Drilling through backbone to mount tank..... Yes or no?

[JP50515]

Hey guys I got a king sporty tank for my build that I still haven't mounted. It has the tabs with the eye holes which I'm assuming are to throw a bolt through, either under or through the frame. I've never dealt with a tank that mounts this way before so someone with experience please chime in here.

I am wondering if its safe to drill a hole through the backbone of the frame to mount the back end of the tank? I mean the frame has holes drilled in other places of less structural importance but would I be seriously weakening the frame by doing this?

Thanks

 

[Paulrxs650]

When I mounted mine I drilled and tapped the top of the tube, threaded in the appropriate stud and finely welded it in to maintain structural rigidity

 

[DogBunny]

The best way is to sleeve the hole with a piece of welded tubing. However, I personally have just drilled a hole -- not that big a hole is required, and as you say, it is not in a place of great structural consequence.

If I ever powder coat the frame I might sleeve it.

 

[Jayh1813]

I drilled through mine with a 1/4" hole and have no problems.

 

[racerdave]

I will be mounting a Champion tracker style tank soon. I've been debating drilling 2, 1/2 inch holes in the top tube for 5/16 nutserts. My other option is 2 180* sleeves with studs welded to them. I'm also concerned with drillinh holes in the fram.

 

[Geers]

I made 2 5/16-18 threaded bungs and welded them for the front of the tank. On the rear I just drilled and hole straight thru and sleeved it with a piece of tubing. Rubber mounted it and no problems

 

[osteoderm]

Weld-in threaded bungs. The "top-hat" style of bung is easier to deal with, and provides you with a little more surface to mount against. Thy're available from a few vendors, but I've found Bungking.com to be fast, reasonable, and reliable.

 

[JP50515]

mine would be through the side of the backbone...not the top and my other issue is that I have a buddy who does all my welding but I may have run that well dry on this project

 

[1974jh5]

Put me in the 'tube welded in' or 'welded blind top hat bung' camp. A tube welded in will prevent crushing the backbone tube with a bolt and the bolt will not be as likely to loosen.

 

[jd750ace]

The welded sleeve or bungs will counter any weakening of the tube from the hole. The worst thing you can do from the standpoint of structural integrity is to just drill a hole and tap it. A smooth drilled hole only has 2 sharp corners for cracks to develop and propigate from, but if you tap the hole, cracks can propigate from both sides of the hole , and any point along the land or groove of the thread. Ideally, any hole you make in a frame tube should be reinforced around it's perimeter so any stresses coming in contact with one side of the hole can be carried around it, via the reinforcement, and continue down the member to the other end. Every induced force that is countered by the frame will travel through the member in a primary wave, which the member will hopefully flex and absorb, and then the secondary (return) wave will be the member returning to it's geometrical shape prior to the induced stress. In the case of engine vibration, this can happen in as many as a couple hundered cycles every second. Always reinforce frome holes, either with an internal or external doubler, or with a sleeve that is preferably around twice the wall thickness of the member drilled through.

 

[jurand]

mine would be through the side of the backbone...not the top...

it does not matter, horizontal or vertical mounting. just weld bungs...

my are drilled and taped for M8, but still can drill it out to M10. I stick to metric screws on my build...

 

[jd750ace]

Those look plenty heavy to drill out a few sizes larger. Where do you get them?

 

[WickedKlown2]

Hugh's Handbuilt : http://hughshandbuilt.com/products-services/diy-tank-bungs/

 

[jurand]

Those look plenty heavy to drill out a few sizes larger. Where do you get them?

diy, or like I like to say "selbst gebaut und programmiert". diameter 22mm, flange dia. 25mm, overall length 20mm, flange thickness 6mm. I think about vertical mounting.
I have some other things made for my bike, and for other bikes too...

 

[JP50515]

My issue with those is the amount of grinding necessary to get my tank back on afterwards lol. that and i'm not sure 2 would fit in the backbone lined up across from eachother.

 

[jurand]

as I wrote before, my tank is intended for vertical mounting. for horizontal you can use round piece of stock, dia. .5'' or similar...

the clou is, use bungs, not drilled/taped holes...

 

[pregrid]

The welded sleeve or bungs will counter any weakening of the tube from the hole. The worst thing you can do from the standpoint of structural integrity is to just drill a hole and tap it. A smooth drilled hole only has 2 sharp corners for cracks to develop and propigate from, but if you tap the hole, cracks can propigate from both sides of the hole , and any point along the land or groove of the thread. Ideally, any hole you make in a frame tube should be reinforced around it's perimeter so any stresses coming in contact with one side of the hole can be carried around it, via the reinforcement, and continue down the member to the other end. Every induced force that is countered by the frame will travel through the member in a primary wave, which the member will hopefully flex and absorb, and then the secondary (return) wave will be the member returning to it's geometrical shape prior to the induced stress. In the case of engine vibration, this can happen in as many as a couple hundered cycles every second. Always reinforce frome holes, either with an internal or external doubler, or with a sleeve that is preferably around twice the wall thickness of the member drilled through.

Damn Ace! Are you an engineer or did you sleep at a Holiday Inn Espress last night?

 

[jd750ace]

I've been reading a lot of mechanical stress reports lately! trying to re-invent a 60 year old aircraft will do that to ya!

That, and about 26 years of looking at busted shit.

I'm a shithouse engineer! That means I know enough to build dangerous crap that will actually stay together!

 

[blackbetty]

I use tophat bungs all over the place, they rule.

I prefer the ones from bungking, lets you drill a slightly smaller hole vs. the ones from lowbrow.