Author Topic: knee denting a tank  (Read 10775 times)

0 Members and 1 Guest are viewing this topic.

Offline wicat

  • Full Member
  • *
  • Posts: 54
knee denting a tank
« on: November 17, 2010, 05:02:02 pm »
Im building a cafe racer and i would like to dent my tank and i was wondering what the best way to do that would be?  Ive seen cutting the sides out and working metal to fit in the spot you want and ive seen where u just hammer the dents in?  Any help would be helpful thanks.

Offline Hannibal Smith

  • 3rd Grade Dropout
  • Hot Shot
  • ***
  • Posts: 502
Re: knee denting a tank
« Reply #1 on: November 17, 2010, 05:27:19 pm »
In my opinion, the "correct" method is to cut/form/weld for a multitude of reasons.
This method also requires the most skill.

The hammer method works, but typically requires copius amounts of filler to even things out and get it presentable, and minimizing filler is the hallmark of a craftsman IMO.

Welding on a gas tank is only hazardous if you are!

I have seen nice hammer jobs, but they were relying on good cosmetic work, but a good cut/weld is really hard to beat. If you have the resources, I would cut/weld no question.
Follow my build "P38 Racer" in Project section

Offline IainC

  • Enthusiast
  • **
  • Posts: 212
Re: knee denting a tank
« Reply #2 on: November 17, 2010, 05:29:09 pm »
Someone will say use the search, so I might as well.

I went the hammer method, it was easy and got exactly what I wanted. It may not be perfect but that depends on your expectations and skill with a mallet I guess.

Offline Kong

  • Expert
  • ****
  • Posts: 1,051
Re: knee denting a tank
« Reply #3 on: November 17, 2010, 05:41:01 pm »
Well, you might as well start off by realistically assessing what you can and can not do.  Do you have the tools and ability to cut and weld thin metal?  Most guys don't.  If you don't then ask yourself do you have the ability to swing a hammer and apply body filler?  Most guys do.

I can make a suggestion that I'm pretty sure you won't find in an search you might do, this applies if you intend to pound them into shape.  First draw up a template of what you want the dents to look like, cut it out of paper or something.  Grind your metal clean where you intend to work.  Then using it as an outline draw it on the tank side with a magic marker or something.  So far this is all standard stuff.  Now, before you go pounding on the tank, take it to a body shop and have them pop a couple of studs along the front line of your dents, let's say three of them.  If they won't do it for free they should only charge you a couple of bucks.   That will give you something to hold onto while you pound out the front of your knee dents and a way to pull it back out if you go too far;  it will save you tons of reinforced (Kitty Hair) filler on your first passes.   Then when you get ready for you filler just grind them off like normal.
2002 FXSTD/I  Softail Deuce
2001 Acura (Honda) CL Type-S
1986 Honda Rebel, 450
1978 Honda CB550K
1977 Honda CB550K

Offline seebee7fiftee

  • Full Member
  • *
  • Posts: 47
Re: knee denting a tank
« Reply #4 on: November 17, 2010, 05:48:06 pm »

That video may be useful if you decide to hammer your own.

Offline apex_seeking

  • Ron Swanson is a
  • Hot Shot
  • ***
  • Posts: 466
Re: knee denting a tank
« Reply #5 on: November 17, 2010, 06:09:23 pm »
I just went through all this about two weeks ago. I wanted knee dents, didn't have the money to hire someone else to do it (besides, doing it yourself gives you a sense of pride) and I didn't have the tools or know-how to cut and weld. I opted for the hammer method and found it to be very easy. Everyone here has pretty much has laid out all the steps but one tip I found to really help out is to fill the tank with sand. It will give you sims resistance so the front section of your dents won't collapse your tank.

I went with a mellow edge for the front of my dents resulting in less filler used. Personally I think they came out nice considering the condition of the tank I was working with and my level of experiance with metal or body work (NONE!)

Offline wicat

  • Full Member
  • *
  • Posts: 54
Re: knee denting a tank
« Reply #6 on: November 17, 2010, 06:28:42 pm »
thanks guys im going to attempt to cut and weld them i think they will look better. 

Offline dave500

  • Really Old Timer ...
  • *******
  • Posts: 16,991
  • WHAT?no gravy?
Re: knee denting a tank
« Reply #7 on: November 18, 2010, 12:08:40 am »
when in trouble or in doubt,get a bigger hammer out.

Offline SilentSteven

  • Full Member
  • *
  • Posts: 12
Re: knee denting a tank
« Reply #8 on: November 21, 2010, 06:50:26 pm »
I would recommend a teardrop mallet over the one used in the youtube video. The one pictured is from summit racing for ~$25


Offline Stev-o

  • Ain't no
  • Really Old Timer ...
  • *******
  • Posts: 34,221
  • Central Texas
Re: knee denting a tank
« Reply #9 on: November 21, 2010, 07:40:20 pm »
Bigger hammer!


'74 "Big Bang" Honda 750K [836].....'76 Honda 550F.....K3 Park Racer!......and a Bomber!............plus plus plus.........

Offline wannabridin

  • Patience made me a
  • Master
  • *****
  • Posts: 2,237
  • -Garrett
    • 1976 CB750K, under construction:
Re: knee denting a tank
« Reply #10 on: November 21, 2010, 08:38:57 pm »
Everyone here has pretty much has laid out all the steps but one tip I found to really help out is to fill the tank with sand. It will give you sims resistance so the front section of your dents won't collapse your tank.

Man I sure hope you washed and washed and washed and washed, then watched your filter like crazy for those pieces that you did miss...  It sure is a good idea, but what about filling it with water instead?  Then you just have to let it evaporate?  Sand just gets EVERYWHERE and it's very tough to get it all out leading to clog a filter and cause a lot of headache...
1976 CB750K, currently under construction:
http://forums.sohc4.net/index.php?topic=64468.0

-And if you don't do it this year, you'll be one year older when you do...

Offline nokrome

  • Hot Shot
  • ***
  • Posts: 640
Re: knee denting a tank
« Reply #11 on: November 22, 2010, 12:39:04 am »
Everyone here has pretty much has laid out all the steps but one tip I found to really help out is to fill the tank with sand. It will give you sims resistance so the front section of your dents won't collapse your tank.

Man I sure hope you washed and washed and washed and washed, then watched your filter like crazy for those pieces that you did miss...  It sure is a good idea, but what about filling it with water instead?  Then you just have to let it evaporate?  Sand just gets EVERYWHERE and it's very tough to get it all out leading to clog a filter and cause a lot of headache...


+1.... filling your tank with sand doesn't sound like a good idea to me and it isn't really necessary anyway,
       putting knee dents in a tank is really easy, the hardest part for me was getting up the courage to take the first swing, after that everything just kind of fell into place,
    you will be really surprised how easy it is, i used a medium sized dead blow rubber mallet and started with really light hits until you feel the metal start to move, you get used to how hard to hit real quick, just go slow.
     i started on one side until it was roughly the shape that i wanted and then worked on the opposite side until they were somewhat symmetrical then just fine tuned the shape from side to side, it takes awhile but its really fun.
    the thing i dont like about the method were you would cut out the side of the tank and then weld it back in is that it seems like you would have a really sharp transition going into the dent, i like the nice round edges that the pounding method gives you
Funny thing about regret is...... its better to regret something you have done than to regret something you haven't done.

Offline SilentSteven

  • Full Member
  • *
  • Posts: 12
Re: knee denting a tank
« Reply #12 on: November 22, 2010, 04:10:36 pm »
you did a really nice job on your tank nokrome

Offline nokrome

  • Hot Shot
  • ***
  • Posts: 640
Re: knee denting a tank
« Reply #13 on: November 22, 2010, 06:48:05 pm »
you did a really nice job on your tank nokrome
  thank you  :)
Funny thing about regret is...... its better to regret something you have done than to regret something you haven't done.