PDA

View Full Version : Burt Munro's Scout



wbks
27th February 2009, 16:52
I was wondering today, how something that began life not being able to reach open road speed could clock 200mph without a different engine? What performance mods do you vintage guys do to extract a lot more power from your engines?

skidMark
27th February 2009, 17:04
I was wondering today, how something that began life not being able to reach open road speed could clock 200mph without a different engine? What performance mods do you vintage guys do to extract a lot more power from your engines?


Something in the water in invercargill....

Spelt Burt btw...

wbks
27th February 2009, 17:07
Something in the water in invercargill....

Spelt Burt btw...Meh, can't change the title now... Re-casted internals with different materials for lighter weight?

tri boy
27th February 2009, 17:16
Its all about fuel n head work.
Get it in (at high volume), squeeze it to within a nano of explosion, and get it out quick.
Everyone likes good head work.:whistle:

wbks
27th February 2009, 17:28
So re-casted alloy high comp pistons, re-made barrels and such? Sounds like fun stuff to me...

JMemonic
27th February 2009, 17:32
As I understand things it was a different engine that Burt hand built from ground up as he rebuilt the original scout each time he killed it, I guess some of the casings remained unchanged but we know he converted it to OHV built new barrels and piston, the crank and rods were hand built.

By an reckoning what he archived was brilliant and the result of years of persistent trial and error. Now days you just buy a chip.

Brian d marge
27th February 2009, 17:35
Its all about fuel n head work.
Get it in (at high volume), squeeze it to within a nano of explosion, and get it out quick.
Everyone likes good head work.:whistle:

and Valve curtain area .. good combustion shape , delays detonation get as much of the boom boom juice through as you can per second ...( 60mm inlets now ..... )

We have done a lot of work with Enfields , they are topping out at 41. 42 bhp without major engine work , using evil juu juu juice ...

Mine is in the region of 32 bhp , and gobs of torque .... I got that with , high comp , and good squish ..its the limit for me ....

Stephen

wbks
27th February 2009, 17:40
Does that cruse at 100 easily enough?

pete376403
27th February 2009, 18:23
it went from a single cam side valve to a quad cam pushrod overhead valve for a start. Capacity increase from around 600cc to around 900cc
Munro made virtually everything in the engine apart from (IIRC) the crankcases, carb and magneto, and even these would have been heavily modified. There were many many years of trial and error, and much hard work. Imagine *filing* a con rod from a solid piece of truck axle. These days we have no concept of the time and effort that Munro took to make a piece that may have lasted all of five minutes before a blowup.
"Offerings to the gods of Speed" indeed

Tim Hannas book, "One Good Run" explains it better

wbks
27th February 2009, 18:50
I'm reading Tim Hannas book on John Britten at the moment, pretty good. I'll get One good run when I'm done. And filing a conrod out of a truck axle... Dedication

GaZBur
27th February 2009, 19:46
Makes you wonder if he had given up on the Indian and moved onto something more modern (1970's) what final speeds he could of managed instead of continuing to push on with a 47 year old bike.
I was at a 2 day meeting in Ingll in the mid-late 70's and Burt turned up, but sadly his bike wouldn't start. He was looking quite old and sick then as I remember. One of the guys there from Dunedin, Errol Healey said he had raced against Burt many times. He would take off on the bunch at the start but eventually the rest would pass him with his bike blown up, apparently he had had time to roll and light a smoke by the time the rest caught up.(might be stretching it a bit but that was the story I was told). Sounds like he entered a lot more races than he finished but won most he did finish in. He also competed on other bikes as I have seen some pics at eh bike club of him competing in Dunedin.
Wonder what he would make of the Burt Munroe weekends.

Paul in NZ
27th February 2009, 20:54
He did try a few other engines... Most were not as 'forgiving'....

One question you need to ask - when does an 'indian' stop being and indian? How could anyone get get 214mph out of a pre unit T110 and give birth to the Bonneville...??

Answer - both men were fecking mad as meat axes and it has been my great privilage in life to meet them both....

PeteJ
28th February 2009, 09:25
If you want some initial clues, get hold of a copy of the Phil Irving classic text Tuning for Speed. It was first published in 1948 ie in era. I believe - from a conversation I had with Burt in the early 70s - that he used a lot of the Irving findings and reasoning.

BTW, my Enfield 350 Bullet was built for classic racing in the early 80s, using a lot of ideas from Tuning for Speed, and was clocked at a sprint at over 100mph.

It presently shows mid 30 rwhp on the dyno (in its early days, was late 20s rwhp), largely as a result of having had the head on a flow bench and gas flowing it using newer ideas than Irving's.

It still has the standard bore and stroke (70x90), because the NZ classic rules require retention of original bore and stroke. This does limit it.

Cheers

Pete

Laava
2nd March 2009, 22:08
Burts Scout was a bit like grandpa's axe. Same axe but had 3 new heads and 10 new handles!

puddytat
2nd March 2009, 22:28
With patience & perserverance youll fit a ducks arse over a bucket.....

DELLORTO
3rd March 2009, 16:13
he would of gave it very small and short pistons that dont last long but realy pump out power......the rest is classified...........:Police:

tri boy
3rd March 2009, 18:07
With patience & perserverance youll fit a ducks arse over a bucket.....
And you know this how, exactly?:laugh:

puddytat
3rd March 2009, 18:19
And you know this how, exactly?:laugh:

:whistle::shifty:

wbks
3rd March 2009, 21:48
he would of gave it very small and short pistons that dont last long but realy pump out power......the rest is classified...........:Police:I'm going to assume you mean a shorter stroke? I'm not sure how short the stock indian one is so maybe he even lengthened it slightly for a little more torque:cool:
Puddytat... Sometimes I worry about people... You're one of those people :blank:

Slyer
4th March 2009, 00:02
Clearly aliens helped, there is no other explanation and there is no evidence you could show me that will ever change my mind.

JacksColdSweat
4th March 2009, 07:11
Clearly aliens helped, there is no other explanation and there is no evidence you could show me that will ever change my mind.

Clearly someone's trying to get himself quoted.... :done:

Forest
8th March 2009, 19:30
You need to remember that Burt didn't work on his own. The movie didn't mention it, but he had a team of like-minded mates (like Duncan Meikle) and they worked on many of the bikes together.

McJim
8th March 2009, 19:40
Heard a story down here about a time someone asked him how he did it. He said "It's simple really, you just need to work out how to get more power per explosion and then have more explosions per second".

I don't think he said much about how he acheived this though....

wbks
8th March 2009, 21:25
You need to remember that Burt didn't work on his own. The movie didn't mention it, but he had a team of like-minded mates (like Duncan Meikle) and they worked on many of the bikes together.Kind of like John Britten? From what I'm reading in the book on John at the moment it seems like although he was the ambitious one with the idea and the motivation for the final product, many other people were the ones with the specialist skills and the materials that spent just as much time on the bike as him to achieve the final product or at least taught him the know how so he could do it himself.

I guess it could have well been the same sort of thing for Burt Munroe. I mean people don't just pop out in to the world knowing casting techniques and aero dynamics:yes:

pete376403
9th March 2009, 21:43
You really need to read the Munro book. Burt was a "trial and error" type of engineer. Not a huge amount of science, but a shit load of perserverance. He had access to some engineering equipment (beyond what was in his shed) and he didn't have distractions of a wife, kids or regular job. He was able to get by without a lot in order to satisfy his passion. The less regulated times he lived in helped a bit too, I guess (so many things you're not allowed to do now)