The loud silence
11-01-2002, 01:38 AM
#1
Thread Starter
My Feedback: (43)
Join Date: Dec 2001
Location: Chehalis,
WA
Posts: 568
Likes: 0
Received 0 Likes
on
0 Posts
The loud silence
I ran out of fuel in my (standard/Ram 500) Bobcat again today at 5.5 min of flight time. I was flying at full thrust most of the time but I know I should be getting almost twice that amount of time. Any suggestions? Has anyone put an extra fuel tank in the standard Bobcat? The timer is set for 6 min and I have 57 flights landing at that time and have fuel left over. Perhaps I just didn't shake the acft. enough while fueling?
Thanks,
Galen
Thanks,
Galen
11-01-2002, 02:29 AM
#2
Senior Member
My Feedback: (1)
Join Date: Dec 2001
Location: Oxford, MS
Posts: 3,241
Likes: 0
Received 0 Likes
on
0 Posts
The loud silence
Galen,
If you are using the hard urethane fuel line that BVM sends with the kit this may be the problem. In the first BC I built I used that line and one of the lines to the wing tanks became kinked. Just enough to let fuel into it so we thought we were getting a full fuel load but when it ran it drained the one tank then the hopper and never did pull much from the other tank. I have used tygon tubing for all the connections up to the hopper tank since then.
DR
If you are using the hard urethane fuel line that BVM sends with the kit this may be the problem. In the first BC I built I used that line and one of the lines to the wing tanks became kinked. Just enough to let fuel into it so we thought we were getting a full fuel load but when it ran it drained the one tank then the hopper and never did pull much from the other tank. I have used tygon tubing for all the connections up to the hopper tank since then.
DR
11-01-2002, 02:51 AM
#3
Senior Member
My Feedback: (11)
The loud silence
Hi Galen,
You shoul be carrying 1 litre in each of the main tanks, plus 4 oz in the UAT. That's what ... 70 0z ? Which means that 5.5 minutes of flying, you'd be using 12.8 oz per minute. That's a bit over the spec's for the RAM 500.
Either you have a more thirsty than normal 500, or you're not getting to use a full load of fuel. Can you fill the tanks completely, then empty them into a measuring jug and see whether you are getting a full load on board ?
If you get less than 1L each, maybe your vent is misplaced, or your clunk is sticking somewhere due to the clunk line being too long ? (note that as the BV fuel lines inside the tank age, they will grow in length slightly - that's why the instructions tell you to keep em a bit short).
Failing that - note that you CAN fit the extra 3rd Kevlar tank inside the standard Bobcat too - I have it in mine and can send you photos if you wish.
Regards,
Gordon
You shoul be carrying 1 litre in each of the main tanks, plus 4 oz in the UAT. That's what ... 70 0z ? Which means that 5.5 minutes of flying, you'd be using 12.8 oz per minute. That's a bit over the spec's for the RAM 500.
Either you have a more thirsty than normal 500, or you're not getting to use a full load of fuel. Can you fill the tanks completely, then empty them into a measuring jug and see whether you are getting a full load on board ?
If you get less than 1L each, maybe your vent is misplaced, or your clunk is sticking somewhere due to the clunk line being too long ? (note that as the BV fuel lines inside the tank age, they will grow in length slightly - that's why the instructions tell you to keep em a bit short).
Failing that - note that you CAN fit the extra 3rd Kevlar tank inside the standard Bobcat too - I have it in mine and can send you photos if you wish.
Regards,
Gordon
11-01-2002, 02:58 AM
#4
My Feedback: (24)
Join Date: Dec 2001
Location: Daytona Beach
Posts: 6,102
Likes: 0
Received 0 Likes
on
0 Posts
The loud silence
Originally posted by DavidR
Galen,
If you are using the hard urethane fuel line that BVM sends with the kit this may be the problem. In the first BC I built I used that line and one of the lines to the wing tanks became kinked. Just enough to let fuel into it so we thought we were getting a full fuel load but when it ran it drained the one tank then the hopper and never did pull much from the other tank. I have used tygon tubing for all the connections up to the hopper tank since then.
DR
Galen,
If you are using the hard urethane fuel line that BVM sends with the kit this may be the problem. In the first BC I built I used that line and one of the lines to the wing tanks became kinked. Just enough to let fuel into it so we thought we were getting a full fuel load but when it ran it drained the one tank then the hopper and never did pull much from the other tank. I have used tygon tubing for all the connections up to the hopper tank since then.
DR
Todd
11-01-2002, 03:44 AM
#5
Thread Starter
My Feedback: (43)
Join Date: Dec 2001
Location: Chehalis,
WA
Posts: 568
Likes: 0
Received 0 Likes
on
0 Posts
Loud Silence
Greetings Gordon,
I believe I followed the assembly of the fuel tanks correctly although you never know. There is something wrong, however , because the UAT is only maintaining at half full when the turbine is running. It's mounted horizontally on top of the center section of the wing. As I understand, it should be full when the turbine is running. It may be the plumbing problem that DavidR and Todd mentioned in the other posts. I will check the capacity as you suggested as well as the lines for kinks. I would really like to see the way you put the extra fuel tank in. The pics would be great. Send them to [email protected]. I think I'll put in the extra tank even when I get the present problem solved.
Thanks,
Galen
BTW - I installed the BVM Duro Struts all around. Makes for a big improvement in ground handling and landing.
I believe I followed the assembly of the fuel tanks correctly although you never know. There is something wrong, however , because the UAT is only maintaining at half full when the turbine is running. It's mounted horizontally on top of the center section of the wing. As I understand, it should be full when the turbine is running. It may be the plumbing problem that DavidR and Todd mentioned in the other posts. I will check the capacity as you suggested as well as the lines for kinks. I would really like to see the way you put the extra fuel tank in. The pics would be great. Send them to [email protected]. I think I'll put in the extra tank even when I get the present problem solved.
Thanks,
Galen
BTW - I installed the BVM Duro Struts all around. Makes for a big improvement in ground handling and landing.
11-01-2002, 03:57 AM
#6
Senior Member
My Feedback: (1)
Join Date: Dec 2001
Location: Oxford, MS
Posts: 3,241
Likes: 0
Received 0 Likes
on
0 Posts
The loud silence
There is something wrong, however , because the UAT is only maintaining at half full when the turbine is running. It's mounted horizontally on top of the center section of the wing.
DR
11-01-2002, 04:27 AM
#7
Thread Starter
My Feedback: (43)
Join Date: Dec 2001
Location: Chehalis,
WA
Posts: 568
Likes: 0
Received 0 Likes
on
0 Posts
The loud silence
DavidR
I did use the hard tubing supplied by BVM so it might be a combination of both. It does seem like a good time to pull the plumbing , substitute the tygon tubing and install the third tank. There is room to mount the UAT vertical at the leading edge of the center section. Thanks for the suggestions.
Regards,
Galen
I did use the hard tubing supplied by BVM so it might be a combination of both. It does seem like a good time to pull the plumbing , substitute the tygon tubing and install the third tank. There is room to mount the UAT vertical at the leading edge of the center section. Thanks for the suggestions.
Regards,
Galen
11-01-2002, 06:23 AM
#8
My Feedback: (92)
Join Date: Dec 2001
Location: Rosamond, CA
Posts: 2,089
Likes: 0
Received 0 Likes
on
0 Posts
The loud silence
Galen,
With my 500 powered BobCat I had the timer set for 6:30, and I would start it just before take-off. I always used the taxi/start tank, and would disconnect as I taxied onto the runway. This time would leave me about a minute or a minute and a half reserve. I highly suspect that you have a problem with the fuel system. Check everything out, even if you have to pull the tanks out of the model. This is especially true if all of a sudden your getting less run time.
It is also possible that the bearings in the engine are getting rough. This means it will burn more fuel to try to get the commanded rpm's. Does the engine still feel smooth, and is it taking the normal time to ramp up during the start?
George Jones installed the extra tank in his BobCat, but I have to say with the 500 on it it was a little doggy until that extra fuel burned off. It could fly for a real long time, however! Personally, I wouldn't install the normal fuse tank. Just a 8 or 10 oz. Sullivan or DuBro will give you plenty of extra fuel instead of adding the usual 3rd tank.
Hope this helps!
With my 500 powered BobCat I had the timer set for 6:30, and I would start it just before take-off. I always used the taxi/start tank, and would disconnect as I taxied onto the runway. This time would leave me about a minute or a minute and a half reserve. I highly suspect that you have a problem with the fuel system. Check everything out, even if you have to pull the tanks out of the model. This is especially true if all of a sudden your getting less run time.
It is also possible that the bearings in the engine are getting rough. This means it will burn more fuel to try to get the commanded rpm's. Does the engine still feel smooth, and is it taking the normal time to ramp up during the start?
George Jones installed the extra tank in his BobCat, but I have to say with the 500 on it it was a little doggy until that extra fuel burned off. It could fly for a real long time, however! Personally, I wouldn't install the normal fuse tank. Just a 8 or 10 oz. Sullivan or DuBro will give you plenty of extra fuel instead of adding the usual 3rd tank.
Hope this helps!
11-01-2002, 01:09 PM
#10
Senior Member
My Feedback: (1)
Join Date: Dec 2001
Location: Oxford, MS
Posts: 3,241
Likes: 0
Received 0 Likes
on
0 Posts
The loud silence
Matt,
NO I use the tygon up to the big hopper tank then switch to the urethane tubing from the big hopper. (XL) Vernon has his plumbed in with Tygon up to the UAT and then he switches to the urethane out of the UAT to the pump.
With the XL tank setup and my P-120 I set my timer for 8 minutes from takeoff roll, I land most of the time with about half the main hopper, and UAT full.
NO I use the tygon up to the big hopper tank then switch to the urethane tubing from the big hopper. (XL) Vernon has his plumbed in with Tygon up to the UAT and then he switches to the urethane out of the UAT to the pump.
With the XL tank setup and my P-120 I set my timer for 8 minutes from takeoff roll, I land most of the time with about half the main hopper, and UAT full.
11-01-2002, 05:11 PM
#11
Senior Member
My Feedback: (11)
The loud silence
Galen,
Have sent pics as promissed. Do take heed of Tony's point about increased weight... though of course you could experiment with only filling the third tank a bit to begin with, gradually filling it a bit more as you wish. Or just go the Dubro way as Tony suggests.
Hey Tony ... does Bob allow you to promote Dubro tanks instead of BVM ones ??? <just kiddin!>
Regs,
Gordon
Have sent pics as promissed. Do take heed of Tony's point about increased weight... though of course you could experiment with only filling the third tank a bit to begin with, gradually filling it a bit more as you wish. Or just go the Dubro way as Tony suggests.
Hey Tony ... does Bob allow you to promote Dubro tanks instead of BVM ones ??? <just kiddin!>
Regs,
Gordon
11-01-2002, 05:37 PM
#12
My Feedback: (92)
Join Date: Dec 2001
Location: Rosamond, CA
Posts: 2,089
Likes: 0
Received 0 Likes
on
0 Posts
The loud silence
Well, you could order a DuBro thru BVM if you wish!
I also use Tygon tubing to interconnect all the tanks up to the UAT. I then use the poly tubing from the UAT to the pump. I usually do not use the tubing BVM supplies for inside the tank, but on the BobCat I did since the clunk needs to be very flexible in the wing tanks. That tubing will lengthen with time, so do cut it about an inch shorter then the length of the tank.
BTW, my UAT would usually be about half full at the end of the flight. With the standard BobCat set-up without the 3rd tank I think you can get a bit more air out of the wing tanks then with the UAT drawing from the 3rd tank. I never had a problem with the air in the UAT though.
I also use Tygon tubing to interconnect all the tanks up to the UAT. I then use the poly tubing from the UAT to the pump. I usually do not use the tubing BVM supplies for inside the tank, but on the BobCat I did since the clunk needs to be very flexible in the wing tanks. That tubing will lengthen with time, so do cut it about an inch shorter then the length of the tank.
BTW, my UAT would usually be about half full at the end of the flight. With the standard BobCat set-up without the 3rd tank I think you can get a bit more air out of the wing tanks then with the UAT drawing from the 3rd tank. I never had a problem with the air in the UAT though.
11-01-2002, 07:04 PM
#13
Senior Member
My Feedback: (1)
Join Date: Dec 2001
Location: Oxford, MS
Posts: 3,241
Likes: 0
Received 0 Likes
on
0 Posts
The loud silence
One other thing I noticed early with the Bobcat was that when the airplane started peeing on the ground there was still quite a bit of air in the tanks. I always fill now with the overflow line attached to the vent and back into the tank I fuel from. This makes sure you have a full fuel load onboard.
11-01-2002, 07:31 PM
#14
Ok I get it
I do the same thing I run ALL tygon up to the UAT, then the urethane for the UAT to the pump. I use tygon as pick up line in the tanks too, but I can see from the BobCat tank configuration that special precautions might have to be taken with the pickup line.
11-02-2002, 05:00 AM
#15
Thread Starter
My Feedback: (43)
Join Date: Dec 2001
Location: Chehalis,
WA
Posts: 568
Likes: 0
Received 0 Likes
on
0 Posts
The loud silence
Hey Tony,
I wish you hadn't said that about the bearings. I do remember several flights back that it seemed the ramping time was a little long. However Thurs. It was quite cold and it started on the third spinup on the first attempt. But the ramping time was very quick. Does temp. have anything to do with the ramping time? Also Is there a home method for checking the bearings?
I have a lot of Dubro tanks around and some stoppers for jet A so I'll probably go that route.
Thanks,
Galen
I wish you hadn't said that about the bearings. I do remember several flights back that it seemed the ramping time was a little long. However Thurs. It was quite cold and it started on the third spinup on the first attempt. But the ramping time was very quick. Does temp. have anything to do with the ramping time? Also Is there a home method for checking the bearings?
I have a lot of Dubro tanks around and some stoppers for jet A so I'll probably go that route.
Thanks,
Galen
11-02-2002, 06:16 AM
#17
My Feedback: (92)
Join Date: Dec 2001
Location: Rosamond, CA
Posts: 2,089
Likes: 0
Received 0 Likes
on
0 Posts
The loud silence
Galen,
Check your spooldown times from the last 10 or 15 flights. See if they have been going down or staying steady. If going down, it's time for bearings. Also, try to note what the PPW is when the engine is idling. If that starts to go up, Hello to Carlos and new bearings. Checking PPW at full throttle is also a good guide. The EGT probe installation on RAM's is so inconsistent I'm not sure you really can tell much with those readings. Move the probe a tiny bit in or out and the readings change, so what is truth? I have never seen OAT have much effect on ramp times.
Have you noticed the gap between the front of the outer case and the back of the inlet cover getting bigger? If so, the 4 bolts that hold the NGV to the shaft tunnel are loosening. This lets things inside slide forward and the turbine wheel gets closer to the NGV. It can start to rub, which is a bad thing. But this typically doesn't happen until 150 or so runs.
Despite some of my comments here I still feel that a "right" 500 is a little jewel. I love mine and it has been as trouble-free as you can expect, I suppose. And I have to say, I just got mine back from Carlos after being repaired from my BobCat's demise. Installed it in the Sabre and after some minor adjustments to the Gas Adjust it is starting and running beautifully. The 500 when it is correct is the best engine RAM made. Mine routinely has gone over 150 flights with no maintenance.
Hope some of this stuff helps you out.
Check your spooldown times from the last 10 or 15 flights. See if they have been going down or staying steady. If going down, it's time for bearings. Also, try to note what the PPW is when the engine is idling. If that starts to go up, Hello to Carlos and new bearings. Checking PPW at full throttle is also a good guide. The EGT probe installation on RAM's is so inconsistent I'm not sure you really can tell much with those readings. Move the probe a tiny bit in or out and the readings change, so what is truth? I have never seen OAT have much effect on ramp times.
Have you noticed the gap between the front of the outer case and the back of the inlet cover getting bigger? If so, the 4 bolts that hold the NGV to the shaft tunnel are loosening. This lets things inside slide forward and the turbine wheel gets closer to the NGV. It can start to rub, which is a bad thing. But this typically doesn't happen until 150 or so runs.
Despite some of my comments here I still feel that a "right" 500 is a little jewel. I love mine and it has been as trouble-free as you can expect, I suppose. And I have to say, I just got mine back from Carlos after being repaired from my BobCat's demise. Installed it in the Sabre and after some minor adjustments to the Gas Adjust it is starting and running beautifully. The 500 when it is correct is the best engine RAM made. Mine routinely has gone over 150 flights with no maintenance.
Hope some of this stuff helps you out.
