Bigdogtrucker Posted February 15, 2013 Share Posted February 15, 2013 Mack paperwork from the museum today for my B81SX.END711 engine,11:00X22 tires,SWD 50K rears with 8:24 ratio and a TRQ7210.Can someone calculate the speed?Thanks Quote Link to comment https://www.bigmacktrucks.com/topic/29960-top-speed/ Share on other sites More sharing options...
VALS327 Posted February 15, 2013 Share Posted February 15, 2013 Here is a link to a web site that makes it easy to calculate the speed.www.angelfire.com/fl/procrastination/rear.html Quote Link to comment https://www.bigmacktrucks.com/topic/29960-top-speed/#findComment-164581 Share on other sites More sharing options...
Lmackattack Posted February 15, 2013 Share Posted February 15, 2013 About 35- 40mph Quote Link to comment https://www.bigmacktrucks.com/topic/29960-top-speed/#findComment-164585 Share on other sites More sharing options...
Bigdogtrucker Posted February 15, 2013 Author Share Posted February 15, 2013 About 35- 40mph How do you figure that? Quote Link to comment https://www.bigmacktrucks.com/topic/29960-top-speed/#findComment-164586 Share on other sites More sharing options...
Lmackattack Posted February 15, 2013 Share Posted February 15, 2013 Engine RPM x 60 / (Axle Ratio x Tire Revolutions per Mile x Transmission Ratio) = Top Road Speed (MPH)2100RPM x 60 = 12600 Rear ratio 8.24 x Tire RPM 498 x trans final drive.78 = 3200.745612600 / 3200 = 39.375MPHmax 2100 RPM8.24 rear ratioI took a standard 11r22.5 tire size with 498 Revs per mile (your tire RPM may vary?)think that trans is .78 overdrive?hope this helps Quote Link to comment https://www.bigmacktrucks.com/topic/29960-top-speed/#findComment-164592 Share on other sites More sharing options...
Vladislav Posted February 15, 2013 Share Posted February 15, 2013 For the best you need to measure the size of rear tires factly.Look for OD (not Other Dog!) or for perfection place a band of inches (roullette) on a ground and run on it by rear tire. Make a mark on a tire and drive the truck for one full rear wheel's rev. Until the mark on the bend. See how many inches it did. RPMx60 mean engine revs in hour. Multiply them by tranny's ratio and axle ratio and you'll get rear wheel's revs per hour. Multiply them by wheel turn's lenght and get what you like to know.You can also count it out for any gear in a box you shift in. Quote Никогда не бывает слишком много грузовиков! leversole 11.2012 Link to comment https://www.bigmacktrucks.com/topic/29960-top-speed/#findComment-164599 Share on other sites More sharing options...
Bigdogtrucker Posted February 15, 2013 Author Share Posted February 15, 2013 Truck has 11:00X22's(44" tire),not tubeles 22.5's. Quote Link to comment https://www.bigmacktrucks.com/topic/29960-top-speed/#findComment-164600 Share on other sites More sharing options...
j hancock Posted February 15, 2013 Share Posted February 15, 2013 That will help but not much. Up to about 48 mph.2100 rpm X 44" =924005.68 gear ratio with over drive X 336 =1910.3692400/1910.36= 48.36 mphJimRevised Quote JimIt doesn't cost anything to pay attention. Link to comment https://www.bigmacktrucks.com/topic/29960-top-speed/#findComment-164602 Share on other sites More sharing options...
Vladislav Posted February 15, 2013 Share Posted February 15, 2013 If using the figures you have we must suppose 44x3.14=138.16" every turn.Doesn't you have double od tranny? If so you must to multiply one by the other.But tire's written sizes may differ up to 10% from the fact. Quote Никогда не бывает слишком много грузовиков! leversole 11.2012 Link to comment https://www.bigmacktrucks.com/topic/29960-top-speed/#findComment-164603 Share on other sites More sharing options...
Bigdogtrucker Posted February 15, 2013 Author Share Posted February 15, 2013 I'm not familiar with the TRQ7210,andbody know the difference from a 7220?EDIT-The 7210 has a .69 OD not sure about the 7220? Quote Link to comment https://www.bigmacktrucks.com/topic/29960-top-speed/#findComment-164609 Share on other sites More sharing options...
Vladislav Posted February 15, 2013 Share Posted February 15, 2013 Everything about B's trannys is still herehttp://www.bigmacktrucks.com/index.php?/topic/10929-b-model-transmission-data/ Quote Никогда не бывает слишком много грузовиков! leversole 11.2012 Link to comment https://www.bigmacktrucks.com/topic/29960-top-speed/#findComment-164612 Share on other sites More sharing options...
j hancock Posted February 15, 2013 Share Posted February 15, 2013 I'm not familiar with the TRQ7210,andbody know the difference from a 7220?The TRQ 7210 has ratio from .69-13.78 and the TRQ 7220 has ratio from.70-13.80.Pretty close ratios. Quote JimIt doesn't cost anything to pay attention. Link to comment https://www.bigmacktrucks.com/topic/29960-top-speed/#findComment-164613 Share on other sites More sharing options...
Bigdogtrucker Posted February 15, 2013 Author Share Posted February 15, 2013 Wonder why they made two different trans. that are so close? Quote Link to comment https://www.bigmacktrucks.com/topic/29960-top-speed/#findComment-164615 Share on other sites More sharing options...
HK Trucking Posted February 15, 2013 Share Posted February 15, 2013 8.24's were usually used with a quad box & 11:00x24 rubber, & IIRC my B81 was good for about 52-54 MPH @ 2100 in 5th hi. I'm guessing (without doing the math) you'll be at about 48 MPH @ 2100 in 5th hi. 7.49's were the ratio usually used with a quad box & 11:00x22 rubber. Quote "If You Can't Shift It Smoothly, You Shouldn't Be Driving It" Link to comment https://www.bigmacktrucks.com/topic/29960-top-speed/#findComment-164616 Share on other sites More sharing options...
Lmackattack Posted February 15, 2013 Share Posted February 15, 2013 I'm not familiar with the TRQ7210,andbody know the difference from a 7220?EDIT-The 7210 has a .69 OD not sure about the 7220?you are correct, that will help speed things up for you. I also used .78 as the overdrive in my math wich was incorrect... here is copy from www.macktrucksrusTRQ-72 TRQ-720 TRQ-7210 TRQ-7220 5HS - 0.85 0.66 0.69 0.70 5D - 1.00 0.78 0.84 0.84 5LS - 1.18 0.91 1.00 1.01 5LL - 2.52 1.95 2.12 2.13 4HS - 1.38 0.85 0.83 0.84 4D - 1.62 1.00 1.00 1.00 4LS - 1.91 1.17 1.19 1.20 4LL - 4.08 2.50 2.53 2.53 3HS - 2.22 1.49 1.45 1.47 3D - 2.60 1.79 1.75 1.76 3LS - 3.07 2.06 2.10 2.10 3LL - 6.56 4.39 4.44 4.44 2HS - 3.68 2.65 2.59 2.61 2D - 4.32 3.12 3.12 3.13 2LS - 5.09 3.66 3.73 3.74 2LL - 10.88 7.82 7.91 7.92 1HS - 6.42 4.62 4.51 4.55 1D - 7.53 5.45 5.45 5.45 1LS - 8.88 6.39 6.51 6.52 1LL - 18.96 13.63 13.78 13.80 1 Quote Link to comment https://www.bigmacktrucks.com/topic/29960-top-speed/#findComment-164617 Share on other sites More sharing options...
Freightrain Posted February 15, 2013 Share Posted February 15, 2013 I'm not familiar with the TRQ7210,andbody know the difference from a 7220?EDIT-The 7210 has a .69 OD not sure about the 7220?One thing to remember, a single "0" on the end is single overdrive(ie: 7220). A "00" on the end means double overdrive. Quote Larry 1959 B61 Liv'n Large...................... Charter member of the "MACK PACK" Link to comment https://www.bigmacktrucks.com/topic/29960-top-speed/#findComment-164618 Share on other sites More sharing options...
Bigdogtrucker Posted February 15, 2013 Author Share Posted February 15, 2013 One thing to remember, a single "0" on the end is single overdrive(ie: 7220). A "00" on the end means double overdrive.My B75 has a TRQ7220 and is a double OD. Quote Link to comment https://www.bigmacktrucks.com/topic/29960-top-speed/#findComment-164619 Share on other sites More sharing options...
Lmackattack Posted February 15, 2013 Share Posted February 15, 2013 so looking at this again with the correct trans info but not knowing your exact RPM of the tire(a quick google search did not find info)... I got 44.5MPHhere is my math...2100x60 =126000Rear ratio 8.24 x 498 tireRPM x .69 final =28312831 / 126000 = 44.5MPHagain....if you can find your exact tire Rev per mile I can get it closer. but you will only gain/louse 2-3mph depending on your exact tire. Quote Link to comment https://www.bigmacktrucks.com/topic/29960-top-speed/#findComment-164620 Share on other sites More sharing options...
Freightrain Posted February 15, 2013 Share Posted February 15, 2013 My B75 has a TRQ7220 and is a double OD.Well...hmmmm, guess that throws that out da window?? Most I have seen were like that. I wonder if there is more to it??Like 72"20", meaning two digits on the end for double OD?720 would be single over? My triplex is TRT 720. Quote Larry 1959 B61 Liv'n Large...................... Charter member of the "MACK PACK" Link to comment https://www.bigmacktrucks.com/topic/29960-top-speed/#findComment-164623 Share on other sites More sharing options...
Bigdogtrucker Posted February 15, 2013 Author Share Posted February 15, 2013 Here is a link to a web site that makes it easy to calculate the speed.www.angelfire.com/fl/procrastination/rear.htmlJust used this one(page wouldn't load earlier for me)I entered 2100,8.24,.69 and 44.It computed 48.3483.This is making my head pound....lol Quote Link to comment https://www.bigmacktrucks.com/topic/29960-top-speed/#findComment-164625 Share on other sites More sharing options...
Bigdogtrucker Posted February 15, 2013 Author Share Posted February 15, 2013 Well...hmmmm, guess that throws that out da window?? Most I have seen were like that. I wonder if there is more to it??Like 72"20", meaning two digits on the end for double OD?720 would be single over? My triplex is TRT 720. Pretty sure RR's the OO is double OD. Quote Link to comment https://www.bigmacktrucks.com/topic/29960-top-speed/#findComment-164626 Share on other sites More sharing options...
HK Trucking Posted February 15, 2013 Share Posted February 15, 2013 One thing to remember, a single "0" on the end is single overdrive(ie: 7220). A "00" on the end means double overdrive.Larry, the compound is overdrive in hi split even on the "72 & 722" transmissions. The main is also overdrive in 5th on the 720 & 7210 & 7220 transmisions, which gives them a double overdrive. Quote "If You Can't Shift It Smoothly, You Shouldn't Be Driving It" Link to comment https://www.bigmacktrucks.com/topic/29960-top-speed/#findComment-164627 Share on other sites More sharing options...
HK Trucking Posted February 15, 2013 Share Posted February 15, 2013 Just used this one(page wouldn't load earlier for me)I entered 2100,8.24,.69 and 44.It computed 48.3483.This is making my head pound....lolSounds about right to me. Quote "If You Can't Shift It Smoothly, You Shouldn't Be Driving It" Link to comment https://www.bigmacktrucks.com/topic/29960-top-speed/#findComment-164628 Share on other sites More sharing options...
Bigdogtrucker Posted February 15, 2013 Author Share Posted February 15, 2013 Sounds about right to me.The headache,or speed?Sorry,couldn't resist...(just took some Advil!) Quote Link to comment https://www.bigmacktrucks.com/topic/29960-top-speed/#findComment-164630 Share on other sites More sharing options...
j hancock Posted February 15, 2013 Share Posted February 15, 2013 One thing that always is different when I mess with the formula is "actual" tire size.The same size tire but different brands are different actual sizes.Even when I have measured the tires myself there are variables.The main deal here is that it is a B81 dump truck and dump trucks of that time period were about a 50 mph truck.I recall that true 24" rubber on trucks so equipped were branded "not to exceed 55 mph".Jim 1 Quote JimIt doesn't cost anything to pay attention. Link to comment https://www.bigmacktrucks.com/topic/29960-top-speed/#findComment-164631 Share on other sites More sharing options...
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