Member postings for Doubletop

Steve

I've got one of those installed, I think it’s an inherent part of the design. In my case the feed tank may have run dry.

I’ve now done this and the Bobcat, in both oil seems to come out of places you’d least expect.

Today is strip down and see how much oil is actually left in the sump and how much there is in the silencer .

Pete

Edited By Doubletop on 23/12/2013 22:08:00

Its a runner!!

All the parts. (I've cheated a bit on the carb. It's a Chinese knock-off clone of a Walbro)

And the ignition is another knock off of a RCxel

A bit more work but its close

Pete

Edited By Doubletop on 23/12/2013 10:32:36

Edited By Doubletop on 23/12/2013 10:33:45

Can't wait; and with the progress so far I can't see us having to wait until until Christmas 2014 for the pudding

One of the many watching with interest....

Pete

Edited By Doubletop on 22/12/2013 07:09:19

Dean

Apart from a general sense of inadequacy the last sequence of shots was an "I've just learned something useful" moment.

Keep them coming

Pete

I'm with you on this Michael. "We own the ball and we'll play by our rules, which includes changing them when we want"

Pete

Interesting

For 'Doubletop' I have checked with our subs bureau and he only has a Print Subscription (he was originally a 'Complete Package Subscriber' ) – this means that he will continue to have access to the Online Archive until July 2014 (because of us honouring the access granted to ‘Complete Package Subscribers'

My ME subscription was renewed around August/September 2012 for three years to October 2015. I haven't intentionally changed my subscription type so when was I downgraded from "Complete Package Subscriber" to "Print Only"?

I guess that the critical date is when the announcement was made that the digital archive would be withdrawn in July 2014. I would imagine that July 2014 was chosen to allow existing contracts to expire, without consideration of handful of long term subscriptions. If this changed happened after subscriptions had been paid MHS are changing the terms of the contract without directly informing the affected subscribers.

No doubt this is all covered by some legal gobbledygook buried somewhere in some obscure page on the website that constitutes "communication", also defined in the same gobbledygook.

Pete

Jason

Thanks for pointing me specific instructions. However, using my ME and MEW subscription numbers doesn't work and i get the message

This Subscription is not active. Please contact [email protected] if you think this is an error or need assistance.

Despite one subscription expiring in 2015 and one in Feb 2014. I've emailed the help link above.

We'll get there.

Pete

OK guys I'm missing something here.

I've downloaded the app, registered with pocketmags and logged in. I can open the magazines I have access to on this (ME) website. How do I get the magazines I've already paid for into the pocketmags viewer without paying for them again?

Pete

I've not shipped stuff to the UK and dealt with regulations there but I have purchased directly from China on a number of occasions. My general experience has been very good, The prices have been unbelievably low, but the shipping can double the cost, even then its cheaper than buying locally. The problem as an individual is you don't have the benefit of volume so heavy items can become prohibitively expensive to ship. When it comes down to it all the regular local suppliers are doing the same thing but have agreements and supply lines established. Most things in their catalogue can be found by searching Alibaba.com, then you just decide which way you want to go.

The only real problem is quality. Numerous suppliers can provide the same product but the quality may not be the same. That said I've weighed up the saving and taken the chance and not been disappointed.

With Seig there is only one source and members of our club looked at buying directly. On balance they went to the local supplier because of the shipping cost. However, for small items I'd suggest looking at going direct

Pete

Here are the promised pics of the valve seat inserts and tappet sleeves

They're made so the internal dimensions remain as the original design, there's plenty of room in the head to accommodate any suitable external dimensions you may choose. They are just pressed in. Take a look at Malcolm's Bobcat drawings and write up to get the idea.

Hope that helps somebody

Pete

Thanks guys I think I have most of this covered off. I'll address each on in turn so it all here for others.

John

It is possible to assemble the camshaft 'out of the (cam) box'. The cam blank is 12mm and this is machined down by 2mm to the base circle. So it ends up as 10mm to the lobe peak so will fit through the 10.5mm hole. BTW I did my hole 11mm which makes the bearing housing 11mm and a bit more robust when pressing in the bearings.

Jason

Yes its the text I was commenting on. If the builder follows the text then the hole is 0.5mm too low and the cam will probably not be able to rotate.

Spacer? There is no drawing for a spacer although the photo shows one. As you say the valve spacing is 13mm and with the 6mm cams the outer edge of the cams is 19mm. The width between the bearings is 29mm minus 19mm (not 13mm as the text) that makes the outer spigots 5mm (measure from job). With 19mm to the outer edges of the cams the inner edges are 7mm apart and therefore the inner spigots are 3.5mm as per the text. (One of our club members had started this build from the 2006 articles when he showed it to me the cam box looked all wrong. When we checked the 2006 version in the online archive the dimensions were all to cock http://www.model-engineer.co.uk/members/digitaleditions/popup.asp?t=8&i=444 Page 137 Not the case in the "Best off" )

David

Got that thanks, and copied here to consolidate the data.

On the missing cam data the direct link to the online copy of the original issue 4281 is on page 262 here.

**LINK**

There was one other thing that isn't an error but a change that I've made to the design. I wasn't happy with the valve seats and tappets running directly in the aluminium head. Malcolm must have come to the same conclusion with the Bobcat/Jaguar as he has designed a bronze seat /guide. There is plenty of meat on the head of the Lynx to do the same so I've copied the combined seat/valve guide from the Bobcat (to Lynx dimensions). I've also made the counter bores for the tappets 11mm vs the 10mm in the drawing and pressed in bronze sleeves. I'll do some photos later as I'm working on the valves at the moment.

Is there anything else not covered?

Pete

Edited By Doubletop on 17/11/2013 19:30:36

Edited By Doubletop on 17/11/2013 19:36:05

I'm in the process of building the Nemet Lynx from the recent "Best of Vol3". I guess that with the original articles being published in 2006 any errors didn't make kit to the online forum, or the forum didn't exist back then..

So apart from

• the "Best of Vol 3" not having the complete set of cam tables
• the drawings for the cam box in the 2006 version being completely wrong (not an issue in "Best of'" )
• the stated offset of 1mm for the bearing holes in the cam box being wrong in both "Best of" and 2006 (it meant to say find the centre and offset by 0.5mm)
• The spacing between the outer faces of the cam lobes being 19mm not 13mm as stated in both versions

Is there anything else I should be aware of?

Regards

Pete

Edited By Doubletop on 17/11/2013 09:54:27

Edited By Doubletop on 17/11/2013 09:55:24

My Northumbrian had been sat on the shelf while I got on with other things. As I had a bit of spare time I decided to do something about the gas wagon. It worked well and completed the set but chasing the thing round the track was getting a bit tedious so I added a single channel RC in the tender for the regulator. You can just see the shaft from the servo in one or two of the shots.

Apologies for the shaky video but RC controller in one hand and camera in the other doesn't work too well.

I do think it could do with another wagon or two

Pete

Edited By Doubletop on 04/11/2013 10:07:21

Ho hum, my copy arrived in my mailbox on the morning of the publicised release date, and I live in New Zealand....

On the missing cam data the direct link to the online copy of the original issue 4281 is on page 262 here.

**LINK**

Of course you’ll need to be a subscriber and logged in to get access to it

If you are looking for all the original articles then you’ll find that issues 4274 and 4275 are missing from the digital editions. 4275 is the one you'd want

I start my build tomorrow

regards

Pete

I'm going to also suggest the 17mm burner is way undersized for 4" tube and 3mm plate. The 50mm Sievert 2944 is 86kW (no the decimal place isn't missing) and the 35mm 2943 is 44Kw that the capacities you need to be looking at

Celcon/Thermalite blocks for insulation along with the thermal blanket.

I did see mention of using wire wool to clean the parts, although Tenacity 5 does a good job of cleaning by itself make it easier and pickle the job in a bath of saturated solution of citric acid (baking section in Tescos)

I'm no expert but one of the been there done that brigade and there’s a similar post from me from only a few years back

Pete

Finally got mine to run

Jason

Thanks for the link, encouraging and now i know what I'm shooting for. I only asked about this as StichNZ had said his was out of balance and needed additional weight. If you go back to the other thread and find StichNZ's details you see he's an engine person. Also the latest ME showed balancing the crank for the V twin Brenda II. Based on the advice I thought I'd see if I needed additional weight.

We'll see and now I've made provision for the additional weights it will be easy to add subtract weights

Pete

Neil

Thanks; I had been asking whether there was a difference between a in line or V configuration, and I can't see why only one piston conrod assembly would be used for static balancing. Anyway I thought if thats the way its done I'll give it a try.

Suspended between two darning needles in my watchmakers lathe and clearly out of balance

A couple of washers hung on to get an idea what was required

A pair of brass weights attached to the middle counterbalance weight and now in balance

It needed balancing so don't assume Malcoms counterbalance weights are correct.

Pete

Neil,

I can see the need to do this but I'm asking how would it be done. I can see why 90deg crank on a steam engine, but single acting would seem that it missed the point somewhat.

Jason,

I assumed that Malcolm would have had the balance weights right but you would have missed the PM dialogue I had with StichNZ after he showed us his video

**LINK**6

He said it ran with some vibration until he added some extra weight to the middle counter balance. So rather than run it and then have to take it apart again to fix the problem I thought I'd ask what the method for balancing was for an in line, same crank angle, twin.

Pete

My next question is how do you balance the crank and pistons?

In Brian Rees article on Brenda II (issue 4455) he explans the Tom Pascoe method for a V twin is to balance with one complete conrod and piston on the common crank. Does the same method apply to an inline twin when the pistons are on a common crank?

Pete