CATRIKE’S BOOM


No, I am not talking about how business is going for Catrike even though it has really taken off and qualifies as a “boom”. Rather, I am talking about the boom of the tadpole trike … that part that sticks out in front and where the crankset and pedals are found. Here is a picture of my boom.

my Catrike boom 2

I am talking about booms here because they are a very important part of a tadpole trike. With the crankset and pedals being a part of the boom one of the inherent problems with tadpole trikes in their design and build is what is called “pedal steer”. Some trikes are worse than others and the amount of pedal steer can be considerable. Pedal steer occurs when (and because of) the boom flexing … actually bending side to side when the pedals are pushed on. This in turn results in the trike “turning” from one side to the other as it is being pedaled along. A well engineered and made trike has very little pedal steer. Some trikes have quite a lot of it. And the further out a boom is extended the worse the problem becomes. Along with the problem of pedal steer when the boom flexes there is also a loss of pedaling efficiency. Catrike has a patented design which greatly strengthens the boom and eliminates most pedal steer and helps with this loss of efficiency. The boom has an internal reinforcement to make the boom more rigid so it can’t flex like it would if it were just a hollow tube as other trike manufacturers’ booms are. Also Catrike booms have a groove in the top which does not allow the boom to rotate out of proper position … something very common with most tadpole trike booms. This groove has a matching “key”  or “pin” which fits down into it to keep in from turning (rotating). I have seen some booms on other brands of trikes which were considerably rotated out of position.

Catrike's patented boom

Here is a look at the patented internal reinforcement and the patented groove …

Catrike boom construction lines added

Those three internal “webs” you see run the full length of the booms. In this image I have added the silver colored lines to show this since it is too dark inside to see it otherwise. I applaud this ingenuity. [ICE (‘Inspired Cycle Engineering) eat your heart out! Your booms and frame members rotate all over the place … although I will give them credit for doing a pretty good job in the matter of pedal steer.]

Here is a closeup image of the groove and key. It is hard to find an image of it which shows it clearly. I worked on this one trying to improve it so you could see it better …

Catrike boom groove and pin 3 cropped

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Here is what Utah Trikes wrote about the Catrike booms:

“The engineering of the Catrike is probably most evident in the boom now found on all models. I think it is safe to say that the Catrike boom design and implementation is second to none in the trike industry. Because the seat is part of the frame all adjustments for rider leg length are made by adjusting the boom. The advantage to this is that there is no cross bar to get in the way for shorter legs, but it also means that the boom can get pretty long when fully extended. A long piece of tubing can flex which robs pedaling power. Big Cat engineering came up with a novel approach to eliminate boom flex, and it’s all hidden inside the boom. To keep the boom strong while maintaining a low weight, Catrike creates their boom with a custom extruded tubing with an inner webbing whose cross section resembles the Mercedes logo. This inner bracing eliminates any flexing in the vertical plane (minimizing power losses), while also having a dramatic effect on removing pedal steer effect.

The Catrike boom is extremely easy to adjust and yet always stays in alignment. Most other trikes that have adjustable booms need to have two bolts to secure the boom position so that it will not rotate as the trike is being pedaled. The Catrike boom is indexed with a groove along the top which align with their proprietary boom clamp system. Because the boom cannot rotate quick release clamps with less pressure can be used to hold the boom in place without worrying the boom will twist. This makes adjusting the boom length on the fly very easy.
To finish the boom off, Catrike has taken the extra step of including an integrated accessory mount on the front derailleur post an all models excluding the Villager. Amazingly simple, but in the end will save you $20-40 when you decide to mount a computer or headlight to the front of your trike. Speaking of mounts, every Cat also comes with a computer sensor mount on the left wheel. It makes installing a wired, or wireless computer very easy.

Instruction to Set the boom length from Catrike owner’s manual:
Sit on the trike, wearing shoes like those you’ll have on when riding, and adjust the boom length. This is done by loosening the boom release enough to allow the boom to move, then putting your instep on one pedal and extending your leg fully (the boom will rotate…just move it back to vertical with your hand). You should be able to lock your knee, but not have to lock your knee. You can fine tune the position later. Re-tighten the boom release (or pinch bolts) enough to keep the boom from slipping.”

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Trike manufacturers need to do all they can to eliminate such things as pedal steer and brake steer. I am glad to see Catrike taking this seriously. It helps riders to …

ENJOY THE RIDE!

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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 May 29, 2015, in construction/design, tadpole trikes and tagged . Bookmark the permalink. 1 Comment.

  1. Jerry Renaud, Sr

    Thanks again Steve for yet another informative post. Although I don’t have a Cat, I always benefit from your info,…well thought out and illustrated. Keep em coming.