Topic: CR750 oil tank mounting

[dakeddie]

I'm finally going to make that CR750 replica tank... well as close to a replica as I can without actually seeing the tank in person.  It doesn't matter to me if it's a little off.

I'm having trouble understanding how the tank is mounted.  I know there are four screws at the top, and this is obviously not enough to keep the tank from vibrating around, so the Honda engineers added the bracket at the bottom.  I also know that plate "A", in the picture below, is not a part of the tank, but simply wedges up into the bracket that is welded on the tank proper.

Now, here's where I'm confused... why is that bracket angled the way it is?  Wouldn't it allow the tank to rotate like I've shown with the arrow in the picture?

[lordmoonpie]

Oil tank mounting was the subject of a discussion not so long ago - lots of pictures on that thread to help you if you want to search for it...

[dakeddie]

Do you mean this thread?... http://forums.sohc4.net/index.php?topic=64974.50

I've searched through many of the threads, but I haven't found an answer to my question.  I think if I could look at the mounted tank in person, the answer would probably be clear.

Perhaps I didn't pose my question clearly enough.  I think the picture below will help, it shows the upper mount... the tank hangs from two horizontal bolts.  If the lower mounts weren't there (and oil lines not attached), the tank would swing like a pendulum.  With the lower mount in, which the tank simply rests on from what I understand, the tank would be prevented from swinging CCW, but what stops it from swinging CW?!

To me, it's underconstrained.

[Sam Green Racing]

It can't swing anywhere when it is sat on its bottom shelf (if you want to call it that).
How can anything swing when it's sat on a flat surface?

Sam.

[dakeddie]

Like this:



Blue is original position, red rotated.  The shelf doesn't stop it rotating up, it just keeps it from rotating down.

Sam, you have a CR750, right?  When you grab the bottom of the tank, does anything (other than gravity), keep it from rotating up?

[lordmoonpie]

Ahhh I see what you mean! You can come and see mine if you like - BC is a bit far though. My uncle lives in Vancouver BC but that won't help you either....well unless you like BBQs!
You're right it is slightly under constrained in that position BUT you haven't connected the oil lines yet. They are big beefy buggers and if you use stainless braided ones like mine they are even more so. That forces the tank to sit nicely on the "shelf" as Sam puts it and it really doesn't move. However, as there is bound to be some micro movement, the shelf brackets are covered in thin high density foam or thick rubber to give it a bit of cushion.

Hope that helps!?

[Sam Green Racing]

I don't have the CR any more and it was never mine in the first place, I built it and looked after it for Benly Bens Dad.
As I can't check, you would be better asking Pieface, sorry, I mean his Lordship to check but if I'm not mistaken, the shelf on the other side is not at the same angle as the left.
Simon could perhaps check for you as both our frames were modded buy the same guy.
I'm not sure if both oil tanks came from the same maker though and could be just that bit different.

Sam.

[H2Eric]

I don't have the CR any more and it was never mine in the first place, I built it and looked after it for Benly Bens Dad.
As I can't check, you would be better asking Pieface, sorry, I mean his Lordship to check but if I'm not mistaken, the shelf on the other side is not at the same angle as the left.
Simon could perhaps check for you as both our frames were modded buy the same guy.
I'm not sure if both oil tanks came from the same maker though and could be just that bit different.

Sam.

You're right Sam, the lower oil tank mounts or shelves as you call them are at a different angle on each side. I got a pair of 'shelves' from Daniel Mercier, but unfortunately they didn't suit the tank made by Peter Kyte so I had to make some more. As for holding the thing down a dollop of Blue Tac works wonders. However, as His Lordship says the oil lines will do a good job of holding things in place as will the weight of the oil itself.

Toodle pip
Eric

[H2Eric]

Some pics




 The right side oil tank mount has since been drilled with four holes, similar to the left one.







Cheers
Eric

[Sam Green Racing]

Very nice Eric, I wouldn't expect anything other from you.

Sam.

[kos]

The weight of the oil in tank and the lower oil line keeps tank from moving. Trust me, it will not Rotate!
And if you have the opportunity to have a real one in your hands, as I have had the chance....the front part of the "ledge" as everyone is calling it... curves up!


No one, including myself makes them 100% accurate.

Mark

[dakeddie]

Thanks guys.  Perhaps the fact that the tank is able to move a bit prevents it from cracking.  In any case, it's good to know that's the way it is and it works.

There is a Honda shop local to me called the Honda Centre.  They apparently have Dick Mann's CR750.  This weekend I asked if I could have a look at it, but it's in their warehouse, I'll have to wait until it's ready for display in the store (next year sometime).  Very nice shop, the kind of shop that makes you want to keep coming back.

Eric, your bike is killer!  Thanks for the pics, they'll help me out.

[lordmoonpie]

Hey Eric - I think you're taking things too far! Is that assembly lube on the TOP of your oil tank?
 

[kos]

Thanks guys.  Perhaps the fact that the tank is able to move a bit prevents it from cracking.  In any case, it's good to know that's the way it is and it works.

There is a Honda shop local to me called the Honda Centre.  They apparently have Dick Mann's CR750.  This weekend I asked if I could have a look at it, but it's in their warehouse, I'll have to wait until it's ready for display in the store (next year sometime).  Very nice shop, the kind of shop that makes you want to keep coming back.

DICK MANN'S RC750 DAYTONA WINNING BIKE? I DON'T THINK SO....


KOS

Eric, your bike is killer!  Thanks for the pics, they'll help me out.

[dakeddie]

I first learned about the CR750 at the Honda Centre from this forum.

Here's the thread: http://forums.sohc4.net/index.php?action=printpage;topic=65044.0

The last time I looked at the thread was when it was first posted.  Looking at it now, it doesn't have an original oil tank!

I have no idea if Dick Mann actually raced the bike or not... maybe someone here can confirm it based on the engine number.

[kos]

That is a CB750 based replica in the picture...has nothing in common with Dick Mann's bike...sorry. Perhaps the rear hub.

KOS