Boom creeping forward

[LarryOz]

I am having trouble with the boom sliding away from the slider as I ride.
Yesterday I was having big issues with my knees and noticed that the boom had actually moved 4". I know that is a lot. The V was brand new to me and I guess I was too focused on too many thing to notice it moved until it was so drastic.
The boom clamp was not noticeably loose. Last night, I loosened it all the way, released the skewer, and BB clamps, and put the boom back to where it was.
Of course I had to re-adust the FD too, as the cable had been stretched.
I tightened the boom clamp about as hard as I thought I could, and also the BB clamp. Also tightened the skewer nice and tight.
I went for 2 20+ mile rides today, and when I got home, I noticed that the boom had moved forward at least an inch again. Boom clamp not noticeably loose.
Has anyone else experience this issue?
is there a known torque that the boom clamp needs to be tightened to?

The only thing that is a little "odd" was that the "original lbs" that assembled this V, actually cut the boom off by about 1.5". It served no real purpose. They must have been terribly confused during the assembly process. The original owner who "commissioned the lbs" told me that it took them 3 months to build the V.

Thanks everyone

 

[LarryOz]

This is how long my slot is

This is how long my slot is on the underside of my boom.
Anyone know how long it should be

 

[Rick Youngblood]

Larry, mine is 1.5" long.

Larry, mine is 1.5" long. Your's looks pretty short, your boom notch that is!

 

[Rick Youngblood]

Hey guys, after reading my

Hey guys, after reading my post above, I just want to make it clear, we are talking about boom notches here !

 

[scabinetguy]

Slot length

Larry, the slot on mine is 1 3/8", which is longer than the clamp width. I think that's your problem. The slot is not long enough for the clamp to squeeze the boom....Steve

 

[Eric Winn]

Slot is fine. I assume you

Edit: Slot is fine maybe too short. How long is the slot in your boom?

The slot on my boom is 38.76mm or 1.526 in from the apex of the stress relief drilling to the edge of the boom. I couldn't hold my camera and my calipers at the same time or I would include the dimensions in the photo. The clamp band is 22mm or 0.866 inches wide and you can see how I have it positioned over the slot.



I have the forward edge of the clamp at 26.35mm or 1.037 in from the edge of the boom. Yeah - the caliper is not sitting right but I secured the measure with the lock nut with it positioned correctly before trying to take the photo.



I assume you moved the clamp off the yellow end to photograph the slot.

My clamp is torqued pretty darn snug. When I first set it up I marked a small black line on the silver slider right up against the yellow boom so I could monitor if anything shifted and by how much. I found it tended to work itself further out than what I measured it ought to be by about a half inch maybe, probably a bit less but never anything like 4 inches! I have very powerful legs, arms, and chest - I'm built kind of like popeye and I'm pretty doubtful the boom and slider will pull that far apart if the clamp is working properly. You should be able to tighten the clamp bolt pretty dang tight without a great deal of effort.

Edit: I don't have any grease on the slider but I did put a little grease on the threads of the clamp bolt.

After the boom kind of worked itself out to about the same spot over a period of checking it I just clamped it there and re-marked and it has never moved since.

I just took this photo. If you look close you can see the small black mark on the silver slider. I would at least do that and make sure the bolt in the clamp ring is OK and you don't have any stripped threads.



-Eric

 

[Rick Youngblood]

Guys, what ever you do, use

Guys, what ever you do, use caution not to over tighten the boom clamps on the Silvio or Vendetta, like I did.

I will do the grease thing, good idea Bob, makes sense.

 

[ratz]

Ok this will sound backwards

Ok this will sound backwards to many people, but did you put geese grease on the boom slider? A Light coat of grease all the way around the slider will let the boom clamp into place better. Same way DF seat posts do. A dry boom would actually be more likely to slip under load, assuming that that clamp is working, had this happen on a Silvio, greased it and it locked in place

Edit: Slot on my boom is about 1.5 inch.

as much as I don't like geese; don't rub them on your boom, you'll just attract more on your rides.

 

[super slim]

I would lubricate the clamp

I would lubricate the clamp bolt with Moly grease as this will double the clamping load for the same bolt tightening torque, especially with SS on soft aluminium.

 

[LarryOz]

thanks everyone!

I will geese (love it -Bob) up the boom slider and see how it helps.
I think Gary and I are going to try and cut the slot to the correct length and put another strain relief "hole" at the end to match what Eric has shown in photo. Great pics Eric by the way!
I am also going to try and get the original owner to hold his LBS to the fire over this one now! If they have any sese of integrity, they should admit what they did and replace the boom.
Thanks again guys

 

[Eric Winn]

They cut the yellow boom?

I re-read your original post. They cut the yellow boom and not the silver slider?!? If so, extremely incompetent...

-Eric

 

[Eric Winn]

Tons of geese here in

Tons of geese here in Michigan. You have to be careful when a horde of them walk across the road or path in front of you and in some places goose poop can be so prevalent that it is almost impossible to avoid and dare I say it? Slippery as grease...

-Eric

 

[scabinetguy]

extremely incompetent

Eric, sometimes to fit a short rider you have to cut the yellow boom, there's no other way to pull the BB toward the rider. I suspect this was their reasoning.

 

[LarryOz]

This rider (John) I think is

This rider (John) I think is about 5'10", considerably taller than me, so I do not think that is the case.
John also said the LBS tech REALLY had a hard time with the bike assembly.
If the Yellow tube is cut, then the slot should at least be lengthened to match the original

 

[John Tolhurst]

Position the clamp flush with

Position the clamp flush with the end of the boom.

 

[LarryOz]

I have done that (clamp at

I have done that (clamp at end of boom) with no real change.
Today Gary (BentSero) and I very carefully extended the groove (to the original length) and also put a strain relief hole at the end.
Also positioning the clamp at the very end.
I rode it about 10 miles after is all.
I will be riding this week and paying close attention to it.
I am really hoping that Cruzbike has a replacement boom in stock that I can purchase however.
What about it John? Do you have any in stock, or have the ability to make an extra one for me?
Thanks,

 

[Eric Winn]

The yellow boom is not

The yellow boom is not designed to be cut/trimmed for shorter riders - the silver colored slider is what you trim. See my build thread. I am a shorter rider and there is still room to trim the slider even more for even shorter riders than me.

-Eric

 

[Andrew 1973]

If I was John, the original

If I were John, the original owner, the shop would have owed me a replacement frame, boom, or a whole lot of cash. That's simply unacceptable.

Fortunately, extending the slot seems like it should fix it. I hope so!

 

[BentAero]

Whoever cut the yellow boom

Whoever cut the yellow boom was simply an idiot with an anxious hacksaw.

"I don't know what's wrong Earl, I cut that boom off twice and it's still too short."

Cut now, think later? Did they misinterpret the instructions? Just didn't think it through?

Anyway, structurally it's fine, just looks a bit different if you know what the original boom should look like. Just think of it as weight savings, Larry!

 

[Robert Holler]

An actual shop cut the outer

An actual shop cut the outer boom? Arrrghhhhhh!!!!!!!!!!