Author Topic: Thorn T bar with grips?  (Read 3396 times)

philb0412

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Thorn T bar with grips?
« on: May 14, 2012, 04:18:51 PM »
Hello once again all. Now I haven't seen anybody else do this on this forum; attaching ski bends to the Thorn T bar.

I have just put some straight bars on my RT, as you can see I am playing around with cable issues for my handlebar bag, whether to buy new grips or cut down a cheap 'ergo' type grip on the right and experimenting with this as a possible hand position. I will use this position for a more aerodynamic position when facing headwinds or cruising on good tarmac. In this position not much weight is being taken by my hands, more just for balance. Is this a death trap? Obviously the T bar is not designed to take extra weight, can people see this as a potential problem?

And I have made sure that the ski bends will not hit the frame if the bike falls. I hope you like my homemade Click Stand too, 2 lengths of PVC pipe, a coupling, a coat hanger and gaffa tape. Not quite so slick or well made as an official Click Stand but the less I spend here the longer I'm on the road!

http://s1171.photobucket.com/albums/r558/philb0412/?action=view&current=P1010371Large.jpg

http://s1171.photobucket.com/albums/r558/philb0412/?action=view&current=P1010372Large.jpg

Danneaux

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Re: Thorn T bar with grips?
« Reply #1 on: May 14, 2012, 04:44:46 PM »
Hi Phil!

Quote
Is this a death trap?
Well, maybe, but I sure admire your thoughtful innovation! Such efforts often result in making a bicycle more well-suited to one's own needs, but in this case, I would suggest some caution.

First, you're going to have far less leverage especially if you carry a load. If you are unladen, there is still the phenomena of "bump-steer" commonly discussed in automotive suspension and steering design. In bicycles, it manifests as the handlebars and wheel deflecting to one side on hitting an obstacle, such as a rock. My biggest concern (since you said you're not putting much more weight on the bar-ends) is the lack of leverage in that position to overcome bump-steer.

Second, placing the bar-ends so they face rearward complicates the problem and can lead to handling problems because you're placing a lot of weight at the steering axis rather than forward of it. Yes, it helps to have cargo weight centered around the steering axis (my steerer-mounted water bottles come to mind), but that is different from rider weight and also different from what is optimal for controlling the bike. Most bar-ends work well because they extend forward, increasing leverage by "extending the tiller". These are located in such a way as to reduce leverage fore-aft as well as side-to-side. What you have here amounts to a "zero-reach" stem.

Third, I am concerned about the lack of brakes in that position. In the event of something unforeseen -- say, a car blowing through a stop sign -- it would be a long, long way up to the regular brakes. I think a set of cross-top or interrupter levers could be modified to allow braking from the new position, but that puts you back to the problem of too little steering leverage to handle bump-steer.

Fourth, I'm not sure the Thorn Accessory T-bar is really rated to carry as much weight as you will/may place on it. Looking at the wall thickness of mine, it is likely far less robust than a proper stem-handlebar combo. It is really intended as a means to mount a handlebar bag or lights and bells and such.

You've got a real winner with the homemade Click-Stand, however! It looks great and should work fine. I would suggest checking it with a touring load before departing on a big trip (look for excess bowing), but the concept and execution look fine -- well-done!

Hope this helps and isn't too discouraging, Phil. I just don't want you to risk getting hurt, and I fear the bar-ends-on T-bar idea is not quite there in terms of safety in an emergency.

All the best,

Dan.
« Last Edit: May 14, 2012, 05:04:23 PM by Danneaux »

julk

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Re: Thorn T bar with grips?
« Reply #2 on: May 14, 2012, 07:37:01 PM »
Phil,
I tried thorn bar ends mounted inboard as they were recommending this some years ago.
I found them a bit scary to use as the leverage is really quite reduced, especially noticeable carrying a lot of luggage or over bumps.
I sold them on.

If you want to persevere with a stronger setup then I can send you (in the UK) a stem which could replace the t-bar if you put a cut down middle section of straight handlebar in it.
Julian.

triaesthete

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Re: Thorn T bar with grips?
« Reply #3 on: May 14, 2012, 09:22:10 PM »
Hi Phil
would it not be easier to mount a set of short tribars above the bar bag. These give you the leverage Dan talks about. The aerodynamic gain comes from the narrowness of the position rather than the lowness per se so it could work. You can also rest on your elbows instead of your hands which is nice.Mounting would just need adapter shims for the smaller diameter of mtb bars.
I seem to recall Sheldon Brown had a bike with two sets of bars. May even have been a Thorn!
Good luck
Ian

philb0412

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Re: Thorn T bar with grips?
« Reply #4 on: May 15, 2012, 10:25:51 AM »
The problem with tri bars is the clearance and ease of access to my handlebar bag.

Thanks for the offer Julian, but I do have a stem that would be the right length, and can get some old bar pretty easily. Good idea! I think I will have a play around on this setup in good conditions to see whether it is worth continuing with. I hope Wednesday is a nice day!

Yes Sheldon Brown did have a Thorn Ian, it had two horizontal bars, flat bars mounted on a separate stem above drop bars. That was how I first found out about Thorns and Rohloffs. After a couple of years of dreaming now I have my own.