.

alcjphil

+1,pulling the derailleur outwards would result in damaging the derailleur. You can use any short cage rear derailleur as a chain tensioner, and it doesn't have to be a particularly good one. Look for an older derailleur designed for 5 or 6 speed freewheels. If your IGH requires a 1/8" chain you will require as wide a cage as possible, most Rapid rise rear derailleurs probably have cages that are too narrow for a wide chain

streetstomper

A chain tensioner should have the cage at near maximum extension, which means it would be extremely difficult to pull the parallelogram to the rear. With low normal, I could pull the parallelogram to the outside to allow me to release the chain, then I could pull the derailleur to clear everything.

That's why I'm asking for a low normal. Spring tension would push it toward the hub, stopped only by the low limit screw. All I'd need to do is disengage the chain from the pulleys then I would be able to pull it outward because there's nothing fighting me except the spring. You're thinking of standard high normal derailleurs where spring tension would push it outward from the hub, so the high limit screw would be used to hold it in the right position.

alcjphil

A derailleur is not a chain tensioner and you wouldn't have the cage at near maximum extension if you were using one. You would size the chain long enough so that you could pull the derailleur back to allow the wheel to drop out, not so that the derailleur cage was at full extension

Cross Creek

Wouldn't it be easier, more effective, and probably cheaper to simply use a chain tensioner than to try to find an unusual deraileur for the job?

cny-bikeman

Rapid rise derailleurs tend to be more expensive, but just for the sake of argument let's say you need to find models. Why not just Google rapid ride derailleur??

alcjphil

A simple chain tensioner is a very different animal than a derailleur. Most of them only have a single jockey wheel so they look very different in use than a derailleur. If you are looking for the cheapest solution, a proper chain tensioner will probably cost the least amount of money and do the best job

fietsbob

A Fools Errand I'd say, I think even Shimano Gave up making them... it was another expensive thing they did , then quit.

Just Buy a chain tensioner .. Rohloff**, Shimano Alfine and Pauls 'melvin' are all 2 pulley types ..

the Limit screws on even cheap High normal RD's can be screwed in far enough to move the cage over the Cog.
if needed put a longer screw in.. low normal you would do the same , you are just resisting the return spring pressure
instead of pulling it with the cable,.

the spring in between the 2 pulleys wraps up the excess chain slack.


** I own one of these the chainline is a shim washer stack to place the pulleys (made by Tacx) under the Cog.

alcjphil

If I were going to kludge something together, I would use something that I already had in my spare parts bin. If I had to go and look to buy something, I would buy the proper component, especially since a chain tensioner is a much simpler and cheaper part to buy

streetstomper

All of you saying "buy a tensioner, it's cheaper," seem to miss the point that the cheap single pulley tensioners don't work well. I've read plenty of reviews about them including on MTBR and here and a huge percentage are negative, including for the famous Surly Singleator. The dual pulley ones like the Paul Melvin are damned expensive, far more expensive than a used derailleur on eBay. The Melvin starts at $65 plus shipping, more than twice what a good used derailleur costs. I don't even want to think about what the Rohloff costs. The Alfine is designed for Shimano's own chainline, although you can use a few washers to shim it outward up to a point. Also, the dual pulley ones are essentially fixed position with non-adjustable angle stops. You can't push them to the side or swivel them back to remove the wheel. With many models, the only option is to unbolt the tensioner from the frame before trying to remove the wheel. And the dual pulley tensioners tend to have small cog limits, usually around 18T maximum. Many people who actually have used tensioners say the best solution is an old derailleur rather than a purpose-built tensioner.

I really don't understand why it's so hard to just answer a question rather than trying to tell me I'm stupid. If you know which derailleurs are low normal, I'd be happy to hear it. If all you're going to say is "Google it," then just go find another topic.

dwmckee

Here you go:

https://www.google.com/webhp?sourcei...%20derailleurs

streetstomper

So much for the assumption that bikeforum members are helpful.

alcjphil

On most derailleurs the chain is contained by the cage, you cannot disengage it from the pulleys without taking the cage apart. That is why you need enough chain to be able to swing the derailleur back so that the wheel can drop down. Your idea of swinging the derailleur out of the way will not work
People are trying to help you by giving the best suggestions they can

streetstomper

You're assuming I would thread the chain between the pulleys. What makes you think I wouldn't just cut off the bent tab and route the chain beneath both pulleys. I don't see you addressing any of the shortcomings I already noted three posts above.

It's a safe guess that you have no experience at all with tensioners.

LesterOfPuppets

I've seen LX, XT and XTR, I think. I bet there was a Deore, too.

Sorry, don't remember part numbers. I don't think I've seen any short cage, but mid cages, yes.

I'm not sure how that helps you though. Just a list of most of the Shimano RDs from 5 years ago

dwmckee

You asked for a list of rapid rise derailleurs and I gave you a link to several model numbers that are rapid rise (and without any commentary). Isn't that precisely what you asked for? If you do not have time to look at the links I sent, here are the model numbers listed:

Shimano XT M770, 771, 772, 761

Good luck.

alcjphil

I have been working on and building bikes for over 40 years. You guess wrong. If you route the chain below both pulleys you won't get sufficient chain engagement or tension

streetstomper

Whoa, no way! You're telling me that putting the chain below the tension pulley wouldn't engage enough teeth or give enough tension? You mean just like the single pulley tensioners you keep trying to push as the ideal solution?

alcjphil

Not pushing the single pulley tensioners necessarily, but they would work far better than the way you propose using a derailleur, Putting any amount of tension on the chain with the chain below both pulleys would force the upper pulley into the cog and grind it away. You have to thread the chain through the cage if you want a derailleur to work as a tensioner which is the way that the 2 pulley tensioners happen to work. If you have to thread the chain through the cage, then you are just as far ahead using any derailleur

streetstomper

There you go with single pulley tensioners work fine again. Read on:
https://www.bikeforums.net/bicycle-me...y-awesome.html

Plenty more comments like that. And your 40 years of working on bikes doesn't impress me since you didn't understand how a low normal derailleur works.

alcjphil

I didn't say that a single cog chain tensioner is the best solution, all I said was that it would work better than the way you want to use a derailleur. I understand perfectly well how a low normal rear derailleur works, I have worked on dozens of bikes that have them. I have tried to point out the flaws in your plan,and have tried to be polite, you have not. My last post in this thread, you can do what you want

fietsbob

repeat Rohloff, chain tensioner, Definitely not cheap @ $85. Universal Cycles -- Rohloff Twin Pulley Chain Tensioners

I own one of these, the chainline is a shim washer stack to place the pulleys (made by Tacx) under the Cog.

nor, for $6 less, is the USA made one from Paul Comp https://www.universalcycles.com/shopping/product_details.php?id=336&category=2622

though this one at $26 is getting down there in cost Universal Cycles -- Q2 Chain Tension Master


by the way .. you remove the wheel by pulling the Whole derailleur Back. its been like that way before you were Born.

just dont cut the chain too Short.

phoebeisis

This xt 760 in short form-would work just fine
and Rapid rise derailleurs are out of favor
So they would be cheap-maybe $20 -and that might include shipping
Nothing wrong with your idea
if you use a rear derailleur you have the option-eventually- of switching back to a geared bike
single speed bikes-are somewhat limited-but each to his own

Yeah they should be cheap
and the POS nashbar single speed chain tensioner I bought-years ago-was a POC
Of course for $1o(on sale) what about what I should have expected

Luck
Charlie
PS This RR will actually shift up into that 41 cog-in the BIG OR MIDDLE FRONT RING- hard to believe but it does
PPS- WOW- you folks are in high form today-you make ME look good natured
Usually just LC vs FRAP brings out this sort of venom
or maybe some Quirky French bike VS any other bike in the world!!(ok I kinda like french stuff-but I hate their quirky threading bass ACKWARDS PEDALS- funny sized stems-seat posts)

dwmckee

It looks like we have provided all of the help that we can possibly provide to you. Good luck!