| The Markbag(tm) [message #150701] |
Sat, 26 November 2011 15:28  |
sgltrac
Messages: 2797
Registered: April 2011
Karma:
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Senior Member |
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Late last week I finally found time to copy the mounting plate drawings that Mark G supplied for his Firestone bag discovery. I obtained two bags #FI 9294 a few weeks ago and dove in on the mounting plates as described by Mark. I did make one alteration however to the standoff. The mounting flange of the bogie will fit a 2 1/2 " wide standoff and I had some laying around and used that instead. I also made the diameter of the plates 9 3/4" because I plan to add a blow out shroud to the plates to protect the bag and the air fill line. The mounting plate and the standoff are 1/4". I used grade 5, 3/4" by 2" coarse bolts to hold the standoff to the bogie with integrated locking type flange head on the nut. Ran out of time last week due to turkey day and came in this morning to see how the Markbag(tm) compared. Here is how the Markbag(tm) compared to the oem as I left one tired oem bag on the right side and put the markbag on the left. For the purpose of consistency I put the non test side at a height of about 15 1/2". All of my height measurements were made from the center bottom of a straight edge(in my case a bamboo paint stir stick) resting across the bogie grease fittings.
ORIGINAL BAG
Max height 17"
Min height 9"
Pressure at max height 105psi
deflation time 2 minutes and 11 seconds from full up to bottom out.
Full inflate from full deflate 10 minutes and 29 seconds.
MARKBAG
Max height 16 3/4" to 16 7/8"(floor on this side has small damage where measuring)
Min height 9 1/2"
Pressure at max height 88 psi
Deflation time 3 minutes and 6 seconds
Full attainable lift height from empty in 5 minutes and 40 seconds
Some observations
1. with both bags deflated the frame is almost touching the concrete maybe an inch away from the collapsed rear frame gliders
2. the braided rear brake lines added by the p.o. bind when bogies pivot up at full down. The hold downs need to allow the lines to slide horizontally or have an exaggerated loop near junction block to avoid pinching of the line.
3. The Markbag only took a minute and 32 seconds to go from full deflate to 16" and another 4 minutes to get the last 3/4"
4. The Markbag reached full height in 5 minutes and 40 seconds but ran it to 88 psi from around 60 just to see if I could get a little more. From empty to 88 psi took 6 minutes and 45 seconds
5. The oem bag moved through its upward lift much slower in its mid travel than the Markbag and really slowed durring the last 3/4" to inch of lift.
6. Cuting the plates round and centering the mounting holes was a bit challenging. I used the cone portion of the Markbag as a template for the diameter cut line and the center hole location. When aligning the standoffs I used a 1/2"bolt passed up from the bottom side of the plate and centered it through the 3/4" standoff mount hole,spun a nut down on it to hold it in alignment and marked the plate where the corners of the standoff touched with a sharpie. You cannot do this once the 3/4" bolt is welded in and you cannot get the 3/4" bolt into the standoff when it is on the plate. If a nut was welded into the standoff instead of a bolt then it could be aligned at the end but this could make bag instal a little more cumbersome.
7. Cant give you a ride comparison as my coach is currently not roadworthy and I have driven it very little since purchase as it is undergoing a bit of a restoration.
8. I did not do a timed lift to travel mode as I do not have a way to tell when one bag stops filling
9. The interior/rear body cap and glass/side windows and air conditioners/water tank/refridgerator and all cabinetry are removed from my coach but the 6kw onan is in place. Both of my fuel tanks are full.
10. Have a lot of play in left front bogie arm. Left rear seems okay. Kinda afraid to check right side 
Out to tac the other side together so I can tig weld the final beads at home shop. Body is all painted except the very front portion which ill do when windshields are out once shes back at home shop. Got to get her home to finish the inside and instal the Howell efi as it turns out I have 3 Quadra Jet carbs none of which are the motor home application.
Sully
77 Royale basket case.
Future motorhome land speed record holder(bucket list)
Seattle, Wa.
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