Jump to content

mk6 cromwell


Recommended Posts

hi Derek

 

glad you like the name, I actually preferred shufti cush but diplomacy got the better of me and seeing as how the tank might end up in a museum i thought it best to change the name :D

 

I named the tank after AJAX which was a 1 RTR tank and part of the desert rats (my grandfather was a desert rat and so was I ) and although not a hussars tank I'm glad you put up the action report on how your grandfathers tank was knocked out, it made for a thought provoking read. please feel free to come over at YWE and say hello.

 

all the best

 

rick

Link to comment
Share on other sites

Rick,

 

As I've read quite a few books and knowing what shufti cush means in Arabic;) you were better off changing the name to AJAX,, much cleaner name I think ha ha:D

 

we will be sure to stop for a chat.

 

 

see you soon

 

 

Derek

Link to comment
Share on other sites

  • 2 weeks later...

I'm playing around with the location of the sprocket and running gear on my 1/6trh scale model and it strikes me that I've got the fifth road wheel too close to the sprocket because it rubs a little with the sprocket teeth when the road springs are fully compressed. I've been poring over drawings trying to figure out what I've done wrong but these pics would seem to indicate that the final road wheel and the sprocket are very, very tight. Is there an issue with the road wheel coming too close to the sprocket ring on the Cromwell?

 

Rgds

 

Pete

Link to comment
Share on other sites

No, I didn't think there would be, LOL :blush: I suppose what I was really trying to ask was if there was some staggering between the sprocket rings and the road wheel tyres to allow them to 'pass' each other at close proximities. As I say I've been going over the drawings and I'm pretty sure I have all the locations for everything correct and I'm also sure that I've got everything scaled to the correct size. But I've obviously missed something somewhere. I can workaround the problem by resizing the bell cranks / swings arms on which the road wheels are mounted, although I'm pretty sure I've scaled those correctly too (unless there was a different sized bell crank for the fifth road wheel?

 

Do you know what is the actual clearance between the sprocket ring and the tyre of the fifth road wheel? If the wheels are 31.6" diameters then the clearance between the sprocket ring and tyres must be just a few inches?

 

Also, what is the distance between centres on the bell cranks (i.e between the centre of torsion bars and the axle mountings for the road wheels)? By my calcs it's 482.4mm (or just under 19" in old money). I don't suppose any of you stopped to take that measurement when you were assembling the old girl :-D

 

 

EDIT: been doing a bit of farting about and have come to the conclusion that the clearance between the fifth road wheel and the sprocket ring is just over 1 3/4" , approximately... and at my scale that's a whole 7.5 mm.

Edited by Old Git
Link to comment
Share on other sites

you are correct about the swinging arms being 19" and it is a well known measurement as it is one of the main differences between Cromwell and cavalier, the crusader (Cromwell was designed as a requirement for a heavy crusader) also had 19" arms but these were changed to 15" on cavalier then back to 19" on Cromwell.

like Adrian pointed out there are no torsion bars although the mountings on the hull floor look like they could be torsion bars. the suspension uses coil springs and dampers. the housings on the hull floor hold the bearings and swinging arm shaft, interestingly the shaft bearings are auto lubed by a pipe system which lets a drop of oil onto the bearings every time the clutch pedal is engaged, bit of Cromwell trivia :-D

Link to comment
Share on other sites

The what bars? ;)

 

like Adrian pointed out there are no torsion bars although the mountings on the hull floor look like they could be torsion bars. the suspension uses coil springs and dampers. the housings on the hull floor hold the bearings and swinging arm shaft, interestingly the shaft bearings are auto lubed by a pipe system which lets a drop of oil onto the bearings every time the clutch pedal is engaged, bit of Cromwell trivia

 

Sadly I know all of this already, I've even modelled the oil tank for lubing the bearings, but as I was in a hurry, and the memory was failing, I thought I'd just call them torsion bars and hope nobody noticed:-D "And I would have gotten away with it too if it wasn't for those meddling kids" (Scooby Doo in case you can't remember).

 

you are correct about the swinging arms being 19" and it is a well known measurement as it is one of the main differences between Cromwell and cavalier

 

Sadly it wasn't well known to me and I had to figure it out myself based on the size of the wheels. Gratifying to know I got it right though! Here's a few progress shots, a bit of artistic licence here and there but in the main it's the nearly 100%

 

assbly-3_zps5ddc4f14.jpg

 

assbly-3a_zps00e2e09a.jpg

 

grp-8_zps7cba82e8.jpg

Link to comment
Share on other sites

Sadly I know all of this already, I've even modelled the oil tank for lubing the bearings, but as I was in a hurry, and the memory was failing, I thought I'd just call them torsion bars and hope nobody noticed:-D "And I would have gotten away with it too if it wasn't for those meddling kids" (Scooby Doo in case you can't remember).

 

 

 

Sadly it wasn't well known to me and I had to figure it out myself based on the size of the wheels. Gratifying to know I got it right though! Here's a few progress shots, a bit of artistic licence here and there but in the main it's the nearly 100%

 

assbly-3_zps5ddc4f14.jpg

 

assbly-3a_zps00e2e09a.jpg

 

grp-8_zps7cba82e8.jpg

 

Some skills you have there!

 

Also love the way the photo from the manual is plonked on a couple of old blocks of wood!

Link to comment
Share on other sites

the detail in those parts is amazing :wow: and yes I figured you knew what you were talking about as it is obvious from the modelling you do but i sometimes post info more for the benefit of others who hopefully like me also enjoy the engineering side as well as the big gun and tracks bit.

I'm just glad I got it right as I was expecting Adrian to pull me up on some detail or other I got wrong :D

Link to comment
Share on other sites

Did you get to the bottom of the ignition problem Rick? Or is it still a short period of fine running before being intermittent again. You mentioned in one thread that the magnetos had been changed but the problem was still not 100% fixed.

Link to comment
Share on other sites

I figured you knew what you were talking about as it is obvious from the modelling you do but i sometimes post info more for the benefit of others who hopefully like me also enjoy the engineering side as well as the big gun and tracks bit.

 

I appreciate all of it Rick, I have learned so much from this site, it's an absolute gold mine of information here! We modellers tend to use line drawings and walk-around photo-shoots of existing vehicles but they only tell part of the story and, as you chaps well know, paint covers a multitude. But watching the tear down and rebuild of a vehicle lets me see absolutely everything and explains why things operate as they do, and what looks like a couple of broken lines on a drawing actually becomes a real part when I see it pulled apart. If my parts look good it's because I've got absolutely stunning reference pics and information from this site and it's amazingly helpful members!

 

Interestingly enough I started life as a Mech Engineer before going off to University and then ending up in the Computer Industry. So it's rather nice to come full circle and find myself back at the engineering end, even if it is only in 1/6th scale!

 

BTW, has anyone got any really good close-up pics of the 'G-Clamp' type affairs that hold the Cowl down at the back of the Cromwell?

 

 

Some skills you have there!

 

Also love the way the photo from the manual is plonked on a couple of old blocks of wood!

 

Thanks for the comments Paul, but 3D printing makes me look better than I actually am! Re the pic from the manual, the main gear wheel has a protrusion on the other side which means it needed to be rested on something elsewise it would not have set flat on the ground. But yes, a different, less polished era. Still we seemed to achieve much more when we were concerned more with what we were doing rather than how it was presented. Oops, there you go, you've set me off. Now I'm going to get all misty-eyed thinking about the Empire!

Edited by Old Git
Link to comment
Share on other sites

  • 10 months later...

it's the time of year to bring the Cromwell out of hibernation and start getting it ready for the show season. my first task is to get to the bottom of the poor running issue. the tank will run great then cough and splutter and then pick up again after 30 seconds of idling which would suggest fuel starvation. I will check the filter but want to get the fuel pumps reconditioned anyway and Viton rubber replacements for the diaphragm. so with that in mind does anyone know where I can send the pumps off to be worked on.

 

once the engine is running alright I will look at changing the gearbox output seals and maybe some new hydraulic lines, I want a trouble free show season. if that's possible !

 

rick

Link to comment
Share on other sites

it's the time of year to bring the Cromwell out of hibernation and start getting it ready for the show season. my first task is to get to the bottom of the poor running issue. the tank will run great then cough and splutter and then pick up again after 30 seconds of idling which would suggest fuel starvation. I will check the filter but want to get the fuel pumps reconditioned anyway and Viton rubber replacements for the diaphragm. so with that in mind does anyone know where I can send the pumps off to be worked on.

 

once the engine is running alright I will look at changing the gearbox output seals and maybe some new hydraulic lines, I want a trouble free show season. if that's possible !

 

rick

 

Hi rick if your intrested were in the same spot has last year at W&P :cool2::cool2:

 

Al

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×
  • Create New...