Milwaukee Midget

[fordboy628]

Midget,

Was trying to post jpegs of mockup for gilmer belt water pump drive, BUT, site would not let me.  Anyway, 1275 short block assembly with stock timing cover as in your pics, 12G940 cylinder head, stock 1275 damper, alloy water pump.  Plenty of room for 48T pump gear, 20T crank gear.  Should use 270L037 belt.  Parts on order from McMaster-Carr.  In an attempt to NOT reinvent the wheel,  APT has longer crank bolts of 5/8 x 16tpi, BUT, they have 1-5/16th flanges built in.  Unsure whether either of the 2 they have available can work.  No luck at ARP either.  I am thinking of either placing an insert into the crank snout to reduce the threads to a standard thread size OR modifying a 5/8 allen bolt of the proper grip length.  What is the torque for the stock damper bolt?  Could also make a complicated split flange drive snout for damper retension, crank trigger mounting and toothed cog mount, but it violates my allegiance to the kiss principle and my devotion to laziness.
 
MB

[Milwaukee Midget]

Cam manufacturers focus on Chevy/Ford/Dodge and let's face it, they pay more attention to flatheads than BMC's........   

I’d love to build a 5 port, BMC 1275, ’27 turtle-deck T with a Track nose, but, yes, the Flatty tends to get the nod in the vintage department.
 
And while the SCTA doesn’t declare it as such, this design is vintage.

Speaking of springs, I’ve got a set of Kawi KZ1100 drag bike valve springs en route.  The new valve guides are installed, Phil at APT did a back cut on the valves, and I should see the head by late next week. 

I remember Captthundarr asking about valve pressures.  Seems my Cranes are a little on the light side - ~70 lbs on the seats, 215 open.  We’ll see what the Kow springs bring to the table – I’m expecting 100+ on the seat, and 250 or more over the nose.

I need to pass on a huge "thank you" to Fordboy – he’s taken an interest in this engine combination equal to, and perhaps exceeding my enthusiasm for it.  For the last two weeks, we’ve been talking across the “Cheddar Curtain” in a Perestroikaesque manner, seeing past the usual antagonisms Wisconsinites and our neighbors to the south normally have (Football is off the table), and as a Wisconsinite, I will say that I’m ready to negotiate with tourists.

So I’ve invited him up for dyno day, April 21.  The beer's on me.

I’ll warn you ahead of time – the car looks better in pictures than it does in real life.

Pics as parts arrive.   

[fordboy628]

Midget,

Any notion of the Crane Part #'s on the valve springs previously being used?  I'd like to be able to look up the spring rate from their catalog.  My experience dictates a spring rate required of about 320/350# per inch, perhaps higher once the moment of inertia and "negative" accelerations are known.  The problem here is not one of spring rate, but of "packaging" or "fitting" into the space available.  A very common problem on small engines.

Best,
Fordboy

[fordboy628]

Midget,

Photos of water pump drive mockup as previously documented.













It appears that photobucket allows you to bend the rules.

 
Reytard

[Milwaukee Midget]

Code talking again -

FB -

Regarding your phone call - yes, the snout is held on with a large allens bolt, seen in this older pic -



Can't pull it without raising the engine, but it is longer than stock.

[fordboy628]

Midget,

Actually, that is good news.  An allen bolt means that the crank is probably not tapped for 5/8-16 BMC, but more likely 5/8-18 UNF or 5/8-11 UNC.  Cool, about time something isn't an orphan.  Hope I'm right.
 
Fordboy

[Milwaukee Midget]

Midget,

Actually, that is good news.  An allen bolt means that the crank is probably not tapped for 5/8-16 BMC, but more likely 5/8-18 UNF or 5/8-11 UNC.  Cool, about time something isn't an orphan.  Hope I'm right.
 
Fordboy

Seeing as I can't check for certain until I pull the front end off, I'll drop a note to the crank grinder.  My instructions were to build it as per BMC specs in every way except stroke.

Worst case scenario, there's a shop in Waukesha that does custom bolts.

[Rob]

5/8" 16 is actually a Whitworth (BSW) thread, socket headed cap screws are readily available though probably hard to find in the US.

If you need a longer one and cannot find it there, by all means shoot me a message Chris, there's a bolt joint just across the river and a post officer aroud the corner.   

Keep up the good work, I';ve been following quietky on the sidelines.

Cheers,
Rob

[fordboy628]

Rob, Midget, et all,

Rob, thanks for the explanation.  Just may need a 5/8-16 Whitworth allen head bolt to make this setup work.  Are there grade8/grade9 (or some other high quality) allen or hex bolts available down under in this thread size?
 
Fordboy

Midget,

I don't want to jump the shark on this, waiting until after the dyno session to confirm bolt thread is OK.  And I really DO NOT want to make a special bolt unless there are no other choices.  Using an allen/hex bolt (whatever the thread type) without the giant BMC hex head simplifies the manufacture of a drive mandrel for both the pump drive cog & the crank trigger timing wheel.   

Also: After talking to cog belt engineer, I am running design parameters for BOTH XL series pitch (.200") & L series pitch (.375").  Trying to make this work with semi-standard bits, instead of orphan size.  Concern is belt length/belt width over center to center distance required.  .200" pitch x .37" width MAY be too "whippy", and advice is to use .50" width belt and/or idler/tensioner.  (Most .200" pitch x .50" width belts are special order, big surprise. There are some sizes readily available but, etc, etc.)  I am concerned about packaging in space available and the aforementioned "cascading nightmare".  Will need crank trigger bits for mockup @ some point in time.

Quote of the day: "Success has many fathers, but failure is always an orphan.”
 
Fordboy
 

[fordboy628]

Midget,

On page 34 of the Build Diary there is a photo of your degree wheel attached to the crankshaft/short assembly with what appears to be a grade 5 hex bolt.  I think I'm going to buy a six pack of Metropolitan Brewing's "Crankshaft" ale.   That bolt has got to be UNF or UNC.  
 
Fordboy

Correction page 36  F/B

[Milwaukee Midget]

Quote of the day: "Success has many fathers, but failure is always an orphan.”
 
Fordboy
 

I think it was Lee Iacocca who said - success has so many fathers, I wouldn't want to be seen in public with the mother.

This from Greg, my crank grinder . . .

"Chris,   Poop!  Can't recall, but typicaly I use 5/8 18  and I would have marked the snout with a marking pen to get your attention.  Stock thread pitch is 5/8 20 and I tend to only use that for purists because of bolt availibility.  Don't trust anyone.  Plenty of guys have forced the 18 in the 20 hole!!   Greg"


We'll know for sure in a month.

[fordboy628]

Midget,

Touche......and right he was.

F/B

[Milwaukee Midget]

Midget,

Any notion of the Crane Part #'s on the valve springs previously being used?  I'd like to be able to look up the spring rate from their catalog.  My experience dictates a spring rate required of about 320/350# per inch, perhaps higher once the moment of inertia and "negative" accelerations are known.  The problem here is not one of spring rate, but of "packaging" or "fitting" into the space available.  A very common problem on small engines.

Best,
Fordboy

Found it - no longer a current item in the Crane catalog

902-4009

Specs as per seller -

Outer Spring O.D.  1.135
 
Outer Spring I.D.  .839
 
Inner Spring I.D.  .629
 
Does Not Have Damper
 
Seat Pressure At Installed Height 80 lbs @ 1.375
 
Open Pressure and Height 224 lbs @ .895
 
Coil Bind .793
 
Average Spring Rate 300 lbs/in

Clearly BS, if at 1.340, we're only seeing ~ 70 lbs.

[fordboy628]

902-4009

Specs as per seller -

Outer Spring O.D.  1.135
 
Outer Spring I.D.  .839
 
Inner Spring I.D.  .629
 
Does Not Have Damper
 
Seat Pressure At Installed Height 80 lbs @ 1.375
 
Open Pressure and Height 224 lbs @ .895
 
Coil Bind .793
 
Average Spring Rate 300 lbs/in

Clearly BS, if at 1.340, we're only seeing ~ 70 lbs.

Midget,

Probably not so much BS as optimism.   But anyway, good engine engineers have to live in the real world, not the optimisty world.  I would expect the springs to lose some tension after being in service, and so what is being measured at this point in time is just that: used high performance valve springs.  Valve springs are one of the most highly stressed components in a racing engine, and the expectation should be replacement at some service interval PRIOR to failure....  Even shimmed up to 95# seat (height unknown) that still only gives 239# open @ 300#/inch spring rate, and this may not be possible (probably too close to coil bind) AND IT IS CERTAINLY NOT WISE.   I don't know about you, but I want to think that I am smarter than to reuse what I'm thinking was a marginal part to begin with.  (Although I'm sure Mrs. Fordboy will have something to say about my "smartiness".)

Bottom line is: my experience tells me the listed rate is too low for this application anyway.  Consulted with RD spring in CA, and was hopeful something could be found from their motorcycle bits, but alas, their Harley/Honda stuff won't work.   

This is one of THE biggest issues I have encountered in flogging small racing engines: Whippy cams with high acceleration forces and no valve springs available to cope with the valve train forces/stresses.   And I just love it when the cam manufacturers say: "Well you could TRY this....   Let us know how it works out."   Yeah, thanks a bunch.  (read my mind here.)  If it appears that it doesn't have an ice cube's chance on a hot "Summerfest" day ON PAPER, why would I take a chance that it "might" work?!?   I'm feeling a lot better about my engineering ability, since I stopped blowing up perfectly good racing engines by not doing dumb things to them.   Maybe it's just me, but it seems to be a waste of money, time, effort and and oh yeah, did I mention money?   Sorry about the rant.   

So the great snipe hunt for the perfect BMC valve spring continues.................. Am hopeful that Kawi's will be the one.
 
Fordboy

 

[charlie101]

Maybe you could compare notes with this guy "hydrolastic" that seems to be pretty deep into BMC's? Sorry I don't have other contact info but his inputs are insightsful.

http://speedtalk.com/forum/viewtopic.php?f=15&t=29701

902-4009

Specs as per seller -

Outer Spring O.D.  1.135
 
Outer Spring I.D.  .839
 
Inner Spring I.D.  .629
 
Does Not Have Damper
 
Seat Pressure At Installed Height 80 lbs @ 1.375
 
Open Pressure and Height 224 lbs @ .895
 
Coil Bind .793
 
Average Spring Rate 300 lbs/in

Clearly BS, if at 1.340, we're only seeing ~ 70 lbs.

Midget,

Probably not so much BS as optimism.   But anyway, good engine engineers have to live in the real world, not the optimisty world.  I would expect the springs to lose some tension after being in service, and so what is being measured at this point in time is just that: used high performance valve springs.  Valve springs are one of the most highly stressed components in a racing engine, and the expectation should be replacement at some service interval PRIOR to failure....  Even shimmed up to 95# seat (height unknown) that still only gives 239# open @ 300#/inch spring rate, and this may not be possible (probably too close to coil bind) AND IT IS CERTAINLY NOT WISE.   I don't know about you, but I want to think that I am smarter than to reuse what I'm thinking was a marginal part to begin with.  (Although I'm sure Mrs. Fordboy will have something to say about my "smartiness".)

Bottom line is: my experience tells me the listed rate is too low for this application anyway.  Consulted with RD spring in CA, and was hopeful something could be found from their motorcycle bits, but alas, their Harley/Honda stuff won't work.   

This is one of THE biggest issues I have encountered in flogging small racing engines: Whippy cams with high acceleration forces and no valve springs available to cope with the valve train forces/stresses.   And I just love it when the cam manufacturers say: "Well you could TRY this....   Let us know how it works out."   Yeah, thanks a bunch.  (read my mind here.)  If it appears that it doesn't have an ice cube's chance on a hot "Summerfest" day ON PAPER, why would I take a chance that it "might" work?!?   I'm feeling a lot better about my engineering ability, since I stopped blowing up perfectly good racing engines by not doing dumb things to them.   Maybe it's just me, but it seems to be a waste of money, time, effort and and oh yeah, did I mention money?   Sorry about the rant.   

So the great snipe hunt for the perfect BMC valve spring continues.................. Am hopeful that Kawi's will be the one.
 
Fordboy