Issue with the top chain tube on the Rambler AT

I have apparently found an issue with the design. My seat is set in the back position and the top tube has worn through the plastic where the seat frame contacts the tube. When the large chain ring is used on the front and rear pressure is put on the top tube causing the chain to wear through the plastic exposing the chain and then rubbing on the metal seat bracket. This is a new issue and there is not a fix at this time. I found this when I removed the seat to wash the trike. I have 980 miles on my RAT as of Oct. 6. Check your top tubes for wear.

Comments

  • the fix is to get a new tube from t-cycle.com and float it. http://t-cycle.com/idlers-chain-management-c-41/chain-management-accessories-c-41_69/

    diy a rubber-lined hose clamp, secure it to the tube and hang it from the seat frame with a zip tie. maybe $1 to hang
  • edited October 2017
    JamesR wrote: »
    the fix is to get a new tube from t-cycle.com and float it. http://t-cycle.com/idlers-chain-management-c-41/chain-management-accessories-c-41_69/

    diy a rubber-lined hose clamp, secure it to the tube and hang it from the seat frame with a zip tie. maybe $1 to hang

    Not going to spend $$ for an issue that should be fixed by TT!
  • Eagle, was wondering if the chain rubs in all gears when you are in the large chain ring or only in certain gears? I too own a RAT, But less miles I shall inspect tomorrow. Thanx for the info.
  • I suspect that it does on at least the largest 2 or 3 on the back. Joshua suggested using the smaller gear in the front exclusively, but I told him that I basicly live in the large cog in the front.
  • By running the larger rear cogs with the front lager chain ring you can end up with that problem; it raises the height the chain is running therefore rubbing on the tube, plus the problems with "cross chaining". {http://www.terratrike.com/faq.php#1}
    TT doesn't recommend "cross chaining". You may have to raise the chain tube to avoid that but you don't have room under the seat.
  • I don't believe that there is any such thing as cross chaining with a trike. This is a new found issue with a new design. I have 20 speeds, If I can't use all 20 that's a problem.
  • eagleeyetv wrote: »
    I don't believe that there is any such thing as cross chaining with a trike. This is a new found issue with a new design. I have 20 speeds, If I can't use all 20 that's a problem.

    Oh ok hey it's your trike do with it as you please.......even IF TT (the manufacturer) warns owners not to do it. I only suggest you remove the top tube, and go thru your gears and see how high the chain rides in the large/large combination. I won't be surprised it it hits the seat. just my opinion. Only been triking for a short time but biked and raced 34 years. best wishes.
  • I understand the issue of cross chaining. However the Rambler AT only has 2 cogs on the front, not 3 as in all of the examples I have seen. Also the length of space between the front and rear sprockets and the fact that I am 6'3" which adds to the distance between them I am very confident that cross chaining is a non issue. In going through the gears the 2 largest cogs on the back raise the chain tube to the seat frame. This caused the chain to saw thru the plastic tube. Now that I know that this is an issue, I will keep a close watch on it. Tube has been replaced, but issue is still there.
  • The worst part of that issue is that the friction losses are dynamic, not static: that is, the harder you pedal, the more the chain is pulled straight (and straight up into your seat frame.) The chain tube helps conceal the noise, but does not do much to reduce the friction. The only way I know of to fix it (besides raising or modifying the seat frame) is to use smaller sprockets, both on front and rear.
  • The worst part of that issue is that the friction losses are dynamic, not static: that is, the harder you pedal, the more the chain is pulled straight (and straight up into your seat frame.) The chain tube helps conceal the noise, but does not do much to reduce the friction. The only way I know of to fix it (besides raising or modifying the seat frame) is to use smaller sprockets, both on front and rear.

    This is the main issue. That was the first suggestion by TT, use only the small front sprocket. I think a real fix is needed for this issue.
  • I heartily concur, eagleeyetv. I sell Ramblers, Rovers, and Travelers equipped only with NuVincis or other 'IGH' non-derailleur transmissions--because I like IGHs, and (with small enough sprockets front and rear) the frame design is ideal for them, with no idler pulley needed or wanted. But for derailleurs, I think those models either should have a well-placed idler pulley like the other TT's do, or else the seat frame needs to be much higher. Even for those single-sprocket setups, with only a 32T on the front, a few mm more seat height (actually, seat frame height, right at the weld-zone of the bracket on Ramblers and Travelers) is often necessary. Any chain tube that deflects the [tensioned-under-load] top run of the chain, even slightly, is a very significant energy-waster, IMO.
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