1937 VB 600 fuel consumption

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simon.holyfield
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Re: 1937 VB 600 fuel consumption

Postby simon.holyfield » Tue May 04, 2021 10:09 pm

jj.palmer wrote:Simon, you enquired of how to hold the carburettor body in the lathe for boring.

The Amal model 276 on my KH rquires a similar renovation, have not got around to do it yet but my current thoughts on how to hold it are as in the attached sketch. The clamping is along the length of the body where there is more stength rather than in a chuck were it may be crushed.

Hope this helps.

John P.


I've only just seen this John, but many thanks. I would probably not have thought of this approach without your help.
cheers

Simes

'51 Square Four,
'58 Huntmaster,
'42 W/NG,
'30 Model A
https://ariel-square-four.blogspot.com

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Re: 1937 VB 600 fuel consumption

Postby Karol Burger » Wed May 05, 2021 6:27 am

jj.palmer wrote:Simon, you enquired of how to hold the carburettor body in the lathe for boring.

The Amal model 276 on my KH rquires a similar renovation, have not got around to do it yet but my current thoughts on how to hold it are as in the attached sketch. The clamping is along the length of the body where there is more stength rather than in a chuck were it may be crushed.

Hope this helps.

John P.


yes, this method definitely works. Your sketch is great
Ariel 500 C, E - 1927 / 1928 Super Sport Racer /Ariel SF-1931 ,Ariel 4F600 - 1934 AOMCC Member 6508

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Re: 1937 VB 600 fuel consumption

Postby jj.palmer » Wed May 05, 2021 11:14 am

Forgot to mention, if feeler gauges are used to tilt the axis of the carburettor body then use 2 feeler gauges, spaced such that there is a 3 point seating location, similar to the farmers milking stool. This will avoid any "rocking" motion.

Thanks Karol, the sketching comes from my younger days, spent some years as a machine/tool designer with a well known UK aero engine manufacturer.

John P.

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Re: 1937 VB 600 fuel consumption

Postby simon.holyfield » Wed May 05, 2021 5:56 pm

jj.palmer wrote:Forgot to mention, if feeler gauges are used to tilt the axis of the carburettor body then use 2 feeler gauges, spaced such that there is a 3 point seating location, similar to the farmers milking stool. This will avoid any "rocking" motion.


Got it, thanks John.
cheers

Simes

'51 Square Four,
'58 Huntmaster,
'42 W/NG,
'30 Model A
https://ariel-square-four.blogspot.com

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Re: 1937 VB 600 fuel consumption

Postby jj.palmer » Thu May 06, 2021 11:40 am

For those of interest, an update to the sketch of the carb. holding fixture,but, more importantly so that I don't forget either.

John P.
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Carb body holding fixture.jpg

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Re: 1937 VB 600 fuel consumption

Postby murray.mckenzie » Sun May 09, 2021 10:15 am

Simon,
I'm sorry I have been very slow in reply to your question on how I machined my carburetor. Whilst I didn't at the time have the presence of mind to photograph it I'll do my best to explain what I did.

I figured the lower section of the carburetor where the jet assembly is located would still be circular and not worn because the slide does not travel down into that area. Based on that assumption I pushed it out of the body. It was firm but came out OK. I then found a piece of steel round bar which was a bit larger and mounted it in the four jaw chuck. I then machined it so it was a tight fit into the lower carb body. I then pushed the carburetor onto it and put a dial indicator into the area where the slide ran and found it was around 0.010" out of round. Because it is a very easy metal to machine, especially with a boring bar that has been finally honed with an oil stone, I proceeded to take a series of light cuts down far enough to allow the slide to travel its full distance. Because the cuts were light, no heat was generated and it was a tight fit on the mandrel, there was no problem in turning it. I continued till it was back to true. I noted there were a few very small areas the tool had not touched but I aimed for a balance between those and avoiding taking out too much metal.
I then removed the chuck from the lathe with the job still in it and put the three jaw in place and fitted up a piece of brass which was a suitable diameter and started to machine a new slide. Bore out the centre first to the diameter of the existing slide so all the heavy machining and heat generation is done first. Then proceed to machine the OD to the new diameter of the carb body. I couldn't guarantee my three jaw accuracy when returning a job back into it so I marked jaw No1 and the stock lengthwise position very carefully then removed it and checked the fit. Prior to this I put a micrometer on the slide diameter and it was prefect along it's length. However when I pushed it into the body it was bit tight when it was deep down in the carb. I remounted the four jaw and ran the bar back in and it took the lightest skim cut. The area where the slide was tight the bar took out just a hair of a cut. Hence my reason for leaving it in the four jaw chuck from the start. There was just the slightest firmness left so I gave the two parts a very light hone with some Brasso, of course with the lathe bedway carefully covered
Now came the section where the needle is mounted on the top of the slide, and for this I used the mill to create that rectangle section. I made another mandrel for the slide to push over, this time again a very firm fit. I held the mandrel in a rotary table which has a three jaw chuck mounted on it. So again lots of light cuts so you creep up on it without it knowing what you are up to and before you know it you are there and there wasn't any sign of movement.
I'm sure there will be other people who will be able to offer better solutions however this worked a treat for me and the bike has the slowest perfect idle. It took time but it worked well.

My original question on this post regards fuel consumption has been sorted with all the help offered. It seems that the main jet may not be the correct size. I think someone must have attacked it with the drill at some stage. I'm currently machining a new one and whether it's correct or not I'm using water as the calibrating medium. As far as I understand the 160 jet number is the number of cc/min that flow through the jet so if I use a constant starting water level head with each measurement then maybe that will work??? The current one is delivering around 230 so I'm keen to see how my one is going to perform in the bike. Maybe my theories are way off but I'm open to suggestions.

Murray

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simon.holyfield
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Re: 1937 VB 600 fuel consumption

Postby simon.holyfield » Sun May 09, 2021 11:32 pm

Excellent notes thanks Murray. I'm planning on reworking a tired 276 myself later this year, just for the experience. Did you use a steady to support the top of the carburettor during boring?

Having been through a similar experience with drilled-out main jets on my W/NG, I take it you have checked the needle and needle jet? I measured my needle against a new one and was alarmed at how bad it was.
cheers

Simes

'51 Square Four,
'58 Huntmaster,
'42 W/NG,
'30 Model A
https://ariel-square-four.blogspot.com

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Re: 1937 VB 600 fuel consumption

Postby nevhunter » Mon May 10, 2021 1:15 am

The Main jet(the little one right at the bottom) is the only one that doesn't wear with use unless someone has monstered it. The needle and the big jet it moves in wear as does the one in the Bowl that affects the fuel level. Each of these makes the motor run richer so the effect is cumulative. You can attend to all these by getting new ones whether you fix the slide play or not. Just boring the body is not enough on it's own. Replacing the jet block or repairing it (hard to do) may be required or the body will wear quickly to where it was before as the jet block helps locate it. A sloppy slide gives an irregular idle and idle speed but won't greatly affect your mileage.. Don't expect a side valve to get the economy an OHV does, but HOW you ride it will have an effect.
As an example my son and I some years ago both entered an economy run with the VMCC of Victoria, where a measured amount of fuel is put in an auxiliary tank and the bike ridden on a set route, till it stops. The distance is recorded and the consumption calculated. We both won our respective classes based on capacity of the engines (600cc and 1,000 ccs on Indian SIDEVALVES 110 MPG on a 600 Scout 1920, and I got 84 MPG on a 1923 1000 cc Powerplus. but believe me we leaned them out and rode "carefully". SOMEONE could quote such a result as proof that sidevalves are more economical but it would not be a realistic conclusion. Expect about 25% less mileage than an equivalent OHV machine as a fair difference allowance on average but there will be wide variations on that likely. Another Indian I had, a 750 101 Indian scout 1928, never got much more than 30 MPG ridden off road most of the time. I wasn't licenced then. Nev

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Re: 1937 VB 600 fuel consumption

Postby jj.palmer » Mon May 10, 2021 3:50 pm

Murray, brilliant, makes my proposal look a little over engineered.

When the carb body is mounted on the mandrel for boring, although it is a tight fit, would it be possible to fit a small clamp to ensure that there is nil slippage between the carb body and the mandrel.

John P.
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Re: 1937 VB 600 fuel consumption

Postby murray.mckenzie » Tue May 11, 2021 10:59 am

Hi Simon & John
I didn’t use any steady support as the mandrel is quite a large diameter and when the carburettor is mounted, it is almost right up against the chuck and very firm, so I figured it had all the support it needed really.
Because it was only about .010 out of round and I was using a very sharp tool I could take ten x 0.001 cuts or there abouts, and being a tight fit the amount of torque applied to it during the cut was very low so there didn’t seem to be any need for any other clamping. Also with the light cuts there was no heat generated so no expansion and loss of fit. Obviously John it would be very little extra work to fit up a clamp and would provide that peace of mind as the work progresses.
I hadn’t looked at the needle or the needle jet in great detail as I didn’t have a new one to compare with or any figures on the delivery rate of that jet so decided to look further at the main jet as it didn’t seem as though it was delivering the correct amount based on my measurements, however based on your comment Simon I will look again thanks.
It maybe seem a bit silly making a jet when they are available but being in NZ the time and cost getting it here warrants a bit of time playing and also the satisfaction of doing it.
I also hadn’t taken into account or even thought about the fact that the side valve engine fuel economy is poorer. I’ve never had a side valve before but I do love it.

Murray


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