BOOM CHAIN TENSIONERS (CRANK ARM SHORTENERS UPDATE)


Note: I started out writing this article about an update on the subject of crank arms shorteners, but it more less evolved into another topic so I changed the title accordingly.

It has warmed up a bit recently and all the snow has melted. Between that and rain we have had recently the rivers have risen and flooded over their banks so that some parts of our local bike trails are flooded over and closed. Boo Hoo!! Never the less I have been able to ride my tadpole trike which I thoroughly enjoyed despite the nasty wind chill factor. In order to ride my trike I removed the crank arm shorteners I had installed on my wife’s recumbent bike I am using for rehab and exercise here at home. I installed the crank arm shorteners on my trike. (I was even able to move the pedals one hole further out so that means my new knee joints are improving.) What a difference! I really like them (Yes, both the crank arm shorteners and my new knee joints.) 🙂

crank-arm-shortener-on-my-tadpole-trike-3

However, there is one thing that I noticed using them on my trike that I didn’t notice on the bike. With the crank arm shorteners installed on my trike I need to readjust my boom … lengthen it … as I am not getting the leg extension I need with the pedals relocated. I have not done that yet, but I should. It probably will require adding some more chain. That is the main reason I haven’t tried moving the boom out yet. It is winter out there folks and I am not too crazy about working out in the cold to accomplish this task.

A rear derailleur is supposed to be able to handle about 2 inches of extra chain length as far as movement of the boom.  That equates to approximately one inch of boom adjustment. However that figure is based on the boom position at the shortest length the rear derailleur handles to the position of the boom at the longest length it can handle. If the boom is already positioned out quite a ways within that range than most of that 2 inches is already used up. If this is the case then additional chain would need to be added.

One nice option is to employ a Universal Boom Adjust Chain Tensioner designed for the boom of a tadpole trike.

crank-arm-shortener-on-tadpole-trike

They are not cheap ($155), but they do make it easy to move the boom in and out and automatically maintain the proper chain tension. They are especially nice to accommodate various riders of differing sizes. The chain can be made up long enough to move the boom out for a tall rider and when the boom is shortened for a shorter rider the chain tensioner automatically takes care of the extra chain the rear derailleur would not be able to handle. Obviously there is a lot of extra chain and hardware involved and it might appear a bit unsightly to many (myself included), but they do work. You definitely would not want to run it into a curb or such as it would likely be damaged. TerraCycle (not to be confused with TerraTrike) manufactures these for several different brands of trikes. They can be purchased from some trike dealers and trike manufacturers as well. Catrike sells it for $150, but it is $145 at most of the other sources I have seen including directly from TerraCycle. The Chain Gobbler fits Greenspeed trikes and sells for $149.

Here is a Utah Trikes video on the subject of these chain tensioners …

So this is a very handy and practical option available. Most definitely if you have various size riders riding the same trike this is the way to go. Adding and removing lengths of chain even if you use links which are supposedly quick and easy to remove is a real pain compared to this slick setup. So if you have $150 or so burning a hole in your pocket here is a place to unload that cash and make your life easier. It is always nicer to ride then to “wrench”. And it will even help you and others to …

KEEP ON TRIKIN’

Advertisements

About Steve Newbauer

I have a few current blogs (tadpolerider1, navysight, and truthtoponder) so I am keeping busy. I hope you the reader will find these blogs interesting and enjoy your time here. Feel free to email me at stevenewbauer at outlook.com

Posted on December 30, 2016, in accessories, components, Disabled, options, rehabilitation, rider comfort, tadpole trikes, tips, videos and tagged , . Bookmark the permalink. 2 Comments.

  1. Great point. Thanks for the link to the boom chain tensioner. My wife is considerably shorter (6″) than I am so she can’t ride my trike without a lot of work – and then I have to reverse that when I ride it again. This looks like a great solution. (Also love the shorteners – those are on my list as I find standard cranks a little long.)

  2. Boy…! The fella’s over at Utah Trikes always seem to make every thing look so easy… But I think it to be a great idea for anyone who share’s a trike on a regular basis.. But as a sole rider I would have to say it is an added expense to a non re accruing issue.. I mean if you are not sharing your ride and it is only intended to be used while you are convalescing, I would say it is an added expense that is totally unnecessary.. But that is only my thinking.. I just don’t see the benefit of it if you are not going to need it all the time and make frequent adjustments to your ride… But maybe I missed something in your translation of your present needs… But the one thing I here and I think it to be a great sign, is the fact you are more anxious to ride more often then you were after your Knee replacement… So I guess all our prayers for your recovery were not in vain, and your recovery time shortened… Best of luck what ever your decision, as only you know best now…! So with all that being said the only thing left to say is that I wish you a Happy New Year…!
    Armadillo Zack